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At present, the influence of man in the current process of climate change. However, there are other natural phenomena that can alter conditions on Earth, including variations in our planet’s orbit: in the beginning, the ‘journey’ around the Sun was much more circular; but it gradually became a much flatter ellipse, giving rise to changes in solar radiation at different points. This fact led to a series of changes in the climate that, according to a study recently published in ‘Nature’, were critical in the course of the evolution of our species and in its path to conquer the entire globe.
The research, carried out by an international group of scientists led by the German physicist and climate oceanographer Axel Timmermancombined climate data and information provided by prehistoric human fossils and their tools from up to two million years ago.
The authors wanted to know if the climate determined by astronomy influenced when and where our ancestors lived, as well as the role this variable played in human evolution.
“This ‘celestial clock’ determined how much radiation reaches each part of our planet, creating glacial cycles and large-scale changes in the tropics, causing alternating dry and wet periods over time,” explains Timmermann. In turn, these changes determined the amount of food available to our ancestors, causing species to migrate and adapt.
A map created by a supercomputer
This hypothesis had already been raised before, but until now a model had not been created to prove it. The researchers combined the most extensive database of well-dated fossil remains and archaeological artifacts in the aleph supercomputer, from the Institute of Basic Sciences in Daejeon (South Korea), one of the most advanced in its field. Thus, including 3,200 data entries, they created the climatic map of the last two million years on Earth and how the Homo sapiensthe Homo neanderthalensis and the Homo heidelbergensis (the three most recent hominin groups) moved from Africa to Europe and Asia and overlaps between species.
To test the strength of the link between climate and human habitats, the scientists repeated their analysis, but with the ages of the fossils mixed up, like a deck of cards. If climate change hadn’t influenced where and when humans lived, both methods would result in the same habitats. However, the researchers found significant differences in patterns between the three groups. “This result implies that, for at least the last 500,000 years, the actual sequence of past climate change, including glacial cycles, played a central role in determining where different groups of hominins lived and where their remains have been found.” Timmerman points out.
Specifically, the model created by the team shows that between one and two million years ago, our ancestors preferred more stable, warm and humid environments. “But when H. heidelbergensis emerged, there was a dramatic change and an extensive migration into Eurasia, including new groups better adapted to dry and cold climates.” In other words, H. heidelbergensis became a global traveler that adapted to very different conditions.
The weather determined who we are
The next question to be resolved was whether the habitats of the different human species overlapped in space and time, to see if climate was also another cause of evolution. From the analysis of these contact zones, the researchers derived a hominin family tree, according to which the Neanderthals – and probably also the Denisovans – evolved from the Eurasian family of Homo heidelbergensis about 500,000 to 400,000 years ago, while the The roots of Homo sapiens -the only one alive today- go back to southern Africa and to populations of late Homo heidelbergensis, some 300,000 years ago. And this coincides with the most critical transformations of the genre, such as the growth of the brain or the sophistication of its tools, which correspond to this stage in which these climatic changes derived from astronomical phenomena occurred.
To further shore up their model, the researchers compared their results with recent genetic studies conducted in recent years, and the data matched. “In other words, H. heidelbergensis was a basic line in human evolution,” says Timmermann, who concludes: “Our study documents that climate played a fundamental role in the evolution of our genus Homo. We are what we are because we have managed to adapt over millennia to slow changes in past climate.”
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