Zaworski’s Blog / Neanderthal – Archaic H. Sapiens

James Zaworski’s Blog

Much more at:  Morphological and Archaeological Comparisons of the Levantine Neandertal and Archaic Homo sapiens Complexes.

Morphological Traits and Variation.

It is imperative to my discussion here to set out the accepted morphological traits that defines how a Neandertal is classified , and how an Anatomically Modern Homo sapiens (AMHS), is classified. This is not as cut and dry as it seems. Depending on which paleoanthropologist is doing the analysis, there really isn’t an accepted laundry list of characteristic traits that are consistently used. When paleoanthropologists compare the morphology of Neandertals and AMHS, it is usually the case to compare the most robust or “classic” Neandertals from Western Europe with the most gracile “Cro-Magnon” Homo sapiens from Europe. This is not a fair comparison by a long shot, in terms of variation, because these two are on the complete opposite ends of the spectrum in terms of general skeletal and cranial robusticity on the one hand with the Classic Western European Neandertals and extreme skeletal and cranial gracility on the part of the Cromagnon. Where this becomes much more confusing is in the Levantine area of the Middle East, in the modern state of Israel, because the specimens that have been discovered at the various sites, such as Skhul, Amud, Qafzeh, Tabun, Kebara, and Mount Carmel all display characteristics that are intermediate in their morphological characteristics.(Wolpoff, 1999:594, 612). Further confusion comes into the picture, as the anatomically modern Homo sapiens have also been dubbed “proto-Cro-Magnons”, implying that these are indeed the true ancestors and precursors of modern Homo sapiens.(Bar-Yosef, 1988:31).

 

 

Anthro Wars / Will Earliest H. sapiens please stand up?

Reconstruction 300,000 y.o. Jebel Irhoud by John Bavarro

reconstruction by Kennis & Kennis

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A post on Dienike’s Anthropology Blog from 2011, before Jebel Irhoud site in  Morocco was reopened and new fossils identified as earliest Homo sapiens (to date) were dated to 300,000 y.a. 

http://dienekes.blogspot.com/2011/05/is-jebel-irhoud-father-of-mankind.html

May 20, 2011

Is Jebel Irhoud the Father of mankind?

The redating of the human Y-chromosome phylogeny to about 142 thousand years ago and the relocation of its most ancient lineages from east and south Africa to the Northwest marks a watershed moment in our understanding of human prehistory.

It is a fortuitous coincidence that there actually is a sample of humans from Northwest Africa from around the same time: Jebel Irhoud, about 160 thousand years ago from Morocco:

Jebel Irhoud is a cave site located about 100 km west of Marrakech, Morocco. The site is known for the numerous hominid fossils discovered there. Currently, the site has yielded seven specimens. The best known of these are portions of two adult skulls, Irhoud 1 and 2, a child’s mandible (Irhoud 3), and a child’s humerus (Irhoud 4). Fossils 1-3 were discovered while the cave was being quarried for barytes and thus their exact context and age has been subject to debate. Originally the Irhoud hominids were considered North African Neandertals. It is now clear that they are best grouped with other early anatomically modern humans such as Qafzeh (Israel) and Skhul (Israel).

A 2007 article by Smith et al. is extremely important for this population: (of course, other Anthropologists disagree) 

Earliest evidence of modern human life history in North African early Homo sapiens

Tanya M. Smith et al.

Recent developmental studies demonstrate that early fossil hominins possessed shorter growth periods than living humans, implying disparate life histories. Analyses of incremental features in teeth provide an accurate means of assessing the age at death of developing dentitions, facilitating direct comparisons with fossil and modern humans.

It is currently unknown when and where the prolonged modern human developmental condition originated. Here, an application of x-ray synchrotron microtomography reveals that an early Homo sapiens juvenile from Morocco dated at 160,000 years before present displays an equivalent degree of tooth development to modern European children at the same age. Crown formation times in the juvenile’s macrodont dentition are higher than modern human mean values, whereas root development is accelerated relative to modern humans but is less than living apes and some fossil hominins. The juvenile from Jebel Irhoud is currently the oldest-known member of Homo with a developmental pattern (degree of eruption, developmental stage, and crown formation time) that ismore similar to modern H. sapiens than to earlier members of Homo. This study also underscores the continuing importance of North Africa for understanding the origins of human anatomical and behavioral modernity. Corresponding biological and cultural changes may have appeared relatively late in the course of human evolution.

In the recent paper on the Ceprano calvarium, Irhoud 1 clearly belonged in the modern human cluster, and so it was in my re-analysis of that data, as were skulls from the Sudan and Tanzania in Africa, and the Qafzeh/Skhul early skulls from the Levant.

It thus seems to me, that the earliest modern human skulls are found in North/East Africa and West Asia, while the root of the Y-chromosome phylogeny is provisionally in Northwest Africa and seems to be in agreement with the autosomal evidence for a bottleneck in the human population at around 150,000 years ago.
Here is the interesting part: Irhoud had been once seen as a Neandertal. Indeed, it displayed some Neandertal-like leanings in a previous analysis. The consensus now (supported by the results of Mounier et al.) seems to be that it was modern human, but the Neandertal connection does not stop there:
The lithic industries of Jebel Irhoud were Mousterian, the same as Neandertals.Mousterian industries link European Neandertals, with modern humans in North Africa and the Near East. The Mousterian industries represented a genuine progress over the Acheulean tools that archaic humans had been using for hundreds of thousands of years before, and they, in turn, were replaced by the Aurignacian at exactly the time that Cruciani et al. date the main Y-chromosome CT clade that encompasses all Eurasians and most Africans.
The evidence seems to be in astonishing agreement with my hypothesis about the so-called “Neandertal admixture” in modern humans:
  • Early modern humans originated in North Africa, or at least somewhere between North and East Africa. Their traces may very well be hidden under the sands of the once (or thrice) green Sahara
  • They formed a clade with Neandertals, and used the same Mousterian tools, while humans elsewhere continued to use the older Acheulean ones. Both of them could very well have descended from Homoheidelbergensis, although the transition is not yet clear.
  • They expanded briefly into West Asia after Marine Isotope Stage 5, 120,000 years or so ago, and appeared in the Levant (Skhul/Qafzeh). As the Sahara dried up, they must’ve spread both to West Asia, and deeper into Africa, and, not surprisingly, the next major branching of the Y-chromosome phylogeny dates to about that time; this accounts for the deep (but not deepest) Y-chromosome lineages in modern day San.
  • Eventually (around 40,000 years ago, after the end of wet Marine Isotope Stage 3), they developed the even more advanced Aurignacian technology, and went on to conquer most of the world, driving the Neandertals to extinction. As the Sahara dried up, they expanded into Sub-Saharan Africa once again, and this time they inundated it with their genes.

Hence, the Modern-Neandertal affinity is not the result of any hypothetical admixture event between the two: Sub-Saharan Africans have also preserved some of the genetic legacy of the older Acheulean-using populations of the continent which shifts them somewhat away from other modern humans and Neandertals.

see original for more…

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A photo identified by John Hawks (2017 tweet) as Jebel Irhoud Homo sapiens left, (assume it’s the “new” 300 K model) and La Ferrassie Neanderthal (50-70,000 K)

La Ferrassie 1 Neanderthal (approx. date 50-70,000 y.a.)

Below: A Jebel Irhoud skull identified (Smithsonian) as 160,000 y.o. Homo sapiens. Ryan Somma.

Above: (see abstract below) 300,000 y.o. Jebel Irhoud composite: Philipp Gunz/MPI EVA Leipzig Image caption: A reconstruction of the earliest known Homo sapiens skull based on scans of multiple original fossils (this is not a complete skull from an individual)

And, let’s not forget: A Homo erectus reconstruction. (there are many…)

Confused yet?

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Abstract of paper introducing new Jebel Irhoud fossil finds and 300,000 y.a. date

New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapien

Jean-Jacques Hublin (see original for authors)

Nature volume 546, pages 289–292 (08 June 2017) doi:10.1038/nature22336

Fossil evidence points to an African origin of Homo sapiens from a group called either H. heidelbergensis or H. rhodesiensis. However, the exact place and time of emergence of H. sapiens remain obscure because the fossil record is scarce and the chronological age of many key specimens remains uncertain. In particular, it is unclear whether the present day ‘modern’ morphology rapidly emerged approximately 200 thousand years ago (ka) among earlier representatives of H. sapiens1 or evolved gradually over the last 400 thousand years2. Here we report newly discovered human fossils from Jebel Irhoud, Morocco, and interpret the affinities of the hominins from this site with other archaic and recent human groups. We identified a mosaic of features including facial, mandibular and dental morphology that aligns the Jebel Irhoud material with early or recent anatomically modern humans and more primitive neurocranial and endocranial morphology. In combination with an age of 315 ± 34 thousand years (as determined by thermoluminescence dating)3, this evidence makes Jebel Irhoud the oldest and richest African Middle Stone Age hominin site that documents early stages of the H. sapiens clade in which key features of modern morphology were established. Furthermore, it shows that the evolutionary processes behind the emergence of H. sapiens involved the whole African continent.

