Hungarian scientist Ádám Kun argues human population continues to evolve

Where the human species is headed and whether humanity is still evolving are tantalizing questions for scientists who study evolution as well as for non-specialists. 

To answer these questions, a Hungarian scientist has written a comprehensive conceptual guide using the knowledge of basic evolutionary genetics. Ádám Kun, an associate professor at Eötvös Loránd University in Budapest, dedicates his article to the professor who sparked his interest in evolutionary biology over many decades, Gábor Vida, on the occasion of his 85th birthday.

The article appears in the Jan. 2 issue of the journal Biologia Futura.

At the outset, Kun says that although he hasn't "seen any peer-reviewed publication claiming that human evolution has stopped," the view is often expressed by prominent scientists. One example he cites is Sir David Attenborough, who stated, "I think that we've stopped evolving."

Some basics of evolutionary biology

Kun begins his guide by presenting a basic definition of evolution as "change in the allele [genotype, genetic variation] frequencies of populations over time." He notes that many people think of evolution as big changes and dramatic extremes. He notes, however, that evolution is "infuriatingly unspectacular," even though it has produced some spectacular things.

Kun goes on to explain some basic evolution concepts, such as the difference between panmixis--random matings--and assortative mating, where couples share similar traits. He describes the lack of gene flow caused by population isolation, both cultural and spatial, as well as the difficulty of estimating the effect of genetic drift, a random process.

The size of the human population, currently 8 billion, is not as important as the size of the actual breeding population, when it comes to drift, he says.

Kun reviews the role of migrations on the gene flow, and the role of mutations. Given the number of babies born annually, 140 million, there are "roughly 9.8 billion new mutations entering the human population" yearly. Most of these are "neutral or deleterious," but there can also be novel mutations that are beneficial. 

Although, as he says, "We are not going to see the beneficial effect anytime soon," because these go unnoticed but they will still help humanity in the long run.

Natural selection and adaptation

By natural selection the traits more beneficial to human survival and reproduction tend to become more common over generations. Those who think that human evolution has stopped point to the marvels of modern medicine and its role in treating and curing diseases, thus removing differences in survival. 

But Kun says, “Most of humanity experiences the same selection pressure as our ancestors for thousands of years: pathogens, lack of food and the dangers of birth.” Consequently, he disagrees with those who think that medical advances and today's health care made natural selection obsolete.

Kun also reviews population differences in birth rate and the relationship of differential fecundity to selection for fitness. His point is that when women have many children, especially if they have the children early, this strongly influences selection by increasing the likelihood of their genes propagating.

Kun elaborates on specific adaptations that arise over thousands of years in response to the local environment. This includes populations who have adapted to cold climates, high altitudes, particular pathogen resistance and lactose digestion. Lack of enough food can still be a selection pressure in some regions of the world. 

Quo vadis humanity?

In the final section of the article, Kun discusses the challenges humanity faces, such as climate change, noting that he expects current evolutionary trends to continue and new evolutionary trends to emerge. He wonders about the prospect of "falling intelligence." On a more positive note, Kun expects that space travel and the colonization of the solar system and beyond will continue the process of adaptation to new environments and therefore evolution.

The article concludes, "Humanity is still evolving, and no amount of advanced technology will stop that. As a species, we can as well adapt to a post-apocalyptic world as to one in which we live more in harmony with mother nature. The choice is ours. The rest is done by the blind watchmaker.”

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Ádám Kun. "Is there still evolution in the human population?"  Biologia Futura, Jan. 2, 2023.

DOI: 10.1007/s42977-022-00146-z

An interview with Ádám Kun

Are humans still evolving?

Your article makes the case that humanity is continuing to evolve, and you provide readers with the scientific criteria supporting this. Can you elaborate on some of these for a non-specialist?

We established that instead of differences in survival, humans now mostly differ in the number of children they have. Survival somehow catches our imagination much more, as we see the "struggle for life" in it.

Big families are viewed favorably by society and not as a tool for our genes to compete for dominance in the next generation. But it does exactly that and, thus, this is a selective advantage.

