The face of a hunter: When judging a book by its cover makes sense

– by Adar Eisenbruch

Photo credits: Hadza hunter (top) by Kristopher Smith; Tsimane hunter (middle) by Michael Gurven

Many of us were taught as children not to judge a book by its cover, meaning not to make assumptions about people based on their appearance. Yet we do it anyway. For example, people whose faces look “competent” – i.e., they look like they will be good at what they do – are no better at running a company than others, but they are nonetheless more likely to get hired as a CEO.

If judging people by their faces is irrational, why do people do it so persistently? Probably because we’ve evolved to. There are many cases in which preferences evolved because they were beneficial to our ancestors (e.g. the desire to eat as much sweet food as possible), but they produce bad outcomes today (e.g. health problems). How we judge other people’s faces might fall into this category, too. Someone’s face might not predict who’d be a good corporate executive, but it can tell you about other traits that were more relevant to our ancestors, like how much they like children or how good a fighter they are.

My colleagues Kris Smith, Chris von Rueden, Cliff Workman, Coren Apicella and I recently combined data from Tsimane foragers from Bolivia and Hadza hunter-gatherers from Tanzania – for whom knowing who in their community is a better or worse hunter is a matter of great importance and interest – with data from American couch potatoes (or to be more polite, online participants in a sedentary, agricultural, post-industrial population) to discover another area in which face perception is accurate. First, Tsimane and Hadza individuals judged the men in their communities on hunting skill. Then, headshots of those Tsimane and Hadza men who had been evaluated were shown to the American participants, who were asked to judge them on “ancestral productivity.” Ancestral productivity refers to how good a hunter-gatherer a person would be (e.g. ability to hunt, gather, make tools, survive the elements). Previous research has shown that American undergraduates (for whom ancestral productivity has no obvious relevance) want to be friends with and are more generous towards individuals they perceive as high in ancestral productivity.

We found a positive correlation between the peer evaluations of hunting ability and the Americans’ perceptions of ancestral productivity based on just one face photo. This means that the men who Americans thought looked like more productive hunter-gatherers actually were the better hunters, at least according to their peers.

Could this be caused by both the peer informants and the American participants picking up on something visible in the target men, like attractiveness, and inferring productivity from that? In other words, could this be an example of the “halo effect” that social psychologists are familiar with? Probably not. There’s evidence that the halo effect doesn’t operate among the Hadza the way it does among Americans, and several studies of forager societies have found that peer judgements of hunting ability track objectively measured hunting returns. In other words, when you ask foragers who in their community is a good hunter, they know what they’re talking about.

Could we have found this positive correlation because the American participants happened to be experienced hunters and outdoors enthusiasts who may have learned what a good hunter looks like? No. We asked them about their hunting experience and other outdoor skills, and we verified that the sample was not stacked with Eagle Scouts and archery instructors.

A better explanation is that humans have evolved to evaluate each other on hunting ability. Our ancestors depended on each other for collaborative hunting and food sharing, and they chose their social partners on those bases. They had to be able tell how good a hunter someone was – quickly, easily, from just a look if that’s all the information they had. Individuals who could accurately perceive hunting skill in others would have had better hunting partners and more reliable food sharing relationships. This means more calories available to themselves and their kin, and therefore more descendants. Played out over evolutionary time, this created the ability to perceive hunting skill from the faces of others, an ability that is still present even in people for whom it has no contemporary utility.

For this to work, there must be some observable traits in the face that correlated with hunting ability ancestrally. In other words, there must be some way(s) in which good hunters look different from bad hunters. What are those cues? We don’t know. We tested some of the usual suspects of face metrics (e.g. facial width-to-height ratio, symmetry), but none were a good explanation. This is an open question.

So far, we’ve only discussed the results for men’s faces. But one of the Hadza datasets also included women’s faces, which had been evaluated on gathering (rather than hunting) ability by their campmates. So can Americans also tell which women are better gatherers? No. In fact, quite the opposite. The better gatherers (based on peer evaluations) were perceived as less ancestrally productive by our online participants.

Why are people not only unable to judge female ancestral productivity from the face, but actually misjudge it? In our data, it seems to be due to age. The American participants perceived older women as less productive, even though their peers reported that they’re better gatherers. Perhaps it was less important for our ancestors to evaluate women’s gathering skill than men’s hunting skill, so we did not evolve a corresponding ability for judging women’s faces. Perhaps there are stereotypes in the US (but not among the Hadza) about older women’s abilities that influenced our participants. Perhaps both, and there are other possible explanations as well. There’s clearly more research to do here.

To return to not judging a book by its cover: I’ve always thought that was a weird saying, because you can actually tell a lot about a book from its cover. Scary stories usually have a picture of misty woods or a font that looks like dripping blood; Moby Dick always has a whale on it. The fact that humans can perceive men’s hunting ability from their faces, and we are socially attracted to those high in hunting ability, might help explain some of the modern cases in which people seem to be misled by others’ looks. In effect, people might be choosing CEOs and congresspeople by relying the same facial features that our ancestors used to choose hunting partners and campmates. It turns out that you can judge people by their looks, if you know the right questions to ask.

Read the original article here: Eisenbruch, A.B., Smith, K.M., Workman, C.I., von Rueden, C., & Apicella, C.L. (2024). US adults accurately assess Hadza and Tsimane men’s hunting ability from a single face photograph. Evolution & Human Behavior, 45(4), 106598.