Homo sapiens have come a long way since arriving at the prehistoric party 100,000 years ago. Sure, we didn’t fit in at first (dearth of fur being a major faux pas), but we changed. Through the process of natural selection, we grew taller and more dexterous and adopted tools that, in turn, affected our evolution.
In the contemporary world, we control most of these factors. We’ve learned to combat many of the deadliest diseases, protect ourselves from the dangers of the environment around us, and feed ourselves, so is evolution still taking place? The evidence shows that, over the past 10,000 years — which, in evolutionary terms, is the blink of an eye — it definitely is.
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Our ability to digest lactose is a relatively recent evolutionary development in humans. Human babies were always able to digest milk, thanks to the function of an enzyme called lactase, but that ability used to be lost in adulthood. Several thousand years ago (the exact date is still unclear), a mutation developed that allowed adults to digest lactase. Then, around 8,000 years ago, around northern Africa, a change took place that started selecting for lactose-tolerant individuals: We began raising dairy animals. It’s not hard to imagine why the ability to drink milk might have increased early humans’ chance for survival, The white stuff is packed with carbohydrates, protein, calcium, and other nutrients, enough to save a life during a famine.
Today, over 95% of Northern European descendants carry the lactose persistence gene. Because the climate was colder, fresh milk probably kept for longer, and the land lent itself well to growing crops to feed milk-producing animals. In contrast, the gene is rare throughout Asia, where dairy farming was not as common.
Mutations enabling us to digest new or different types of foods could play a big role in our future evolution. As the type of food we have access to changes — crickets, lab-grown meat, and other synthetic food could one day become the norm — our ability to derive nutrients from it could determine our survival.
Perhaps one of the most important factors driving our evolution is our ability to resist disease. A 2007 study at the University of Wisconsin found 1,800 genes that have been favorably selected for in the past 40,000 years, and many of them were genes determining disease resistance. For example, they discovered about a dozen genetic variants involved in fighting malaria that were spreading throughout African populations.
As new viruses and diseases keep appearing — and they will, given that they evolve so much faster than we do — we’ll continue to discover genes that confer resistance against them. This point was driven home by Bill Nye in an article for Popular Science: “Those who survive into the future will probably have resistance to certain diseases that none of us have today.”
The emergence of blue eyes in the human population is another fairly recent development. At one point, we all had brown eyes, but about 10,000 years ago, mutation developed that caused those brown eyes to turn blue. The reasons why this mutation persisted are vague, but researchers speculate that early blue-eyed men sought out blue-eyed women as a sort of ‘paternity guarantee’: It’s virtually impossible for two blue-eyed individuals to produce a brown-eyed child.
Longer Reproductive Periods
A 2012 study using data on Finnish populations born between 1760-1849 (they were very meticulous about record keeping) showed selection was tending toward a lengthening of the reproductive period. Both age at first birth and age at menopause had changed in a way that increased the amount of time a woman is fertile. Whether this speaks to the current trend among women to have children later in life is unclear, but we could be continuing to select for these traits today.