Wednesday, April 20, 2022

Our Early Years

Environmental & Science Education, STEM, Anthropology, Nature of Science, History of Science, Biological Evolution, Climate Change, Global Change

Ed Hessler

There is now evidence that climate change played a role in the evolution of humans according to a post  in NatureBriefing for April 13, 2022. It is based on "a record-breaking simulation (see below) that temperature and other planetary conditions influenced early human migration -- and possibly contributed to the emergence of the modern-day human species around 300,000 years ago."

Freda Kreier wrote a short story about it in Nature with a more modest subtitle, one I prefer. "model suggests that a shift in weather patterns in southern Africa might have contributed to the rise of Homo sapiens" (that's us). The article has a link to the research paper in Nature, available to read, including a PDF. It is technical but you may be interested in parts of this paper.

Among the items included in Kreier's reporting are the following. The idea is not new. You may recall the debate about "walking on two feet, to adapt to life on the savanna." However, the evidence is not strong at all.

The computer climate model - took a supercomputer six months for the reconstruction of the influence of "temperature and rainfall might have shaped" available resources "to humans over the past few million years." The model's focus is on the earth's orbit during this time." Earth is subject to "the push and pull of other planets "changing both the planet's tilt, and the shape of its orbit. These occur in well known cycles of 40,000 and 100,000 years and the planet's orbit changes from "having a more circular orbit -- which brings more sunlight and longer summers -- to having a more elliptical orbit, which reduces sunlight and can lead to periods of glacial formation."

You can imagine the amount of data generated in a "simulation that incorporated these astronomical changes, and combined their results with thousands of fossils ... to work out where and when six species of humans...could have lived." Kreier quotes the lead researcher, Axel Timmerman on what they found. "'The global collection of skulls and stools is not randomly distributed in time. It follows a pattern."

You'd be also right in thinking that not everyone agrees. Kreier notes that Tyler Faith's response to the research was "'To make the case that a particular climate event led to a speciation event is really hard.'" Kreier continues that this is due "in part because of gaps in the fossil and genetic record."

Kreier closes this fascinating bit of reporting by writing "Most researchers that spoke to Nature say that more evidence will be needed to prove that astronomical cycles influenced the trajectory of human ancestry. 'If solving the mystery of climate change and human evolution could be dealt with in one paper, it would have been done 40 years ago,' Faith says.

"Which is why Timmermann and his colleagues are planning to run even larger models, including ones that integrate genetic data."

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