More to come…

 

Bipedality and Hair Loss / model revised for altitude

Bipedality and hair loss in human evolution revisited: The impact of altitude and activity scheduling

Journal of Human Evolution, Volume 94, May 2016, Pages 72-82

 1. Introduction

Brain tissue is extremely sensitive to heat, and must be kept within very narrow tolerances to avoid rapid cell death (Precht and Brück, 1973). Mammals have evolved a number of strategies to reduce heat accumulation in the brain when they occupy open habitats subject to high levels of direct radiant heat from the sun, especially at midday in the tropics when the sun is directly overhead. Such strategies include the evolution of a complex nasal rete that allows heat exchange between arterial and venous blood (many antelopes [Maloiy et al., 1988]), long muzzles that allow cerebral blood to be cooled by panting (baboons: Hiley, 1976), dense coats that keep incident radiation from the sun away from the skin surface (klipspringer antelope: Dunbar, 1979) and behavioural strategies such as seeking dense shade during the heat of the day (reedbuck: Roberts and Dunbar, 1991; baboons: Hill, 2006).

In a seminal series of papers, Wheeler (1984, 1990, 1991a,b, 1992) used a physiological model to argue that bipedal locomotion and hair loss in early hominins might have been an adaptation to reduce incident heat load when foraging in more open habitats. Unlike their great ape sister species that remained within the tropical forests, early hominins began to make increasing use of forest edge and more open woodland (but probably not open savannah) habitats where exposure to the direct rays of the sun was considerably greater, especially during the hottest times of the day when the sun is overhead. The australopiths and their allies were uncontroversially bipedal by at least 5 Ma (millions of years ago) (Pickford et al., 2002; Lovejoy et al., 2009) and more controversially so as early as 6 Ma (Brunet et al., 2002), although it is generally accepted that the earliest taxa were not particularly efficient bipeds (and may have used bipedalism for rather different purposes in a more semi-arboreal lifestyle: Thorpe et al., 2007; Crompton et al., 2008).

Recently, Ruxton and Wilkinson (2011a,b), introduced an amendment to the Wheeler model by noting that, in addition to the exogenous heat load from the sun, an active hominin would generate much endogenous heat from walking. Including a factor for endogenous heat generation adds substantially to the heat load of bipedal hominins, effectively removing the advantage that Wheeler (1984, 1990, 1991a,b, 1992) claimed for it. Ruxton and Wilkinson (2011a,b) argue that only hair loss could have been selected for in terms of heat load reduction. They conclude that, with little or no thermal advantage, bipedalism must have evolved for some other reason.

The Ruxton and Wilkinson (2011a,b) (RW) model made a number of implicit assumptions that have radical implications for heat load. One assumption was that the temperature regimes under which australopiths lived were, in effect, those at sea level at the equator (where maximum day time temperatures can rise to 40 °C or above). The evidence from the fossil record suggests that all currently known australopith sites lie at altitudes above ∼1000 m above sea level (asl) (Fig. 1A; Supplementary Online Material [SOM] Table S1) and so models of heat load must take this into account. Indeed, even chimpanzees do not live at sea level today, but typically live at altitudes between 500 and 1000 m asl. The Rift Valley floor has dropped some considerable distance since 3 Ma as a result of tectonic activity (Partridge, 1997), and current australopith sites in Ethiopia are estimated to be as much as 1000 m below their original position (Bonnefille et al., 1987), while those in northern and central Kenya are about 500 m lower (Dowsett et al., 1999). Only the South African sites are at approximately the same altitude as they were (they are thought to have dropped by only about 90 m). All the sites in Figure 1A have been corrected by these amounts. The mean altitude (corrected for tectonic effects) for South African sites is 1488 m asl, for East African sites 1313 m, and for the chimpanzee sites 819 m. Figure 1A suggests that modern day chimpanzees live at lower altitudes than australopiths did. However, this is somewhat misleading if taken at face value: current temperatures are 2–3 °C lower than they were in the Pliocene (Demenocal, 1995; Bartoli et al., 2005; Robinson et al., 2008). Crucially, the mean Plio-Pleistocene temperatures for the East African australopith sites (from Bettridge and Dunbar, 2012; for details, see SOM Table S1) do not differ from those for modern day chimpanzee sites (from Lehmann et al., 2007) (Fig. 1B: F1,48 = 0.53, p = 0.470).

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Figure 1. (A) Median (±50% and 95% ranges) altitudes of East African (n = 9) and South African (n = 3) fossil australopith (Australopithecus and Paranthropus) sites, compared to modern chimpanzee study sites (n = 14). Outliers are indicated by a solid dot. Altitudes for fossil sites are corrected from current altitude to reflect the fact that the Rift Valley floor is now much lower than it was c. 3 Ma (see text for details; fossil sites are listed in SOM Table S1). Sources: Lehmann et al. (2007), Bettridge and Dunbar (2012). (B) Median (±50% and 95% ranges) mean annual temperature at fossil australopith sites in East Africa (n = 35 horizons) and South Africa (n = 5) and for modern chimpanzee populations (n = 14), compared to the mean temperature assumed in the Ruxton and Wilkinson (2011a,b) model (dashed line). The value for the Ruxton–Wilkinson model is the mean value integrated across their diurnal temperature distribution; values for fossil sites are for individual horizons, with temperatures being estimated from modern sites matched as closely as possible for faunal profile (see SOM Table S1). Sources: australopith sites (Bettridge and Dunbar, 2012); chimpanzees (Lehmann et al., 2007).

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Palaeoanthropologists often advise caution when drawing biogeographical conclusions on the basis of fossil evidence: absence of evidence, we are reminded, is not necessarily evidence for absence. However, in this case, there are three reasons for thinking that the claim that australopiths did not live below ∼1000 m asl is robust.

First, there are low altitude sites from this period that have not yielded hominins despite the fact that they contain monkeys, and are thus evidently suitable for primates. The Chiwondo beds of Lake Malawi (∼500 m asl), for example, contain mainly papionins, whereas the high altitude specialist Theropithecus (Dunbar, 1998) is rare (Frost and Kullmer, 2008) despite being common at most of the contemporary classic higher altitude australopith sites in both eastern and southern Africa. Hominins (Paranthropus bosei and Homo rudolfensis) only appear late in the sequence after 2.5 Ma (Sandrock et al., 2007; Frost and Kullmer, 2008; Bocherens et al., 2011), coincident with the dramatic decline in temperature associated with the 2.5 Ma climatic event. Other low altitude sites that contain monkeys but no australopiths include Ahl al Oughlam (100 m asl) in Morocco, dated to ∼2.5 Ma (Alemseged and Geraads, 1998), the late Miocene Libyan site of Qasr as Sahabi (0 asl; Boaz et al., 2008) and the late Miocene to early Pliocene site of Langebaanweg in the Western Cape (30 m asl; Hendey, 1981). Additionally, while there is uncontroversial evidence for coastal migrations of ungulates (but not australopiths) between Eurasia and sub-Saharan Africa during this period (e.g., Bibi, 2007). In contrast, the appearance of Homo around 2.8 Ma is marked in due course by the presence of Homo fossils at various sites around the Mediterranean (Ternifine: Geraads et al., 2008; Kocabas, Turkey: Kappelman et al., 2008), as well as evidence of Olduwan/pre-Acheulian industries (e.g. Ain Hanech at∼650 m asl in Algeria, and various litoral sites in the Magreb and coastal Morocco and Algeria, including the aforementioned Ahl al Oughlam: Biberson, 1961; Sahnouni, 2006). In addition, there is the indirect evidence for coastal occupation implied by the early Homo ergaster/erectus migrations out of Africa into Eurasia – but still no low altitude australopith fossils even though these continued to be around for some considerable time.

