Archives par mot-clé : Science

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Key phases of human evolution coincide with flickers in eastern Africa’s climate

by University of Cologne, Sep 26, 2022 in ScienceDaily

Three distinct phases of climate variability in eastern Africa coincided with shifts in hominin evolution and dispersal over the last 620,000 years, an analysis of environmental proxies from a lake sediment record has revealed. The project explores the youngest chapter in human evolution by analysing lacustrine sediments in close vicinity to paleo-anthropological key sites in eastern Africa using scientific deep drilling. The research endeavour included more than 22 researchers from 19 institutions in 6 countries, and was led by Dr Verena Foerster at the University of Cologne’s Institute of Geography Education. The article ‘Pleistocene climate variability in eastern Africa influenced hominin evolution’ has now appeared in Nature Geoscience.

Despite more than half a century of hominin fossil discoveries in eastern Africa, the regional environmental context of the evolution and dispersal of modern humans and their ancestors is not well established. Particularly for the Pleistocene (or Ice Age) between 2,580,000 to 11,700 years ago, there are no continuous high-resolution paleo-environmental records available for the African continent.

The research team extracted two continuous 280-metre sediment cores from the Chew Bahir Basin in southern Ethiopia, an area where early humans lived and developed during the Pleistocene. Chew Bahir is very remotely situated in a deep tectonic basement in close vicinity to the Turkana area and the Omo-Kibish, key paleo-anthropological and archaeological sites. The cores yielded the most complete record for such a long period ever extracted in the area, revealing how different climates influenced the biological and cultural transformation of humans inhabiting the region.

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Journal Reference:

Verena Foerster, Asfawossen Asrat, Christopher Bronk Ramsey, Erik T. Brown, Melissa S. Chapot, Alan Deino, Walter Duesing, Matthew Grove, Annette Hahn, Annett Junginger, Stefanie Kaboth-Bahr, Christine S. Lane, Stephan Opitz, Anders Noren, Helen M. Roberts, Mona Stockhecke, Ralph Tiedemann, Céline M. Vidal, Ralf Vogelsang, Andrew S. Cohen, Henry F. Lamb, Frank Schaebitz & Martin H. Trauth. Pleistocene climate variability in eastern Africa influenced hominin evolution. Nature Geoscience, 2022 DOI: 10.1038/s41561-022-01032-y

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David Attenborough gets a namesake: the oldest known relative of living animals

by T. Joose,  July 25, 2022, in Science

If you visited the oceans more than 500 million years ago, you’d find yourself in an alien world. Beings with quilted folds of soft tissue sat on the seabed like rugs, and life forms that looked like fronded plants but were actually animals made anchor on the ocean floor. But one organism might be somewhat familiar: a stalked, cuplike creature with waving tentacles resembling those of a jellyfish. The newly described fossil of this organism, named Auroralumina attenboroughiiafter naturalist and broadcaster David Attenborough, is between 556 million and 562 million years old and may be the oldest example of an evolutionary group still living today.

When co-author and University of Oxford paleobiologist Frances Dunn saw a cast of the fossil, she says, “It was instantly clear that this was really special and really rare.” With other fossils from the Ediacaran period, between 635 million and 541 million years ago, her first impression often is “What is this? How can I relate this to anything that’s alive today?” But with this specimen, she thought, “I know what this is.”

Classical scientific wisdom places the origin of modern animals about 539 million years ago during what’s called the Cambrian explosion. At this time, creatures with specialized tissues, organs, guts, and symmetrical left and right sides—all traits we recognize in the animals of today—began popping up.

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