Furthermore, evolution is not just about adaptation, which is the result of natural selection. For example there's "genetic drift," which can be understood as genetic differences between two populations due to purely random processes which have no consequence on fitness.

Many of the genetic markers that allow us to discover our ancestry are like this, non-consequential changes in our genetic makeup that rose to prominence (out of pure luck) in some part of the globe and not in others.

You use basic evolutionary genetics to explain why human beings are continuing to evolve. Why do you think some scientists simply assert that we've stopped evolving?

There are some misconceptions floating around about what is evolution, even among biologists. For an evolutionary biologist, it is undisputedly the "change in the frequency of a heritable trait over generations." 

For example after the mutation allowing lactose digestion into adulthood appeared, its frequency began to rise in the European population. Nearly everyone of British or Scandinavian descent is lactose tolerant now.

It is a heritable trait as it is coded in our genome, and the frequency of this trait changed (rose) over numerous generations. It is also an adaptation, as there was a strong selection acting on it. People who could drink milk without much adverse effect would survive more that those without this trait.

We can tell similar stories about other traits, which are adaptations through increased survival. Compared to the early 19th Century--when nearly 50% of children died before reaching the age of 5--nowadays every baby can expect to become an adult. This is generally true all across Earth now.

This marvelous development is not because of high-tech medical care, but very old-school hygiene, better nutrition and vaccination. The high survival rate to adulthood can give the false impression that there is no selection going on with humanity, and thus there could not be evolution.

But survival is simply one factor. There are still differences in the number of children we have. Actually, the difference (variance) between the number of children among people has become enormous. The average woman has around 1.5 children in Hungary. Anyone having three children has twice as many as the average. That is in itself a considerable selective advantage.

Where do you think evolution is leading humanity, in particular, how the colonization of the solar system opens up new possibilities.

There is no place like home. Any other celestial body, especially here in the solar system, is just a very poor substitute for Earth. Still, if people can live there, we will colonize these planets and moons.

Gravity is different. Blood travels differently in our body in lower gravity (this is extensively studied on astronauts). 

People on these colonies would have to endure this new environment. They might even be selected on how much they endure it. Here selection does not have to mean that some of the brave colonizers perish. They might just struggle for a while and then ask for a ticket back.

The ones remaining might be able to cope with the adverse effects of off-Earth environment better. And if the trait affording better endurance is heritable, i.e. written in our genes, then they pass it on to their kids. In some thousands of years there might be "Martians" who are more adapted to Mars compared to "earthlings."

When earthlings go for a vacation on Mars, they might feel a bit odd or might need to take some medications. The locals, on the other hand, will be in their then-already natural environment. We will still be the same species though.

Our evolution is fascinating, and we uncover more and more of it nearly every day. But our immediate future is not about how we evolve or not evolve but if we as a species can cope with the challenges ahead. Here we need to rely more on our brains than our genes.

Some definitions

Kun provided these basic definitions of elements involved in evolutionary genetics:

Migration is what we would think it is, people coming from elsewhere. For any locality or local population, the genetic composition can change by adding people who differ in some of their genes. Migration is an evolutionary process. It does not affect humanity as a whole. The same number of alleles (gene variations) are around. But if people mix, then new combinations of genes can come around.

Founder effect refers to when a new population is established. When humanity began to populate Earth, there were plenty such events. And whatever genetic variation was present in those people would be present in their offspring. Even if a genetic variation is present in, let's say, only 0.1% of the human population, but 10% of those founding a new population had that genetic variation, then it would be quite common there.

Mutation rate refers, for example, to the number of changes in our genome in one generation. There are around 70 such changes between any parent-children pair. It might sound high, but we get 3 billion bases from one of our parents. Out of those only 70 of these are changes.

Fecundity or fertility (the former used more in evolutionary biology, the latter in human demography) is the number of kids any given woman has.

Environment adaptation in a narrow sense is adaptation to the abiotic environment, be it cold or heat, lower oxygen pressure, greater humidity, etc. We also adapt to our pathogens, to our food, and to each other as well.