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A study suggests that a supernova explosion 2.6 million years ago could have led hominids to walk upright

An article published in Journal of Geology exposes that supernovae bombarded the Earth with cosmic energy, starting 8 million years ago, peaking about 2.6 million years ago, initiating an avalanche of electrons in the lower atmosphere and setting off a chain of events that ended the hominids As the homo habilis walking upright, adopting bipedalism.

The authors believe that atmospheric ionization likely triggered a huge increase in cloud-to-ground lightning discharges that sparked wildfires around the world. These hells could be one of the reasons why the ancestors of the Homo sapiens they developed bipedalism, to adapt in the savannahs that replaced the burned forests in northeast Africa.

According to study lead author Adrian Melott, professor emeritus of physics and astronomy at the University of Kansas, it is believed that hominins already had some tendency to walk on two legs, even before this event, but they were mainly adapted to climb trees. After this conversion to savannah, they would have to walk much more often from tree to tree across the grasslands, which they did better upright. This way they could see over the grass and keep an eye out for predators. This conversion to savannah is thought to have contributed to bipedalism as it became more and more dominant.

Based on analysis of a layer of iron-60 deposits covering the world’s seabeds, astronomers are highly certain that supernovae exploded in Earth’s immediate cosmic neighborhood, between 100 and 50 parsecs away ( 163 light-years), during the transition from the Pliocene to the Ice Age.

The approximate galactic cosmic ray flux (dashed line) and the cosmic ray flux calculated in Melott et al. (2017) 100 years after the arrival of photons from a supernova 50 pc away. The units are such that equal areas under the lines correspond to equal total energy flow on Earth. There is an increase of more than two orders of magnitude in the upper range of energies / photo Adrian L.Melott

They calculated the ionization of the atmosphere from cosmic rays that would come from a supernova at about that distance, as indicated by iron-60 deposits. According to Melott, it appears that this was the closest event in a much longer series. We think that would increase the ionization of the lower atmosphere by about 50 times. Ionization is not usually detected in the lower atmosphere because cosmic rays do not penetrate as far, but the most energetic ones from supernovae reach the surface, which would cause the release of many electrons. That abundance of electrons would favor the formation of numerous rays.

The likelihood that this lightning spike triggered a global increase in wildfires is supported by the discovery of carbon deposits found in soil layers that correspond chronologically to the time of the cosmic ray bombardment.

According to the researchers the fact is that there is much more coal and soot in the world for a few million years. It’s everywhere, and no one has any explanation why it would have happened at the same time all over the world in different climate zones. This could be an explanation. That increase in fires is thought to have caused the transition from forest to savannah in many places. And this would be related to human evolution in Northeast Africa, specifically in the Rift Valley.


Sources

From Cosmic explosions to terrestrial firesAndrian L. Melott, Brian C. Thomas, arxiv.org/abs/1903.01501 / The University of Kansas.


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