To find out if this effect on testosterone production might affect mice's fertility, the team knocked out the gene for osteocalcin in a group of the rodents.

Although the researchers only looked at a handful of specimens, the findings suggest that Neanderthals and early humans were more testosterone fuelled than modern men.

The researchers also reported that when a man's status was threatened in the presence of a female by a display of wealth by a male acquaintance, his testosterone levels surged.