The 10,000 Year Explosion: How Civilization Accelerated Human Evolution Paperback – October 19, 2010

This review is on the book, "The 10,000 Year Explosion" and the authors are Gregory Cochran and Henry Harpending. Their book presents an important and revolutionary idea about humanity, namely that we are currently evolving at a pace faster than we can imagine. This idea is in sharp contrast to the conventional wisdom that human evolution has ground to a halt. For example, evolutionary biologist, Stephan Jay Gould, wrote that there has been no change in humans in the last 40,000 or 50,000 years.

The book's title suggests that the book focuses on the period of time about 10,000 years ago and that is correct. However before going there, the authors address an earlier period and present their startling take on why it happened. The period is around 30-40,000 years ago and is often referred to as the Great Leap Forward. There was an extraordinary change in human behavior during this period. Innovation for the first time had suddenly become part of very human activity. One example is a proliferation of polychromatic cave art depicting animals, which to us are now long extinct. Other examples are: sculptures (fertility goddesses), music instruments ( bone flutes), jewelry, and improved tools and weapons. The authors believe that the spark for this creative surge may have been the secondary result of an injection of new and different genes into our genome. Those new genes came from interbreeding with Neanderthals. The fact that interbreeding occurred is argued for by the authors, but it is not clear to me that they were aware that Paabo Svante had concurrent to their book, developed procedures for restoring ancient DNA and had decoded nuclear Neanderthal DNA. He proved interbreeding to be true.

The authors then turn their attention to the period 10,000 years ago when humans invented agriculture, which gradually displaced the hunter-gatherer way of life throughout much of the world. Agriculture was a mixed blessing for these early farmers. It made a huge difference in the availability of food, but that benefit came at a heavy price. Unlike the healthy diet of the hunter-gatherer, early farm crops were inadequate in nourishment. Stated more precisely, human bodies had not yet adapted to these new foods. Moreover, disease became a stressor for the farming communities. Human and animal waste made its way into drinking water and living in close proximity to domesticated animals allowed animal diseases to crossover to humans. As agriculture allowed for larger populations and the idea spread throughout the world, it left fossil evidence that humans had become far less healthy compared to hunter-gatherer cultures. When a species is confronted by life-or-death stressors, superior genes are passed forward into future generations whereas inferior genes are eliminated. In other words, the strong live and have offspring whereas the weak die and do not. Favorable mutations allow for genetic adaptations to be made. Just consider how superior our immune systems are compared to the Indians of both North and South America to Europeans diseases like measles, whooping cough, mumps, etc. They are non-fatal childhood diseases to us, whereas they were exterminating diseases to the Amerindians. Perhaps ninety percent of the Amerindians were killed by such diseases. The earliest farmers in the Fertile Crescent were in the vulnerable condition as the Amerindians until generations of evolutionary adaptation produced protection.

The authors made an argument that I found to be breathtaking; namely that evolutionary change is accelerated by a larger population size. Mutations are the change agents in evolution, but mutations are extremely rare. Either a mistake is made in the sexual reproduction process or cosmic rays change the code of a nucleotide. However as population size increases, the occurrence of mutations increases too. The agricultural revolution increased food production and allowed the population to rapidly expand. Since then, innovation after innovation has accelerated the control humans have over their lives. Today the world population is at 7.4 billion people. The number of favorable mutations occurring worldwide must be mind-boggling. Many of these genetic changes affect mental capability. The more useful the genetic change is, the faster it will spread through the population. It appears that we have not stopped evolving, we are evolving faster and faster.

Ralph D. Hermansen, March 27, 2016

As the authors note in the opening chapter, the common dogma passed down by many prominent popularizers of evolutionary biology is that with the origin of anatomically modern humans, cultural evolution has completely supplanted biological evolution in our species. A corollary of the central dogma that all post-paleolithic human adaptation has been cultural rather than biological is that there are no significant biological differences between groups of people.

Cochran and Harpending provide a much-needed antidote to this completely inaccurate view of human biology and history. They make a strong case that far from cultural evolution circumventing the forces of natural selection and biological evolution, cultural changes serve as a powerful impetus for genetic changes in human populations. Obvious examples include the independent origins of adult lactose tolerance among cattle herding peoples in both Africa and the Middle East. Less obvious but nonetheless compelling examples include potentially strong selective pressures leading to changes in cognitive and personality traits as a result of sociocultural circumstances. In a sense, none of these findings should come as a great surprise, since human society and culture obviously creates the environment in which people differentially survive and reproduce, implying that the forces of natural selection have been and remain as active as ever.

I hope that Cochran and Harpending's book is widely read (particularly by social scientists and the general public) and helps to refute the stubbornly held view that only culture and environment matter as the driving forces of modern human history..

A fascinating read. Much of what the authors write is speculative, for example, the nature of the traits that civilization would select. But their speculations are also very plausible. The chapter on Ashkenazi Jews was particularly interesting. They propose a very plausible, and testable, model for how the Ashkenazi Jews developed their high intelligence over the span of only ~1000 years. I suppose the only reason there has not been more research on the subject is due to the taboo surrounding race differences in intelligence.
One thing that is certain is that evolution never ceases and can occur quite rapidly. Clearly people evolving within the context of civilization are going to be exposed to different selective pressures than those who do not. People whose ancestors evolved within advanced civilizations are, in essence, selected to be civilized, whereas those whose ancestors did not, are not. This simple concept goes a long way towards explaining the state of the world as it is today.

I have now read this book twice on Kindle and then ordered the hardcover version, which is easier to leaf back and forth and make notes in. It is incredibly dense and detailed with information that has been compressed and given almost in outline form. I plan to work my way through the references and do more reading. I have been struggling to read Lewin's Gene XI and will spend renewed effort with this book as inspiration. I was also pleased to see that it agrees pretty much with the first chapter of my own medical history book, in which I tried to summarize human evolution in brief form. My own book is called "A Brief History of Disease, Science and Medicine," http://www.amazon.com/Brief-History-Disease-Science-Medicine/dp/0974946656.