One characteristic that sets us apart from many other mammals is we walk on two legs. How that happened is probably not something you think about every day, but some scientists do. And recently those scientists have included astronomers.
A paper published May 28, 2019, in the Journal of Geology advances the theory that we walk upright because of a series of supernovae explosions in our cosmic neighborhood several million years ago. Consequently, Earth was bombarded with cosmic energy that caused a wave of electrons in the lower atmosphere. This atmospheric ionization would have triggered a huge increase in lightning strikes which would have started forest fires all around the world. The burned forests would’ve ended up as savannas, and our ancestors started walking on two legs to adapt to the changing environment.
The study’s lead author is Adrian Melott, professor emeritus of physics and astronomy at the University of Kansas. His explanation:
“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.”
If you’re interested in the science behind this, go to https://earthsky.org/human-world/supernova-humans-to-walk-upright?. The photo came from that site.