The Tyranny of Reductionist Gene Theory

Much has been made of MtDNA  studies as a way to trace female lines of inheritance, but what do mutations in MtDna mean? These changes are random, and occur throughout time at a predictable rate: that’s all. If anything, MtDNA studies merely prove the prediction that changes in MtDNA occur at a predictable rate. It’s important to realize that MtDNA results are MATHEMATICAL models and do not attempt to reflect or match concrete reality. In principle, it’s like using radioactive decay rates to date objects. MtDNA maps are maps of these random mutations through time, like a log of a railroad journey that tracks train stations where a new passenger got on the train. This itinerary says nothing about the people on the train, except that they took the journey.  

hqdefault

Another popular trend in the evolution sciences is the absolutism of genes as the basis for identification of species: Genes have become the objects of evolution, not whole individuals or groups of individuals. That is, you are not you; you are your genes. This is so obviously absurd that one wonders how scientists get away with such extreme reductionism that ignores the contributions that an individual makes to its own existence and to that of others; the effects of environment, including epigenetic changes, and also the effects of culture and social environment, factors that are especially important in humans. Many popular science and genealogy sites have jumped on the reductionist train to nowhere; customers pay large sums to have their fortunes cast in the search for a significant ancestral “blood line.” Genetic testing can screen for possible health risks, but to believe that one’s genes predict fame & fortune, or a slot somewhere near the top of the social pyramid, is magical thinking.

Science has a problem: What is a species?

My favorite mind blower is the assertion that anyone who joined the latest ‘Exodus’ from Africa (approximately 50-70,000 years ago) was  a modern human and that  all other humans who existed at that time (regional variations on earlier migrations such as Homo erectus) simply fell over and died like the Dinosaurs to make room for a fabulous new creature, Homo sapiens. Or it may be that Homo sapiens cannibalized its way to world domination. This idea is silly.

Here’s a an interesting bit of genetics the public hears little about:

At any point in time, there are likely to be many different versions of a gene in the population.

xwomantree1

Most of these gene versions are likely to be closely related to one another.

However, some gene versions may be ancient and may have hung around in the population for a long time.xwomantree3

Sometimes these gene versions are so old that they are actually more closely related to a gene version found in a separate species than they are to other gene versions in the same population.

X woman denotes a Denisovan sample

For example, some humans have versions of immune system genes that are more closely related to chimpanzee versions of immune system genes than they are to other human versions. That’s just because these gene versions are extremely old and have   six million years ago, not because the humans carrying those genes are more closely related to chimps than to other humans. In this case, the gene tree and species tree don’t match.

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s