Examples of human evolution in the past 10000 years

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examples of human evolution in the past 10000 years

The 10,000 Year Explosion: How Civilization Accelerated Human Evolution by Gregory Cochran

I was seriously underwhelmed by this work. At a high level, I think its great that theres a new publication that presents a case for the biological and genetic drivers of human evolution even during the recent historic period. I certainly agree with this perspective, and it adds a nice layer of evidence to other recent popular works dealing with human history in the Holocene. The devil is in the details, however, and this is where the book comes up short.

I was very frustrated by this books orientation very firmly in the popular science genre rather than being more scientifically rigorous. There were far fewer citations than appropriate, and many claims were presented as fact without a shred of supporting evidence. Far too often, the authors (Cochran and Harpending) resorted to descriptions like completely obvious or undoubtedly to refer to their own arguments and simply incorrect, etc. to diminish opposing viewpoints without actually exploring WHY their own ideas were correct and opposing ideas might not be accurate. The authors sometimes acknowledge contradictory arguments or evidence but never explore them in anything but the most cursory fashion.

One of my biggest problems is that most of this book presents one big straw man argument. The authors repeatedly assert that conventional wisdom stipulates that no evolution has occurred in recent human history, and that current anthropological thought indicates that all patterns and changes in the last 10,000 years may be ascribed to cultural or environmental forces rather than biological ones. I suspect they are primarily aiming their sights at Jared Diamonds Guns, Germs, & Steel as well as selected works of Stephen Jay Gould. But really, this is not at all conventional wisdom in the scientific community, and there are plenty of books, papers, and people who will argue that a combination of cultural, environmental, and yes, biological and genetic factors have been important shapers of recent human destiny.

Im not going to get up on my soapbox and impress myself with my own intelligence by detailing a catalogue of complaints about the specific arguments in this work, or expounding upon what I believe to be more compelling arguments. Suffice to say that I have advanced degrees in related areas and worked as a professional anthropologist/archaeologist for years, so I consider my perspective to be an informed one. Here are two examples that I would consider to be representative of the flawed logic, methods, and philosophy of the entire work:

Chapter two presents their conclusion that Homo sapiens must have exchanged genes with Homo neanderthalensis. Based on what new evidence that now proves this old idea, you might ask? NONE! Its a compelling theory, but as of yet there is no conclusive support. Among their claims? We can only say that humans are known to have had sexual congress with [all sorts of things:]...any port in a storm, as well as a gene that plays a role in speech was replaced by a new variant some 42,000 years ago...it is likely that the migrating humans picked it up from Neanderthals, since thats about the time they encountered them in their expansion out of Africa. These kind of unsupported and ridiculous leaps of faith do not have a logical link to Cochran and Harpendings ultimate conclusions, and it is irresponsible to reach such a firm and adamant conclusion when supported by such a weak foundation of evidence. Dont get me wrong, I agree that genetic admixture between these groups was possible (perhaps even likely). Just dont insult my intelligence by building such a poor case with such strong and decisive language.

The final chapter discusses the reasons why Ashkenazi Jews are more intelligent than everyone else. The whole idea of measuring intelligence is subject to a variety of biases and problems. Rather than building a case that the pattern they describe is indeed real and valid - by first systematically reviewing objections to the concept of IQ measurement - they breeze through these objections in a single paragraph. That is intellectually dishonest - lets see some systematic scientific arguments rather than ad hoc rationalization, please. Not to mention that they ignore the social implications of their perspective - namely, that this type of thinking can be used to support racism in all its pernicious guises. If some groups are smarter than others, it follows that other groups would be dumber than average, and it is a slippery slope from this kind of thinking to arguing for institutionalized discrimination, eugenics, etc.

In short, this work leaves much to be desired. The style is unscientific and many of the conclusions are non sequiturs based on weak presentation of evidence and avoidance of opposing views. I would suggest skipping this one for something less partisan and more soundly scientific.
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Seven Million Years of Human Evolution

Are humans still evolving?

With this comes a dampening on the forces of natural selection, and a stagnation, or even weakening, of the human species. Over the past 5 to 10 thousand years, says Nature , reporting on a new study , the genetic diversity in the human population has exploded, a bloom that serves as stage one in the process of evolution. The human genome has been busy over the past 5, years. Human populations have grown exponentially, and new genetic mutations arise with each generation. Humans now have a vast abundance of rare genetic variants in the protein-encoding sections of the genome. Most of the mutations that we found arose in the last generations or so. Most of the new genetic shifts are extremely rare, appearing in only a small slice of the human population.

Even the founders of evolutionary psychology, Leda Cosmides and John Tooby, signed on to the notion that our brains were mostly sculpted during the long period when we were hunter-gatherers and have changed little since. So to suggest that humans have undergone an evolutionary makeover from Stone Age times to the present is nothing short of blasphemous. Yet a team of researchers has done just that. They find an abundance of recent adaptive mutations etched in the human genome; even more shocking, these mutations seem to be piling up faster and ever faster, like an avalanche. The new genetic adaptations, some 2, in total, are not limited to the well-recognized differences among ethnic groups in superficial traits such as skin and eye color. The mutations relate to the brain, the digestive system, life span, immunity to pathogens, sperm production, and bones—in short, virtually every aspect of our functioning. Many of these DNA variants are unique to their continent of origin, with provocative implications.

It has been argued that human evolution has stopped because humans now adapt to their environment via cultural evolution and not biological evolution. However, all organisms adapt to their environment, and humans are no exception. Culture defines much of the human environment, so cultural evolution has actually led to adaptive evolution in humans. Examples are given to illustrate the rapid pace of adaptive evolution in response to cultural innovations. These adaptive responses have important implications for infectious diseases, Mendelian genetic diseases, and systemic diseases in current human populations. Moreover, evolution proceeds by mechanisms other than natural selection. The recent growth in human population size has greatly increased the reservoir of mutational variants in the human gene pool, thereby enhancing the potential for human evolution.

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