How Homo Sapiens could he have the upper hand over his Neanderthal cousin? Researchers show that a simple morphological innovation modifying the anatomy of his thumbs could have played a major role...
Reconstruction of the grip used by Neanderthals, with the thumb extended along the handle and directing the force.
What if Homo sapiens , during its victorious confrontation with its Neanderthal cousin 40,000 years ago, had benefited from a boost from evolution? In the literal sense of the word! Ameline Bardo from the University of Kent (Canterbury, England) and her colleagues wanted to check whether the two species of hominins differed in their way of handling and handling tools. To do this, the researchers analyzed and measured the joints between the thumb bones of our missing cousin using a 3D methodology. “We were lucky enough to have 5 Neanderthal fossils , says Ameline Bardo. Three were discovered on French territory, one in Israel, and one in Iraq .“Second step of their work:compare the measurements with those obtained on 5 fossil humans and 40 modern adult humans at the same trapezium-metacarpal complex, the bones located at the base of the thumb.
A major difference between the thumbs of the two species
The result, published November 26, 2020, in the journal Scientific Reports , validates the intuition of scientists:there is indeed a major difference between the thumbs of the two species. In Neanderthals, the finger joint was found to be flatter, giving it fewer degrees of freedom than ours. Which suggests that our cousin, if he was good at holding an object powerfully like a hammer with his thumb extended along the handle (see illustration), must have been much more numb for precision grips such as, for example, picking up an object. between thumb and forefinger. Larger, more curved, the articular surfaces of the thumbs of modern humans seem, on the contrary, perfect for performing such gestures. "If Neanderthals were still capable of such skill, explains Ameline Bardo. it must have taken a lot more effort. In addition, the grip had to be less forceful and the pressure applied less than what Homo sapiens and modern humans are capable of."
What about the thumbs of Homo naledi or Homo habilis?
A startling difference that must have had a huge impact on the history of early humans, favoring some, namely us, over others. This unprecedented anatomical characteristic would then have allowed our ancestors to design better weapons and objects, giving them an undeniable evolutionary advantage over the other hominins with whom they disputed territories and resources.
A question remains, however:did this anatomical upheaval appear in Homo sapiens or would the beginnings of it already be perceptible in his ancestors? To find out for sure, Ameline Bardo intends to continue her study by looking at the thumbs of some of them, "notably Homo naledi (discovered in 2013 in South Africa) and older specimens such as Homo habilis " , she says. Another question:could this new characteristic have consequences on the entire anatomy of Homo sapiens and modify its general posture? Did he walk better, run better, because of this increased manual skill? To find out for sure, this specialist in prehistoric hands is collaborating with a specialist...in the feet.