Scientists have long suspected natural climate change played a role in the evolution of the genus. Homo. Today, thanks to an unprecedented simulation, researchers have managed to confirm it.
the global warming that we live today is, “unequivocally possible”, the result of our emissions of greenhouse gas. But, in the past, the climate of our Earth has experienced natural changes in sunshine according to what scientists call the Milankovitch cycle. A particular consequence of theeccentricity of the’orbit earthly,obliquity of the axis of rotation of our Planet with respect to the plane of the ecliptic and some precession from equinoxes. From Pusan National University researchers (South Korea) now report that these changes have shaped human evolution over the past two million years.
It must be said that our ancestors were probably more closely linked to their environment than we are. A river that was drying up and now we had to break camp. However, the hypothesis of climate change having contributed to stimulating the evolutionary developments of the gender Homo — changes intended to make humans more adaptable and able to survive a variety of conditions — had so far remained difficult to prove. Due to a lack of climate data – often from carrots glaciers or sediment marine — geographically related to the discoveries of fossils archaic humans. This problem, the researchers finally managed to circumvent it by modeling the changes in environmental conditions over the last two million years and by incorporating the climatic changes linked to the Milankovitch cycle.
For six months, the simulation ran on a supercomputer generating some 500 terabytes of data and representing climate responses to rising and falling ice capsto changes in past concentrations of greenhouse gas, as well as the marked transition in the frequency of glacial cycles about 1 million years ago. The objective being to finally specify the climate which could reign in the regions for which the researchers have archaeological artefacts and fossil archives documenting the presence of several species ofhominidsamong Homo erectus, Homo heidelbergensis or Homo neanderthalensis and ours, Homo sapiens. In all, more than 3,000 geochronologically constrained fossils.
Adaptations that end up evolving under climate pressure
From there, the researchers claim to be able to tell us the complexity of how different groups of hominids dispersed on our Earth over the centuries. Dispersals that they now link to climate models affecting for example temperatures and food availability. According to them, the climate played a fundamental role in the evolution of the genre. Homo. “We are what we are because we have succeeded in adapting over the millennia to the slow changes of the past climate»says Axel Timmermann, the lead author of the study, in a press release from Pusan national university.
We are what we are because we have managed to adapt over millennia to the slow changes of the past climate.
This work shows how species have developed cultural adaptations, such as the mastery of fire , allowing them to survive in colder environments, for example. How also, some stress environmental — the droughts in particular — have reduced the size of the most vulnerable populations. Lowering pool diversity genetic of these species. And finally only allowing the survival of individuals with a genetic advantage which would then have been transmitted to their descendants.
And some of those benefits may have been so great that they triggered a species transition Homo to another. Moreover, by studying contact zones — the habitats of different human species that overlap in space and time — the researchers have reconstructed a tree genealogy of hominids. A strikingly similar climate-based tree to the one obtained from genetic data or morphological analyses.
The researchers even go a little further by suggesting the evolution of the genus Homo cannot be fully explained without integrating the climatic factors that affected the ecosystems— the availability of water and food, for example — during the Pleistocene. But the idea will still need to be confirmed by new field investigations that will examine the fossil record for undiscovered paleoenvironmental clues.
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