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Sci Tech
Tectonics and human evolution
Scientists long have focused on how climate and vegetation allowed human ancestors to evolve in Africa. Now, University of Utah geologists are calling renewed attention to the idea that ground movements formed mountains and valleys, creating environments that favored the emergence of humanity.
“Tectonics [movement of Earth’s crust] was ultimately responsible for the evolution of humankind,” Royhan and Nahid Gani of the university’s Energy and Geoscience Institute write in the January, 2008, issue of Geotimes, published by the American Geological Institute.
Blocked moisture
They argue that the accelerated uplift of mountains and highlands stretching from Ethiopia to South Africa blocked much ocean moisture, converting lush tropical forests into an arid patchwork of woodlands and savannah grasslands that gradually favoured human ancestors who came down from the trees and started walking on two feet – an energy-efficient way to search larger areas for food in an arid environment.
Changed landscape
“Because of the crustal movement in East Africa, the landscape changed over the last 7 million years,” says Royhan Gani a research assistant professor of civil and environmental engineering.
“That landscape controlled climate on a local to regional scale and in turn spurred human ancestors to evolve from apes.” Hominins – the new scientific word for humans (Homo) and their ancestors (including Ardipithecus, Paranthropus and Australopithecus) – split from apes on the evolutionary tree roughly 7-4 million years ago.
Superplume
The tectonic forces shaping Africa begin deep in the Earth, where a “superplume” of hot and molten rock has swelled upward for at least the past 45 million years.
This superplume helped push apart the African and Arabian tectonic plates of Earth’s crust, forming the Red Sea, Gulf of Aden and the Great Rift Valley.
“Although the Wall of Africa started to form around 30 million years ago, recent studies show most of the uplift occurred between 7 and 2 million years ago, just about when hominins split off from African apes, developed bipedalism and evolved bigger brains,” the Ganis write. — Our Bureau
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