November 3, 2010

Finger Fossils Suggest Neanderthals Were Promiscuous

Human ancestors from over four million years ago were quite promiscuous, with monogamous relationships developing as hominins evolved over time, claims a new study published in the British scientific journal Proceedings of the Royal Society B.

The research, which was led by Emma Nelson of the University of Liverpool's School of Archaeology, Classics and Egyptology, involved the study of the fossilized fingers of Neanderthals and ancient apes, as well as the species Ardipithecus ramidus and Australopithecus afarensis.

According to Nelson and her colleagues, the length of the index finger in relation to the ring finger can indicate the levels of prenatal androgens, including testosterone. In turn, the finger-length ratio can be used to extrapolate the levels of masculine characteristics, including aggressiveness and sex drive. More promiscuous species of primates tend to have low index to ring finger ratios, while monogamous species are more likely to have high ones.

"The team found that the fossil finger ratios of Neanderthals, and early members of the human species, were lower than most living humans, which suggests that they had been exposed to high levels of prenatal androgens," said a University of Liverpool press release. "This indicates that early humans were likely to be more competitive and promiscuous than people today."

"The results also suggest that early hominin, Australopithecus--dating from approximately three to four million years ago--was likely to be monogamous, whereas the earlier Ardipithecus appears to have been highly promiscuous and more similar to living great apes," it added. "The research suggests that more fossils are needed to fully understand the social behavior of these two groups."

In a statement, Nelson pointed out that the fossil record for the time period being studied was "limited" and that additional evidence was "needed to confirm our findings," she said that using the index to ring finger ratio measurement "could prove to be an exciting new way of understanding how our social behavior has evolved" over the years.

According to AFP, "The study's conclusions add a new element of debate over human lineage. More promiscuous species of hominins would have an advantage over monogamous ones, in terms of numbers and the size of the gene pool."


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