Accelerated Human Evolution: From Agriculture to Conquest

About the authors

Gregory Cochran is a physicist and Adjunct Professor of Anthropology at the University of Utah. Henry Harpending was a Distinguished Professor in the Department of Anthropology at the same university.

Introduction

The central point of this work is that humans continue to evolve, contrary to what one might initially believe. This evolution has even accelerated over the last 10,000 years.

Humans adopt new techniques that advance their customs, making some of their old attributes obsolete. Thus, for example, tools like spears, which allow for killing larger predators, caused the human body to evolve and become more fragile, because now these large muscles had become useless, even debilitating. It was better to prioritize endurance to run after prey over long distances, waiting for them to tire.

A Catastrophe at the Origins

Around 10,000 years ago, global warming allowed for the emergence of agriculture. This had a great influence on the populations concerned. Most prosperous nations today had among their descendants peoples who had been exposed for millennia to agriculture. Agriculture forced the peoples who practiced it to evolve. The first changes concerned resistance to bacteria, because new agricultural practices and reduced selection pressure influenced human anatomy.

Post-Civilization Acceleration

The idea that human evolution ended tens of thousands of years ago is clearly erroneous. On the contrary, evolution intensified after the emergence of civilization, reaching a pace about a hundred times faster than its average over the 6 million years of our existence. This acceleration was so rapid that humans changed significantly, both physically and mentally, within recorded history.

These changes are striking and obvious: distinctive traits like resistance to malaria, the appearance of blue eyes, or adult lactose tolerance, all appeared within the last 10,000 years.

This intensification was fueled by an immense demographic explosion linked to agriculture, which multiplied the world population by about a hundred between 10,000 BC and 1 AD. More individuals means that the production of favorable mutations increased, with genetic innovations occurring much more frequently than before.

Agricultural Constraints and Biological Responses

The new agricultural lifestyle imposed unprecedented problems on populations. Sedentary living and high population density allowed virulent infectious diseases, such as smallpox or measles, to prosper where they could not exist among hunter-gatherers. Farmers were subjected to intense selective pressures, developing much more effective genetic defenses. This is how sickle cell disease and other variants protecting against malaria appeared, often very recent and localized adaptations depending on the regions.

Another major biological adaptation was adult lactose tolerance, a mutation that allows the digestion of milk even after weaning. This characteristic is one of the most strongly selected that we know. Appearing among European breeders and certain peoples of East Africa, it allowed a much more efficient use of animal resources, conferring such a powerful competitive advantage that it could explain the rapid expansion of Indo-European peoples.

Domestication and Evolution of the Mind

Changes are not only metabolic. Humans became more gracile and less robust, and the volume of their skull decreased. Above all, the establishment of sedentary, dense, and hierarchical societies – where escape is difficult and local violence limited by states – subjected humans to a form of “domestication.”

Post-agricultural evolution led to modifications of the central nervous system, selecting new versions of genes affecting neurotransmitters. Selective pressures favored “bourgeois virtues”: obedience to authority (because the elite had an interest in “taming” its subjects), diligence, and the ability to delay gratification. These traits were crucial for farmers who had to save seeds instead of consuming them immediately, a behavior useless or even harmful among hunter-gatherers. These genetic changes, affecting cognition and personality, prove that human evolution gallops in all directions.

Evolution and Conquest: A Question of Immunity

The dazzling success of Europeans in global expansion was often a biological success, a direct consequence of their post-agricultural genetic history. However, the effectiveness of this biological superiority depended entirely on the environment encountered. These examples illustrate how recent evolution shaped the destiny of populations worldwide, but the story does not end there.

The New World: Victory by Germs

When Europeans initiated the “Columbian explosion” towards the New World, their conquest was propelled by fundamental biological differences – notably an increased resistance to diseases. Native Americans, having migrated from Northeast Asia approximately 15,000 years ago, had left behind the crowd diseases born of agriculture, as well as the corresponding genetic defenses. Their population had not experienced intense selective pressure regarding infectious diseases. As a result, they were decimated by an avalanche of Eurasian and African diseases (such as smallpox, measles, or diphtheria).

This vulnerability of Native Americans was the main reason for European success. The mortality rate of smallpox, for example, sometimes reached 90% among Native Americans, compared to about 30% among Europeans. The Spanish, with a few hundred men, were able to defeat empires of millions of individuals, because they were assisted by their microscopic allies. The biological advantage of Europeans over Native Americans in this situation was enormous.

The African Contrast: The Impasse of the Black Continent

When Europeans attempted to conquer and settle in sub-Saharan Africa, the situation was reversed. Europeans encountered incredible disease risks. For centuries, European expansion was blocked in coastal areas.

Virulent tropical diseases, such as falciparum malaria and yellow fever, acted as a natural barrier, preventing Europeans from penetrating inland. Local African populations, on the other hand, possessed biological defenses that had evolved at great cost, maintaining sufficient resistance to survive.

Even if European military technology was superior, Africa did not become another America because local populations did not die en masse, thus preventing their replacement by European settlers. Africans survived Europeans despite their technologically less developed civilization, while Native Americans were decimated by germs. Powerful tropical diseases, combined with local biological defenses, kept Africa African.

A Case Study: Ashkenazi Success

These examples of evolutionary differentiation are not limited to large continental populations. The authors apply the same method of analysis – gene-culture coevolution – to smaller groups, revealing equally fascinating evolutionary dynamics.

Steinitz, Botvinnik, Kasparov, Fischer, Tal: these names may not mean anything to you, but they are chess champions, all Ashkenazi Jews. Of the fifteen chess world champions crowned so far, four are Jewish, a remarkable overrepresentation given the tiny size of this population. This success is not limited to chess: Ashkenazi Jews disproportionately excel in many intellectual fields, from mathematics to theoretical physics, including finance.

How to explain this phenomenon? The authors propose a bold hypothesis based on two key factors: reproductive isolation and selection pressure from intellectually arduous professions. For nearly a millennium in Europe, Ashkenazi Jews lived in relative reproductive isolation, essentially marrying among themselves. Simultaneously, they were confined to cognitively demanding professions – notably finance, trade, and professions requiring literacy – while manual labor was often forbidden to them.

This unique combination created intense selective pressure favoring intellectual abilities. Individuals most successful in these difficult professions fared better economically, which translated into more numerous offspring. Generation after generation, this selection could have favored genetic variants associated with increased cognitive abilities. Certain genetic diseases common among Ashkenazim, such as Tay-Sachs disease, could even be the evolutionary price of this selection, mutations that in the heterozygous state would confer cognitive advantages.

This case perfectly illustrates the central thesis of the work: human evolution is not a process frozen in a distant past, but a living force that continues to sculpt human populations, sometimes in the space of only a few dozen generations. Recent human evolution, and the biological differences it has generated, have played a key role in determining the winners and losers in major historical expansions, but also in the success of smaller groups in specific fields.

To delve deeper into these fascinating and controversial questions, and discover how gene-culture coevolution has shaped modern humanity in ways we are only just beginning to understand, a complete reading of this work is essential. The authors develop these theses with scientific rigor and a wealth of detail that invites reflection on our past, our present, and perhaps even our evolutionary future.