Book Summary: “The 10,000 Year Explosion: How Civilization Accelerated Human Evolution” by Cochran & Harpending


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

Title: A 10,000 Year Explosion: How Civilization Accelerated Human Evolution
Author: Gregory Cochran and Henry Harpending
Scope: 4 stars
Readability: 4 stars
My personal rating: 5 stars
See more on my book rating system.

Topic of Book

The authors seek to understand whether human genetic evolution has continued over the past 10,000 years.

Key Take-aways

  • Many who claim to accept the idea of natural selection, reject most of the obvious implications of the theory when it is applied to humans
  • While most people assume that human genetic evolution stopped 10,000 years ago, it has actually accelerated 100-fold.
  • Technological evolution is constantly changing our environment which puts humans under increasing genetic pressure.
  • The direction and rate of change differs by region.
  • Even small genetic differences between populations can dramatically increase the size of outliers who create innovation, particularly if those people are networked together.
  • Among the most important genetic differences between peoples are:
    • Regulation of blood sugar to protect against diabetes
    • Ability to digest Cow’s milk
    • Ability to metabolize alcohol
    • Lighter skin to aid Vitamin D production
    • Immunity to new infectious diseases, such as measles and malaria

Important Quotes from Book

“We intend to make the case that human evolution has accelerated in the past 10,000 years, rather than slowing or stopping, and is now happening about 100 times faster than its long-term average over the 6 million years of our existence. The pace has been so rapid that humans have changed significantly in body and mind over recorded history.”

“The most accessible examples are the products of domestication. Domesticated animals and plants often look and act very different from their wild ancestors, and in every such case, the changes took place in far less than 100,000 years. For example, dogs were domesticated from wolves around 15,000 years ago; they now come in more varied shapes and sizes than any other mammal”

“In an extreme example, the Russian scientist Dmitri Belyaev succeeded in developing a domesticated fox in only forty years”

“Since we have sequenced the chimpanzee genome, we know the size of the genetic difference between chimps and humans. Since we also have decent estimates of the length of time since the two species split, we know the long-term rate of genetic change. The rate of change over the past few thousand years is far greater than this long-term rate over the past few million years, on the order of 100 times greater. If humans had always been evolving this rapidly, the genetic difference between us and chimpanzees would be far larger than it actually is”

“The ultimate cause of this accelerated evolution was the set of genetic changes that led to an increased ability to innovate. Sophisticated language abilities may well have been the key. We would say that the new alleles (the product of mutation and/or genetic introgression) that led to this increase in creativity were gateway mutations because innovations they made possible led to further evolutionary change”

“Every major innovation led to new selective pressures, which led to more evolutionary change, and the most spectacular of those innovations was the development of agriculture”

“Agriculture imposed a new way of life (new diets, new diseases, new societies, new benefits to long-term planning) to which humans, with their long history as foragers, were poorly adapted. At the same time it led to a vast population expansion that greatly increased the production of adaptive mutations.”

“Naturally, increased population size had a similar impact on the generation of new ideas. All else equal, a large population will produce many more new ideas than a small population, and new ideas can spread rapidly even in large populations”

“This is a new picture of recent human evolution. It implies that humans have changed not just culturally, but genetically, over the course of recorded history, and that we must allow for such changes when we try to understand historical events. The implications of this contention are vast: If correct, it means that peoples in different parts of the world have changed in varying ways, since they adopted different forms of agriculture at different times—or in some cases not at all.”

“Recent studies have found hundreds of ongoing sweeps— sweeps begun thousands of years ago that are still in progress today ”

“It’s time to address the old chestnut that biological differences among human populations are “superficial,” only skin- deep. It’s not true: We’re seeing genetically caused differences in all kinds of functions, and every such difference was important enough to cause a significant increase in fitness (number of offspring)—otherwise it wouldn’t have reached high frequency in just a few millennia”

“The point here is that a modest difference in the mean of some trait can have a tremendous effect on the frequency with which members of a group exceed a high threshold. If some important cultural task can only be accomplished by individuals who are unusually good at solving certain kinds of puzzles, then the course of cultural evolution may change radically with modest changes in the group’s average puzzle-solving ability. There are many other factors that might influence such events, but a difference in mean ability due to genetic differences is one of them. And both of these factors—social phase transitions and increases in the frequency of people with specific talents—may have played a part in the birth of modern science”

“We believe that science requires communication and cooperation between people who are unusually good at (and interested in) puzzle-solving. Science is a social enterprise, and scientists never truly work alone: They always build on the work of others.”

“So the number of such people, and their social connections, is crucial to the progress of science. We also know that modest differences in mean ability can have a big effect on how common such people are”

“there can also be phase transitions in connectivity. Imagine that the average budding scientist in Europe in 1450 knew a few other people like himself. Those acquaintances knew others, but since such people were rare, the potential scientists of Europe fell into small, isolated groups rather than a single connected community. There was no efficient way for new ideas and discoveries to spread. We are positing that as the frequency of such people increased, there was a sharp transition at a certain critical value. Suddenly all groups connected, and there was a path between any two members”

“many who claim to accept the idea of natural selection reject most of the obvious implications of the theory when it is applied to humans”

“One of the largest of all known expansions—the spread of the Indo-Europeans—was likely driven by the mutation that conferred lactose tolerance, one of the most strongly selected alleles that Europeans possess.”

Among the genetic changes that Cochran documents are:

  • Regulation of blood sugar to protect against diabetes
  • Cow’s milk digestion
  • Alcohol metabolism
  • Lighter skin to aid Vitamin D production
  • Smaller jaws and brow ridges; larger cranial vault
  • Change shape of inner ear to understand language.
  • Immunity to new infectious diseases:
    • Measles
    • Malaria

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