Why the male gaze is inevitably drawn to the female chest has sparked many a Freudian discussion and elicited an even greater number of eye rolls from women. What is it about boobs that fuels this eternal fascination? A team of European scientists recently received funding to study exactly that, shedding a bright evolutionary light on the everlasting male obsession with female breasts.

In a report actually entitled “Men’s preferences for women’s breast size and shape in four cultures,” published in the journal Evolution and Human Behavior, a team of researchers (both male and female) report that it might be shape, not size, that the male brain actually considers when appraising a breast’s attractiveness. Despite the general Western belief that men think bigger is better — and a number of previous scientific studies that corroborate this idea — it appears that firmness trumps all, and that quality, in turn, is probably dependent on shape.

That’s cool. But this conclusion leads us to what is, arguably, the more important question: That is, why are scientists studying this at all?

Breast shape, not size, might be the better indicator of fertility in females.

While the study’s premise may seem unnecessarily indulgent and its results troublingly exclusionary, it does shed some light on the evolutionary basis of the male obsession with boobs. The leading theory proposes that breasts are, first and foremost, an indicator of what disturbingly utilitarian scientists have called a woman’s “residual fertility.” Natural sexual selection is what led to the specific breast shapes and sizes we see on women today. This makes sense: If you imagine a bunch of early cavemen trying to gauge which of the local cave ladies would make the healthiest, fittest mother for their children, it’s not a stretch to say that they’d rely mostly on visual cues to inform their decision, similar to peacock females sizing up a male’s grand tail feathers.

And because the cross-cultural survey at the heart of this study suggested that — at least among the men from Brazil, Cameroon, the Czech Republic, and Namibia that were studied — the more important visual element was breast morphology, not size, the authors speculate that there’s something about breast shape that tells a male that a female is especially fertile.

What might this tell you about female fertility?

Why might firmness be more important than size? Breast size, they note, tends to change with age and the number of babies a woman has had, so it could very well be shape — and thereby firmness — that is the better indicator of fertility. They came to this conclusion after literally asking 267 men to rate pictures of different-sized boobs and then analyzing the results. While size preferences fluctuated (most men preferred medium-sized breasts, followed by large ones), preference for firmness stayed roughly consistent. What exactly firmness says about a woman’s health overall remains to be seen.

While it provides an evolutionary explanation for breast-obsessed men, the so-called “potential fertility indicator hypothesis,” of course, also assumes that early Sapiens ladies didn’t have much of a choice in who they mated with, being subjected, as it were, to the judgmental eyes of their male peers. This theory makes a biological excuse for humankind’s historically uncouth behavior but can’t, by any means, be used to guide or excuse how we act today. There’s more to modern romance than sizing up a person’s natural physiology, just as there’s more to modern human culture than hanging out in man caves and looking at boobs.

Or, at least, one would hope.