In a as yet unpublished study in Proceedings of the Royal Society B, 80% of male monkeys tested were able to tell which female was ovulating by picture alone.
They presented male monkeys with two pictures of the same female’s face: one from a day on which she was ovulating, and one from a time before she was ovulating. More than 80 percent of males from the female’s group were able to discriminate between the two faces, looking longer at the photograph in which she was ovulating than the one in which she was pre-fertile. Males who did not know the specific female in the photograph showed no such preference.
Any time monkeys score 80% on a test, I want to know about it. But what are the appropriate conclusions to draw from this study, assuming this is true? Here’s an inappropriate conclusion:
“The study raises new questions about whether familiarity might be used by the males of our own species to detect when women are fertile,” noted Santos.
Let’s grant that the monkeys gazed longer at the ovulating faces. That doesn’t mean they could tell they were ovulating, just that they were more attractive.
In fact, while it would be evolutionarily advantageous for the female to be more attractive during evolution, it would not be advantageous to advertise that she was ovulating. Especially in humans, and especially to men. Females, especially ones in relationships, take too much of a gamble broadcasting their fertility to strangers. If we take their own studies at face value, it makes men go completely bananas.
When you read studies about mate selection and evolutionary psychology in general, remember a simple fact: once we got consciousness, all bets were off.