Fluctuating environment may have driven human evolution


A series of rapid environmental changes in East Africa roughly 2 million years ago may be responsible for driving human evolution, according to researchers at Penn State and Rutgers University. “The landscape early humans were inhabiting transitioned rapidly back and forth between a closed woodland and an open grassland about five to six times during a period of 200,000 years,” said Clayton Magill, graduate student in geosciences at Penn State. “These changes happened very abruptly, with each transition occurring over hundreds to just a few thousand years.”

According to Katherine Freeman, professor of geosciences, Penn State, the current leading hypothesis suggests that evolutionary changes among humans during the period the team investigated were related to a long, steady environmental change or even one big change in climate.

“There is a view this time in Africa was the ‘Great Drying,’ when the environment slowly dried out over 3 million years,” she said. “But our data show that it was not a grand progression towards dry; the environment was highly variable.”

According to Magill, many anthropologists believe that variability of experience can trigger cognitive development.

“Early humans went from having trees available to having only grasses available in just 10 to 100 generations, and their diets would have had to change in response,” he said. “Changes in food availability, food type, or the way you get food can trigger evolutionary mechanisms to deal with those changes. The result can be increased brain size and cognition, changes in locomotion and even social changes — how you interact with others in a group. Our data are consistent with these hypotheses. We show that the environment changed dramatically over a short time, and this variability coincides with an important period in our human evolution when the genus Homo was first established and when there was first evidence of tool use.”

Written By: e! Science News
continue to source article at esciencenews.com


  1. Humans are omnivorous and very adaptable. These traits do not arise or become selected for, in a long-term-settled stable environment!

  2. The evolution of culture and cultural wisdom is a key mechanism I would guess allowing the reliable and rapid evolution of new survival strategies. This would co-opt the mammalian invention of mirror neurons to help copy skilled others, and indeed we see a significant uplift in their numbers in hominims. But another mechanism is required to make this turn-on-a-sixpence cultural evolution possible. Brains whilst needing more capacity for greater motor skills need to be less pre-wired to more readily learn this generations answers. We have to become less grown up at birth, more neotenous.

    And here’s the thing. This makes us more dependent, less capable at birth, which in turn demands cultural coping strategies. Like no other ape humans share the child rearing burdens. This demands co-operation involving very high degrees of trust between unrelated individuals. In developing the capacity for sophisticated, rapidly evolving and problem solving culture, with the new vulnerabilities it creates, we need a sophisticated co-operative culture right from the start.

    Though we are not blank slates, we are more so than any other creature before us, more loaded with potential. And it is interesting to contemplate how this cultural evolution might be proceeding.

    It is a thesis of mine, which I would love to develop further that the Industrial Revolution occurred first in Britain because it was at a time when childhood could really be said to have been invented. At least for the middling, merchant classes children were broadly educated. They had leisure time rather than being put to work. They had books and toys commercially supplied and had four times the amount spent on them than in other countries. French and other visitors were generally appalled at this indulgence. My thesis has it that extended play, education and the confidence that comes from an extended period of nurturing combine to yield the people who can take such big cultural strides. The cultural investment in our children pays dividends like no no other.

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