As a species, humans have populated almost every corner of the earth. We have developed technologies and cultures that shape the world we live in.
The idea of ”natural selection” or “survival of the fittest” seems to make sense back in the Stone Age, when we were fighting over scraps of meat, but does it still apply now?
We asked 12 experts if humans are still evolving. The consensus of experts is unanimously “yes”, however scientists say that we may have a wrong idea of what evolution actually is.
Evolution is not the same as natural selection
Evolution is often used interchangeably with the phrases “survival of the fittest”
“Evolution” simply means the gradual change of a population over time.
“Natural selection” is a mechanism by which evolution can take place. Our fastest-running Stone Age ancestors avoided being trampled by mammoths and were more likely to have children. This is “natural selection”.
Over time, the human population has gotten faster running. This is evolution.
Evolution can happen without natural selection
This makes sense for Stone Age humans, but what about modern day? We don’t need to outrun mammoths, we have medicine for when we’re sick, and we can go shopping for food.
Natural selection needs “selective pressure” (eg Dangerous mammoths trampling), so if we don’t have them anymore, does that mean we stop evolving?
Even without selective pressures, experts say evolution still happens with other mechanisms.
Professor Stanley Ambrose, a University of Illinois anthropologist, explains that “any change in the proportions of genes or gene variants over time is also considered evolution. Variants can be functionally equivalent, so evolution is not automatically equated with ‘improvement’ “.
Although some genes may be influenced by natural selection (eg genes that help us run faster), other changes in our DNA may not have any noticeable effect on us. “Neutral” variations can also spread across a population by a different mechanism called “genetic drift”.
Genetic drift works by accident: Some individuals may be unlucky and die for reasons that have nothing to do with their genes. Their unique genetic variations will not be passed on to the next generation and therefore the population will change.
Genetic drift does not require selective pressure, and it is still happening today.
Natural selection is still happening in humans
As much as we have made things easier for ourselves, there are still selection pressures around us, which means that natural selection is still happening.
Like all mammals, humans lose the ability to digest milk when they stop breastfeeding. This is because we stop making an enzyme called lactase. In some countries, the population has acquired “lactase persistence,” which means that people produce lactase for life.
In European countries we can thank a specific gene variation for our lactase persistence, which is called “-13910 * T”. By studying this specific genetic variation in ancient and modern DNA samples, the researchers suggest it became common after humans began domesticating and milking animals.
This is an example of natural selection where we actually exert selection pressure ourselves – we started drinking milk, then evolved to digest it!
Another example of humans undergoing natural selection to adapt to a lifestyle is the Bajau people, who traditionally live in houseboats in Southeast Asian waters and spend much of their life diving to hunt for fish or gather. crustaceans.
The ultrasound found that Bajau people have larger spleens than their neighbors, an adaptation that allows them to stay underwater longer.
There are always selective pressures around us, even the ones we create ourselves.
As Dr Benjamin Hunt of the University of Birmingham states, “Our technological and cultural changes alter the strength and composition of the selective pressures within our environment, but the selective pressures still exist.”
Evolution cannot be stopped
Hence, evolution can occur through different mechanisms such as natural selection and genetic drift. As our environment is constantly changing, natural selection always happens. And even if our environment were “right” for us, we would still evolve!
Dr Alywyn Scally, an expert in evolution and genetics at the University of Cambridge, explains: “As long as human reproduction involves randomness and genetic mutation (and the laws of the Universe practically guarantee that this will always be the case at some level), they will continue. there are differences from one generation to the next, which means that the process of evolution can never really be stopped “.
Takeaway: Evolution means change in a population. This includes both easy-to-spot modifications to suit an environment and more subtle genetic changes.
Humans are still evolving and this is unlikely to change in the future.
Article based on 12 expert answers to this question: Are humans still evolving?
This expert response was published in collaboration with the independent fact-checking platform Metafact.io. Sign up for their weekly newsletter here.