Scientists believe lightning strikes during the peak period of supernovae explosions, approximately 2.6 million years ago, destroyed much of the earth’s forests and forced early humans to adapt from living in and around trees to surviving in open savannas of Northeastern Africa, thus prompting them to shift from a quadruped lifestyle to walking on two feet
A paper in the Journal of Geology says that experts at the University of Kansas found clues to the heavy period of supernovae activity around the turn of the Pliocene Epoch and ice age at the bottom of the sea, according to The Telegraph UK.
A “telltale” layer of iron-60 deposits, referring to a type of isotope, pointed to an ionization of the atmosphere from cosmic rays.
The bottom mile of the atmosphere is never usually affected in this way, apart from when blasted with energy from exploding stars.
Writing in the Journal of Geology, the scientists said this 50-fold increase in cosmic energy enabled a surge in cloud-to-surface lightening bolts that turned forests into infernos.
Professor Adrian Melott, who led the research, was quoted as saying: “It is thought there was already some tendency for hominins to walk on two legs, even before this event.
“But they were mainly adapted for climbing around in trees.
“After this conversion to savanna, they would much more often have to walk from one tree to another across the grassland, and so they become better at walking upright.
“They could see over the tops of grass and watch for predators.
It's thought this conversion to savanna contributed to bipedalism as it became more and more dominant in human ancestors."
The researcher said the probability is supported by the discovery of carbon deposits found in soils that correspond with the timing of the cosmic-ray bombardment.
The abundance of supernova activity took place between approximately 320 and 160 light years from earth, which in astronomical terms is relatively close.
Professor Melott said the nearest star capable of exploding into a supernova in the next million years is Betelgeuse, some (652 light years) from Earth.
"Betelgeuse is too far away to have effects anywhere near this strong," Melott said.
"So, don't worry about this. Worry about solar proton events,” he added. “That's the danger for us with our technology -- a solar flare that knocks out electrical power.”