Down and Dirty Primitive Hunting Technology / Videos

HUNGER: The prime motivator of human behavior and technology. Primitive tools compensate for “puny human” lack of claws, reduced olfactory sense, and other assets possessed by the competition: other hungry animals, including many much smaller than humans, had superior strength, speed, meat-or tough vegetation-tearing teeth (cooking required), protective fur, athletic ability, specialized body parts and instinctive tactics. Early humans HAD TO develop tools!

Our type of brain most likely developed as a “tool” that compensated for (and competed with) the “equipment” of other animals in particular environments. The brain as technology – think about it! LOL


Thermodynamic Function of Life / Darwinian Theory Questioned

K. Michaelian, Instituto de Física, Universidad Nacional Autónoma de México Cto. de la Investigación Científica Cuidad Universitaria, Mexico D.F., C.P. 04510

Equations that govern physical reality.


Darwin suggested that life was at the mercy of the forces of Nature and would necessarily adapt through natural selection to the demands of the external environmental. However, it has since become apparent that life plays a pivotal role in altering its physical environment (Lovelock, 1988) and what once appeared to be biotic evolution in response to abiotic pressure is now seen as coevolution of the biotic together with the abiotic to greater levels of complexity, stability, and entropy production (Ulanowicz and Hannon, 1987). Such an understanding, difficult to reconcile within traditional Darwinian theory, fits perfectly well within the framework of non-equilibrium thermodynamics in which dissipative processes spontaneously arise and coevolve in such a manner so as to increase the entropy production of the system plus its environment (Prigogine, 1972, Ulanowicz and Hannon, 1987, Swenson, 1989, Kleidon and Lorenz, 2005, Michaelian, 2005, Michaelian, 2009a).

Life is found everywhere on Earth. On the surface, the components of greatest biomass are the archea, prokaryote, and eukaryote life based on photosynthesis. In the sea, photosynthetic phytoplankton (archea, diatoms, cyanobacteria, and dinoflagallates) can be found in great density (up to 109/ml at the surface) in the euphotic zone which extends to a depth of 50 meters. Almost all photosynthesis ends at the bottom of the Epipelagic zone at about 200 m. Approaching these depths, special pigments are needed to utilize the only faint blue light that can penetrate. On land, diatoms, cyanobacteria, and plants, which evolved from ocean cyanobacteria some 470 million years ago (Wellman and Gray, 2000; Raven and Edwards, 2001), cover almost every available area, becoming sparse only where conditions are extremely harsh, particularly where liquid water is scarce. Photosynthesizing cyanobacteria have been found thriving in hotsprings at over 70 °C (Whitton and Potts, 2000) and on mountain glaciers and Antarctic ice (Parker et al., 1982) where absorption of solar radiation and its dissipation into heat by organic and lithogenic material produces the vital liquid water, even deep within the ice (Priscu et al., 2005).
The thermodynamic driving force for the process of photosynthesis that sustains surface life derives from the low entropy of sunlight and the second law of thermodynamics. Only twenty seven years after Darwin’s publication of the theory of evolution through natural selection, Boltzmann (1886) wrote: “The general struggle for existence of animate beings is therefore not a struggle for raw materials – nor for energy which exists in plenty in any body in the form of heat — but a struggle for entropy, which becomes available through the transition of energy from the hot sun to the cold earth”.


In photosynthesis, high-energy photons in the visible region of the Sun’s spectrum are converted by the chloroplasts into low energy photons in the infrared region. Part of the free energy made available in the process is utilized to maintain and propagate life. In this manner, photosynthetic life obtains its sustenance through the conversion of the low entropy of sunlight into the higher entropy of heat and thereby contributes to the positive entropy production of the Earth as a whole.

However, the proportion of the Sun’s light spectrum utilized in photosynthesis is small and thus the entropy producing potential of photosynthesis is small. Gates (1980) has estimated that the percentage of available (free) energy in solar radiation that shows up in the net primary production of the biosphere is less than 0.1%. Respiration consumes a similarly small quantity (Gates, 1980). Of all the irreversible processes performed by living organisms, the process generating by far the greatest amount of entropy (consuming the greatest amount of free energy) is the absorption of sunlight by organic molecules in the presence of water leading to evapotranspiration. Great quantities of water are absorbed by the root systems of plants and brought upwards to the leaves and then evaporated into the atmosphere. More than 90% of the free energy available in the sunlight captured by the leaves of plants is used in transpiration. In the oceans, phytoplankton within the euphotic zone absorb sunlight and transform it into heat that can be efficiently absorbed by the water. The temperature of the ocean surface is thereby raised by phytoplankton (Kahru et al., 1993) leading to increased evaporation, thereby promoting the water cycle.
There appears to be no important physiological need for the vast amount of transpiration carried out by land plants. It is known that only 3% of the water transpired by plants is used in photosynthesis and metabolism. In fact, most plants can grow normally under laboratory conditions of 100% humidity, at which the vapor pressure in the stoma of the leaves must be less than or equal to that of the atmosphere, and therefore transpiration is necessarily zero (Hernández Candia, 2009). Transpiration has often been considered as an unfortunate by-product of the process of photosynthesis in which water is unavoidably given off through the stoma of plants which are open in order to exchange CO2 and O2 with the atmosphere (Gates, 1980). Plants consist of up to 90% water by mass and thus appear to expose themselves to great risk of drying by transpiring so much water. Others have argued
that transpiration is useful to plants in that it helps to cool its leaves to a temperature optimal for photosynthesis. Such an explanation, however, is not convincing since Nature has produced examples of efficient photosynthesis at temperatures of up to 70 °C (Whitton and Potts, 2000). In any case, there exists other simpler and less free energy demanding strategies to reduce leaf temperature such as smaller or less photo-absorbent leaves. On the contrary, the evolutionary record indicates that plants and phytoplankton have evolved new pigments to absorb ever more completely the Sun’s spectrum. Dense pine forests appear black in the midday sun. Most plants appear green, not so much for lack of absorption at these wavelengths, as for the fact that the spectral response of human eyes peaks precisely at these wavelengths (Chang, 2000).

Transpiration is in fact extremely free energy intensive and, according to Darwinian Theory, such a process, with little direct utility to the plant, should have been eliminated or suppressed through natural selection. Plants which are able to take in CO2 while reducing water loss, by either opening their stoma only at night (CAM photosynthesis), or by reducing photorespiration (C4 photosynthesis, see below), indeed have evolved 32 and 9 million years ago respectively (Osborne and Freckleton, 2009). However, the water conserving photosynthesis has not displaced the older, heavily transpiring C3 photosynthesis which is still relevant for 95% of the biomass of Earth. Instead, new ecological niches in water scarce areas have opened up for the CAM and C4 plants, as, for example, the cacti of deserts.

All irreversible processes, including living systems, arise and persist to produce entropy. This is not incidental, but rather a fundamental principle of Nature. Excessive transpiration has not been eliminated from plants, despite the extraordinary free energy costs, precisely because the basic thermodynamic function of a plant is to increase the global entropy production of the Earth and this is achieved by dissipating high energy photons in the presence of water and thereby augmenting the global water cycle.

The Water Cycle Absorption of sunlight in the leaves of plants may increase their temperature by as much as 20°C over that of the ambient air (Gates, 1980). This leads to an increase of the H2O vapor pressure inside the cavities of the leaf with respect to that of the colder surrounding air. H2O vapor diffuses across this gradient of chemical potential from the wet mesophyll cell walls (containing the chloroplasts), through the intercellular cavities, and finally through the stoma and into the external atmosphere. There is also a parallel, but less efficient, circuit for diffusion of H2O vapor in leaves through the cuticle, providing up to 10% more transpiration (Gates, 1980). The H2O chemical potential of the air at the leaf surface itself depends on the ambient relative humidity and temperature, and thus on such factors as the local wind speed and insolation. Diffusion of H2O vapor into the atmosphere causes a drop in the water potential inside the leaf which provides the force to draw up new water from the root system of the plants.

Evaporation from moist turf (dense cut grass) can reach 80% of that of a natural water surface such as a lake (Gates, 1980), while that of a tropical forest can often surpass by 200% that of such a water surface (Michaelian, 2009b). Single trees in the Amazon rain forest have been measured to evaporate as much as 1180 liters/day (Wullschleger et al., 1998). This is principally due to the much larger surface area for evaporation that a tree offers with all of its leaves. Natural water surfaces, in turn, evaporate approximately 130% of distilled water surfaces due to the increased UV and visible photon absorption at the surface as a result of phytoplankton and other suspended organic materials, including a large component (up to 109/ml at the surface) of viral and dissolved DNA resulting from viral lysing of bacteria (Wommack and Colwell, 2000).

