Human responses to hydroclimate fluctuations over the last 200 kyr in Ethiopia
2020-03-09

&amp;lt;p&amp;gt;&amp;lt;span&amp;gt;Humans &amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;have been adapting to more demanding habitats in the course of their evolutionary history&amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;. &amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;Nevertheless&amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;, environmental changes coupled with overpopulation naturally limit competition for resources. In order to find such limits, reconstructions of climate and &amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;population changes &amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;are increasingly used for the continent of our origin, Africa.&amp;lt;/span&amp;gt; &amp;lt;span&amp;gt;However, &amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;continuous and high-resolution records of climate-human interactions are still scarce. &amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;span&amp;gt;Using a 280 m sediment core from Chew Bahir*, a wide tectonic basin in southern Ethiopia,&amp;lt;/span&amp;gt; &amp;lt;span&amp;gt;we reconstruct the paleoenvironmental conditions during the development of &amp;lt;em&amp;gt;Homo sapiens.&amp;lt;/em&amp;gt; The complete multiproxy record of the composite core covers the last ~600 ka &amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;, allowing tests of hypotheses about the influence of climate change on human evolution and technological innovation from the Late Acheulean to the Middle/Late Stone Age, and on dispersal within and out of Africa&amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;. &amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;span&amp;gt;Here we present results from the uppermost 100 meters of the Chew Bahir core, spanning the last 200 kiloyears (ka). &amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;The record shows two modes of environmental change that are associated with two types of human mobility. The first mode is a long-term trend towards a more arid climate, overlain by precession-driven wet-dry alternation. Through comparison with the archaeological record, humid episodes appear to have led to the opening of &amp;amp;#8216;green&amp;amp;#8217; networks between favourable habitats and thus to increased human mobility on a regional scale. The second mode of environmental change resembles millennial-scale Dansgaard-Oeschger and Heinrich events, which seem to coincide with enhanced vertical mobility from the Ethiopian rift to the highlands, especially in the time frame between ~65&amp;amp;#8211;21 ka BP. The coincidence of climate change and human mobility patterns help to define the limiting conditions for early &amp;lt;em&amp;gt;Homo sapiens&amp;lt;/em&amp;gt; in eastern Africa.&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;span&amp;gt;___________________&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;lt;span&amp;gt;*&amp;lt;/span&amp;gt; &amp;lt;span&amp;gt;cored in the context of HSPDP (&amp;lt;em&amp;gt;Hominin Sites and Paleolakes Drilling Project&amp;lt;/em&amp;gt;) and CRC&amp;amp;#160;&amp;lt;/span&amp;gt;&amp;lt;span&amp;gt;(&amp;lt;em&amp;gt;Collaborative Research &amp;lt;/em&amp;gt;&amp;lt;em&amp;gt;Centre&amp;lt;/em&amp;gt;) 806 &amp;amp;#8220;&amp;lt;em&amp;gt;Our way to Europe&amp;lt;/em&amp;gt;&amp;amp;#8221;&amp;lt;/span&amp;gt;&amp;lt;/p&amp;gt;