|Themes > Science > Life Sciences > Physical Anthropology > Human Organic Evolution > Climate Changes and Human Evolution|
Researchers examining deep-sea sediments off the coast of Namibia, West Africa, have found evidence that global cooling of 10 degrees Celsius -- five times greater than was previously believed -- has occurred since 3.2 million years ago.
The discovery adds weight to the theory that climate change played a significant part in the evolution of early humans.
Dr. Jeremy Marlow, of Newcastle University's Department of Fossil Fuels and Environmental Geochemistry, who led the team of English, American and German scientists, said:
"There have been arguments for many years about whether the emergence of our ancestors was linked to climate change. By looking at the molecular fossils of microscopic marine algae, we began to discover evidence of a 10 degree fall in temperature in the region of Africa where much of the early human fossil evidence has been discovered.
"We didn't believe it at first, but further tests kept producing similar results until we had to conclude that temperatures really had decreased so dramatically."
The scientists, from the Universities of
Newcastle, Durham, California and Bremen, found that cooling was
particularly rapid about 2 million years ago -- at the time when the first
ancestors of modern humans emerged in sub-tropical southern Africa.
By examining the rate of sediment
deposition and the levels of organic carbon within the sediments, the
researchers obtained evidence of a well-defined cycle in which a cooling
atmosphere causes increased upwelling of nutrient-rich deep waters in
specific parts of the oceans, leading to increased biological uptake of
carbon dioxide from the atmosphere, which then cools further, causing more
upwelling and uptake of carbon dioxide.
(Editor's Note: This news story is based on an article in Science concerning factual findings. That article did not discuss the implications for human evolution.)