Yesterday, the bearded men of the internet started freaking out.

beard science says a lot of contradictory things

A new study determined that women find a man more attractive when he grows a beard — but only if most other men around are clean-shaven. If beards become common, on the other hand, shaving makes a man more attractive. Or, as FiveThirtyEight put it, "Beards Are Less Attractive When They’re Everywhere."

The reason for this preference, the researchers argue, is an evolutionary principle called negative frequency dependance, in which an uncommon trait provides some sort of benefit, in terms of survival or reproduction. (For instance, guppies are less likely to be eaten by predators if they have colored spot patterns that are different from other guppies.)

But the idea that atypical facial hair is evolutionarily most attractive is a curious finding, given that just last year, another study arrived at the opposite conclusion: that women find stubble more attractive than beards or clean shaven faces. Two other studies published over the last few years, meanwhile, found that on the whole, women simply prefer clean shaven men to beards.

And that's the problem: if you're bearded, stubbled, or clean shaven, it's hard to put a lot of stock in these beard studies — because they all suffer from the same basic problem.

All these beard studies reflect the preferences of a WEIRD group of people

WEIRD is an acronym — it stands for Western, Educated, Industrialized, Rich, and Democratic — and it was coined to describe a problem common to a ton of different sociological studies.

The issue is that, when researchers in the US or Europe or Australia — who are responsible for the vast majority of social research published — need people to participate in a study, they generally recruit nearby. As a result, about 96 percent of the subjects in psychological studies are from Western industrialized nations.

About 96 percent of subjects in psychological studies are from western industrialized nations

If you're a reader in such a country, this might seem fine, but you're actually a relative rarity: these Western subjects only represent about 12 percent of the world's total population.

Extrapolating species-wide truths and evolutionary trends (like "women prefer beards, but only if they're rare") from this unusual population is problematic, because people behave differently and have different preferences in different countries.

For instance, in the ultimatum game — an exercise widely used in economic research — American subjects have been found to behave much more equitably than residents of Russia or China.

This even applies to very basic tests that you might think are universal across humans. When American and Europeans look at the Müller-Lyer illusion, below, they're likely to be fooled, and perceive the line labeled (a) as longer. But people from the San group, in Africa, generally (and correctly) perceive the two lines as the same length.

To their credit, the researchers of the latest beard study tried to escape the WEIRD trap, recruiting the 1665 participants online, so they could have been from anywhere.

Still, they couldn't escape the trap entirely. Here were the ethnicities of the respondents: 70.47 percent European, 9.6 percent Asian, 6.12 percent Central or South American, 2.46 percent Oceanian, 2.28 percent African or Middle Eastern, 1.86 percent Native American, and 7.2 percent who chose not to answer.

Additionally, these people judged the attractiveness of 36 white men with a few different facial hair styles (example below). If all this doesn't sound like a representative sample of humanity that could tell us a lot about human nature, innate preferences, and our species' evolution, it's because it's not.

WEIRD people probably have different beard preferences

Given that people from WEIRD countries behave differently in economic experiments and perceive optical illusions differently from people elsewhere, it's not a stretch to say that the preferences of the people polled in the new beard study — mostly WEIRD themselves — might not apply to our whole species. They might not even apply to facial hair preferences in the US.

the preferences of the people polled in the new beard study might not apply to our whole species

There are many cultures, after all — such as Sikh, Muslim, and Jewish culture — where religious rules dictate that all men keep a beard for their entire adult life. In many areas of South India, essentially all adult males traditionally grow a mustache. Growing up in one of these cultures or religions would likely lead to a person having different definitions of what constitutes attractive facial hair than the mostly white people included in the study.

Arguing that humans innately prefer rare facial hair styles for evolutionary reasons is a pretty tough claim to make. If you read about a study that said beards are always more attractive for evolutionary reasons — because a group made up largely of observant Sikh people thought they were more attractive — the problem would probably pop into your head immediately. But we're so used to extrapolating the preferences of Western research subjects into truths about human nature that we don't bat an eye.

In the end, testing people on their beard preferences can probably tell you about one thing — what that group of people, and others like them, think about facial hair. What it can't reveal, though, is anything meaningful about human nature or evolution.