The emergence of humans is an important turning point in evolution, or at least it seems so to us. Not only do we want an explanation for our existence, but we want that explanation to be sufficiently prominent and legendary.

A new study reveals an unexpected topic about human evolution. In a word, competition between members of the human race seems to have given rise to new species. It’s weird and complicated, but it doesn’t negate some of the existing stories about our origins. In short, this is the story of how evolution works.

The study cited was published in April in the journal Nature Ecology & Evolution by Laura van Holstein and Robert Foley of the University of Cambridge. They tried to find out why the new species of hominid evolved.

In other groups of animals, evolution usually follows recognizable patterns. One of these patterns is speciation dependent on negative diversity; It means that if there are many species in a group, the possibility of creating new species in that group is less.

Suppose there are many different species of sparrows living in an area. There are many ways to live as a sparrow, and the existing species go all of them. Therefore, new sparrow species rarely evolve. But if there are only one or two species, there are many opportunities, so they may become abundant new species.

The described rule is not absolute, a study from 2023 showed that the said rule is not true in many animal groups. But for some groups, such as birds, there is acceptable evidence to support it. So Van Holstein and Foley wondered if the same was true for hominins. If many anthropogenic species live in an area, does it become less likely that new species will emerge?

The researchers focused on three genera (orders) of anthropoids. The first genus is Australopithecus, or Southern Copy, which includes a variety of hominids that lived in Africa about 4 million to 2 million years ago. Second, it was paranthropus or populous; A small-brained hominid that survived into the age of large-brained hominids and is the third human lineage, which includes our species as well as famous species such as Neanderthals and Flores. Four other hominin genera were excluded due to lack of data; Because there were not enough samples to ascertain the duration of existence or the number of species of each genus.

Van Holstein and Foley used two data sets to estimate how speciation changed. One was the family tree of the anthropoids, which showed how different species were related. Another thing was the fossils and their approximate age. Both datasets had shortcomings and large uncertainties, but yielded the same results.

In Australopithecus and Paranthropus, greater species diversity means fewer new species evolved. According to Van Holstein, this is the classic pattern that exists. But in the human race, this process is reversed and we see speciation dependent on positive diversity.

The above pattern is unusual. Similar patterns have been confirmed in only a few species, such as cockroaches that live on islands. Therefore, it seems that the dynamics of evolution in the human genus is significantly different from the pattern of evolution of other anthropoid species and is generally unusual in the animal kingdom.

What is the reason for this? There are several possible explanations. One possibility is range expansion. As far as we know, the human race was the first human species to spread beyond Africa. This could have created many opportunities and helped form new species: think Luzonian Man in the Philippines and Floresian Man on the island of Flores in Indonesia.

Why did members of the human race manage to expand their range, while other hominids did not? Wasn’t it because they made more or better tools?

Technology can also be part of the explanation for the evolution of new species. Species that were able to develop new tools, for example by accessing food that others could not, were able to occupy new habitats.

“I don’t think dispersion explains everything,” Van Holstein says. Speciation is seen in places where other members of Homo are present.

The actions of one human species could also create a habitat for others. Think of water dogs that manipulate their environment by building dams and thus changing the flow of rivers, creating new habitats for insects and other creatures in the process.

If a species of the human race hunted large animals or cut down certain plants, it could create new spaces and opportunities for the evolution of anthropoids. “It changed the landscape and created new dimensions for other people’s lives,” says Van Holstein.

It is difficult to understand the role of each of these factors. But it is clear that the interactions between intelligent people were important not only for the fate of individual populations, but also for the emergence of new human species, including ourselves.

How can we fit interspecies competition in the human genus into the larger story of human evolution? We should also think about the other dominant explanations that have been offered for the fossil record of hominids.

Many of these explanations have to do with the environment: something in the environment changed and this forced hominids to adapt, which led to the evolution of diploidy or larger brains or other traits. One of the famous versions of these environmental narratives is the savannah hypothesis.

However, the savannah hypothesis has been challenged by the reconstruction of past ecosystems. The expansion of African savannas began before the existence of humans, and many habitats were a mixture of grasslands and forests.

A 2014 paper in its title questioned whether the Savannah hypothesis is a dead concept. However, he concluded that the answer is no, provided you accept that the savanna was not an absolute grassland, but rather a combination of habitats.

In the 1980s, Yale University paleontologist Elizabeth Verba proposed the idea that extreme environmental changes could cause waves of extinction. He suggests that the cold climate two to three million years ago caused the rapid extinction of African mammals and led to the evolution of new species, including hominins. Again, the reconstruction data of past environments contradicts this hypothesis.

In the 1990s, Richard Potts of the National Museum of Natural History in Washington put forward an argument in support of the above hypothesis. The idea here is that Africa’s climate became more unpredictable, so hominins had to adapt to this variability. The best way to do this is to become more adaptable, for example by becoming smarter and more innovative.

If all of the above ideas sound reasonable, that might be because they really are. A 2015 review suggested that multiple evolutionary mechanisms operated on hominins.

This is where Van Holstein and Foley’s study comes in. If hominids faced evolutionary pressures ranging from savanna expansion to unpredictable climates, then interspecies competition must be added to the mix.

So, here we are with a story about the evolution of humanity that has several aspects. Old ideas like the Savannah Hypothesis have the simplicity of a classic myth, which is fascinating and incomplete at best. But the story we are telling is more like the novel “A Song of Ice and Fire” by George R. R. Martin is: too long, too many characters, too many subplots, and so far painfully unfinished.