Between 8 and 2 million years ago, cosmic ray energy from one or more nearby supernovae reached the earth and pummeled the planet's atmosphere and initiated an avalanche of electrons and settled a chain of events ending with bipedal hominins according to a radical study published in Geology Journal of Geology
"It is believed that there was already a tendency for hominins to walk on two legs, even before this event. But they were primarily adapted to climb trees," said Professor Adrian Melott of the University of Kansas. .
"After this conversion to savannah, they would very often have to move from one tree to another across the grassland, and so they would be better off going up. They could look over the top of the grass and look at predators."  "It is believed that this conversion to savannah contributed to bipedalism as it became more and more dominant in human ancestors."
Based on a "telltale" layer of former seabed deposits in the radioactive isotope iron-60, professor melott and his colleague dr. Brian Thomas Washburn University has great confidence one or a number of supernovae exploded in the Earth's immediate cosmic neighborhood during the transition from the Pliocene era to the Ice Age.
"We calculated the ionization of the atmosphere from cosmic rays that would come from a supernova about as far away as the iron-60 instances indicate," said Professor Melott.
"It seems that this was the closest one in a much longer series. We claim that it would increase the ionization of the lower atmosphere by 50 times. Normally you do not get lower atmospheric ionization because cosmic rays do not penetrates so far, but the more energetic from supernovae come right down to the surface – so there would be many electrons being knocked out of the atmosphere. "Ionization in the lower atmosphere meant that an abundance of electrons would form more roads for lightning strikes.
"The lower mile or so is influenced by ways it usually never does. When high-energy cosmic rays strike atoms and molecules in the atmosphere, they knock out electrons out of them – so these electrons run around loose instead of binding to atoms, says Professor Melott.
"Usually in the lightning storm, there is a buildup of tension between the clouds or clouds and the earth – but the flow cannot flow because there are not enough electrons to carry it. So it must build high voltage before the electrons begin to move. As they move, electrons knock more electrons out of several atoms, and it is based on a flash bolt. But with this ionization, this process can be started much easier, so there would be much more lightning bolt. "
The likelihood that this lightning tip affected a worldwide recovery in wildfires is supported by the discovery of carbon deposits found in soils corresponding to the time of cosmic ray bombardment.
" The observation is that there is much more coal and soot in the world that starts a few million years ago, "said Professor Melott.
" It's everywhere and no one has any explanation why it would have happened all over the world in different climate zones. This can be an explanation. This increase in fires is believed to have stimulated the transition from forest to savannah in many places – where you had forests, now you had virtually open grassland with bushy things here and there. "
" It is believed to be related to human development in northeastern Africa. Especially in the Great Rift Valley where you get all these hominin fossils. "
Adrian L. Melott & Brian C. Thomas. From Cosmic Explosions to Earth-Fires? Journal of Geology published online May 28, 2019; doi: 10.1086 / 703418