Are Humans Still Evolving?
This isn’t a question we find ourselves asking all too often, mostly because we as humans don’t really face the same life or death pressures to stay one step ahead in the game of evolution that our very distant relatives may have. We have no true predators (other than ourselves), food is widely abundant (for most) and medical advances have extended the average lifespan, meaning that most of us can get sick and still end up having children successfully and pass on our genes. From this standpoint, it would be easy to assume that evolution no longer applies to the average human, but we want to know, are humans still under evolutionary pressure?
Let’s start with an example of evolution. Some of the most rapid and easily explainable evolutionary changes are seen between predator and prey. The rough-skinned newt and the common garter snake are a great example. Somewhere along the line, the rough-skinned newt developed a mutation that allowed them to develop skin glands containing a neurotoxin that defended them against predation. Then, a mutation in the common garter snake occurred that allowed resistance to the newt’s toxin. Individuals that exhibited this trait were able to eat more newts, didn’t die when attempting to eat one, and were ultimately more successful in passing on that mutation to their offspring. Now, common garter snakes that live in the same range as the rough-skinned newt all share this evolutionary trait. And on top of that, the newts that live in the same range as the common garter snake have now been shown to produce higher levels of the toxin in response. The evolutionary pressure for survival between these two species is something that humans don’t experience anymore. But are there still small evolutionary changes taking place within our species?
With the genomic revolution in full swing, scientists now have the ability to track specific genes within populations and understand how humans are evolving, even in a very short period of time. A study conducted in Framingham, Massachusetts found that evolution still plays a role in the human population when it comes to reproductive ability. The study found that woman in the town who were shorter and more plump had more children on average and that if reproductive ability were to follow this trend, by 2409 the average woman in Framingham would be 2cm shorter and 1kg heavier on average. Of course, there are dozens of other factors that contribute to reproductive success and the researchers behind the study admitted that any number of events such as disease or even change in diet could change this evolutionary trend, but the fact that the trend was seen over several generations shows that an individuals’ ability to pass on their genes to the next generation plays a role in human evolution.
Of course, evolutionary changes such as the one in Framingham will always be heightened in isolated populations. This explains why blatantly obvious evolutionary changes are no longer present in humans, because we’ve turned into such a massive global population. Any new mutation will either be quickly bred out of the population, or will go unnoticed due to the sheer size of our gene pool. That being said, there are certain genetic variations that have become widespread throughout populations within the past generation alone. Those nearly 1,800 new variations include malaria resistance, a heightened ability to digest milk and even a difference in brain development in relation to an increase in technology use.
There has also been a general trend in genetic variation towards a “weaker” form. Evidence suggests that because we no longer have to hunt for our food, run from predators or exert ourselves physically every day, our genetics in that department have softened. We no longer show the muscular strength that our ancestors did and we’ve certainly lost the ability to sprint as quickly as our ancestors would have. Many have seen this as a sort of “de-evolving” for humans. It’s also why ancestral diets and work out regimes have become so popularized as of late, because our bodies used to be designed by evolution to function at peak performance, but modern lifestyle has switched those genes off. Regardless, humans are still evolving, albeit with much less environmental pressure. And while most geneticists have no solid understanding of where our evolution will take us in the next 10-200 years, many agree that massive advances in genetic medicine could make evolution completely obsolete for humans, but a cataclysmic event such as a plague could also bring evolution and natural selection back into the picture.