The water vapor transpired by the leaves, or evaporated by the phytoplankton, rises in the atmosphere, because water vapor at 0.804 g/l is less dense than dry air at 1.27 g/l, to a height corresponding to a temperature of about 259 K (-14 °C) (Newell et al., 1974) at which it condenses around suspended microscopic particles forming clouds. Over oceans, an important constituent of these microscopic particles acting as seeds of condensation are the sulfate aerosols produced by the oxidation of dimethylsulfide released by the phytoplankton themselves (Charlson et al., 1987). Condensation of the water releases an amount of latent heat of condensation ( 6 10427.2 × J /kg) into the upper atmosphere, much of which is then radiated into outer space at infrared wavelengths. In this manner, the Earth maintains its energy balance with space; the total energy incident on the biosphere in the form of sunlight is approximately equal to the total energy radiated by the biosphere into space at infrared wavelengths. Energy is conserved while the entropy of the Universe is augmented in the process.

The formation of clouds may at first consideration seem to have a detrimental effect on the water cycle since cloud cover on Earth reflects approximately 20% of light in the visible region of the Sun’s spectrum (Pidwirny and Budicova, 2008), thereby reducing the potential for evaporation. However, evapotranspiration is a strong function of the local relative humidity of the air around the leaves of plants or above the surface of the oceans. By producing regions of local cooling during the day on the Earth’s surface, clouds are able to maintain the average wind speed at the Earth’s surface within dense vegetation (see for example, Speck (2003)) at values above the threshold of 0.25 m/s required to make the boundary-layer resistance to water loss almost negligible in a plant leaf, thus procuring maximal transpiration (Gates, 1980).
Sublimation and ablation of ice over the polar regions, promoted in part by photon absorption of cyanobacteria within the ice, is also important to the water cycle, evaporating up to 30 cm of ice per year (Priscu et al., 2005).

Production of Entropy

The driving force of all irreversible processes, including the water cycle, is the production of entropy. The basic entropy producing process occurring on Earth is the absorption and dissipation of high energy photons to low energy photons, facilitated in part by the plants and cyanobacteria in the presence of water.

Much math / physics / chemistry / geology / planetary geology skipped: go to original. 

The Importance of Life to the Water Cycle

The very existence of liquid water on Earth can be attributed to the existence of life. Through mechanisms related to the regulation of atmospheric carbon dioxide first espoused in the Gaia hypothesis (Lovelock, 1988), life is able to maintain the temperature of the Earth within the narrow region required for liquid water, even though the amount of radiation from the Sun has increased by about 25% since the beginnings of life (Newman and Rood, 1977, Gough, 1981). Physical mechanisms exist that disassociate water into its hydrogen and oxygen components, for example through photo-dissociation of water by ultraviolet light (Chang, 2000). Photo-dissociation of methane has been suggested as a more important path to loosing the hydrogen necessary for water (Catling et al., 2001). Free hydrogen, being very light, can escape Earth’s gravity and drift into space, being dragged along by the solar wind. This loss of hydrogen would have lead to a gradual depletion of the Earth’s water (Lovelock, 2005). However, photosynthetic life sequesters oxygen from carbon dioxide thereby providing the potentiality for its recombination with the free hydrogen to produce water. For example, hydrogen sulfide is oxidized by aerobic chemoautotrophic bacteria, giving water as a waste product (Lovelock, 1988). Oxygen released by photosynthetic life also forms ozone in the upper atmosphere which protects water vapor and methane in the lower atmosphere from ultraviolet photo-dissociation. In this manner, the amount of water on Earth has been kept relatively constant since the beginnings of life.

It has been estimated that about 496,000 km3 of water is evaporated yearly, with 425,000 km3 (86%) of this from the ocean surface and the remaining 71,000 km3 (14%) from the land (Hubbart and Pidwirny, 2007). Evaporation rates depend on numerous physical factors such as insolation, absorption properties of air and water, temperature, relative humidity, and local wind speed. Most of these factors are non-linearly coupled. For example, local variations in sea surface temperature due to differential photon absorption rates caused by clouds or local phytoplankton blooms, leads to local wind currents. Global winds are driven by latitude variation of the solar irradiance and absorption, and the rotation of the Earth. Relative humidity is a function of temperature but also a function of the quantity of microscopic particles available for seeds of condensation (a significant amount of which are supplied by biology (Lovelock, 1988)).

The couplings of the different factors affecting the water cycle imply that quantifying the effect of biology on the cycle is difficult. However, simulations using climate models taking into account the important physical factors have been used to estimate the importance of vegetation on land to evapotranspiration. Kleidon (2008) has shown that without plants, average evaporation rates on land would decrease from their actual average values of 2.4 mm/d to 1.4 mm/d, suggesting that plants may be responsible for as much as 42% of the actual evaporation over land. There appears to be little recognition in the literature of the importance of cyanobacteria and other organic matter floating at the ocean surface to evaporation rates. Irrespective of other factors such as wind speed and humidity, evaporation rates should be at least related to the energy deposited in the sea surface layer. A calculation can therefore be made of the effect of biology on the evaporation rates over oceans and lakes.
Before attempting such a calculation, it is relevant to review the biological nature of the air / sea surface interface, and energy transfer within this layer, based on knowledge that has emerged over the last decade. This skin surface layer of roughly 1 mm thickness has its particular ecosystem of high density in organic material (up to 104 the density in water slightly below (Grammatika and Zimmerman, 2001)). This is due to the scavenging action of rising air bubbles due to breaking waves, surface tension, and natural buoyancy (Grammatika and Zimmerman, 2001). The organic material consists of cyanobacteria, diatoms, viruses, free floating RNA/DNA, and other living and non-living organic material such as chlorophyll and other pigments. Most of the heat exchange between the ocean and atmosphere of today occurs from within this upper 1 mm of ocean water. For example, most of the radiated infrared radiation from the sea comes from the upper 100 µ m (Schlussel, 1999). About 52% of the heat transfer from this ocean layer to atmosphere is in the form of latent heat (evaporation), radiated longwave radiation accounts for 33%, and sensible heat through direct conduction accounts for the remaining 15%.

Science, calculations, tables skipped; go to original.

Some theories have the origin of life dissipating other sources of free energy, such as chemical energy released from hydrothermal vents at deep ocean trenches. Whether life originated to dissipate the free energy in sunlight or the free energy in made available through chemical transformations, the quantity of life at hydrothermal vents today corresponds to a very minute portion of all life on Earth implying that its contribution to the actual entropy production of the Earth can be considered negligible. The rich ecosystems existing at these vents are, in fact, not completely autonomous, but dependent on the dissolved oxygen and nutrients of photosynthetic life living closer to the surface. An Earth without photosynthetic life would thus correspond to one in a wholly different class of thermodynamic stationary states, one probably with little involvement of a water cycle.

Evidence for Evolutionary Increases in the Water Cycle

Plants, far from eliminating transpiration as a wasteful use of free energy, have in fact evolved over time ever more efficient water transport and transpiration systems (Sperry, 2003). There is a general trend in evolution, and in ecosystem succession over shorter times, to ever increasing transpiration rates. For example, conifer forests are more efficient at transpiration than deciduous forests principally because of the greater surface area offered for evaporation by the needles as compared to the leaves. Conifers appeared later in the fossil record (late carboniferous) and appear in the late successional stage of ecosystems. Root systems are also much more extended in late evolutionary and successional species, allowing them to access water at ever greater depths (Raven and Edwards, 2001). New pigments besides chlorophyll have appeared in the evolutionary history of plants and cyanobacteria, covering an ever greater portion of the intense region of the solar spectrum, even though they have little or no effect on photosynthesis, for example, the carotenoids in plants, or the MAA’s found in phytoplankton which absorb across the UVB and UVA regions (310-400 nm) (Whitehead and Hedges, 2002). This is particularly notable in red algae, for example, where its total absorption spectrum has little correspondence with its photosynthetic activation spectrum (Berkaloff et al., 1971).

