It’s all in the eyes. Especially our prominent whites. You know, the old telltale for musket-armed soldiers worrying when to fire.
Our prominent whites can be a disadvantage, especially if you’re marching headlong at a formation of unfriendlies who understand they’re wasting ammo if they can’t see your sclera.
Whites also give us away when we’re otherwise trying to hide. Think of that in practical terms, blinking eyes in a darkened forest, and as metaphor, which I’ll return to in a moment.
The sclera is a tough, fibrous tissue that holds the eyeball’s shape. It wraps around the eye, from cornea to optic nerve, protecting the precious contents inside.
Humans are not the only species with sclera. It’s just that in most other animals, including primates, the sclera is pigmented, making it indistinguishable from the darker iris or the skin and fur surrounding the eye socket. Imagine gorillas with their dark orbs peering out from jet-black faces.
Hard to get a read on that critter.
This suggests there was some evolutionary advantage gained by camouflaging your eyes. If not, most species would not have evolved with eyes designed this way. Then humans came along and it’s as if the danger posed by formations of soldiers armed with ballistically erratic muskets was somehow predicted in our latent DNA.
Of course, humans are the species that habitually turns convention on its head. Somewhere along the line we traded stealth for expression. By a weird roll of the evolutionary dice, Marty Feldman eyes became an edge that resulted in 8 billion of us swarming the planet.
There’s no hiding us now.
Evolutionary history seems clear — eye camo was an advantage until the human horde proved otherwise. So, it’s reasonable to now wonder, what is the advantage of sclera?
After verbal skills, there may be no more effective communication device than human eyes. We’re told eyes are the window to the soul and you know what that means if you’ve ever caught someone you care for in a lie, or better yet, recognized someone telling you they love you with only a glance.
Maybe gorillas discern meaning from another’s coaly orbs, but I suspect silverbacks developed their chest-thumping, over-the-top theatrics because nuance ain’t their thing.
But it is ours, which leads me to that oft-speculated time in pre-history, when, at the end of the last ice age, homo sapiens became the primary hominid in the previously Neanderthal-dominated Europe. Eyes might have played a role.
Neanderthals had larger, more prominent eyes than Homo sapiens. That may be because Neanderthals evolved in darker, northern latitudes where keen eyesight was an advantage for a hunter-gatherer hominid. But the advantage lasted only until Homo sapiens migrated north.
This is because there are also drawbacks to larger eyes and the sight-centric orientation they generate. Bigger eyes mean more brain mass devoted to processing all the data those eyeballs collect.
This may have meant Neanderthals had less brain capacity to do things like develop and manage the complex relationships associated with larger groups. Clan-sized units are great for introverts, but they aren’t big enough to support the planet-dominating trajectory humans eventually assumed.
There’s another thing about our prominent whites. We not only use them to communicate with other humans, but also with another species that understands our eye language: dogs.
It’s hard to say which is the canine’s true superpower — its amazing nose or its ability to read, communicate and engage with humans. No other animal is capable of such mental intimacy with just a glance. Not wolves. Not our closest biological relatives, chimpanzees.
And certainly not cats.
Our relationship with dogs — as hunting partners, as nighttime sentinels while we sleep, or as pack animals — may have tipped the scales in favor of Homo sapiens.
What great luck. We revealed to them the whites of our eyes, they saw our soul and decided they love us.