Modern humans formed an alliance with wolves soon after entering Europe:
We tamed some and the dogs we bred from them were then used to chase prey and to drive off rival carnivores, including lions and leopards, that tried to steal the meat.
“Early wolf-dogs would have tracked and harassed animals like elk and bison and would have hounded them until they tired,” said Shipman. “Then humans would have killed them with spears or bows and arrows.
“This meant the dogs did not need to approach these large cornered animals to finish them off — often the most dangerous part of a hunt — while humans didn’t have to expend energy in tracking and wearing down prey. Dogs would have done that. Then we shared the meat. It was a win-win situation.”
At that time, the European landscape was dominated by mammoths, rhinos, bison and several other large herbivores. Both Neanderthals and modern humans hunted them with spears and possibly bows and arrows. It would have been a tricky business made worse by competition from lions, leopards, hyenas, and other carnivores, including wolves.
“Even if you brought down a bison, within minutes other carnivores would have been lining up to attack you and steal your prey,” said Shipman. The answer, she argues, was the creation of the human-wolf alliance. Previously they separately hunted the same creatures, with mixed results. Once they joined forces, they dominated the food chain in prehistoric Europe — though this success came at a price for other species. First Neanderthals disappeared to be followed by lions, mammoths, hyenas and bison over the succeeding millennia. Humans and hunting dogs were, and still are, a deadly combination, says Shipman.
Humans slowly changed wolves into dogs, but humans may have changed to:
Consider the whites of our eyes, she states. The wolf possesses white sclera as does Homo sapiens though, crucially, it is the only primate that has them.
“The main advantage of having white sclera is that it is very easy to work out what another person is gazing at,” added Shipman. “It provides a very useful form of non-verbal communication and would have been of immense help to early hunters. They would been able to communicate silently but very effectively.”
Thus the mutation conferring white sclera could have become increasingly common among modern humans 40,000 years ago and would have conferred an advantage on those who were hunting with dogs.
(Hat tip to HBD Chick.)
This explains why some native sub-Saharan Africans have yellow or brown sclera (aside from liver problems and malaria). If dog culture never developed then white sclera wouldn’t necessarily be an advantage. If you’ve been around a lot of Africans (for example Nigerians) then you’ve probably seen a decent number of healthy people with yellow sclera.