Sometimes a Species is just a Species: Individual Selection Trumps “Benefit of the Species”

What did Genghis Khan (circa 1162-1227) have that you don’t? He had hundreds of children and the power to absorb a vast number of tribes into his Mongolian Empire. His power can be used as an example to show that natural selection operates at the level of the individual and most often has no role in what is good for the species.

As a quick review, adaptation is the process of becoming better fit to an environment. A specific adaptation is a trait that provided its carrier with a survival and/or reproductive advantage in the past. Traits are heritable, meaning they are passed from parent to offspring. A beneficial trait is passed on more often than other traits that may prove less beneficial, and will start to characterize a subset of a species or a species – but only by way of the individual.

Let us assume that Khan’s power was a composite of heritable traits (e.g. ruthlessness, cunning, persistence), biologically passed down from parent to offspring. Power is an adaptation because it gave the possessor an increased access to resources and mates. From his wife and concubines alone, Khan is believed to have fathered hundreds of children. Indeed, a recent study found that roughly 8% of the former Mongolian Empire shares genetic material on the Y-chromosome at levels indicating the shared material isn’t due to random mutation or genetic drift, but a shared ancestor. This translates to 0.5% of the world! The shared material has been traced back about 1,000 years, around the time of Genghis Khan’s rule, and due to other circumstances is believed to be from his lineage. Thus Khan’s power helped him acquire many mates, passing on the power trait quite often. In other words, the trait benefited Genghis Khan directly – it resulted in more partial copies of himself. It was social inheritance that split Khan’s empire amongst his sons after his death; it was biological inheritance (of the power trait) that gave them the ability to expand his empire even further.

Khan’s power enabled him to invade and conquer areas stretching from the Caspian Sea to the Sea of Japan. He persuaded tens of thousands of men to join his ranks and commanded them in fierce battles. He was responsible for thousands of deaths in his quest for power and dominion over his quickly growing Mongolian Empire. His power was surely related to his vast death toll (more numerous even than his offspring) – and no one can command in such great numbers without power. In other words, the trait did not benefit the species, and in fact led to a decrease in the population of his species.

The same trait (power) that was so detrimental to the pawns in the rapidly growing Mongolian empire (e.g. part of the species) was so beneficial to Genghis Khan that he ended up with more offspring than most of us could ever imagine – and half of us (i.e. women) could ever produce in a lifetime. Thus power is a quite adaptive trait, but more importantly, explicates that natural selection operates upon what is beneficial for the individual, not the species. If Khan’s power had operated so as to benefit the pawns, and not Khan, he would not have been an effective leader in those times, and therefore he would not have left any offspring to carry on his traits.

Further Reading:

Dawkins, R. (1990). The selfish gene (2nd ed.). Oxford: Oxford University Press.

Zerjal, T., Xue, Y., Bertorelle, G., et al. (2003). The genetic legacy of the Mongols. American Journal of Human Genetics, 72, 717-721.

Rosemarie Sokol Chang

About Rosemarie Sokol Chang

Rosemarie Sokol Chang is an evolutionist trained as a psychological scientist. She is the editor of EvoS: The Journal of the Evolutionary Studies Consortium; the creator of the EvoS Consortium website and the EvoS Blogs; and co-founder of the Journal of Social, Evolutionary, and Cultural Psychology. She also has been involved in the NorthEastern Evolutionary Psychology Society since its inception. She recently edited and contributed to the book Relating to Environments: A New Look at Umwelt. Evolution Matters is a recurring blog focused on concepts and evidence of evolution by natural selection.
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