Big bollocks = small brain

Struggling to find bat ball pics –
so here’s some bat sperm

The analysis of 334 species of bat found that in species where the females were promiscuous, the males had evolved larger testes but had relatively small brains. In species, where the females were monogamous, the situation was reversed.

Researchers suggest the correlation exists because both organs require a lot of energy to grow and maintain, leading individual species to find the optimum balance.

And in humans? Feedback welcome… 😉

Interesting stat I didn’t know until today — in some species of bat, testes mass is 8.4% of body mass!
Unfeasibly large testicles…

As seen in Viz