Second, models of time budgets for australopiths suggest, using an entirely different approach, that they could not survive in high temperature, low altitude habitats (Bettridge, 2010), whereas fossil papionins were able to occupy a much wider range of habitats (Bettridge and Dunbar, 2012). Third, estimates of the mean annual temperature for fossil sites (estimated by faunal profile matching to modern sites [Bettridge and Dunbar, 2012]) indicate that the temperature range within which australopiths are known to have lived is identical to that for modern chimpanzees: the mean temperature is ∼25 °C for all three taxonomic groups (Fig. 1B). Given the climatic cooling that has occurred since 3 Ma, it follows that australopiths would have occupied sites that are around 500–600 m higher in altitude than those currently occupied by chimpanzees (note that even these do not occupy coastal habitats). This suggests that the mean temperature value of 32.5 °C assumed in the RW model (the dashed line in Fig. 1B) significantly exceeds the range of values at which both chimpanzees and australopiths live.

The second assumption made in the Ruxton–Wilkinson model is that australopiths were continuously active throughout the day, and would thus have generated substantial additional endogenous heat from walking. While accounting for the extra endogenous heat load from walking is important, the assumption that animals are continuously walking is incorrect. Most primate species spend only about 20% of their day walking (including both travel and foraging movements within food sites) (Dunbar et al., 2009). The mean actual travel time for chimpanzee populations, for example, is 17.1% (range 7.5–27.6%: Lehmann et al., 2007), while baboons – the taxon with the longest day journeys that make most use of wooded and grassland-edge habitats – devote only 20–35% of their day to moving (Bettridge et al., 2010). Estimates from time budget models for the australopiths suggest that they would have devoted only about 16% of their day to travel (Bettridge, 2010). More importantly, living primate species, such as baboons, that occupy similar forest edge and riverine habitats to those occupied by australopiths typically travel to and from foraging areas only in the morning and late afternoon/evening (Hill, 2006), precisely the times when the RW model suggests that australopiths might have had sufficient spare thermal capacity to allow travel. For most tropical species, the hottest part of the day is spent resting in shade to minimize endogenous heat production (Roberts and Dunbar, 1991; Hill, 2006). Indeed, animals typically rest rather than groom when temperatures rise significantly above their thermoneutral zone (Hill, 2006).

A third implicit assumption made by both the Wheeler and the RW models is that animals do not incur any thermal costs overnight, and the night time thermal environment is therefore ignored. In fact, even at altitudes of ∼1000 m asl in East Africa, ambient night time temperatures are commonly as low as 10 °C, and can fall to as low as 5 °C on occasion (R. Dunbar, unpublished field data), imposing substantial thermal costs on hairless animals. This is not usually an issue at sea level, where ambient night time temperatures remain high and heat-shedding is more often a problem than heat loss. But at high altitudes, it is a problem, and if animals can lose heat overnight a heat load model needs to cover the full 24 h diurnal cycle.

In this paper, we explore the consequences for the RW model of accounting of adjusting altitude, travel time and night-time thermal costs. We show that when the model is corrected for altitude and activity scheduling, both bipedalism and hair loss would have generated consequential heat load savings, just as Wheeler (1984, 1990, 1991a,b, 1992) argued. However, cool night time temperatures would have made it impossible for substantial hair loss to have evolved in species occupying the sites where australopiths appear to have lived in the absence of cultural (e.g. shelter, clothing) or other behavioural (nesting, group sleeping) developments.

2. The model

Our basic model is identical to the RW (2011a) model, which itself was a variation of the Wheeler model (Wheeler, 1984, 1990, 1991a,b, 1992). We give the full set of equations for the model in the Appendix. Here, we give only a brief summary of the main details of the parameterization.

In the revised model we present here, the total heat load (Qtotal) that the animal’s body has to deal with is a combination of two main factors, environmental heat load and internal metabolic heat load.

The environmental heat load has six main components:

(i)

effect of outside air temperature, dependent on the stature of the animal and the time of day;

(ii)

effect of air moving past the body (in the Wheeler model, this is due to wind; in the RW version it is due to the body moving);

(iii)

effect of short and long wave radiation, dependent on the time of day;

(iv)

effect of the pelt, and the degree to which it absorbs (short wave) radiation;

(v)

effect of the total body surface, at the same time both absorbing solar radiation and allowing the body to cool by both convention and evaporation; and

(vi)

effect of the proportion of the body that is exposed to direct sunlight.

Internal metabolic heat load has four key components:

(i)

effect of basal metabolic heat production;

(ii)

effect of metabolic heat generated by the body while active (due to movement);

(iii)

effect of heat loss through respiration; and

(iv)

effect of heat loss through sweating.

To adjust for the additional refinements, we:

(i)

reduced the total proportion of the day spent moving to 16%, and allocated that evenly across the hours 06:00–11:00 and 14:30–18:00 (with travel time = 0% across the intervening midday period);

(ii)

recalibrated the diurnal temperature regime so that it has a maximum midday value of 33.5 °C instead of 40 °C (where 33.5 °C is the maximum that would be given by the diurnal temperature regime in the RW model, but set to yield a mean temperature across the day of ∼26 °C, the value for the upper 75th centile in Fig. 1B; see SOM Table S1).

In addition, to allow for the fact that most tropical animals, including baboons that occupy a habitat similar to that argued for australopiths, rest in shade during the hottest part of the day (Hill, 2006), we also separately adjusted the model such that:

(iii)

animals incur limited incident radiation (that is, they are in at least partial shade) over the midday period (11:00–14:30) when ambient temperatures are at their highest.

2.1. Parameterisation

In line with the Wheeler and the RW models, we assume that the female and male animals are different in leg length and body mass (52 cm and 30 kg, versus 72 cm and 55 kg respectively). Apart from these and the physical constraints of solar radiation, the original RW equation system, Equations (1–19) in the Appendix, assume the following:

The percentage of the day spent moving is 100%;

The temperature at 2 m, τ200 , is assumed to be 40 °C;

The portion of the day the hominins spend in shade is assumed to be 0%.

We also included wind speed (based on sampled wind speeds from an East African Rift Valley site, Gilgil, at ∼622 m asl: mean wind speed across the day = 0.46 m/s, n = 2910 records [R. Dunbar, field site records]) in the model, but it made little difference to the results, so we disregarded it in the final version. Wind speed is therefore assumed to be 0 m/s.

We first ran the model both in the original RW formulation (to confirm that we obtained the same results as Ruxton and Wilkinson) and with the new adjustments we outline below.

2.1.1. Refinement 1

To correct for the fact that hominins were more likely to spend 16%, rather than 100%, of the day moving (Bettridge, 2010), and confined this to the morning and afternoon periods with a 3.5 h rest period (as predicted by the australopith time budget model [Bettridge, 2010]) over midday, we allocate the overall daily average of 16% travel to the morning and afternoon periods. For computational simplicity, we assume this travel time is evenly distributed within these 12–3.5 = 8.5 morning and afternoon hours, which means that (16% × 12)/8.5 = 22.6% of each hour would be spent moving, while the animals are assumed to be effectively motionless over the 3.5-h midday period. Since, in the RW equation system, speed of travel and percentage of time spent travelling transform linearly, we opted to simplify the calculation by simply adjusting the speed of travel variable, v, as follows:

For0600−1100hand1430−1800h:v=.226*1.7L=0.384L
For1100−1430h:v=0

(NB. In the calculations we assume that the posture is maintained during the resting period, i.e., quadrupedals stay quadrupedal, bipedals stay bipedal. This is for simplicity, and does not affect the model’s results.)

2.1.2. Refinement 2

From Figure 1A, we take an altitude of 1000 m asl as the lowest altitude at which australopiths lived, and we use the standard environmental lapse rate of 6.49 °C temperature drop per 1000 m (Jacobson, 2005) to calculate the baseline temperature for the model. This is slightly more conservative than the 7.5 °C difference that would be implied by the mean values in Figure 1B. Moreover, the value of 6.5 °C is derived from climatological theory and is thus not open to the methodological criticisms that fossil habitat climate estimates might be. Hence, in this refinement, we use the base temperature parameter of τ200=33.51° . In effect, we consider a worst case scenario for the australopiths: any altitudes above 1000 m represent increasingly benign thermal conditions. (NB: solar irradiance also increases with altitude and will add to the thermal load. To check for this, we ran some additional simulations that included this effect [data not shown], but, at the altitudes occupied by australopiths, the effect is too small to alter the qualitative results of the model, and thus we do not include it in the model.)

