As a species, humans have inhabited 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 in the Stone Age, when we fought over pieces of meat, but is it still applied?
We asked 12 experts if people are still developing. Expert consensus is unanimous “yes”, but scientists say we may have a misconception about what evolution really is.
Evolution is not the same as natural selection
Evolution is often used interchangeably with the phrases “survival of the fittest” or “natural selection.”
“Evolution” simply means a gradual change in population over time.
“Natural selection” is a mechanism by which evolution can take place. Our Stone Age ancestors, who were faster runners, avoided being trampled by mammoths and were more likely to have children. This is “natural selection”.
With overtime, the human population has become faster to work. This is evolution.
Evolution can happen without natural selection
This makes sense for the people of the Stone Age, but what about today? We don’t have to outrun mammoths, we have medicine when we are sick and we can go to the shops to get food.
Natural selection needs “selective pressure” (eg, dangerous trampling mammoths), so if we don’t already have them, does that mean we’re stopping evolving?
Even without pressure on selection, experts say that evolution is still carried out by other mechanisms.
Professor Stanley Ambrose, an anthropologist at the University of Illinois, 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 does not automatically equate to ‘improvement.’ “”.
While some genes may be affected by natural selection (eg, genes that help us work faster), other changes in our DNA may not have an obvious effect on us. “Neutral” variations can also spread through a population through 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 so the population will change.
Genetic drift does not need selection pressure, and it still does today.
Natural selection still happens in humans
As much as we have made things easier for ourselves, there is still pressure on the selection 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 producing an enzyme called lactase. In some countries, the population has acquired “lactase resistance”, which means that people produce lactase throughout their lives.
In European countries, we can thank a specific genetic variation for our lactase resistance called ‘-13910 * T’. Examining this specific gene variation in modern and ancient DNA samples, the researchers suggest that it became common after humans began to domesticate and milk animals.
This is an example of natural selection, in which we actually exerted the selection pressure ourselves – we started drinking milk, so we evolved to absorb it!
Another example of people subjected to natural selection to adapt to lifestyle is the Bajau people, who traditionally live in vessels in the waters of Southeast Asia and spend much of their lives diving to fish or to collect crustaceans.
Ultrasound revealed that Bajau people have larger spleens than their neighbors – an adaptation that allows them to stay underwater longer.
There is always selective pressure around us, even one that we create ourselves.
As Dr. Benjamin Hunt of the University of Birmingham says, “Our technological and cultural changes are changing the strength and composition of selection pressure in our environment, but there is still selection pressure.”
Evolution cannot be stopped
Thus, evolution can occur by various mechanisms such as natural selection and genetic drift. Because our environment is always changing, natural selection always happens. And even if our environment was “just right” for us, we would have evolved anyway!
Dr Alywyn Scally, an expert in evolution and genetics at the University of Cambridge, explains: “As long as human reproduction involves chance and genetic mutation (and the laws of the universe largely ensure that this will always be the case at some level), that there are differences from one generation to the next, which means that the process of evolution can never be truly stopped. “
Conclusion: Evolution means a change in the population. This includes both easily noticeable changes to adapt to the environment and more subtle genetic changes.
People are still evolving and this is unlikely to change in the future.
Article based on 12 expert answers to this question: Are people still evolving?
This expert response was published in partnership with the independent fact-finding platform Metafact.io. Subscribe to their weekly newsletter here.