The 150 year anniversary of Charles Darwin's seminal book on evolution, "The Origin of the Species," is an appropriate time for an important expansion on his ideas. This has come in the form of "The 10,000 Year Explosion" by Gregory Cochran and Henry Harpending.
The cultural conservatives, who are fond of emphasizing that Darwin's analysis is still the "theory" of evolution, are not going to like this new book any better than they like "Origin." The reason for this is that the scientific evidence for natural selection is even stronger now than it was in Darwin's time, due to advances in the understanding of genetics. This area of research supplied the biological mechanisms that explained patterns that Darwin was observing. Since Darwin did not have the benefit of this genetic science to support his analysis, his insights about natural selection are nothing short of spectacular.
The basic premise of "The 10,000 Year Explosion" is a refutation of paleontologist Stephen Gould who said that "there's been no biological change in humans for 40,000 to 50,000 years." This is roughly the time period when early humans began departing Africa for Europe and Asia.
Authors Cochran and Harpending disagree with Gould's argument. In their opinion, not only did evolution continue, but it has accelerated since humans left Africa and continues in the present day. Over the course of the book they present an overwhelming case for this new hypothesis.
In a March interview on a National Public Radio show ("Think"), Cochran noted that evolution proceeds by changing the frequency of the genetic variants, known as "alleles." In the case of natural selection, alleles that enable their bearers to leave behind more offspring will become more common in the next generations.
The two authors persuasively argue that the rate of change in the human genome has been increasing in the recent millennia. Thus, literally thousands of alleles are under selection now. This means that our social and physical environments are favoring newer alleles over those that are older.
What caused the human evolution to speed forward in the past 10,000 years? In the book and on the radio interview, Cochran emphasized that the major changes came forth as a result of food production.
During this "recent" evolutionary period, humans learned agricultural techniques and then abandoned the hunter-gatherer lifestyles. This led to the establishment of more domestic existence, the development of communities and then the establishment of cities and governments.
Living in close proximity with animals and among a higher concentration of people led to infectious diseases such as smallpox and malaria. The alleles of the descendents of these early communities evolved in a manner that allowed more resistance to these infectious diseases. As more of them survived, there was more resistance. This is a classic natural selection scenario.
The book notes the deadly result of human populations in North America NOT having had the benefit of this resistance to these infectious diseases. When the Europeans began exploration of the "new world," and coming into contact with the population without the gene variants to resist these diseases, the non-evolved populations were decimated.
Another interesting effect of evolution that is related to food production is the domestication of cattle. About 8,000 years ago, Europeans were lactose intolerant. Obviously, this is not the case today. This was the result of the alleles of these early humans favoring the consumption of milk. Since there are more calories from milk than from the meat of the slaughtered cows, these early humans evolved to tolerate milk. This was an enormous change.
There are other big ideas from "The 10,000 Year Explosion" that will have genetic scientists nodding and creationists fuming. For example, the authors note that the larger supply of mutations in large populations can mean large populations evolve faster than smaller populations. The authors also present an interesting analysis of the reasons for the disproportionately high intelligence of the Ashkenazi Jews.
While the book is fascinating, it is not without flaws. The primary one lies in the authors' failure to expand on the new developments in genetic science. Unless the reader is professionally involved with the latest genetic research, it is difficult to understand the genetic basis for many of their conclusions.
Another weakness of the book is found in the authors' attempts at humor. Most of their jokes are lame and come across as forced attempts by these very intelligent men to make them "one of the guys." These attempts at humor are not uncommon among scientists and they almost never work.
These minor flaws aside, "The 10,000 Year Explosion" is a brilliant analysis of the biological changes brought about by civilization that have recently occurred and continue today. This collection of knowledge is further confirmation of the causes and effects of natural selection - the foundation of the science of evolution.