2.1.3. Refinement 3

To account for hominins sheltering in shade during the hottest part of the day, we assumed that the short wave radiation is reduced by 50% in this time period. For computational convenience, we have assumed that this midday break is centred on 13:00 h (when the RW temperature curve peaks), and runs from 11:00 to 14:30 h. In practice, tropical temperature regimes are not strictly symmetrical in the way Ruxton and Wilkinson (2011a) assumed, but are temporally displaced so that the hottest part of the day is usually 12:00–16:00 h. However, for computational convenience, the RW model assumes that the temperature regime is perfectly symmetrical, and we will follow suit since this window covers the period when temperature is maximized in the model. Hence,

S={865Sin(π(t−6)12)ift<11or14.5<t0.5·865Sin(π(t−6)12)if11<t<14.5.
2.1.4. Refinement 4

Finally, we extended the model to cover the full 24-h day/night cycle. Rather than making arbitrary assumptions about the diurnal pattern of temperature change, we use diurnal temperature profiles for three contemporary East African sites (Lodwar, 507 m; Kisumi, 1171 m; and Nakuru, 1850 m) that bridge the minimum altitude occupied by australopiths. For each site, we averaged hourly temperature across the past 25 years (NOAA, 2014) and used these values to parameterize the model. We assumed that there is zero sunshine and zero movement before 06.00 h in the morning, and after 18.00 h in the afternoon; we also assumed that during the day the animals move on average 16% of the time, concentrated in the morning and evening.

3. Results

Our version of the model (see also SOM Tables S2–S4 and Figs. S1–S5 for additional model results and sensitivity analyses) replicated exactly the results obtained by Ruxton and Wilkinson (2011a) during the same standard 12 h day that they used (Fig. 2, red lines). Thus, we can be certain that any differences that might emerge between their results and ours cannot be due to differences in the way the two models are built. We then consider the impact of each of the additional refinements on heat load one by one. In each case, we consider the two sexes separately, and examine the heat load for a quadruped versus a biped, and a haired (100% hair cover) versus a partially haired (15% hair cover) individual, just as Ruxton and Wilkinson (2011a) did.

Figure 2. The combined effect of the re-parameterisation of the Ruxton–Wilkinson (RW) model: walking is limited to 16% of the day and confined to the morning and evening, and the altitude is at 1000 m asl. Separate values for the impact of the individual parameters are given in Fig. 3. X-axis: time of day, y-axis: total heat load (Qtotal). Red: RW model baseline; blue: RW model with all three additional refinements included. Dash: quadrupedal; continuous: bipedal. Orange: heat dissipation limit (from RW model). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

In each case, correcting the parameterisation of the original model separately for the lower travel time and higher altitude results in a considerable reduction in heat load compared to the RW model (Fig. 3, SOM Table S2). With or without the midday rest effect, the combined effect of the travel time and altitude refinements yields a marked shift in the results from those predicted by the RW model (Fig. 2). (Note the scale difference in the upper [furred] and lower [hairless] panels in Fig. 2: the difference between the revised model and the original RW values is in fact of the same magnitude in the two conditions.) Adjusting for the use of shade at midday would add a further modest reduction in heat load during the hottest part of the day (Fig. 3).

Figure 3. Comparing the three refinements added to the RW model individually shows that each reduces total heat load. Left column: females; right column: males. Rows: travelling only 16% of the day concentrated in the morning and evening, altitude at 1000 m, and hiding in shade at midday (11.30–14.30 h) when ambient temperatures are at their highest. Midday is defined as 11:30–14:30 h. Continuous line: 100% hair cover; dashed line: 15% hair covered; blue: RW quadruped; red: RW biped; black: modified model quadruped; green: modified model biped. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

An animal’s ability to survive in open/woodland habitats depends ultimately on how much of this additional heat can be shed across the day (Ruxton and Wilkinson, 2011a). We use the RW model assumption that female and male hair-covered hominins could shed 107W and 160W, respectively, by heat exchange with the environment, while hairless females and males could shed 473W and 710W, respectively, mainly due to the additional benefits of sweating (Ruxton and Wilkinson, 2011a,b; Wheeler, 1984, 1990, 1991a,b, 1992). Note that the benefits of sweating only accrue to hairless animals, since, for furred animals, sweating simply cools the tips of the fur and not the skin beneath and is thus to no purpose; only if the fur is completely soaked is there any consequential benefit from sweating (Mount, 1979; Gebremedhin and Wu, 2001). These heat dissipation limits are represented by the orange lines in Figure 2: it is assumed that the animal is unable to shed heat above this limit, and as a consequence it overheats and dies.

Four points may be noted about the results presented in Figures 2 and 3. First, the adjusted model indicates that both haired and hairless animals would be able to lose sufficient heat by heat-dumping mechanisms like evaporative cooling and convection to maintain thermoneutrality throughout the day. However, in the hairless case, this comes at a substantial cost of water loss. Second, despite this, there might be an advantage to being haired because furred animals have an absolutely lower heat load throughout much of the sunny part of the day, and especially at midday when temperatures are at their highest.

Third, there is always an advantage in being bipedal, especially over the midday period, and this is actually true of both the original RW model and our adjusted model. Notice that the advantage from being bipedal is substantially bigger in absolute terms for hairless animals than it is for furred ones, although the proportional gain over baseline is similar in both cases. This advantage is especially large at midday when heat stress is at its maximum: the thermal advantage from bipedality at midday is more than 11% in the RW baseline model, and more than 12% when taking into account the additional refinements we propose (Fig. 4). In other words, there is always a benefit to be gained from being bipedal rather than quadrupedal in these environments (Fig. 4, SOM Table S3). From an evolutionary ecological perspective, any such savings translate directly into fitness gains because the animal is under less stress and has to use less energy in heat dissipation (which becomes increasingly energetically costly as the thermal environment exceeds the animal’s thermoneutral zone [see Mount, 1979]).

Figure 4. The relative advantage of switching from a quadrupedal to a bipedal stance for (a) females and (b) males, respectively. X-axis: time of day; y-axis: relative fall in heat load due to switching to bipedality. Red: RW model baseline; blue: RW model with all three additional refinements included. Dash: hairless; continuous: hair covered.

Fourth, while in absolute terms there is a benefit from being hairless over being hair covered (the difference between heat load and the capacity to shed heat is absolutely greater for hairless animals than for hair covered ones, as shown in Fig. 2), hairless animals incur a substantial cost in terms of heat loss early and late in the day that furred animals do not, and this would act as an important drag on the advantages of evolving hairlessness. Since nights are much cooler than the day at altitudes of 1000 m asl and above (at this altitude, the day–night temperature differential can be as much as 15 °C at the equator [R. Dunbar, unpublished field data]), the night-time cost of losing hair increases further at this altitude (SOM Table S4).

To explore this issue in more detail, we estimated net heat load across the whole 24-h night/day cycle for haired and hairless quadrupedal individuals using the thermal profiles for the three contemporary East African sites (Lodwar, Kisumi and Nakuru). The results (Fig. 5) show that hair covered individuals remained in positive heat balance even at night when ambient temperatures fall and there is no sunshine and no additional body heat generated from movement. In contrast, individuals that have only 15% hair cover run into considerable heat deficit during the night, and the deficit increases with altitude: even at an altitude of 1000 m, females would require an additional 3500 kcal a day, while males would need 5600 kcal, to offset the costs of night time heat loss (SOM Table S4). Set against a daily energy requirement for australopiths of 1250 kcal for females and 1740 kcals for males (Aiello and Wells, 2002) and a time budget with no spare capacity at all for extra feeding (Bettridge, 2010), australopiths would have been incapable of balancing their energy budgets if they had been hairless at the altitudes where they seem to have (lived).

Figure 5. Heat load over the 24 h day for (a) females and (b) males in the quadrupedal case using current day temperature data from three locations: Lodwar (red) at 507 m, Kisumi (black) at 1171 m, and Nakuru (green) at 1850 m. X-axis: time of day; y-axis: total heat load (Qtotal). Continuous line: hair covered; dashed line: hairless individuals. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).

Finally, as a check on the travel time assumption, we used the model to calculate the maximum time that hominins could spend travelling in each hour of the day without exceeding their heat loss capacity. The results suggest that, in the limit, they could in fact devote up to 40% of the time to travel during the middle hours of the day and up to 60% to travelling during the morning and evening hours without compromising their thermal balance (SOM Fig. S3). No primate species spends as much as 40% of the time travelling, not least because the demands of other time budget components (in particular, feeding and resting) severely restrict the time available for travel (Dunbar et al., 2009). The bottom line, however, is that the australopiths would have been well within their thermal limits even if they had spent considerably more than the 16% of the day moving estimated by Bettridge (2010). Fully furred animals would have been thermoneutral at midday providing they did not spend more than 30% of their day moving (the maximum observed in both contemporary baboons (Bettridge, 2010) and chimpanzees [Lehmann et al., 2007]), and hairless ones would always have been thermoneutral (SOM Fig. S3). This spare thermal load capacity would have allowed sufficient extra capacity for the modest amounts of heat generated during the day by the act of feeding and by grooming behaviours that have been ignored in the model. This is important, because it means that omission of these additional thermal load costs from the model is not sufficient to negate the main findings.

