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Climate change may have given ancient human ancestors bigger brains, study finds


Climate change may have boosted humanity’s evolution by giving humanity’s ancestors bigger brains, a new study suggests.

Researchers at Washington University in St. Louis found increases in brain size of ancient hominids (ancestors of humanity) aligned with the glacial phases more than 600,000 years ago.

The team developed a computer simulation to show mathematically how the new mating habits and “parental cooperation” required to survive during a harsh Ice Age would have “accelerated” the evolution of the human brain.

The simulation suggested that hominids sought similar mates due to the increasing importance of necessities such as fire, food and shelter in order to survive the deadly cold.

The new mating habits, which the researchers call “positive selective mating,” could also have helped improve critical human skills, such as the development of language and fire-based communication.

The team at Washington University in St Louis developed a computer simulation to show, mathematically, how the new mating habits and “parental cooperation” needed to survive during a harsh Ice Age would have “accelerated” the evolution of the human brain.

In addition, greater ingenuity and a willingness to cooperate among parents, according to their study, would have greatly helped humanity’s ancestors prevent cold-related deaths, including hypothermia.

“It has long been argued that climate change was a major driver of hominin evolution, and considerable attention was paid to glacial phases,” according to the lead author of the new study, economist bruce petersen.

In The Descent of Man, and Selection in Relation to Sex, Charles Darwin placed great emphasis on sexual selection for hominid evolution,” Petersen said.

“However, its role as an evolutionary force was largely ignored for more than a century.”

In other words, an Ice Age truce in the war between the sexes improved the chances of intelligent parents who got along with each other and taught their children well.

Using anthropological and climate data to develop the simulation, Petersen found that “periods of severe climate change” beginning with a great glacial freeze 676,000 to 621,000 years ago would have led to a period of increased sexual fussiness.

This ‘Ice Age within an Ice Age’, termed MIS 16 after the marine isotopes used to identify it, would have led to what Petersen calls ‘positive selective mating.’

“This means that the partners are less specialized,” Petersen said, “in part because complementarities arise only when the partners work together.”

“An efficient mating system undoubtedly became increasingly important with the prolongation of offspring dependency and the onset of severe glacial phases,” he noted.

The research team’s simulation pitted three categories of primitive men against each other: first, a group that was the most intelligent but physically weak, a second ‘intermediate’ group, and lastly, a third that was the strongest but least intelligent. .

Their mathematical models found that positive selective mating of pairs in the first category not only produced the fittest offspring, but was often the only pairing with enough offspring for their genes to survive the brutal glacial freeze.

“Many scientists have argued that the enormous advantages of both language and fire would have exerted strong selective pressures on these behaviors,” Petersen said.

Using economic models, Petersen described them as ‘home-produced family public goods’ that were ‘demanding to produce’ and included fire, language, housing and child training.

The new research also suggests that survival pressures due to climate change may have caused physical changes, reducing ‘dimorphism’, or body differences between the sexes.

“Finally, this paper suggests that family economics, particularly the focus on selective mating, may be useful for future research on the evolution of sexual dimorphism in Homo (early hominids in general, not just Homo sapiens or other )”.

“One prediction from the model in this paper,” Petersen noted, is a “decrease in body size dimorphism.”

These changes in the difference based on sex (height, weight, and strength)’ may have continued well into the time period of Homo heidelbergensis: an extinct species of humans known from fossils dating to 600,000 to 200,000 years ago in Africa, Europe and possibly Asia. ,’ he said.

Petersen believes that the extreme hardships of the Ice Age were a key case in which ‘positive’ natural selection, i.e. co-parenting choices, had a greater impact on human evolution than ‘negative’ natural selection, of deaths and competition.

“The paper applies basic economic principles, which are rarely used to explain human evolution before Homo sapiens,” Petersen added.

“Sexual selection and parental cooperation, along with severe glacial phases, helped drive hominin intelligence in the Middle Pleistocene.”

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