Researchers from the University of Liverpool are analyzing the finger bones of Neanderthals and the upright walking primate Australopithecus afarensis to see if pairing and mating is encoded in our digits, writes Discovery News.
The discovery may offer insight into how humans emerged as evolutionary winners.
The team used literature on the fossils of early human-like primates that contained hands with intact index and ring fingers, the second and fourth digits on a hand.
The ratio between those two fingers is thought to be a telltale marker for how much of the androgen class of hormones -- specifically, testosterone -- a human or primate was exposed to while in the womb.
The thinking is that additional androgen leads to longer ring fingers. "Highly contentious" studies indicate that men and women who receive high levels of androgen before birth are more likely to be stronger, faster and more sexually competitive, according to the article.
So the researchers wanted to see if these results were true among our forebears, using two Neanderthal and one A. afarensis skeletons with first bones of index and ring fingers intact.
The scientists found that Neanderthals had long ring fingers, suggesting that they were rather indiscriminate in their sexual partners, mating with several. (Neanderthals are thought to have lived in groups.)
But the short ring fingers of A. afarensis indicates that it may have been faithful to a single mate -- directly contrasting theories that the diminutive A. afarensis lived in groups and were prey to others.
The implications of this research -- no doubt highly speculative -- could help scientists piece together why "pair-bonded" modern humans bested non-pair-bonded Neanderthals in Europe.