4. Discussion

Ruxton and Wilkinson (2011a,b) suggested that the internal heat production due to movement during the day would make it impossible for bipedality to have been a response to moving out into more open wooded habitats, assuming that (a) the hominins were fully hair covered at the time they entered the savannah and (b) they were moving 100% of the time. We confirm that this result is correct, given the assumptions of the original RW model. In this respect, Ruxton and Wilkinson (2011a,b) introduced an important modification to Wheeler’s (1984, 1990, 1991a,b, 1992) heat load model of early australopiths. However, we suggest that, in doing so, they made several unrealistic assumptions that led them to conclude prematurely that Wheeler was wrong in concluding that bipedality yielded significant heat load savings. We identified two particularly important ones: that animals are continuously active throughout the day, and that australopiths lived at sea level. Correcting their model for these assumptions suggests that not only would the australopiths have been able to maintain their heat load within reasonable limits, but, more importantly, there would always have been a consistent, if modest, advantage to being bipedal under these conditions, whether or not they were furred.

In fact, with the assumptions they make, the Ruxton–Wilkinson model implies that even chimpanzees would be in heat overload if they moved all the time, and so should not be able to survive even now. Since this is clearly not the case (Fig. 6), it should alert us to the fact that there is a problem with the model. In fact, in terms of thermal regime, the habitats where chimpanzees live turn out to be very similar in respect of their thermal conditions to those occupied by the australopiths (Fig. 1B), and chimpanzees in fact spend only ∼17% of the day moving (Lehmann et al., 2007). As it happens, travel time is the main constraint on great ape biogeography (Lehmann et al., 2007; also see SOM Fig. S2), and great apes pursue behavioural strategies (such as fission-fusion sociality) that allow them to reduce travel time to around 15–20% of the day (Lehmann et al., 2010). Even so, most chimpanzee populations are on the edge of survival (Lehmann et al., 2007, 2010; Lehmann and Dunbar, 2009). Given this, it is small wonder that the assumptions made by Ruxton and Wilkinson made it difficult for australopiths to survive.

Figure 6. Overheating when there is no direct solar radiation at all (as would be the case in closed forest) in the case of a quadrupedal, hair covered individual. X-axis: time of day; y-axis: total heat load (Qtotal). Continuous red line: RW baseline; dashed red line: zero solar radiation case; orange: RW heat dissipation limit.

Correcting the RW model for altitude and amount of time spent moving indicates that there is no thermal advantage to being bipedal in a completely shaded habitat such as forest (SOM Fig. S1). This is in striking contrast to more open habitats where there is a substantial (>10%) advantage to being bipedal. Since most real world selective advantages are in fact around 5–10% (Kingsolver et al., 2001), an advantage of this magnitude is clearly significant.

It is important to be clear that we are not suggesting that australopiths occupied open savannah grasslands. The palaeoenvironmental evidence indicates that they occupied a range of ecotone habitats that included wooded grasslands, open woodland, gallery forest and open riverine/lacustrine floodplains (Harris, 1991; Reed, 1997; White et al., 2006; Copeland et al., 2011; see also White et al., 2009; Bedaso et al., 2013) – in many ways, not dissimilar to the habitats preferred by Papio baboons today (Bettridge, 2010). The C4-pathway underground storage organ (USO) diet (with or without termites) that seems to have formed the foundation of the australopith diet (Sponheimer and Lee-Thorp, 2003; Sponheimer et al., 2005; Ungar et al., 2006; Cerling et al., 2011; Ungar and Sponheimer, 2011) is predominantly associated with the relatively open floodplains that border large rivers and lakesides. These kinds of habitats will have exposed australopiths to moderate to high levels of direct incident radiation. Even the wooded parts of these habitats are far from being shaded and are quite unlike closed forest, although they often do provide the same kind of rich ‘supermarket’ feeding patches such as fruiting figs (Ficus spp.) that forests do. Of more importance is the fact that travel between gallery forest night time refuges and the relatively open floodplains that provided access to USOs would have unavoidably exposed them to direct sunlight for significant parts of the day.

Our results also suggest that, with more appropriate parameterisation, the Ruxton–Wilkinson model provides an important novel finding: it offers an explanation for why australopiths typically apparently did not live at low altitudes or in coastal environments, as indeed is still the case for chimpanzees (see Lehmann et al., 2007; Lehmann and Dunbar, 2009). Surprisingly, perhaps, the ecological significance of this seems not to have been noticed: it would have made it difficult for australopiths to leave Africa, as they may have found it difficult to cope with the increased heat load in coastal habitats. The claim that australopiths did not live below ∼1000 m asl is open to empirical testing: if australopith fossils are ever found significantly below this altitude in the future, it would disprove the findings of the model and imply that some other important factor has been overlooked.

We are not, of course, necessarily suggesting that thermal savings from bipedalism are the reason why bipedalism first evolved in the hominin lineage. Our claim holds even if a form of bipedalism first emerged in the pre-australopith lineage(s) inhabiting more heavily forested environments in connection with food gathering (e.g. Thorpe et al., 2007; Crompton et al., 2008). It is important to distinguish between the factor(s) that selected for the adoption of competent, albeit imperfect, bipedal locomotion in trees (associated with a foot and lower limb still capable of efficient arboreal movement, as in Ardipithecus [Lovejoy et al., 2009]) and the factor(s) that selected for a subsequent radical shift in foot structure that allowed the kind of more efficient plantar bipedal locomotion found in the australopiths and later Homo. Our concern has been with this second step. Our claim would be that if partial bipedalism provided the australopiths with a window of ecological opportunity that made it possible for them to invade novel terrestrial habitats, thermoregulation is likely to have provided further significant selection for efficient bipedal locomotion, resulting in the final transition into Homo-style skeletal adaptations.

Given this, we should perhaps still ask whether bipedalism conferred other advantages sufficient on their own to promote this second phase. One possibility is that bipedalism offers substantial efficiency savings for long distance travel in long legged hominins (genus Homo; Pontzer et al., 2009). Bipedal locomotion is quite inefficient for chimpanzees due to their bent-hip/bent-knee posture: they consume ∼25% more energy when walking bipedally than they do when walking quadrupedally (Sockol et al., 2007). Nonetheless, only a modest change in limb length and/or muscle fascicle length would have been sufficient to make hominin bipedalism more energy efficient than chimpanzee quadrupedalism (Sockol et al., 2007). Consequently, there might well have been an added efficiency benefit to bipedalism if the australopiths were making short forays out onto more open areas beyond the lacustrine/riverine gallery forests in search of new food sources (such as USOs). However, early australopiths, at least, were markedly less efficient bipedal walkers than modern humans (Pontzer et al., 2009), and, while they must have gained some advantage, it is unlikely that this benefit on its own would have been sufficient to have provided the selection pressure for the final transition to a fully bipedal stance, especially bearing in mind that time amount of time for which this benefit would have been gained is quite small. Even allowing for australopith bipedalism being 25% more efficient than that of chimpanzees (the value pertaining to modern humans), the net energy gain for spending only 16% of the time travelling would only about to ∼4% – considerably less than the >10% benefit from thermoregulation.

An alternative possibility that has been suggested is that bipedalism offers advantages in terms of food (or tool) carrying, since this has been observed in chimpanzees (Hunt, 1994; Carvalho et al., 2012). However, chimpanzees typically do this only when crop raiding and subject to intense threat from humans; moreover, it typically involves cultivars like maize cobs, and cassava or large fruits (such as papaya) that can be gathered and carried relatively easily. Given the archaeological and trace element evidence that australopiths developed a specialization for USOs (Sponheimer and Lee-Thorp, 2003; Sponheimer et al., 2005; Ungar et al., 2006; Ungar and Sponheimer, 2011), and these are not the kind of foods that can be grabbed up in armfuls to carry away when under threat, it is difficult to see this being sufficiently advantageous to provide the needed selection pressure. Such benefits are certainly an advantage, but they are more likely to have accrued as a consequence of bipedalism rather than its cause.

