A new research by an archaeologist from the University of York suggests that the moral disputes that have arisen from betrayals of trust made ancient humans spread across various new regions of the Earth nearly 100,000 years ago. The research says that movement of archaic humans was slow and largely governed by environmental events due to population increases or ecological changes.

But after this point, movement around the planet became much more rapid, and even traversed major ecological barriers and events.

This new research, published in Open Quaternary, says that this change was actually down to a shift in human relationships. Emotional relationships became more important at this point and social groups became more motivated to identify “the dark side of human nature” — things like lying and cheating. Subsequently, disputes, mainly caused by broken trust, became far more common, leading groups to fracture and put distance between themselves and their new rivals.

Penny Spikins, the lead author of this new study, believes the shift is related to the change in human emotional relationships. She explained that neither changes in the Earth’s ecology nor increases in population offers a sufficient explanation for patterns of human dispersal into new areas around 100,000 years ago.

“Moral conflicts provoke substantial mobility — the furious ex-ally, mate or whole group, with a poisoned spear or projectile intent on seeking revenge or justice, are a strong motivation to get away, and to take almost any risk to do so,” says Penny.

‘While we view the global dispersal of our species as a symbol of our success, part of the motivations for such movements reflect a darker, though no less “collaborative”, side to human nature,’ she concluded the paper.