Here’s an interesting little thing about the differences between the sexes. Women’s voices sound sexier when they’re at their most fertile part of the cycle.

Researchers found that the female voice altered according to the time of the month.

They recorded women counting from one to 10 at different stages of the menstrual cycle, then played the voices back at random to a group of students.

Both men and women judged the voices to be most attractive when they were recorded at periods of peak fertility and less attractive during non-fertile periods.

This ties in with various things that we’ve already discussed here: for example, the way that female singers’ voices change over their cycle as well.

And, of course, the way in which lapdancers‘ earnings seem also to change with their position on that same cycle.

All of these findings are pointing to very much the same finding. That while the basic and outward signs of oestrus in human beings are no longer visible, in the same way that the bright red bottom of a baboon in heat (or the yowling of a domestic cat when she is) are, the more subtle signs are still there.

And the explanations of all of this are well understood too. Humans (and to a lesser extent, other apes and monkeys) are slightly odd in that they mate when not necessarily fertile. We’re also a long lived pair bonding species, something else which sets us apart. There’s thus an advantage to the female side to keeping the knowledge of when she is fertile private: it aids in both beating off the unwanted attentions of those she has not bonded with but also keeps her mate guessing about when she is fertile. This is important knowledge in the battle of the sexes.

However, it’’s such important knowledge in that battle that the ploy is not going to go unanswered: males are going to try to work out the fertility or not, the point in the cycle, from other more subtle clues. And some of them, at least, are going to work it out and many of us will be descended from those who did, thus providing a genetic strengthening of such a talent down the generations.