On balance, then, a combination of energy savings with thermal benefits and locomotor advantages would seem to provide the most likely selection pressures favouring bipedalism in the australopiths, with the locomotor advantages probably becoming increasingly important with Homo in order to facilitate a more nomadic ranging pattern and the occupation of lower altitude habitats under significantly cooler thermal regimes.

Our results suggest that, while hair loss would have provided australopiths with substantial thermal advantages in more open habitats, the night time costs of reduced fur cover were very considerable and thus likely to militate against it so long as the australopiths occupied moderately high altitude habitats. Hairlessness would seem to have necessitated strategies to counteract overnight cooling and/or the occupation of lower altitude habitats. Heat loss at night can be reduced by the use of caves (which can raise mean ambient temperatures by as much as 4 °C [Barrett et al., 2004; Dunbar and Shi, 2013]) or by the regular use of fire. Although there is evidence of occasional use of fire from around 1 Ma (Gowlett et al., 1981; Goren-Inbar et al., 2004), and indirect evidence of fire use 1.9 million years ago (Wrangham et al., 1999), there is in fact little direct evidence for habitual fire use prior to ∼400 thousand years ago (ka) (Roebroeks and Villa, 2011; Dunbar and Gowlett, 2014; Shimelmitz et al., 2014), and there is no evidence at all that any australopith populations ever made use of fire. Although caves probably have been used as night time refuges intermittently throughout hominin evolution, the use of caves may not have become a regular feature until hominins developed home bases, and that may have coincided with control over fire (Shimelmitz et al., 2014) and the acquisition of a more human-like life history (Dean et al., 2001; Martin-Gonzalez et al., 2012) around 500 ka, with both being particularly associated with the occupation of high latitudes.

A more plausible suggestion is that hair loss appeared with the arrival of Homo around 2.0 Ma, once the climate cooling that set in after 2.5 Ma (Demenocal, 1995; Bartoli et al., 2005) allowed hominins to occupy somewhat lower altitude habitats. It is doubtful that australopiths were sufficiently mobile to make hair loss advantageous, but the appearance of a genus with a body shape better adapted to long distance travel (Homo ergaster locomotion was ∼50% more efficient energetically than that of early australopiths [Steudel-Numbers, 2006; Pontzer et al., 2009]), combined with the first uncontroversial evidence for the occupation of lower altitude (including coastal) habitats (as evidenced by the fact that H. ergaster was able to migrate out of Africa into Eurasia quite soon after its first appearance), might signal the appearance of a suite of adaptations enabling greater mobility in more open, hotter habitats. Hair loss may thus be a peculiarity of our genus, and may have played a small but important role in allowing Homo to escape the confines of Africa.

One Species / Erectus, Neanderthal, Sapiens Re-Post

imagesELC4DMTTHomo_erectus_reconstruction489px-Homo_neanderthalensis_2_cogitas3dimagesangryJPEGWilt Chamberlin, Willy Shoemakercaption100412

One species?

Every few days I run through bookmarked websites to see which can be deleted or have useable information. Today it was a slew of anthropology sites with general opinions as to how Human evolution occurred and continues to unfold. What continues to pop out is the species-naming mess. 

A New View

The authors of the following article go much farther than what I “see”, which is that “homo” ought to refer to variations of Homo erectus. They propose that chimpanzees, living humans and all fossil humans be classified Homo. ______________________________________________________________________

Number of ancestral human species: a molecular perspective

Curnoe D1, Thorne A. Department of Archaeology and Natural History, Research School of Pacific and Asian Studies, Australian National University, Canberra, Australia.

Abstract

Despite the remarkable developments in molecular biology over the past three decades, anthropological genetics has had only limited impact on systematics in human evolution. Genetics offers the opportunity to objectively test taxonomies based on morphology and may be used to supplement conventional approaches to hominid systematics. Our analyses, examining chromosomes and 46 estimates of genetic distance, indicate there may have been only around 4 species on the direct line to modern humans and 5 species in total. This contrasts with current taxonomies recognising up to 23 species. The genetic proximity of humans and chimpanzees has been used to suggest these species are congeneric. Our analysis of genetic distances between them is consistent with this proposal. It is time that chimpanzees, living humans and all fossil humans be classified in Homo. The creation of new genera can no longer be a solution to the complexities of fossil morphologies. Published genetic distances between common chimpanzees and bonobos, along with evidence for interbreeding, suggest they should be assigned to a single species.

The short distance between humans and chimpanzees also places a strict limit on the number of possible evolutionary ‘side branches’ that might be recognised on the human lineage. All fossil taxa were genetically very close to each other and likely to have been below congeneric genetic distances seen for many mammals. Our estimates of genetic divergence suggest that periods of around 2 million years are required to produce sufficient genetic distance to represent speciation.

Therefore, Neanderthals and so-called H. erectus were genetically so close to contemporary H. sapiens they were unlikely to have been separate species.

Thus, it is likely there was only one species of human (H. sapiens) (or H. erectus) for most of the last 2 million years.

We estimate the divergence time of H. sapiens from 16 genetic distances to be around 1.7 Ma which is consistent with evidence for the earliest migration out of Africa. These findings call into question the mitochondrial “African Eve” hypothesis based on a far more recent origin for H. sapiens and show that humans did not go through a bottleneck in their recent evolutionary history. Given the large offset in evolutionary rates of molecules and morphology seen in human evolution, Homo species are likely to be characterised by high levels of morphological variation and low levels of genetic variability. Thus, molecular data suggest the limits for intraspecific morphological variation used by many palaeoanthropologists have been set too low. The role of phenotypic plasticity has been greatly underestimated in human evolution. We call into question the use of mtDNA for studies of human evolution. This DNA is under strong selection, which violates the assumption of selective neutrality. This issue should be addressed by geneticists, including a reassessment of its use for molecular clocks. There is a need for greater cooperation between palaeoanthropologists and anthropological geneticists to better understand human evolution and to bring palaeoanthropology into the mainstream of evolutionary biology.

Did our ape ancestors really fall out of the trees? / Updated

New paper added at bottom, below large illustration. 

The usual story of human evolution goes like this:

imagesdwn

There were apes living in the forest just like chimpanzees do today, but something happened to make the trees go away, and the apes were forced to stay on the ground and eat grass instead of nuts and fruits. Why this only affected that particular ape, and not the other creatures in the forest, is ignored. Anyway – at times there were trees nearby, and the apes ran back, climbed the trees and like yoyos ran back and forth between habitats until they could walk on two legs.

What happened next is usually glossed over, but the apes end up walking around as savannah-living, walking, running, obligate bipeds who scavenge or hunt meat, having switched from eating grass, like a cow, to digesting meat, like a lion.

The problem is that most of this story is based on equating “us” (modern Homo sapiens) with the chimpanzee, which is not our ancestor. Our ape ancestors diverged from chimpanzee ancestors 5-7 m.y.a. – that’s what a split is. Their ancestors evolved into the chimpanzees we see today – living in tropical forests. Our common ancestor before the split was not a modern chimpanzee or a modern human. This mistake of confusing species that exist today with archaic forms is so egregious, that it makes talking about evolution nearly impossible.

Another example: Bipedalism dates back at least 3-4 million years ago, and that date is possibly conservative. Homo sapiens did not “become bipedal” – our ape ancestors evolved a bipedal habit. Homo sapiens is an obligate biped!

It is entirely possible that our ape ancestors were ground dwellers, not tree dwellers.

It makes far more sense to begin with a ground dwelling ape than to conjure a bipedal animal directly from a tree-swinging one – the structural changes are daunting, which doesn’t account for all the brain changes necessary to  reorganize how the body orients itself in space; balances gravitational force, coordinates muscles, reorients vision, etc. But here we are, stuck with a torturous scenario (and in a New York minute!) that must turn a shared chimpanzee blue print into a human blueprint.

It should be obvious that modern humans, archaic humans and our bipedal ape ancestors departed on distinct evolutionary path compared to chimpanzees, gorillas and orangutans, and yet the chimpanzee is a favorite model for the evolution of modern Humans.
Reconstruction of Australopithecus sediba ape skeleton 2 m.y.a. compared to those of a modern human (left) and a modern chimpanzee (right).

Reconstruction of Australopithecus sediba ape skeleton 2 m.y.a. compared to a modern human (left) and a modern chimpanzee (right).

