Early humans were more competitive and promiscuous than people today, research shows.
A team of scientists studied the fossilised finger bones of extinct apes and hominins – extinct members of human lineage – to learn more about their hormonal activity.
The novel approach to understanding how our ancestors behaved was conducted by a team from Liverpool, Oxford, Southampton and Calgary Universities, and is published in the latest issue of Proceedings of the Royal Society.
The finger ratios from fossilised skeletal remains of early apes and hominins can be used as indicators of the levels of exposure species had to prenatal androgens – a group of hormones that are important in the development of masculine traits such as aggression and promiscuity, the study says.
High levels of the hormones increase the length of the fourth finger in comparison with the second finger, resulting in a low index-to-ring-finger ratio.
The team found that the fossil finger ratios of Neanderthals and early members of the human species were lower than those of most living humans, suggesting they had been exposed to high levels of prenatal androgens.
This indicates that early humans were likely to be more competitive and promiscuous than people today.
Emma Nelson, from the University of Liverpool’s School of Archaeology, explains: “It is believed that prenatal androgens affect the genes responsible for the development of fingers, toes and the reproductive system.
“We have shown that promiscuous primate species have low index-to-ring-finger ratios, while monogamous species have high ratios.
“We used this information to estimate the social behaviour of extinct apes and hominins.
“Although the fossil record is limited for this period, and more fossils are needed to confirm our findings, this method could prove to be an exciting new way of understanding how our social behaviour has evolved.