“Don’t shoot until you see the whites of their eyes!”

It was more than just a Revolutionary War cry at the battle of Bunker Hill. The white part of human’s eyes, the sclera, may have had an important part in the extinction of Neanderthals and Homo sapiens dominance of Europe (and the world) 40,000 years ago.

According to Professor Pat Shipman of Pennsylvania State University, early dogs, bred from wolves, played a critical role in the modern human’s takeover of Europe when we vanquished the Neanderthal locals.

Most scientists argue that modern humans – armed with superior skills and weapons – were responsible for forcing Neanderthals into oblivion. Professor Shipman adds a twist. We had an accomplice: the wolf.

Professor Shipman’s book, “The Invaders: How Humans and Their Dogs Drove Neanderthals to Extinction“, delves into the symbiotic relationship that early man and wolves forged.

Professor Shipman’s hypothesis is that early modern humans, also known as Cro-Magnon, formed alliances with wolves soon after they entered Europe. These early humans tamed and domesticated some wild wolves, and the dogs bred from them were then used to chase prey and to drive off rival carnivores, including leopards and other large predator cats, that tried to steal the meat from the Cro-Magnon kill.

One key feature of Homo sapiens, alone among other primates, and presumably Neanderthals, is that we have white eyes. “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.

By contrast, there is no evidence of any kind that Neanderthals had any relationship with dogs and instead they appear to have continued to hunt mammoths and elks on their own, a punishing method for acquiring food. Already stressed by the arrival of modern humans in Europe, our alliance with wolves would have been the final straw for Neanderthals.

Professor Shipman’s theory about white sclerae is intriguing. I haven’t yet learned of any genetic data suggesting whether Neanderthals had white sclerae. Certainly, it would have been a disadvantage to Neanderthals if their attempts to domesticate or cooperate with wild dogs were hindered by this anatomical difference.

I wonder if there is any connection with the development of white sclerae and other behavioral characteristics that are related to Mirror Neuron theories? A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron “mirrors” the behavior of the other, as though the observer were itself acting. Mirror neurons have been said to have the potential to provide a mechanism for action-understanding, imitation-learning, and the simulation of other people’s behavior. I did reference mirror neurons in my novel “Relic”; in the story, the military found that Neanderthals had a “mirror neuron deficit” which would become a hindrance when trying to get a platoon of Neanderthals cooperating while on a mission. They couldn’t read each other’s body language.

I would imagine that this sort of deficit could affect the success of a hunting group that is attempting to stealthily stalk their prey. Perhaps not as important when bringing down large game in a brute force manner (bison, mammoth). However, perhaps more important when stalking small or skittish prey. Non-verbal communication skills would also be advantageous to the younger, less strong members of a hunting group; perhaps having these superior non-verbal skill allowed younger members of a Cro-Magnon to become active members of a hunting group at an earlier age. This would have resulted in larger, more capable hunting groups. It also would have allowed younger Cro-Magnons to hunt for small game without the assistance of the larger, stronger hunters. The experienced hunters would go after big game while the younger hunters would stalk smaller game, resulting in overall larger food supply for the tribe.

I could see how cooperation with dogs could play into this. Hunting dogs would not have been as important in bringing down bison or mammoth. Certainly, finding a herd of bison would not require a dog’s hunting skills. Again, this sort of hunting would be the domain of the stronger adult hunters. However, a young Cro-Magnon child or adolescent hunter, paired with a hunting dog, would be much more productive compared to a lone Neanderthal adolescent. A larger percentage of a Cro-Magnon tribe could become productive hunters as compared to an equivalent sized tribe of Neanderthals.

Professor Shipman’s hypothesis, coupled with mirror neuron deficit in Neanderthals, could have packed a one-two punch that ultimately led to the Neanderthals’ demise. Superior non-verbal communication skills for stealthy hunting of smaller prey, along with an alliance of younger human hunters with wolves, may have created the tipping point that drove Neanderthals into extinction.