High hormone levels drove cavemen to promiscuity

LONDON - High hormone levels drove primitive men to promiscuity and combativeness.

Our ancient ancestors had far higher levels of the male sex hormone testosterone than people living today, a study of fossils has suggested.

The study was carried out by British and Canadian scientists who worked out the testosterone levels of extinct apes by looking at the length of fossilised finger bones, according to the journal Proceedings of the Royal Society B.

Emma Nelson, of Liverpool University, Britain, said: “It is believed that prenatal androgens (male sex hormones) affect the genes responsible for the development of fingers, toes and the reproductive system.”

Past studies have shown that exposure to testosterone in the womb can make humans and apes more aggressive and more promiscuous, reports the Daily Mail.

The same hormones also alter the way babies develop physically in the womb. Boys exposed to high levels tend to have a longer ring finger relative to their index finger, while in males exposed to lower levels, the two fingers tend to be of similar length.

The scientists worked out the ratio of the two finger lengths for a range of ancient hominins - or ancient members of the humans’ family tree - including four Neanderthals and an early modern human from 70,000 years ago.

They also studied the finger lengths of an ape-like ancestor called Australopithecus afarensis which lived three million years ago and an even older species called Ardipithecus ramidus from 4.4 million years ago.

The results also found that Australopithecus, a species that walked on two legs and whose best known fossil is the female nicknamed Lucy, may have been monogamous.

Ardipithecus, however, was more promiscuous - and may have behaved like modern great apes.