It was once thought by scientists that variations in climatic factors played a major role in the evolution of hominins (modern and extinct humans). However, recent studies from the University of Cambridge have revealed that the hominin evolution may have been primarily driven by interspecies competition instead of climatic factors. The study was conducted by Dr Laura van Holstein, a biological anthropologist from Clare College and her team. The rate at which new hominin species evolved over a period of five million years has been examined in new research that was published in a peer-reviewed journal, viz., Nature Ecology & Evolution.
What the Study Says
A different narrative has been revealed from the new findings, which suggest that the competition between several hominid species was a very crucial evolutionary force. Till now, this evolutionary competition between species was ignored by the scientists. Instead, climatic factors on hominin species used to be considered as the only factor of human evolution. According to the new research, early human species saw an initial spike in evolution as they adapted to fill different environmental niches, just like vertebrates. They found this speciation in our lineage which is unlike almost anything else.
According to researchers, as the ecological niches were eventually plateaued, this phase of rapid diversity eventually came to a saturation. Competition among species led to increased rates of extinction. The pattern of early human evolution is almost identical to that of mammals. This bizarre evolution of the group ‘Homo’ or ‘man’ in the generic sense of ‘human being’ or ‘mankind’ included modern-day humans and emerged around two million years ago with Homo habilis (handy man), an extinct species of archaic human from the Early Pleistocene of East and South Africa about 2.8 to 1.65 million years ago.
Early Pleistocene refers to an unofficial sub-epoch, representing the earliest division of the Pleistocene Epoch within the ongoing period—the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS (International Commission on Stratigraphy)
Significance of the Study
This study completely reversed the trend of speciation, the more species of Homo there were, the higher the rate of speciation was. Thus, after those niches were occupied, something prompted the emergence of more species. Speciation rates increase and then flatline, and at this point extinction rates start to increase. In the field of evolutionary science, this is nearly unmatched. The closest analogy that could be seen is in the species of beetles that inhabit islands, where isolated habitats could give rise to peculiar evolutionary patterns.
Database of All Hominin Species
The researchers have created a database of every hominin species found and dated so far, which consists of 385 records in total. By modelling, the researchers aim to overcome the gaps in the fossil record. This helped them calculate the dates for the emergence and extinction of species.
According to the researchers, a number of species must have evolved through anagenesis.
Anagenesis is an evolutionary process when one species slowly transforms into another species. In other words, the new species would have budded from the existing ones and thus the species continue to exist. For instance, the hominin species Australopithecus afarensis (an extinct species of australopithecine which lived from about 3.9–2.9 million years ago in the Pliocene of East Africa) was believed to have evolved from Australopithecus anamensis (is a hominin species that lived approximately between 4.2 and 3.8 million years ago) through anagenesis. However, the model suggests that they would have been overlapped by about half a million years.
Probably, early hominins may have evolved to fill a larger niche. For instance, Paranthropus may have adjusted their teeth to eat a variety of foods approximately 2.9 and 1.2 million years ago.
Paranthropus is a genus of extinct hominin which contains two widely accepted species: P. robustus and P. boisei.
However, the Homo species pattern indicates that technology would have been more significantly important in the process of their speciation. Technology may have also contributed to the rise of Homo sapiens and the eventual extinction of all other earlier species of Homo.
Conclusion
According to van Holstein, our evolutionary tree is so weird because it has something to do with the use of technology. Adoption of stone tools or fire, or intensive hunting techniques are extremely flexible behaviours. Therefore, a species that could tackle them could swiftly find place in new niches and did not have to survive vast tracts of time while evolving new body plans.
This study has thrown light on the paradox where the presence of more Homo species drove the evolution of even more species within this genus in contrast to other vertebrates. Use of technology enabled our ancestors to compete for space and resources across different niches and ultimately led them to rise above other species. Those who could not, went extinct. And lastly, this very rule holds good even today—Survival of the fittest.
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