Early humans may have learned how to walk on two legs as a result of a massive supernova that happened millions of years ago.

While early apes were able to walk on all fours, the ancestors of humans somehow developed the ability to walk upright. This gave these ancient people an advantage over their quadrupedal contemporaries.

However, it was unclear what exactly spurred humans to learn bipedal movement.

In a study featured in the Journal of Geology, researchers from the University of Kansas explored the possibility of a cosmic event influencing how prehistoric humans were able to move about. Prof. Adrian Melott and his team focused on a supernova that occurred about 7 million years ago.

Cosmic Rays From An Ancient Supernova

The Kansas researchers point to an explosion of stars in the Milky Way that scattered cosmic rays throughout the galaxy for several million years. The radiation from this event eventually reached the Earth about 2.6 million years ago.

The cosmic rays caused the ions in the Earth's atmosphere to go haywire, making the planet's covering more conductive. The increased occurrence of lightning strikes led to massive wildfires that ravaged African forests and turned them into grasslands.

With only a few trees left, early humans were forced to adapt to their new environment. This is what might have caused them to learn how to walk upright, according to the researchers.

Early Humans Walking On Two Legs

The ability to walk on two legs were first seen in an ancestor of humans known as Sahelanthropus. This 6-million-year-old human species had physical features that bore some resemblance to those of apes and humans. Fossils of this ancient being were recovered from a site in the African country of Chad.

A popular theory among scientists is that early humans may have picked up the ability to walk upright as a result of climate change transforming their environment. The forests where these people once lived were later turned into savannahs.

Melott said prehistoric humans were already trying to learn how to stand upright even before the supernova occurred. However, he and his colleagues believe the cosmic event may have played a role in spurring these people to pick up the skill faster.

"Bipedalism had already gotten started, but we think this may have given it a strong shot in the arm," the professor noted.

Lightning has been known to cause of fires even before humans came along. The fires that were triggered throughout the years may have led to the destruction of many habitats, according to Melott.

The burned forests eventually gave way to the creation of grasslands, which were more advantageous to creatures that were able to walk upright. Melott explained that the new environment allowed early people to simply walk from tree to tree and look over tall grass for potential predators.

The study's findings suggest that supernovae may affect the frequency of lightning strikes on Earth. If this proves true, then future cosmic events may lead to more wildfires occurring across the planet.

However, scientists do not expect any supernova happening any time soon. The nearest star to the Earth that is expected to explode is the Betelgeuse, located some 642 light-years away. It will not become a supernova for at least a few billion years.