 

pelvis

 

kadanuumuu-graphicjpg-e2a799a7312c5413

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Neither chimpanzee nor human, Ardipithecus reveals the surprising ancestry of both

Tim D. White, C. Owen Lovejoy, Berhane Asfaw, Joshua P. Carlson and Gen Suwa

Abstract / Australopithecus fossils were regularly interpreted during the late 20th century in a framework that used living African apes, especially chimpanzees, as proxies for the immediate ancestors of the human clade. Such projection is now largely nullified by the discovery of Ardipithecus. In the context of accumulating evidence from genetics, developmental biology, anatomy, ecology, biogeography, and geology, Ardipithecus alters perspectives on how our earliest hominid ancestors—and our closest living relatives—evolved.

Charles Darwin famously suggested that Africa was humanity’s most probable birth continent, but warned that without fossils, it was “…useless to speculate on this subject” (2). Nevertheless, Darwin and his less cautious contemporaries and intellectual descendants used humans and modern apes to triangulate ancestral anatomy and behaviors, which promulgated the erroneous metaphor of a hominid “missing link.” Even today, despite thousands of available fossils, this deeply embedded metaphor reinforces the misconceptions that extant apes—particularly chimpanzees—can be viewed as “living missing links,” or that that modern African apes combined can be used to represent the past “as time machines” (3).

The notion that modern great apes are little changed from the last common ancestors we shared with them promoted the assumption that hominid fossils anatomically intermediate between living apes and ourselves would eventually be found. Now, however, long sought and recently discovered African fossils provide escape from such persistent but inaccurate projection. These paleontological discoveries do not yet include the common ancestor we shared with chimpanzees (the CLCA). However, they substantially reveal the early evolution of the hominid clade (the term “hominid” denoting all species on the human side of the human/chimpanzee phylogenetic split). These fossils have begun to rectify the mistaken notion that contemporary apes, in particular common chimpanzees, can serve as adequate representations of the ancestral past.

Much, much more!

 

Modern Humans / Social “Racism” vs. Science

Subspecies (science Def.)

A subdivision of a species of organisms, usually based on geographic distribution. The subspecies name is written in lowercase italics following the species name. For example, Gorilla gorilla gorilla is the western lowland gorilla, and Gorilla gorilla graueri is the eastern lowland gorilla.

Note: Subspecies is usually a natural division based on geography – so we might designate African Homo erectus and Asian Homo erectus as subspecies of H. erectus, but the problem is, which one is the “original”? Is African Homo erectus the original species, with Asian (and a possible “mess” of other fossil groups), a subspecies?

We have the same problem in “our” species designations: Homo sapiens sapiens is a subspecies of Homo sapiens, which is terribly confusing – just who is the “original” Homo sapiens? (One must consider, given EuroAmerican prerogative in these matters, that Homo sapiens sapiens = “white EuroAmericans”) 

Up until widespread “globalization” – world travel – Asian Homo sapiens sapiens would have been geographically isolated from other groups, such as European Homo sapiens sapiens, for both to be designated as “subspecies” – along with other many other geographic subspecies.

Speciation would likely have followed, if world-wide migration and travel had not occurred.

Breed (science Def.)

Whereas subspecies refers to geographic isolation, breed refers to social isolation due to domestication.

Genetics. a relatively homogenous group of animals within a species, developed and maintained by humans.

A group of organisms having common ancestors and sharing certain traits that are not shared with other members of the same species. Breeds are usually produced by mating selected parents.

You can’t say that humans DON’T maintain and even enforce “limited breeding” by mating selected parents! Marriage laws and customs, especially arranged marriages, in many, if not most cultures, designate exactly who may marry whom, by religion, “race”, social class, ethnic origin, language, education, wealth etc.

These are attempts to preserve “blood lines” by groups who place themselves at the “top of the pyramid” – and abuse those groups of people considered to be inferior, subhuman or even “not human” at all, but equivalent to “domestic  animals”! This panoramic “control” of reproduction, points to “breeds” of humans being the proper terminology. 

The American Heritage® Science Dictionary Copyright © 2002. Published by Houghton Mifflin. All rights reserved.

An evolutionary history of Homo sapiens must explain the range of physical differences that are expressed in individuals, despite low genetic diversity for our species (and apes in general) Despite differences, reproduction is successful between Homo sapiens across regional (geographic and climatic) types – previously designated as “races” – race is a “social” category, and is not based in science, but in social prejudice, as are too many invalid “concepts” about Homo sapiens.

Papua FB JPEGWilt Chamberlin, Willy Shoemaker

Size diversity within Homo sapiens is extreme.

Size diversity in domestic dog breeds is extreme. Most dog breeds have been “created” by humans in the previous 100 years.

A Wolf species was the wild genetic reservoir for modern dogs, a gene reservoir manipulated by humans for specific physical and behavioral characteristics, especially for arrested development, from puppyhood to “almost” adult behavior.

Was Homo erectus the wild genetic reservoir for Neanderthal, Homo sapiens and a confusing array of fossil humans (“Bones of Contention”) that are classified and reclassified as separate species?

 

 

 

 

 

Evolutionary History of Female Homo Sapiens

Am I joking? No.

There’s not much material on this topic, because “evolution” and “male” have always been accepted as encompassing “human evolution”. Evolution scientists and amateurs alike still argue over “manly things” as determining what characterizes “being human”. Female Homo sapiens and her ancestors – female apes and archaic homo; Homo sapiens (early and late,) have been all but ignored, hanging around in the mists of time doing nothing important. Which is ironic, since “evolution” cannot occur without the production of successful offspring, which also must reproduce, etc. Sexual reproduction requires male and female. How difficult is that to grasp?

Sadly, topics which might become less “mysterious” in human evolution require understanding the evolution of the female body and brain, and in particular, the literal “growing” of new humans within the female body, and their introduction into the environment. But, reproduction is all but ignored by the “definers of species characteristics and boundaries”. The body of myth, mystery and rumor that surround the process of reproduction today, and in an evolutionary context, is ASTOUNDING.

Much is made of “difficult human birth” but curiosity as to “Why is this so?” generally begins with religious prejudice (God makes women suffer and die in childbirth because women are evil, inferior and weak) and ends in the scientific conclusion that “big-brain=big head” makes delivery difficult. (Gee whiz! Males don’t have to experience this phenomenon, so who cares?)

Gynecologists and other “specialists in human reproduction” care. It’s their job, but that doesn’t mean that there is much curiosity as to the evolution of human childbirth. The literature is jam-packed with the excruciating details of the “problem” of difficult childbirth and how to “deal with” the situation, but not much more than passing concern is directed to “the big picture” of human reproduction as a product of evolutionary process.

Modern women, especially in the U.S., are consumed by the pressure to “have children as proof of their femininity” and become obsessed by the “acquisition” of children in a social context. The changes that have taken place in society, which “allow” women to pursue lifestyles other than “domestic goddess” have produced a backlash, which is in essence a punishment. If women want a “career” they must compensate by also being a “super mother” – a demand something like having to tie one hand behind the back in a boxing match. Any difficulty in conception is taken personally – and any and all “fixes” by medical and technical intervention are required. This fear of bio-social incompetence extends throughout pregnancy, delivery and infant care, and indeed for the life of the child, until “Mom” dies. And in many families, Mom is still responsible for guiding her children’s behavior, but from the afterlife!

It is also astounding how little women know about their own bodies.

Where to start? Who were those female critters that are considered to be enough like us to be species that “led to” us, Homo sapiens. The important characteristic is bipedalism – standing and walking on two legs.

The following is highly simplified and covers a huge span of time – 4+ million years to the present. Needless to say, there is actually very little known that is “definite” due to the scarcity of fossil evidence and competing “arguments” as to interpretation of the evidence. __________________________________________________________________________________________

Pelves in anteroposterior  (front to back) (top row) and axial views (bottom row).

Fig. 2 Changes in female pelvis over 4.4 million year time span in 6 species. Chimpanzees are NOT our ancestors and are not in our evolutionary group. The apes shown are in our group, the Hominins. Note the birth canal first widens transversely (side to side),  but from Au. afarensis to H. sapiens only anteroposterior (front to back) deepening occurs (adapted from Bergé and Goularas40, Lovejoy et al41 and Simpson et al42, with permission). In Darwin’s day, only the specimens far right and far left were known.

From left to right: Chimpanzee (Pan troglodytes), (Anthropoid pelvis)

Ardi (Ardipithecusramidus, (ape species) 4.4 million years ago), (Anthropoid Pelvis)

Lucy (Australopithecus afarensis, (ape species) 3.2 million years ago), (Platypelloid Pelvis – rare in modern females and requires C-section)

Australopithecus africanus (ape species) (2.7 million years ago), (Becoming less Platypelloid as pelvis becomes more narrow)

Homo erectus (human species) (1.2 million years ago) (first “Gynecoid” Pelvis (?)

and Homo sapiens; there are between 2-4 “types” in modern females, according to the Caldwell-Malloy system, from 1933, with various “combination types” in individual women. (There are more human species, such as “Neanderthal” – not shown here.)

