A new study has revealed that climate change may have driven evolution by endowing our ancient ancestors with larger brains. The challenges of the Ice Age tested early humans’ ingenuity, accelerating natural selection. According to scientists, cold temperatures fostered “parental cooperation” and enhanced language skills in our early forebears.
Climate Change Challenges Accelerated Human Brain Evolution
Researchers found evidence of increased brain size in ancient hominins (our ancestors) corresponding with glacial phases over 600,000 years ago. The team developed a computer simulation to mathematically demonstrate how new mating habits and the “parental cooperation” necessary for survival during the inhospitable Ice Age “sped up” the evolution of the human brain.
The simulation indicated that hominins sought partners based on the growing importance of needs such as fire, food, and shelter to survive the deadly cold. The new mating habits, which researchers refer to as “positive assortative mating,” may have also contributed to the development of crucial human abilities, such as language communication and fire-making. Furthermore, the study suggests that greater ingenuity and willingness to cooperate among parents significantly helped our ancestors prevent deaths related to cold exposure, including hypothermia.
Sexual Selection Played a Role in Human Evolution
As noted by the lead author of the new study, economist Bruce Petersen, it has long been asserted that climate change was a significant driving force behind the evolution of hominins, with considerable focus on glacial phases.
Charles Darwin was one of the first to emphasize the importance of sexual selection in hominin evolution. However, his claims were largely ignored for over a century. In other words, the Ice Age improved the odds for intelligent parents who got along with each other and effectively taught their children.
Charles Darwin
Mr. Petersen utilized anthropological and climatic data to develop the simulation. He discovered that “periods of significant climate change,” beginning with the major glacial freeze 676,000 to 621,000 years ago, led to a time of increased sexual selectivity. It was during this period that “positive assortative mating” emerged.
According to the researcher, this means that partners were less specialized, partly because compatibility arises only when they work together. Mr. Petersen notes that an effective mating system became even more crucial as reliance on offspring increased and the harsh glacial phases began.
The modeling conducted by the research team pitted three categories of early humans against each other. The first group was the smartest but physically weak, the second was “intermediate,” and the third was the strongest but least intelligent. The mathematical models revealed that positive assortative mating among pairs from the first category not only produced the fittest offspring but often was the only pairing with enough children for their genes to survive during the harsh glacial freeze.
An Economic Approach to Evolutionary Theory
As Mr. Petersen points out, many scientists argue that the immense advantages of both language and fire would exert strong selective pressure on such behaviors. Using economic models, the researcher described them as “home-produced family public goods” that “require production,” including fire, language, shelter, and child-rearing.
According to the Daily Mail, the new study also suggests that survival pressures from climate change could have stimulated physical changes (in height, weight, strength), reducing “dimorphism” or differences in body structure between sexes. Moreover, researchers believe that family economics, particularly the focus on assortative mating, could be beneficial for future studies on the evolution of sexual dimorphism in other early human ancestors.
Mr. Petersen believes that the extraordinary challenges of the Ice Age were a key example of how “positive” natural selection, meaning the choice of shared parenting, had a greater impact on human evolution than “negative” natural selection through deaths and competition.
He also notes that this study applies fundamental economic principles that are rarely used to explain the evolution of human ancestors. According to the researcher, sexual selection and parental cooperation, combined with severe glacial phases, helped stimulate the intelligence of hominins during the Middle Pleistocene.