Humans, hyenas moved out of Africa at about the same time: Study

Hyenas left Africa about the same time when prehistoric humans left the continent for the first time about two million years ago, according to a study that may help better understand how large animals historically moved across the planet.

In the study, published in the journal Science Advances, scientists sequenced the complete genomes from both modern spotted hyenas in Africa, and fossils of the extinct cave hyena from Europe and Asia.

"Our new study shows that prehistoric humans and hyenas left Africa at approximately the same time," said Michael Westbury, study co-author from the University of Copenhagen in Denmark. "And like humans, spotted hyenas have had extensive and complex migration between continents.

We can observe repeated gene flow events between Africa and Eurasia," Westbury said. They said the two hyenas -- spotted and cave -- were previously believed to form a closely related evolutionary lineage. Earlier studies, according to the researchers, showed that the two types of hyena were genetically intermingled.

However, in the current study, with more genetic data, the scientists have reported that this genetic intermingling is limited, revealing an ancient separation between the two Hyena kinds.

While the prehistoric hyenas showed similarities with humans in their trans-continental migration patterns, the researchers also found signs that modern humans -- the species Homo sapiens -- had significant impact on hyenas. "Historical population sizes of spotted hyenas seem to correlate negatively with that of humans after about 100,000 years ago, echoing similar results we found for herbivores," said study co-author Rasmus Heller.

Heller explained that humans may have played a role in the extinction of cave hyenas around the end of the last ice age. Based on the findings, the scientists believe that the coexistence between humans and hyenas -- like that between humans and other large mammals -- may have changed from being relatively benign to detrimental as humans became more advanced.

According to the researchers, the study also reveals new aspects of when and how animals moved across continents in the Earth's prehistory. "Our results conform with the hypothesis that animal migration may have occurred in pulses during which several species migrated more or less at the same time, possibly as a response to climate change," said Michael Westbury, another co-author of the study. "More comparative work is needed to confirm this hypothesis," Westbury added.