Since the dawn of agriculture, humans have been making technological advances that insulate us more and more from the selective pressures that once shaped our evolution — but they've also made the question of whether and how human populations are still affected by Darwinian evolution increasingly unclear.
Now, newly published research has painted one of the most lucid pictures to date of how evolutionary forces have continued to shape our development as a species, and how they still affect us even to this day.
"It is a common misunderstanding that evolution took place a long time ago, and that to understand ourselves we must look back to the hunter-gatherer days of humans," explains researcher Virpi Lummaa, first author on the paper describing the findings, published in this week's Proceedings of the National Academy of Sciences.
To get a better handle on the impact of technological advances on recent human evolution, Lummaa and her colleagues examined the church records of people born in farming and fishing villages of Finland between 1760 and 1849. The researchers chose these records for two reasons. For one thing, the documents were meticulously maintained; genealogy is popular in Finland, and these particular records contained a remarkably thorough account of birth, death, mating, and even the wealth status of close to six-thousand Finns.
The second reason had to do with Finland's strict cultural mandates against divorce and extramarital affairs. Taken together, these factors not only provided the team with large sample sizes and data covering the entire lifespan of each individual person, it also did so within a well-controlled experimental context. What they found was some of the most compelling evidence to date that natural selection has persisted even in more recent human populations. Over at Science Magazine, Elizabeth Pennisi explains:
Natural selection was alive and well in all of the villages the researchers surveyed. Almost half of the people died before age 15, for example, suggesting that they had traits disfavored by natural selection, such as susceptibility to disease. As a result, they contributed none of their genes to the next generation. Of those that made it through childhood, 20% did not get married and had no children, again suggesting that some traits prevented individuals from obtaining mates and passing on their genes to the next generation.
The Finns were also subject to sexual selection, in that men who were able to attract new mates had more offspring. With one partner, the average was about five children; with four partners, that jumped to 7.5, Courtiol notes. Men benefited more than women in terms of begetting more children, most likely because they tended to remarry young women with good child-bearing potential. Thus sexual selection was more important in men than in women.
Interestingly, the researchers found that well-to-do Finns were just as susceptible to selective pressures as their poorer peers, suggesting that not even wealth could "prevent natural selection from culling or favoring individuals."
The authors ultimately conclude that humanity's advances have not prevented us from evolving — just like all the other species 'in the wild,'" as Lummaa puts it — though it remains to be seen how their findings might be extended forward into even more moden societies. Given the ever-increasing rate of humanity's development (both technologically and socially), can evidence of evolution from 160 years ago really apply to contemporary society? With food production higher now than at any other point in history, and medicine prolonging and enriching lives in ways 19th century Finns couldn't even imagine (for example), is it realistic to expect that humans will continue to adapt to evolve "just like" other species?
Top image via Shutterstock; church records and Finnish family photo via Virpi Lummaa