There exist complex mechanisms in plants to dissipate photons directly into heat, bypassing completely photosynthesis. These mechanisms involve inducing particular electronic de-excitations using dedicated enzymes and proteins and come in a number of distinct classes. Constitutive mechanisms, allow for intersystem crossing of the excited chlorophyll molecule into triplet, long-lived, states which are subsequently quenched by energy transfer to the carotenoids. Inducible mechanisms can be regulated by the plant itself, for example, changing lumen pH causes the production of special enzymes that permit the non-photochemical de-excitation of chlorophyll. Sustained mechanisms are similar to inducible mechanisms but have been adapted to long term environmental stress. For example, over-wintering evergreen leaves produce little photosynthesis due to the extreme cold but continue transpiring by absorbing photons and degrading these to heat through non-photochemical de-excitation of chlorophyll. Hitherto, these mechanisms were considered as “safety valves” for photosynthesis, protecting the photosynthetic apparatus against light-induced damage (Niyogi, 2000). However, their existence and evolution can better be understood in a thermodynamic context as augmenting the entropy production potential of the plant through increased transpiration.

The recent findings of microsporine-like amino acids (MAAs) produced by plants and phytoplankton having strong absorption properties in the UVB and UVA regions follows their discovery in fungi (Leach, 1965). They are small (< 400 Da), water-soluble compounds composed of aminocyclohexenone or aminocycloheximine rings with nitrogen or imino alcohol substituents (Carreto et al., 1990) which display strong UV absorption maximum between 310 and 360 nm and high molar extinction (Whitehead and Hedges, 2002). These molecules have been assigned a UV photoprotective role in these organisms, but this appears dubious since more than 20 MAAs have been found in the same organism, each with different but overlapping absorption spectrum, determined by the particular molecular side chain (Whitehead and Hedges, 2002). If their principle function were photoprotective, there existence would be confined to those UV wavelengths that cause damage to the organism, and not to the whole UV broadband spectrum.

Plants also perform a free energy intensive process known as photorespiration in which O2 instead of CO2 is captured by the binding enzyme RuBisCo, the main enzyme of the light iindependent part of photosynthesis. This capture of O2 instead of CO2 (occurring about 25% of the time) is detrimental to the plant for a number of reasons, including the production of toxins that must be removed (Govindjee, 2005) and does not lead to ATP production. There is no apparent utility to the plant in performing photorespiration and in fact it reduces the efficiency of photosynthesis. It has often been considered as an “evolutionary relic” (Niyogi, 2000), still existing from the days when O2 was less prevalent in the atmosphere than today and CO2 more so (0.78% CO2 by volume at the rise of land plants during the Ordovician (ca. 470 Ma) compared with only 0.038% today). However, such an explanation is not in accord with the known efficacy of natural selection to eliminate useless or wasteful processes. Another theory has photorespiration as a way to dissipate excess photons and electrons and thus protect the plants photosynthesizing system from excess light-induced damage (Niyogi, 2000). Since photorespiration is common to all C3 plants, independent of their insolation environments, it is more plausible that photorespiration, being completely analogous to photosynthesis with respect to the dissipation of light into heat in the presence of water (by quenching of excited chlorophylls) and subsequent transpiration of water, is retained for its complimentary role in evapotranspiration and thus entropy production.

Plants not only evaporate water during sunlight hours, but also at night (Snyder et al., 2003). Common house plants evaporate up to 1/3 of the daily transpired water at night (Hernández Candía, 2009). Not all the stoma in C3 and C4 photosynthetic plants are closed at night and some water vapor also diffuses through the cuticle at night. The physiological reason, in benefit of the plant, for night transpiration, if one exists, remains unclear. It, of course, can have no relevance to cooling leaves for optimal photosynthetic rates. Explanations range from improving nutrient acquisition, recovery of water conductance from stressful daytime xylem cavitation events, and preventing excess leaf turgor when water potentials become large during the day (Snyder et al., 2003). However, night transpiration is less of an enigma if considered as a complement to the thermodynamic function of life to augment the entropy production of Earth through the water cycle. In this context, it is also relevant that chlorophyll has an anomalous absorption peak in the infrared at between about 4,000 and 10,000 nm (Gates, 1980), close to the wavelength at which the blackbody radiation of the Earth’s surface at 14 °C peaks.

Cyanobacteria have been found to be living within Antarctic ice at depths of up to 2 m. These bacteria and other lithogenic material absorb solar radiation which causes the formation of liquid water within the ice even though the outside air temperatures may be well below freezing. This heating from below causes excess ablation and sublimation of the overlying ice at rates as high as 30 cm per year (Priscu et al., 2005).
Finally, by analyzing latent heat fluxes (evaporation) and the CO2 flux for plants from various published data sets, Wang et al. (2007) have found vanishing derivatives of transpiration rates with respect to leaf temperature and CO2 flux, suggesting a maximum transpiration rate for plants, i.e. that the particular partition of latent and sensible heat fluxes is such that it leads to a leaf temperature and leaf water potential giving maximal transpiration rates, and thus maximal production of entropy (Wang et al., 2007).

The Function of Animals

If the primary thermodynamic function of the plants and cyanobacteria is to augment the entropy production of the Earth by absorbing light in the presence of liquid water, it may then be asked: What is the function of higher mobile animal life? Because of their intricate root system which allows the plants to draw up water for evaporation from great depths, plants are not mobile and depend on insects and other animals for their supply of nutrients, cross fertilization, and seed dissemination and dispersal into new environments. The mobility and the short life span of insects and animals mean that through excrement and eventual death, they provide a reliable mechanism for dispersal of nutrients and seeds.

Crustaceans and animal marine life in water perform a similar function as insect and animal life on land. These higher forms of life distribute nutrients throughout the ocean surface through excrement and dying. It is noteworthy that dead fish and mammals do not sink rapidly to the bottom of the sea, but remain floating for considerable time on the surface where, as on land, bacteria break down the organism into its components, allowing photon dissipating phytoplankton to reuse the nutrients, particularly nitrogen. It is interesting that many algae blooms produce a neurotoxin with apparently no other end than to kill higher marine life. There is also a continual cycling of nutrients from the depths of the ocean to the surface as deep diving mammals preying on bottom feeders release nutrients at the surface through excrement and death. Because of this cycling and mobility of animals, a much larger portion of the ocean surface is rendered suitable for phytoplankton growth, offering a much larger area for efficient surface absorption of sunlight and evaporation of water than would otherwise be the case.

From this thermodynamic viewpoint, animal life provides a specialized gardening service to the plants and cyanobacteria, which in turn catalyze the absorption and dissipation of sunlight in the presence of water, promoting entropy production through the water cycle. There is strong empirical evidence suggesting that ecosystem complexity, in terms of species diversity, is correlated with potential evapotranspiration (Gaston, 2000). The traditional ecological pyramid should thus be turned on its pinnacle. Instead of plants and phytoplankton being considered as the base that sustains animal life, animals are in fact the unwitting but content servants of plant and phytoplankton life, obtaining thermodynamic relevance only in how they increase the plant and phytoplankton potential for evaporation of water.


We have argued that the basic thermodynamic function of life (and organic material in general) is to absorb and dissipate high energy photons such that the heat can be absorbed by liquid water and eventually transferred to space through the water cycle. Photosynthesis, although relevant to cyanobacteria and plant growth, has only minor relevance to the thermodynamic function of life. Augmenting the water cycle through increased photon absorption and radiation-less relaxation, life augments the entropy production of the Earth in its interaction with its solar environment. We have presented empirical evidence indicating that the evolutionary history of Earth’s biosphere is one of increased photon absorption and dissipation over time, whether on shorter successional, or longer evolutionary, time scales.

This thermodynamic perspective on life views it as a catalyst for entropy production through the water cycle, and ocean and wind currents. It ties biotic processes to abiotic processes with the universal goal of increasing Earth’s global entropy production and thus provides a framework within which coevolution of the biotic with the abiotic can be accommodated. In important distinction to the hypothesis of Gaia, that mixed biotic-abiotic mechanisms have evolved to maintain the conditions on Earth suitable to life, it is here suggested instead that these biotic-abiotic mechanisms have evolved to augment the entropy production of Earth, principally, but not exclusively, through the facilitation of the water cycle. Life, as we know it, is an important, perhaps even inevitable, but certainly not indispensable, catalyst for the production of entropy on Earth.

How does life arise from randomness? / Physics to the rescue…

see also:

Why does life exist?

For figures and illustrations go to original. 

Popular hypotheses credit a primordial soup, a bolt of lightning and a colossal stroke of luck. But if a provocative new theory is correct, luck may have little to do with it. Instead, according to the physicist proposing the idea, the origin and subsequent evolution of life follow from the fundamental laws of nature and “should be as unsurprising as rocks rolling downhill.”

