Geoscientist Prof. A. Cohen and his team combined records of climate change during the last 3.5 million years with fossil evidence of mammals in Africa revealing that times of erratic climate change are not followed by major upheaval in evolution.

April 12, 2022

Figure caption:  Processing drill cores in the field: Here, Veronica Muiruri, one of the study's co-authors (left), and Andrew Cohen (background) label a freshly sealed sediment core sample from Lake Magadi in Kenya.  Anne Billingsley

University of Arizona Geoscientist Prof. A. Cohen and his team have investigated the climatic drivers of environmental variability and its influence on mammalian macroevolution in Africa during the past 5 million years.  Environmental variability had previously been widely discussed as a possible driver of mammal evolution and extinction, including that of humans and our close relatives, the hominins, referred to as the variability selection hypothesis. Cohen’s team’s results reveal a long-term trend of increasing variability since about 3.7 million years ago, as well as a 400.000 year frequency correlation with seasonal insolation variability. However, using data of fossils of many species from East Africa and after accounting in their analysis for sampling variation, they do not find any statistically significant correlation between environmental variability and speciation and extinction rates in fossil mammals, as the variability selection hypothesis predicts. Their results appear in the Journal Proceedings of the National Academy of Sciences.

University of Arizona Communications features an interview with Prof. A. Cohen in this week's University of Arizona News by Daniel Stolte.

Kiriaki Xiluri
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