Neanderthal thumbs were best adapted to holding tools with handles

Neanderthal thumbs were better suited to holding tools in the same way we hold a hammer, according to an article published in Scientific reports. The results suggest that Neanderthals may have found precision grips – where objects are held between the fingertip and thumb – more challenging than “ squeeze ” grips, where objects are held like a hammer, between the fingers. and the palm with the thumb direct the force.

Using 3D analysis, Ameline Bardo and colleagues mapped the joints between the bones responsible for the movement of the thumb – collectively referred to as the trapeziometacarpal complex – of five Neanderthal individuals and compared the results with measurements taken from the remains of five early beings. modern humans and 50 recent modern adults.

The authors found covariations in the shape and relative orientation of the complex trapeziometacarpal joints that suggest different repetitive thumb movements in Neanderthals than in modern humans. The joint at the base of the thumb of the Neanderthal remains is flatter with a smaller contact surface and better suited to an extended thumb positioned along the side of the hand. This thumb posture suggests the regular use of “squeeze” grips, such as the ones we now use to hold tools with handles. In comparison, these joint surfaces are generally larger and more curved in recent modern human thumbs, an advantage when grasping objects between the finger and thumb pads, known as precision grip.

Although the morphology of the Neanderthals studied is best suited for power “ squeeze ” grips, they would still have been capable of precision hand postures, but would have found it more challenging than modern humans, according to the authors.

Comparing the fossil morphology between Neanderthal hands and modern humans can provide further insight into the behaviors of our ancient relatives and early use of tools.

Reference: “The implications of thumb movements for Neanderthals and modern human manipulation” November 26, 2020, Scientific reports.
DOI: 10.1038 / s41598-020-75694-2