From the standpoint of physics, there is one essential difference between living things and inanimate clumps of carbon atoms: The former tend to be much better at capturing energy from their environment and dissipating that energy as heat. Jeremy England, a 31-year-old assistant professor at the Massachusetts Institute of Technology, has derived a mathematical formula that he believes explains this capacity. The formula, based on established physics, indicates that when a group of atoms is driven by an external source of energy (like the sun or chemical fuel) and surrounded by a heat bath (like the ocean or atmosphere), it will often gradually restructure itself in order to dissipate increasingly more energy. This could mean that under certain conditions, matter inexorably acquires the key physical attribute associated with life.

“You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant,” England said.

England’s theory is meant to underlie, rather than replace, Darwin’s theory of evolution by natural selection, which provides a powerful description of life at the level of genes and populations. “I am certainly not saying that Darwinian ideas are wrong,” he explained. “On the contrary, I am just saying that from the perspective of the physics, you might call Darwinian evolution a special case of a more general phenomenon.”


England’s theoretical results are generally considered valid. It is his interpretation — that his formula represents the driving force behind a class of phenomena in nature that includes life — that remains unproven. But already, there are ideas about how to test that interpretation in the lab.

“He’s trying something radically different,” said Mara Prentiss, a professor of physics at Harvard who is contemplating such an experiment after learning about England’s work. “As an organizing lens, I think he has a fabulous idea. Right or wrong, it’s going to be very much worth the investigation.”

At the heart of England’s idea is the second law of thermodynamics, also known as the law of increasing entropy or the “arrow of time.” Hot things cool down, gas diffuses through air, eggs scramble but never spontaneously unscramble; in short, energy tends to disperse or spread out as time progresses. Entropy is a measure of this tendency, quantifying how dispersed the energy is among the particles in a system, and how diffuse those particles are throughout space. It increases as a simple matter of probability: There are more ways for energy to be spread out than for it to be concentrated. Thus, as particles in a system move around and interact, they will, through sheer chance, tend to adopt configurations in which the energy is spread out. Eventually, the system arrives at a state of maximum entropy called “thermodynamic equilibrium,” in which energy is uniformly distributed. A cup of coffee and the room it sits in become the same temperature, for example. As long as the cup and the room are left alone, this process is irreversible. The coffee never spontaneously heats up again because the odds are overwhelmingly stacked against so much of the room’s energy randomly concentrating in its atoms.

Although entropy must increase over time in an isolated or “closed” system, an “open” system can keep its entropy low — that is, divide energy unevenly among its atoms — by greatly increasing the entropy of its surroundings. In his influential 1944 monograph “What Is Life?” the eminent quantum physicist Erwin Schrödinger argued that this is what living things must do. A plant, for example, absorbs extremely energetic sunlight, uses it to build sugars, and ejects infrared light, a much less concentrated form of energy. The overall entropy of the universe increases during photosynthesis as the sunlight dissipates, even as the plant prevents itself from decaying by maintaining an orderly internal structure.

Life does not violate the second law of thermodynamics, but until recently, physicists were unable to use thermodynamics to explain why it should arise in the first place. In Schrödinger’s day, they could solve the equations of thermodynamics only for closed systems in equilibrium. In the 1960s, the Belgian physicist Ilya Prigogine made progress on predicting the behavior of open systems weakly driven by external energy sources (for which he won the 1977 Nobel Prize in chemistry). But the behavior of systems that are far from equilibrium, which are connected to the outside environment and strongly driven by external sources of energy, could not be predicted.

This situation changed in the late 1990s, due primarily to the work of Chris Jarzynski, now at the University of Maryland, and Gavin Crooks, now at Lawrence Berkeley National Laboratory. Jarzynski and Crooks showed that the entropy produced by a thermodynamic process, such as the cooling of a cup of coffee, corresponds to a simple ratio: the probability that the atoms will undergo that process divided by their probability of undergoing the reverse process (that is, spontaneously interacting in such a way that the coffee warms up). As entropy production increases, so does this ratio: A system’s behavior becomes more and more “irreversible.” The simple yet rigorous formula could in principle be applied to any thermodynamic process, no matter how fast or far from equilibrium. “Our understanding of far-from-equilibrium statistical mechanics greatly improved,” Grosberg said. England, who is trained in both biochemistry and physics, started his own lab at MIT two years ago and decided to apply the new knowledge of statistical physics to biology.

David Kaplan explains how the law of increasing entropy could drive random bits of matter into the stable, orderly structures of life. Filming by Tom Hurwitz and Richard Fleming. Editing and motion graphics by Tom McNamara. Music by Podington Bear.

Using Jarzynski and Crooks’ formulation, he derived a generalization of the second law of thermodynamics that holds for systems of particles with certain characteristics: The systems are strongly driven by an external energy source such as an electromagnetic wave, and they can dump heat into a surrounding bath. This class of systems includes all living things. England then determined how such systems tend to evolve over time as they increase their irreversibility. “We can show very simply from the formula that the more likely evolutionary outcomes are going to be the ones that absorbed and dissipated more energy from the environment’s external drives on the way to getting there,” he said. The finding makes intuitive sense: Particles tend to dissipate more energy when they resonate with a driving force, or move in the direction it is pushing them, and they are more likely to move in that direction than any other at any given moment.

“This means clumps of atoms surrounded by a bath at some temperature, like the atmosphere or the ocean, should tend over time to arrange themselves to resonate better and better with the sources of mechanical, electromagnetic or chemical work in their environments,” England explained.

Self-replication (or reproduction, in biological terms), the process that drives the evolution of life on Earth, is one such mechanism by which a system might dissipate an increasing amount of energy over time. As England put it, “A great way of dissipating more is to make more copies of yourself.” In a September paper in the Journal of Chemical Physics, he reported the theoretical minimum amount of dissipation that can occur during the self-replication of RNA molecules and bacterial cells, and showed that it is very close to the actual amounts these systems dissipate when replicating. He also showed that RNA, the nucleic acid that many scientists believe served as the precursor to DNA-based life, is a particularly cheap building material. Once RNA arose, he argues, its “Darwinian takeover” was perhaps not surprising.

The chemistry of the primordial soup, random mutations, geography, catastrophic events and countless other factors have contributed to the fine details of Earth’s diverse flora and fauna. But according to England’s theory, the underlying principle driving the whole process is dissipation-driven adaptation of matter.

This principle would apply to inanimate matter as well. “It is very tempting to speculate about what phenomena in nature we can now fit under this big tent of dissipation-driven adaptive organization,” England said. “Many examples could just be right under our nose, but because we haven’t been looking for them we haven’t noticed them.”

Scientists have already observed self-replication in nonliving systems. According to new research led by Philip Marcus of the University of California, Berkeley, and reported in Physical Review Letters in August, vortices in turbulent fluids spontaneously replicate themselves by drawing energy from shear in the surrounding fluid. And in a paper appearing online this week in Proceedings of the National Academy of Sciences, Michael Brenner, a professor of applied mathematics and physics at Harvard, and his collaborators present theoretical models and simulations of microstructures that self-replicate. These clusters of specially coated microspheres dissipate energy by roping nearby spheres into forming identical clusters. “This connects very much to what Jeremy is saying,” Brenner said.

Besides self-replication, greater structural organization is another means by which strongly driven systems ramp up their ability to dissipate energy. A plant, for example, is much better at capturing and routing solar energy through itself than an unstructured heap of carbon atoms. Thus, England argues that under certain conditions, matter will spontaneously self-organize. This tendency could account for the internal order of living things and of many inanimate structures as well. “Snowflakes, sand dunes and turbulent vortices all have in common that they are strikingly patterned structures that emerge in many-particle systems driven by some dissipative process,” he said. Condensation, wind and viscous drag are the relevant processes in these particular cases.

“He is making me think that the distinction between living and nonliving matter is not sharp,” said Carl Franck, a biological physicist at Cornell University, in an email. “I’m particularly impressed by this notion when one considers systems as small as chemical circuits involving a few biomolecules.”

Prentiss, who runs an experimental biophysics lab at Harvard, says England’s theory could be tested by comparing cells with different mutations and looking for a correlation between the amount of energy the cells dissipate and their replication rates. “One has to be careful because any mutation might do many things,” she said. “But if one kept doing many of these experiments on different systems and if [dissipation and replication success] are indeed correlated, that would suggest this is the correct organizing principle.”