The Caldwell-Malloy classification of modern female pelvis types, 1933.

It is the modern Android “male” pelvis type that is  causing problems.

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Below: comparison of lower skeleton, Chimp, the Australopithecine apes and modern Homo sapiens. It’s easy to see that although we share a distant common ancestor with chimpanzees, we are not on the same evolutionary path. Our distinct path began with bipedal apes.

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This illustrates a comparison between an ape pelvis (called “Lucy” – (Australopithecus afarensis) although “she” may be a “he” – misidentified?) and Homo erectus, a “human” species over which there is much disagreement as to whether or not it is our direct ancestor. By the time of this H. erectus fossil pelvis, brain size had increased, and due to more advanced bipedalism, the pelvis is more narrow, producing a more “round” opening – what is today called a Gynecoid pelvis type. (It has been “assumed” that the gynecoid pelvis only appeared when Homo sapiens evolved) This is considered to be the pelvis that best provides for successful vaginal delivery.

Body shape, fat distribution, and body composition: Just as in males who developed a characteristic body shape, girls also respond to rising levels of estrogen. The lower half of the pelvis widens to provide a larger birth canal. This results in a widening of the hips and the characteristic hour glass shape of the female form. Fat tissues increases compared to males…especially in the breasts, hips, buttocks, thighs, upper arms and pubis. On average, by age 10 girls have 6% more body fat than boys. Source: Bacha, Saad, Gungor, Janosky, & Arslanian, 2002.

The “Android” (male) pelvis is the result of a “lack of” female development (widening of pelvis at puberty). The pelvis remains a “male type” pelvis which is obviously not adapted to pregnancy and birth! Vaginal delivery is difficult. A C-section is often required or chosen.

Why does the “Android” pelvis appear in modern Homo sapiens? Next post!

 

Overlap in Prey / Neanderthal, Hyena

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Comparison of Neanderthal and Hyena as “top predators”.

Isotopic evidence for diet and subsistence pattern of the Saint-Césaire I Neanderthal: review and use of a multi-source mixing model.

Author information

  • 1Institut des Sciences de l’Evolution, UMR 5554, Université Montpellier 2, Place E. Bataillon, F-34095 Montpellier cedex 05, France. bocheren@isem.univ-montp2.fr

Abstract

The carbon and nitrogen isotopic abundances of the collagen extracted from the Saint-Césaire I Neanderthal have been used to infer the dietary behaviour of this specimen. A review of previously published Neanderthal collagen isotopic signatures with the addition of 3 new collagen isotopic signatures from specimens from Les Pradelles allows us to compare the dietary habits of 5 Neanderthal specimens from OIS 3 and one specimen from OIS 5c.

This comparison points to a trophic position as top predator in an open environment, with little variation through time and space. In addition, a comparison of the Saint-Césaire I Neanderthal with contemporaneous hyaenas has been performed using a multi-source mixing model, modified from Phillips and Gregg (2003, Oecologia 127, 171). It appears that the isotopic differences between the Neanderthal specimen and hyaenas can be accounted for by much lower amounts of reindeer and much higher amounts of woolly rhinoceros and woolly mammoth in the dietary input of the Neanderthal specimen than in that of hyaenas, with relatively similar contributions of bovinae, large deer and horse for both predators, a conclusion consistent with the zooarchaeological data. The high proportion of very large herbivores, such as woolly rhinoceros and woolly mammoth, in Neanderthal’s diet compare to that of the scavenging hyaenas suggests that Neanderthals could not acquire these prey through scavenging. They probably had to hunt for proboscideans and rhinoceros. Such a prey selection could result from a long lasting dietary tradition in Europe.

PMID:
15869783

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(Below: Not the Saint-Cesaire 1 specimen) “Mystery” Neanderthal species allows artists to speculate on the “reality” of multiple human types. There is no satisfactory evidence of blue eyes in Neanderthal.

neanderthal female reconstruction, viktor deak

Neanderthal female reconstruction, Viktor Deak

reconstruction of the La Chapelle aux Saints Neanderthal, by Fabio Fogliazza

reconstruction of the La Chapelle aux Saints Neanderthal, by Fabio Fogliazza 2

reconstruction of the La Chapelle aux Saints Neanderthal, by Fabio Fogliazza 2

Geologists discover 5.7 myo “human-like” footprints / CRETE

ORIGINAL PAPER: http://www.sciencedirect.com/science/article/pii/S001678781730113X

Fossil footprints challenge established theories of human evolution

August 31, 2017 / Uppsala University

Summary: Newly discovered human-like footprints from Crete may put the established narrative of early human evolution to the test. The footprints are approximately 5.7 million years old and were made at a time when previous research puts our ancestors in Africa — with ape-like feet.

Ever since the discovery of fossils of Australopithecus in South and East Africa during the middle years of the 20th century, the origin of the human lineage has been thought to lie in Africa. More recent fossil discoveries in the same region, including the iconic 3.7 million year old Laetoli footprints from Tanzania which show human-like feet and upright locomotion, have cemented the idea that hominins (early members of the human lineage) not only originated in Africa but remained isolated there for several million years before dispersing to Europe and Asia. The discovery of approximately 5.7 million year old human-like footprints from Crete, published online this week by an international team of researchers, overthrows this simple picture and suggests a more complex reality.

Human feet have a very distinctive shape, different from all other land animals. The combination of a long sole, five short forward-pointing toes without claws, and a hallux (“big toe”) that is larger than the other toes, is unique. The feet of our closest relatives, the great apes, look more like a human hand with a thumb-like hallux that sticks out to the side. The Laetoli footprints, thought to have been made by Australopithecus, are quite similar to those of modern humans except that the heel is narrower and the sole lacks a proper arch. By contrast, the 4.4 million year old Ardipithecus ramidus from Ethiopia, the oldest hominin known from reasonably complete fossils, has an ape-like foot. The researchers who described Ardipithecus argued that it is a direct ancestor of later hominins, implying that a human-like foot had not yet evolved at that time.

The new footprints, from Trachilos in western Crete, have an unmistakably human-like form. This is especially true of the toes. The big toe is similar to our own in shape, size and position; it is also associated with a distinct ‘ball’ on the sole, which is never present in apes. The sole of the foot is proportionately shorter than in the Laetoli prints, but it has the same general form. In short, the shape of the Trachilos prints indicates unambiguously that they belong to an early hominin, somewhat more primitive than the Laetoli trackmaker. They were made on a sandy seashore, possibly a small river delta, whereas the Laetoli tracks were made in volcanic ash.

‘What makes this controversial is the age and location of the prints,’ says Professor Per Ahlberg at Uppsala University, last author of the study.

At approximately 5.7 million years, they are younger than the oldest known fossil hominin, Sahelanthropus from Chad, and contemporary with Orrorin from Kenya, but more than a million years older than Ardipithecus ramidus with its ape-like feet. This conflicts with the hypothesis that Ardipithecus is a direct ancestor of later hominins. Furthermore, until this year, all fossil hominins older than 1.8 million years (the age of early Homo fossils from Georgia) came from Africa, leading most researchers to conclude that this was where the group evolved. However, the Trachilos footprints are securely dated using a combination of foraminifera (marine microfossils) from over- and underlying beds, plus the fact that they lie just below a very distinctive sedimentary rock formed when the Mediterranean sea briefly dried out, 5.6 millon years ago. By curious coincidence, earlier this year, another group of researchers reinterpreted the fragmentary 7.2 million year old primate Graecopithecus from Greece and Bulgaria as a hominin. Graecopithecus is only known from teeth and jaws.

During the time when the Trachilos footprints were made, a period known as the late Miocene, the Sahara Desert did not exist; savannah-like environments extended from North Africa up around the eastern Mediterranean. Furthermore, Crete had not yet detached from the Greek mainland. It is thus not difficult to see how early hominins could have ranged across south-east Europe and well as Africa, and left their footprints on a Mediterranean shore that would one day form part of the island of Crete.

‘This discovery challenges the established narrative of early human evolution head-on and is likely to generate a lot of debate. Whether the human origins research community will accept fossil footprints as conclusive evidence of the presence of hominins in the Miocene of Crete remains to be seen,’ says Per Ahlberg.