You really have to wonder, from an evolutionary perspective, how and when this skill became so modular and specialized, that mostly everyone is born with this innate capability.

If you take this idea, that facial recognition is a modular specialization that most humans have inherited at birth (such that it can be added or subtracted from a person's instinctive skills, leaving everything else more or less untouched), and cross it over to other species, I'd take a wild guess that this is the missing piece in animals that fail to recognize themselves in mirrors.

Comparing elephants and dolphins with dogs and cats, it's tempting to contemplate that while dogs and cats can become familiar with us, they're likely face blind. Elephants and dolphins, while capable of passing mirror self recognition tests to a certain degree, are probably not as adept, because they lack the same socialization demands that have intensely pressured humans for a couple thousand years.

I have to figure in earlier periods of human history, an inability to recognize individuals, especially in similarly peopled enclaves might have been supremely deadly. Not just boss-in-the-elevator deadly (as mentioned in the article), but literally stab-you-in-the-back deadly.

So much so, that we aren't born with other skills like capable of walking directly after being birthed, like other animals, but for the most part, by age three, if we can recognize faces, we can pick our parents out of a line up.

We know literacy and written language is a hard driver of civilization. I wonder how much, the innate capacity for human facial recognition plays into the ability to read text? It seems like dyslexia is related to the degree of rendomization of the pattern of receptors in the eyes, but facial recognition seems strongly bound to processing and memory.

Is it a prevailing trait that predates history, or is the capacity to record history, and history's emergence and fidelity concurrent with the prevalence of human facial recognition as almost pure instinct?

Furthermore, imagine a world where the selective pressure is removed, and the trait is replaced by an augmented reality product, a device that recognizes people for you. How easily ruled would those people of the future be?