Brenner said he hopes to connect England’s theory to his own microsphere constructions and determine whether the theory correctly predicts which self-replication and self-assembly processes can occur — “a fundamental question in science,” he said.

Having an overarching principle of life and evolution would give researchers a broader perspective on the emergence of structure and function in living things, many of the researchers said. “Natural selection doesn’t explain certain characteristics,” said Ard Louis, a biophysicist at Oxford University, in an email. These characteristics include a heritable change to gene expression called methylation, increases in complexity in the absence of natural selection, and certain molecular changes Louis has recently studied.

If England’s approach stands up to more testing, it could further liberate biologists from seeking a Darwinian explanation for every adaptation

and allow them to think more generally in terms of dissipation-driven organization. They might find, for example, that “the reason that an organism shows characteristic X rather than Y may not be because X is more fit than Y, but because physical constraints make it easier for X to evolve than for Y to evolve,” Louis said.

“People often get stuck in thinking about individual problems,” Prentiss said. Whether or not England’s ideas turn out to be exactly right, she said, “thinking more broadly is where many scientific breakthroughs are made.”

Emily Singer contributed reporting. This article was reprinted on and

We have to start somewhere / What is cognition?

I’m working up to the problem of visual and sensory thinking being all but ignored (or even dismissed) by the “cognition and behavior sciences” as a primary mode of perception and cognition in evolutionary history. This ignorance or arrogance on the part of “researchers” is especially negligent on the part of those whose declared interest is ASD / Asperger’s and other non-typical diagnosis. The irony is that these diagnosis of “abnormality” may simply demonstrate the bias or outright prejudice that only the “social” language of scripted word concepts / formal academic constructs  is “important” to human thought and behavior. That is, rigid restrictions have been placed on human thought, behavior and personal expression that may reflect the inability of the “social engineering class” to think in any other mode. Can this group have become so isolated from “natural” human behavior, that only individuals who are similarly limited to social constructs and rigid narratives are “accepted, selected for” inclusion in the class of those who dictate social behavior, thus increasingly diminishing the diversity of ideas about “what it is to be human” to their own impoverished experiences? The peasant classes are urged to function only on emotional reactivity and scripted social behavior, thus remaining powerless.

WIKI on Cognition: 

“Cognition is “the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses”.[1] It encompasses processes such as attention, the formation of knowledge, memory, and working memory, judgement and evaluation, reasoning and “computation,” problem-solving and decision making, comprehension and production of language. Cognitive processes use existing knowledge and generate new knowledge.” 

Note that “producing language” is only one of many thinking processes; the “expressive – action based” fields of art and music, dance and kinesthetic “thinking” must be assumed to be included under experience and the senses; otherwise these thought processes are missing from the list. Why? The stress is on “conscious” cognition; “unconscious” cognition is considered to be “low-level” cognition and has been segregated from “high-level cognition” – an error that has had severe consequences to the understanding of “how the brain works” in relation to the “whole” human organism and how it interacts with the environment. This “social conception” of human biology, physiology and behavior serves the western socio-religious narcissism of “man” as a special creation isolated from the reality of evolution.  

“The processes are analyzed from different perspectives within different contexts, notably in the fields of linguistics, anesthesia, neuroscience, psychiatry, psychology, education, philosophy, anthropology, biology, systemics, logic, and computer science. These and other different approaches to the analysis of cognition are synthesized in the developing field of cognitive science, a progressively autonomous academic discipline.”  

Again, we must assume that “the arts” are included somewhere in this disconnected “chopped salad” of academic reserves, which often are “at war” with each other over “domains of expertise” (territories) without much flow of information or “honest” discussion between academics. Genuine scientific competition and progress requires constant questioning of assumptions (hypothesis, theories); this necessity is hampered by most of these disciplines being based on theories, rather than truly investigative “reality-based” research that is open to challenges by other researchers.

A severe problem with current concepts of cognition and intelligence: The 300,000 y.o. Jebel Irhoud Homo sapiens, considered to be the “earliest so far” true Homo sapiens. If judged on the decision / conceit that only “conscious social cognition and behavior” count toward being classified as Homo sapiens, how do we explain the survival of any hominid? The current explanation is that these early Homo sapiens were “cognitively and socially identical to modern social humans.” A reality based conclusion would be, that given the variety and range of difficult environments and conditions in which they survived and successfully reproduced, these humans would have had to be more intelligent than modern domesticated humans, who have the advantage of 300,000 years of collective human experience and culture HANDED TO THEM by default. 

The “human brain and behavior” community would have us believe that this fellow survived by relying on modern social word-concepts and social theories of behavior.

Au contraire! Survival would have demanded the “action” intelligences of sensory processing: art and technology production, acute and immediate visual-sensory analysis of threats and opportunities presented by a wild ‘natural’ environment, memorization / mapping of geographical, geological and faunal-flora details of food availability; cooperation, sharing and mutual respect for individual skills and talents, and a precise (not vague or generalized) use of verbal language, gestures, imitative animal communication and graphic symbols.





Neanderthal Cave Art? / Anthropology Wars

Why is it that in any anthropologic scenario, one group must win and “the other” group must become extinct? There is a difference between one community of people (let’s say the Roanoke Colony), failing to thrive, and this “failure” being proof that all English people became extinct.  We project the “winner versus looser” plot onto evolutionary history, that as yet, we do not understand. 

Video from the scientific article “U-Th dating of carbonate crusts reveals Neanderthal origin of Iberian cave art” (

One comment: It continues to baffle the logical Asperger, as to why neurotypicals insist that any intentional mark on a rock, or any other object, is automatically “symbolic” expression and “proves” abstract thought in the brain of the “mark maker” when a drawing can be (and usually is) concrete and literal: the drawing of a cave lion is a lion. The arrangement of lines in a drawing into which animals are being driven, is a corral; the animals are specific animals. “Bad” prehistoric drawings (inept person attempting to draw an object) are not 20th C. abstract art!

John Hawks on evidence of Neanderthal / H. sapiens occupation and cultural sharing  in the Carmel area of northern Israel.

The always sane and rational John Hawks…


And for two other narratives, go to:


Beauty and Curiosity / Instinct

Note: No words needed! Demonstration is superior for transmitting many skills and types of knowledge. “Human types” have been doing this for hundreds of thousands of years. Only the efficiency of the technology changes. 

This video is an example of how VISUAL CURIOSITY was key to how and why humans developed tools and other objects that enhanced everyday life. It wasn’t until very recently that “art” became separated from “craft.” That is, the cult of the artist, in which a “name” such as Picasso, adds millions of dollars in value to mundane objects (everything from actual paintings to wall plaques to mugs and T-shirts) is a product of economic power elitism. That object is MINE because I have the wealth to possess it.  The intrinsic aesthetic value of an art object is secondary to the social status of the owner – where they exist in the wealth hierarchy.  Modern people tend to project this social relationship backward; misapplying the word “art” to functional objects, whose aesthetic appeal is intrinsic to its function. The cave paintings found in Europe are attributed to “great artists” (male of course) when this is not the case. In modern social environments art is an approved function controlled and defined by an “elite” who select and interpret which “art” is socially useful and a “good investment.” The cave painters lived what they painted: it’s not abstract but descriptive; the animals are not alien creatures observed from afar. This art is personal: Beautiful because REAL animals are beautiful.

“In the beginning” it was visual curiosity that drove humans to learn about materials; to pick them up and absorb their physical properties – to break and bend and find applications through trial and error. This activity is inseparable from an instinct for beauty. The quality that set human species apart is intense curiosity that extends to the entire environment. We not only copied each other, we copied other animals:  how wolves hunt in a pack; how male birds attract females with outlandish colors and dances; how patterns camouflage fish, how rain is  captured by depressions in rock, how animals behave when a predator is near.

Homo habilis tools; indistinguishable from naturally formed chert fragments that I can pick up any day in my geologic neighborhood. Very sharp edges!

I walk frequently in an area littered with chert fragments that were spread by wandering streams millions of years ago, and which have been exposed by erosion. Despite weathering (wind scour), the sharp edges of recently fractured pieces (freeze thaw, concussion) are very sharp; one could select a few and butcher a small animal – crudely maybe, but the principle is there. Curiosity is enough to urge me to pick up slivers; the polished surfaces, dark color and odd shapes that stand out against the yellow dirt is “eye-catching” – a process in human perception that is unchanged. Add some trial and error with these and other stones and cobbles, and you’re on your way to being an effective predator, gatherer, inventor.

