Extinct human species evolved rapidly to survive a period of climate change 2 million years ago

An ancient human species that lived two million years ago was forced to evolve and change its physical traits in order to survive climate change.

The emergence of Paranthropus robustus occurred around the same time as the more primitive hominid species Australopithecus were becoming extinct.

This period of rapid change in South Africa is believed to have occurred due to significant climate change forcing animals to adapt or die.

During this period, the first members of the genus Homo, from which modern humans are descended, also emerged.

Homo erectus and P. robustus have taken different approaches to the changing world, the former developing a large brain to make tools to tackle the problem of hard and chewy food sources.

The latter, however, underwent physical changes and developed larger teeth and powerful chewing muscles over 200,000 years – a rapidly scalable intervention.

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“ These two very different species, H. erectus with their relatively large brains and small teeth, and P. robustus with their relatively large teeth and small brains, represent divergent evolutionary experiences, ” said Angeline Leece of the University of La Trobe, the other first author of the study.

“While we were the lineage that eventually triumphed, the fossil record suggests that P. robustus was much more common than H. erectus in the landscape two million years ago.

Researchers have discovered a new fossil of the species P. robustus in the fossil-rich Drimolen cave system northwest of Johannesburg, in the so-called Cradle of Humankind.

They compared it to others of the same species that had been found before.

Existing theories claimed that there was great variance in the size of males and females of the species, a phenomenon known as sexual dimorphism observed in many living animals.

However, the new specimen, called DNH 155, which is clearly male and considered the best-preserved example of its species, dispels this.

Researchers, at the University of Washington in St. Louis and La Trobe University in Australia, now believe this illustrates how the species has physically changed.

One notable trait that has changed over time is his teeth.

Dr Leece says: “We now know that tooth size changes over time in the species, which begs the question of why.

“There is reason to believe that environmental changes have put these populations under food stress, and this points to future research that will allow us to test this possibility.

Existing fossils from when this species existed prove that mammals that depended on the woods and bush became extinct while other species associated with drier, more open environments first appeared in the region. .

P. robustus, which appeared at this time of flux, was built for arid conditions.

Professor David Strait, professor of biological anthropology at the University of Washington, says that, therefore, he was well suited for eating the hard foods that grew in this new climate.

“P. robustus is notable in that it possesses a number of characteristics in its skull, jaws and teeth indicating that it has been adapted to eat a diet consisting of very hard or very hard foods, ”he said. declared.

“We believe these adaptations enabled him to survive on foods that were mechanically difficult to eat as the environment changed to be cooler and drier, resulting in changes in local vegetation.

The researchers found that the first members of this species had chewing muscles that were weaker than their descendants.

Over 200,000 years, a dry climate has probably led to natural selection favoring the evolution of a more efficient and powerful feeding system for the species, ”explains Professor Strait.

The results are published in the journal Nature Ecology & Evolution.