Exploding stars in the distant past may have led to humans walking on two legs. According to a group of scientists, a supernova that exploded millions of years ago greatly influenced our ancestors to transition to bipedalism.
If we humans walk on two feet today, it may be because of a supernova that bombarded the earth with cosmic energy millions of years ago. American astronomers and physicists came to this amazing conclusion in The Journal of Geology on May 28th, 2019.
The explosion of this star at the end of its life would have “played a role in the evolution of humans.” It would have favored the transition of forests to savannahs on the land, an element considered as “a central factor in the evolution of Hominini towards bipedalism,” the scientists write.
A supernova is, according to NASA, the biggest explosion that can occur in space. The event occurs when a change takes place in the center of a star. Many elements found on Earth come from those hearts of stars that exploded. As astrophysicist Natalie Hinkel explains in this Ted Talk, “we are all stardust.”
According to the authors of this study, a supernova occurred 8 million years ago (with a peak of activity 2.6 million years ago) and brought electrons into the lower atmosphere. This contribution of particles would be at the origin of a series of events, which led to bipedalism. These “electron cascades” have caused “increased nitrate deposition and forest fires,” according to scientists. These fires turned some of the forests into savannahs in the north-east of the African continent. The ancestors of homo sapiens became bipedal to adapt to this environment.
“Hominini already tended to walk on two legs before this event,” says physicist Adrian Melott of the University of Kansas, co-author of the study. “But they were mainly adapted to climb trees. After this conversion to savannas, they would have been much more often forced to walk from one tree to another in the meadow, which allowed them to walk better.”
Iron deposits, which are found in several seabeds of the Earth, have suggested to scientists that a supernova has probably exploded near our planet. They indicated that it was 163 light years away at the end of the Pliocene age (2.58 million years ago). By simulating the cosmic rays of such a supernova, both researchers suspected that they entered the lower atmosphere, which does not usually happen.
Could this rare phenomenon happen again if another supernova explodes in the future? Scientists are interested in Betelgeuse, a star that should be visible from Earth when it becomes a supernova. It is located about 500 light-years from Earth. The researchers note that the incident should not have “serious consequences” given the distance that separates us from the star.