Everyday I see countless ways that early humans learned from what was simply in front of their eyes. My “neighborhood” is desert; few animals are out by day, but if I show up in early morning, on a muddy or snowy day, the number of animal tracks is astounding. Even with my feeble knowledge (which you can bet would quickly increase if I were looking for food) a source of “symbols” and “time” is apparent. These ideas are VISIBLE: specific tracks record an animal’s presence, even though it is “invisible” at this moment. Time can be seen in the spatial distribution of tracks, the medium of clay or sand, ice or snow, in the patterns of track overlays and in beginnings and endings.

For me, there is no discontinuity or “magic” in human evolution; no intervention by supernatural entities or aliens, because there is no need to resort to these props. Humans accumulated a working knowledge of many environments; that knowledge is both specific (tropical forest / mountain valleys) but also general, because the Laws of Nature apply to every environment. The rapidity of technical advancement depended on where you lived (you have to have resources) a few “little bit smarter” individuals, and the opportunity to beg, borrow, steal, or copy the tools, skills and materials in use by both animals and other people. Techno Culture makes our human world different to previous apes.


See also:

The Use of Tools by Human and Non-human Primates

A. Berthelet and J. Chavaillon


Clouds are important to a plain landscape / Re-Post



Clouds are important to a plain landscape; those familiar shapes that skate above

the horizon, trailing shadows that examine the featureless plateau;

extracting details that cannot be seen on a clear day

and thereby adjusting our foolish estimates of near and far.

Any stranger who trifles with our two-part scheme of land and sky risks losing

the outer world: the fate of isolation is best embraced as a gift

that one could not have known was waiting in Wyoming.


What I’m reading today / Organic life on other planets


Book: The National Academies Press

The Limits of Organic Life in Planetary Systems, 2007 (100 pages readable online)


For generations the definition of life has eluded scientists and philosophers. (Many have come to recognize that the concept of “definition” itself is difficult to define.3) We can, however, list characteristics of the one example of life that we know—life on Earth:

  • It is chemical in essence; terran living systems contain molecular species that undergo chemical transformations (metabolism) under the direction of molecules (enzyme catalysts) whose structures are inherited, and heritable information is itself carried by molecules.

  • To have directed chemical transformations, terran living systems exploit a thermodynamic disequilibrium.

  • The biomolecules that terran life uses to support metabolism, build structures, manage energy, and transfer information take advantage of the covalent bonding properties of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur and the ability of heteroatoms, primarily oxygen and nitrogen, to modulate the reactivity of hydrocarbons.

  • Terran biomolecules interact with water to be soluble (or not) or to react (or not) in a way that confers fitness on a host organism. The biomolecules found in terran life appear to have molecular structures that create properties specifically suited to the demands imposed by water.

  • Living systems that have emerged on Earth have done so by a process of random variation in the structure of inherited biomolecules, on which was superimposed natural selection to achieve fitness. These are the central elements of the Darwinian paradigm.

Various published definitions of life understandably incorporate those features, given that we are the life form defining it. Indeed, because the chemical structures of terran biomolecular systems all appear to have arisen through Darwinian processes, it is hardly surprising that some of the more thoughtful definitions of life hold that it is a “chemical system capable of Darwinian evolution.”4


Many of the definitions of life include phrases like undergoes Darwinian evolution. The implication is that phenotypic changes and adaptation are necessary to exploit unstable environmental conditions and to function optimally in the environment. Evolutionary changes have even been suggested for the hypothesized “clay crystal life” of Cairns-Smith,5 referring to randomly occurring errors in crystal structure during crystal growth as analogous to mutations. Would a self-replicating chemical system capable of chemical transformations in the environment be considered life? If self-replicating chemical compounds are not life, replication by itself is not sufficient as a defining characteristic of life. Likewise, the ability to undergo Darwinian evolution, a process that results in heritable changes in a population, is also not sufficient to define life if we consider minerals that are capable of reproducing errors in their crystal structure to be equivalent to evolution. Although that property of clays may have been vital in the origin of life and particularly in the prebiotic synthesis of organic macromolecules and as catalysts for metabolic reactions, can the perpetuation of “mistakes” in crystal structure result in the selection of a “more fit” crystal structure? It is important to emphasize that evolution is not simply reproducing mutations (mistakes in clays), but also selecting variants that are functionally more fit.

The canonical characteristics of life are an inherent capacity to adapt to changing environmental conditions and to interact with other living organisms (and, at least on Earth, also with viruses).6 Natural selection is the key to evolution and the main reason that Darwinian evolution persists as a characteristic of many definitions of life. The only alternative to evolution for producing diversity would be to have environmental conditions that continuously create different life forms or similar life forms with random and frequent “mistakes” in the synthesis of chemical templates used for replication or metabolism. Such mistakes would be equivalent to mutations and could lead to traits that gave some selective advantage in an existing community or in exploiting new habitats. That random process could lead to life forms that undergo a form of evolution without a master information macromolecule, such as DNA or RNA. It is difficult to imagine such life forms as able to “evolve” into complex structures unless other mechanisms, such as symbiosis or cell-cell fusion, are available.

Evolution is the key mechanism of heritable changes in a population. However, although mutation and natural selection are important processes, they are not the only mechanisms for acquiring new genes. It is understood that lateral gene transfer is one of the most important and one of the earliest mechanisms for creating diversity and possibly for building genomes with the requisite information to result in free-living cells.7 Lateral gene transfer is also one of the mechanisms to align genes from different sources into complex functional activities, such as magnetotaxis and dissimilatory sulfate reduction.8 It is possible that this mechanism was important in the evolution of metabolic and biosynthetic pathways and other physiological traits that may have evolved only once even though they are present in a wide variety of organisms. Coevolution of two or more species is also a hallmark of evolution manifested in many ways, from insect-plant interactions to the involvement of hundreds of species of bacteria in the nutrition of ruminant animals. Organisms and the environment also coevolve, depending on the dominant characteristics of the environment and the availability of carbon and energy sources.

If the ability to undergo Darwinian evolution is a canonical trait of life no matter how different a life form is from Earth life, are there properties of evolving extraterrestrial organisms that would be detectable as positive signs of life? Evolution provides organisms the opportunity to exploit new and changing environments, and one piece of evidence for the cosmic ubiquity of evolution is that on Earth life occupies all available habitats and even creates new ones as a consequence of metabolism. Another hallmark of evolution is the ability of organisms to coevolve with other organisms and to form permanent and obligatory associations. It is highly probable that an inevitable consequence of evolution is the elimination of radically different biochemical lineages of life that may have formed during the earliest period of the evolution of life. Extant Earth life is the result of either selection of the most fit lineage or homogenization of some or all of the different lineages into a common ancestral community that developed into the current three major lineages (domains). All have a common biochemistry based on presumably the most “fit” molecular information strategies and energy-yielding pathways among a potpourri of possibilities.

Thus, one of the apparent generalizations that can be drawn from extant Earth life, and the explanation for the development of a “unity of biochemistry” in all organisms, is that lateral gene transfer is an ancient and efficient mechanism for rapidly creating diversity and complexity. Lateral gene transfer is also an efficient mechanism for selecting the genes that are most “fit” for specific proteins and transferring them into diverse groups of organisms. The results are the addition of genes and the replacement of less-fit genes that have similar functions. Natural selection based solely on mutation is probably not an adequate mechanism for evolving complexity. More important, lateral gene transfer and endosymbiosis are probably the most obvious mechanisms for creating complex genomes that could lead to free-living cells and complex cellular communities in the short geological interval between life’s origin and the establishment of autotrophic CO2 fixation about 3.8 billion years ago and microbial sulfate reduction 3.47 billion years ago on the basis of isotope data.9 An important implication of the existence of viruses or virus-like entities during the early evolution of cellular organisms is that their genomes may have been the source of most genetic innovations because of their rapid replication, high rates of mutation due to replication errors, and gene insertions from diverse host cells.10

Is evolution an essential feature of life? Cells are more than the information encoded in their genomes; they are part of a highly integrated biological and geochemical system in whose creation and maintenance they have participated. The unity of biochemistry among all Earth’s organisms emphasizes the ability of organisms to interact with other organisms to form coevolving communities, to acquire and transmit new genes, to use old genes in new ways, to exploit new habitats, and, most important, to evolve mechanisms to help to control their own evolution. Those characteristics would probably be present in extraterrestrial life even if it had a separate origin and a unified biochemistry different from that of Earth life.


