Once we left the trees, we stayed together and used out front facing eyes for other means including eventually aiming and throwing projectiles. Now we have a direct link between front facing eyes and community in primates. One monkey sees an eagle, scratches out a warning call and all the nearby monkeys duck for cover. If you look at modern primates, you’ll see (with some exceptions) mostly communal living. So what’s the next best defence? Another pair of eyes. So at some point our ancestors moved up to the trees and started evolving front facing eyes so they could accurately leap from branch to branch but in doing so lost the ability to see predators like eagles. Consider a rabbit which can almost see behind itself because of the shape of its skull. As others have mentioned, front facing eyes give great depth perception but the trade off is poor peripheral vision. 'When you hold up your finger vertically and fixate your eyes on something far beyond it,' he writes, 'you perceive two copies of your finger, and both copies of your finger appear transparent.' Thus, you have the ability to 'see through' your finger, as though you were seeing with X-ray vision.This is actually a really fascinating part of our history. The catchy name for his hypothesis comes from a curious phenomenon. In short, forward-facing eyes allowed our ancestors to see through the dense leaves and branches in their forest habitat. In 2008 in the Journal of Theoretical Biology, he offered up the 'X-ray vision hypothesis'. Theyre designed less to look out for our own protection than to locate prey. Theoretical neurobiologist Mark Changizi has yet another idea. Like other predators, our eyes face forward. As it happens, early primates were also nocturnal hunters, and their adaptation for nighttime predation may have granted forward-facing eyes to all their descendants, including our own species. Allman's contribution was to suggest that forward-facing eyes proved beneficial for creatures that hunt at night, such as owls and cats, because they can take in more light than sideways-facing eyes. Cats, primates and owls do, but not mongooses, tree shrews, and robins. Not all predators, after all, have forward facing eyes.

Neurobiologist John Allman picked up on Cartmill's hypothesis and expanded it to focus on nocturnal predation. Cartmill thought that the reduction in their ability to smell was a side effect of the eyes' convergence, simply because the space available for the nose and its connections to the brain became smaller as it was crowded out by the eyes. Early primates, for example, hunt by sight rather than by scent. Cartmill thought his explanation was the most elegant, because it also explained other evolutionary changes that are distinctive to primates. That would help them to better locate and more effectively take down their prey, whether that's a leopard stalking a gazelle or a raptor snatching a rabbit in its talons, or one of our primate ancestors grabbing an insect from the branch of a tree. Predators are best served, ostensibly, by having extremely good depth perception. Guy on the right has deeper set eyes and. yet, its obvious he has no hunter eyes, but the guy on the left has: Exhibit 3. Guy on the right has super deep set eyes, sunken eyes even, his eye sockets literally look like they are in holes in his face. So, in 2005, biological anthropologist Matt Cartmill proposed a different idea: the 'visual predation hypothesis'. Answer: hunter eyes is based on eyelid exposure, NOT on browbone: I hereby produce exhibit 2.

The problem with Collins’ hypothesis is that many animals that thrive in trees have eyes on the sides of their heads – squirrels, for instance. “The price of failure was to drop many metres onto a ground inhabited by carnivorous beasts,' wrote visual psychotherapist Christopher Tyler in 1991. 1 In Caucasians, men's eyes have a greater width-to-height ratio than women's, while women's eyes are rounder, 2 i.e. a high width-to-height ratio (with a low level of vertical scleral show) is considered the essential aspect of hunter eyes.

After all, the stakes for failing to work out the true distance between trees were high. Hunter eyes are a sexually dimorphic trait. In the decades since, it has been expanded and refined, but the basic idea that our ancestors evolved forward facing eyes to accurately judge distances while leaping from tree to tree remained central for quite a while. Collins' idea has become known as the 'arboreal locomotion hypothesis' – arboreal meaning living in trees.

Predator eyes vs prey eyes human