Nature's Law: Large Testes, Small Brains

"God gave men two brains, but not enough blood to keep them working simultaneously."

The above proverb, although a little bit vulgar, is not a joke, as some might think, but a scientific truth.

A study carried out on bats showed that the size of the brain is inversely proportional with the size of the testes, or in other words, the larger the testes are, the smaller their brains and the other way around.

According to the researchers, the proof behind this truth is that both organs require a large amount of energy for growth and maintenance.

The study looked at 334 species of bats, in some, the females having a random sexual behavior (promiscuous), while in others, the females being monogamous.

In the first case, males had developed large testes, but had suffered a brain involution, and in the second case, the inverse applied.

"When females mate with more than one male, sperm compete to fertilize the female's eggs," Scott Pitnick, author of the study, said.

"The male who ejaculates the greatest number of sperm may win at this game, and hence many bats have evolved outrageously big testes, as much as 8.5% of their body mass," he concluded.