As discussed in the literature,11 chemical models of non-Earth-centric life reveal much about what the scientific community considers possible, particularly regarding ways in which systems organize matter and energy to generate life. Thus, truly “weird” life might utilize an element other than carbon for its scaffolding. Less weird, but still alien to human biological experience, would be a life form that does not exploit thermodynamic disequilibria that are largely chemical. Weirder would be a life form that does not exploit water as its liquid milieu. Still weirder would be a life form that exists in the solid or gas phase.12 In a different direction, yet also outside the scope of life that most communities think possible, would be a life form that lacks a history of Darwinian evolution.

Some features of terran life are almost certainly universal, however. In particular, the requirement for thermodynamic disequilibrium is so deeply rooted in our understanding of physics and chemistry that it is not disputable as a requirement for life. Other criteria are not absolute. Terran biology contains clear examples of the use of nonchemical energy; photosynthesis is the best known, although energy from light is soon converted to chemical energy. Silicon, in some environments, can conceivably support the scaffolding of large molecules. This report explicitly considers nonaqueous environments.

Even Darwinian evolution is presumably not an absolute. For example, depending on how human civilization applies gene therapy, our particular form of life could be able to evolve via Lamarckian,a as opposed to Darwinian, processes. Humankind will be able to perceive and solve problems in human biology without needing to select among random events, thus sparing the species the need to remove unavoidable genetic defects through the death of individuals. That will make the human biosphere no less living, even to those who make Darwinian evolution central in their concept of life.

Likewise, we can easily conceive of robots that are self-reproducing or computer-based processes that grow and replicate.13 Here, information transfer is not based on a specific molecular replication but on a replication involving information on a matrix. Whether such entities will be called life remains to be seen.

What is clear is that the scientific community does not believe that Lamarckian, robotic, or informational “life” could have arisen spontaneously from inanimate matter. At the very least, its matrix would have to be constructed initially by a chemical, Darwinian life form arising from processes similar to those seen on Earth. Again, it is not clear whether those views are constrained by our inability to conceive broadly from what we know or whether they reflect true constraints on the processes by which life might emerge in natural history.

Lamarck recognized a similar principle of evolution referred to as “inheritance of acquired characters,” stating that variations in characteristics seen in organisms were acquired in response to the environment.

Those thoughts introduce a subsidiary theme of this report. It is conceivable that chemistry, structure, or environments able to support life were not suited for the initiation of life. For example, Earth can support life today, but prevailing views hold that life could not have originated in an atmosphere that is as oxidizing as Earth’s today. If that is true, the surface of Earth would be an environment that is habitable but not able to give rise to life.



We have only one example of biomolecular structures that solve problems posed by requirements for life, and the human mind finds it difficult to create ideas truly different from what it already knows. It is thus difficult for us to imagine how life might look in planetary environments very different from what we find on Earth. Recognizing that difficulty, the committee chose to embrace it. The committee exploited a strategy that began with characterization of the terran life that humankind has known well, first because of its macroscopic visibility and then through microscopic observation that began in earnest 4 centuries ago. This, of course, is like life that is associated with humankind. As the next step in the strategic process, the committee assembled a set of observations about life that is considered exotic when compared with human-like life. Exploration of Earth has taken researchers to environments that human-like organisms find extreme, to the highest temperatures at which liquid water is possible, to the lowest temperatures at which water is liquid, to the depths of the ocean where pressures are high, to extremes of acidity and alkalinity, to places where the energy flux is too high for human-like life to survive, to locales where thermodynamic disequilibria are too scarce to support human-like life, and to locations where the chemical environment is toxic to human-like life.

The committee then asked, Can we identify environments on Earth where Darwinian processes that exploit human-like biochemistry cannot exploit available thermodynamic disequilibria? The answer is an only slightly qualified no. It appears that wherever the thermodynamic minimum for life is met on Earth and water is found, life is found. Furthermore, the life that is found appears to be descendant from an ancestral life form that also served as the ancestor of humankind (perhaps we would not necessarily have recognized it if its ancestry were otherwise) and exploits fundamentally human-like biochemistry.

The committee then reviewed evidence of abiotic processes that manipulate organic material in a planetary environment. It asked whether the molecules that we see in contemporary terran life might be understood as the inevitable consequences of abiotic reactivity. Although signatures of such predecessor reactivity can be adumbrated within contemporary biochemistry, they are generally faint.14 Some 4 billion years of biological evolution have attached a strong Darwinian signature to whatever went before; hypotheses regarding evidence of our inanimate ancestry within modern biostructures are the subject of intense dispute.

If life originated first on Earth, it was long ago when conditions on the surface of this planet were very different from what they are today. We do not know what those conditions were, and we may never know. Furthermore, the organisms around today are all highly evolved descendants of the first life forms and probably contributed long ago to the demise of their less fit, more primitive competitors. The historical slate has been wiped clean both geologically and biologically. Finally, because life forms replicate, singular events can have enormous impacts on future developments. Life does not have to be a probable outcome of spontaneous physicochemical processes, although it may well be. Arguments based on probability are not as powerful in this sphere as they usually are in the physical sciences.

The committee surveyed the inventory of environments in the solar system and asked which non-Earth ones might be suited to life of the terran type. Such locales are few, unless there are laws not now understood that could govern the early stages of the self-organization of biochemical structures and processes that could lead inevitably to evolving life forms.15 Subsurface Mars and the putative sub-ice oceans of the Galilean satellites are the only locales in the solar system (other than Earth itself) that are clearly compatible with terran biochemistry.

The committee’s survey made clear, however, that most locales in the solar system are at thermodynamic disequilibrium—an absolute requirement for chemical life. Furthermore, many locales that have thermodynamic disequilibrium also have solvents in liquid form and environments where the covalent bonds between carbon and other lighter elements are stable. Those are weaker requirements for life, but the three together would appear, perhaps simplistically, to be sufficient for life. The committee asked whether it could conceive of biochemistry adapted to those exotic environments, much as human-like biochemistry is adapted to terran environments. Few detailed hypotheses are available; the committee reviewed what is known, or might be speculated, and considered research directions that might expand or constrain understanding about the possibility of life in such exotic environments.

Finally, the committee considered more exotic solutions to problems that must be solved to create the emergent properties that we agree characterize life. It considered a hierarchy of “weirdness”:

  • Is the linear dimensionality of biological molecules essential? Or can a monomer collection or two-dimensional molecules support Darwinian evolution?

  • Must a standard liquid of some kind serve as the matrix for life? Can a supercritical fluid serve as well? Can life exist in the gas phase? In solid bodies, including ice?

  • Must the information content of a living system be held in a polymer? If so, must it be a standard biopolymer? Or can the information to support life be placed in a mineral form or in a matrix that is not molecularly related to Darwinian processes?

  • Are Darwinian processes and their inherent struggle to the death essential for living systems? Can altruistic processes that do not require death and extinctions and their associated molecular structures support the development of complex life?

  • Suggested Citation:“1 Introduction.” National Research Council. 2007. The Limits of Organic Life in Planetary Systems. Washington, DC: The National Academies Press. doi: 10.17226/11919.



1. Sagan, C. 1973. Extraterrestrial life. Pp. 42-67 in Communication with Extraterrestrial Intelligence CETI (C. Sagan, ed.). MIT Press, Cambridge, Mass.


2. Ward, P. 2005. Life as We Do Not Know It. Viking, New York.


3. Cleland, C.E. 2001. Historical science, experimental science, and the scientific method. Geology 29:987-990.


4. Joyce, G.F., Young, R., Chang, S., Clark, B., Deamer, D., DeVincenzi, D., Ferris, J., Irvine, W., Kasting, J., Kerridge, J., Klein, H., Knoll, A., and Walker, J.1994. In Origins of Life: The Central Concepts (D.W. Deamer and G.R. Fleischaker, eds). Jones and Bartlett, Boston, Mass.


5. Cairns-Smith, A.G. 1982. Genetic Takeover and the Mineral Origins of Life. Cambridge University Press, Cambridge, U.K.


6. See Brown, J.R., 2003, Ancient horizontal gene transfer, Nature Rev. Genetics 4:121-132; Martin, W., Rotte, C., Hoffmeister, M., Theissen, U., Gelius-Dietrich, G., Ahr, S., and Henze, K., 2003, Early cell evolution, eukaryotes, anoxia, sulfide, oxygen, fungi first (?), and a tree of genomes revisited, IUBMB Life 55:193-204; Ochman, H., Lawrence, J.G., and Groisman, E.S., 2000, Lateral gene transfer and the nature of bacterial innovation, Nature 405:299-304; and Woese, C.R., 2002, On the evolution of cells, Proc. Natl. Acad. Sci. U.S.A. 99:8742-8747.


7. Martin, W., Rotte, C., Hoffmeister, M., Theissen, U., Gelius-Dietrich, G., Ahr, S., and Henze, K. 2003. Early cell evolution, eukaryotes, anoxia, sulfide, oxygen, fungi first (?), and a tree of genomes revisited. IUBMB Life 55:193-204.


8. See Grünberg, K., Wawer, C., Tebo, B.M., and Schüler, D., 2001, A large gene cluster encoding several magnetosome proteins is conserved in different species of magnetotactic bacteria, Appl. Environ. Microbiol. 67:4573-4582; Mazel, D., 2006, Integrons: Agents of bacterial evolution, Nature Rev. Microbiol. 4:608-620; and Mussmann, M., Richter, M., Lombardot, T., Meyerdierks, A., Kuever, J., Kube, M., Glöchner, O., and Amann, R., 2005, Clustered genes related to sulfate respiration in uncultured prokaryotes support the theory of their concomitant horizontal transfer, J. Bacteriol. 187:7126-7127.


9. See Rosing, M.T., 1999, 13C-depleted carbon microparticles in >3700-Ma sea-floor sedimentary rocks from West Greenland, Science 283:674-676; Shen, Y., Buick, R., and Canfield, D.E., 2001, Isotopic evidence for microbial sulphate reduction in the early Archaean era, Nature 410:77-81; and Shidlowski, M.A., 1988, A 3800-million-year isotopic record of life from carbon in sedimentary rocks, Nature 333:313-318.


10. Claverie, J.M., 2006, Viruses take center stage in cellular evolution, Genome Biol. 7:110; Forterre, P., 2006, The origin of viruses and their possible roles in major evolutionary transitions, Virus Res. 117:5-16; Forterre, P., 2006, Three RNA cells for ribosomal lineages and three DNA viruses to replicate their genomes: A hypothesis for the origin of cellular domain, Proc. Natl. Acad. Sci. U.S.A. 103:3669-3674; and Koonin, E.V., and Martin, W., 2005, On the origin of genomes and cells within inorganic compartments, Trends Genetics 21:647-654.


11. Benner, S.A., Ricardo, A., and Carrigan, M.A. 2004. Is there a common chemical model for life in the universe? Curr. Opinion Chem. Biol. 8:672-689.


12. Allamandola, L.J., and Hudgins, D.M. 2003. From interstellar polycyclic aromatic hydrocarbons and ice to astrobiology. In Proceedings of the NATO ASI, Solid State Astrochemistry (V. Pirronello and J. Krelowski, eds.). Kluwer, Dordrecht.


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First land plants trigger mass extinction / Ordovician

If present day life is getting you down, try a getaway to the Ordovician.

Why it’s great to have a geologist in the house

By Nancy Shute, March 22, 2018

Science has a way of surprising us when we least expect it. Like with mud rocks.We science journalists can be a cranky lot, eternally skeptical as to whether a touted advance is really significant enough to warrant coverage. So when Science News’ managing editor Erin Wayman waxed enthusiastic about a study explaining how ancient plants may have played a key role in making Earth muddier, I perked up.

Geologists have long known that mud started to take hold at some point, but as earth and climate writer Carolyn Gramling reports in this issue, “no one had ever pinpointed when that muddening happened.”

Clearly erosion must have been a factor, but that’s as far as my mud expertise goes. A geologist I am not. Fortunately, Gramling is a geologist, with bachelor’s degrees in both geology and European history and a Ph.D. in marine geochemistry. I asked her what it was about this study that convinced her it was worth a look. “It struck me because I like to know what makes things tick,” she said during a conversation in my office. “It was surprising.”

This wasn’t a big sexy science story: no neutron star collisions, no gene-editing breakthroughs, no advances in immunotherapy. Instead, we have grayish rocks. But they have something to tell us. The researchers, at the University of Cambridge, looked at ancient riverbed deposits and found that the amount of mud rock, which is primarily made of clay, silt and other fine particles, increased about 458 million years ago. (Ordovician) That’s also when a group of primitive land plants known as bryophytes, which include modern mosses and liverworts, became common on Earth. The fact that bryophytes could have had that much impact is another surprise, Gramling said. “These are not rooted plants,” she added. “They’re these little mats of mosses on the surface, but they still have this profound effect.” Indeed, the author of a commentary accompanying the study in Science called the plants “tiny, little scrappy things.”

I like the notion of scrappy little underdog plants helping to transform the face of our planet. And I very much like having a writer on staff who’s a scientist with deep expertise who can say, yes, this is as neat as it sounds.

Gramling was quick to note that we don’t know exactly how ancient plants made Earth muddier. But even simple plants can help keep wind and water from eroding sediments. Plants may also help break down rock chemically, too.

Researchers study ground-covering plants, resembling the earliest land-dwelling plants, on a lava field in Iceland (Credit: Paul Kenrick)


Origin and early evolution of land plants

Problems and considerations


The origin of the sporophyte in land plants represents a fundamental phase in plant evolution. Today this subject is controversial, and scarcely considered in textbooks and journals of botany, in spite of its importance. There are two conflicting theories concerning the origin of the alternating generations in land-plants: the “antithetic” theory and the “homologous” theory. These have never been fully resolved, although, on the ground of the evidences on the probable ancestors of land plants, the antithetic theory is considered more plausible than the homologous theory. However, additional phylogenetic dilemmas are the evolution of bryophytes from algae and the transition from these first land plants to the pteridophytes. All these very large evolutionary jumps are discussed on the basis of the phyletic gradualist neo-Darwinian theory and other genetic evolutionary mechanisms.


First land plants plunged Earth into ice age

Never underestimate moss. When the simple plants first arrived on land, almost half a billion years ago, they triggered both an ice age and a mass extinction of ocean life.

The first land plants appeared around 470 million years ago, during the Ordovician period, when life was diversifying rapidly. They were non-vascular plants, like mosses and liverworts, that didn’t have deep roots.

About 35 million years later, ice sheets briefly covered much of the planet and a mass extinction ensued. Carbon dioxide levels probably fell sharply just before the ice arrived – but nobody knew why.

Tim Lenton of the University of Exeter, UK, and colleagues think the mosses and liverworts are to blame.

Moss versus rock

It’s not the first time that plants have been fingered as a cause of glaciation. Researchers already suspect that the rise of vascular plants in the Devonian period, some 100 million years later, triggered another ice age. The plants’ roots extracted nutrients from bedrock, leaving behind vast quantities of chemically altered rock that could react with CO2 and so suck it out of the atmosphere.

Non-vascular plants like mosses don’t have deep roots, so it was thought that they didn’t behave in the same way. Lenton suspected they might have played a role nevertheless. To find out, he set up an experiment to see what damage a common moss (Physcomitrella patens) could inflict on granite. After 130 days, rocks with moss living on them had weathered significantly more than bare ones – and about as much as they would have if vascular plants were living on them. “The secret seems to be that the moss secrete a wide range of organic acids that can dissolve rock,” Lenton says.

When Lenton added this effect of non-vascular plants to a climate model of the Ordovician, the CO2 dropped from about 22 times modern levels to just eight times modern levels. That was enough to trigger an ice age in the model of Ordovician Earth.

In his experiments, the non-vascular plants also released lots of phosphorus from rocks. Much of this would have wound up in the ocean, where we know it can trigger vast algal blooms. As other bugs feasted on the algae, they would have used up the oxygen in the water – suffocating oxygen-breathing animals and accounting for the mass extinction of marine life known to have occurred at the end of the Ordovician.

Although the first land plants were responsible for these mass deaths in their ocean-dwelling neighbours, Lenton says they themselves probably came out of the Ordovician ice age largely unscathed. That’s because the ice was concentrated around the South Pole, while the plants lived in the tropics.

Life may also have caused an even harsher cold snap much earlier in Earth’s history. The first complex animals appeared some time around 800 million years ago, and may have sucked so much CO2 from the atmosphere that the entire planet froze over in a “snowball Earth“.

Journal reference: Nature Geoscience, DOI: 10.1038/ngeo139

 Crinoids and Rugose Corals. 

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