A new study conducted by a biologist at the University of Utah suggests that the need to throw punches is the reason for the evolution of our opposable thumbs.
"The idea that aggressive behavior played a role in the evolution of the human hand is controversial," said David Carrier, senior author of the study, according to a press release. "Many skeptics suggest that the human fist is simply a coincidence of natural selection for improved manual dexterity. That may be true, but if it is a coincidence, it is unfortunate."
The study utilized male cadaver arms and tied tension lines to the tendons, which were used to adjust the arms and hands in any way that the researchers wanted. Afterwards, the arms were used to throw punches and slaps at a dumbbell designed to detect force, and the researchers measured the power of impact.
"Each one of these hands took about a week of work," said Carrier. "First we had to dissect it to expose the muscles, apply one or more strain gauges, and then attach the lines to all the tendons so you can control the position of the wrist, thumb and fingers to create a buttressed fist, unbuttressed fist or open-palm posture. Everything had to be lined up just right - all the joints, tension in muscles, the orientation of bones."
Carrier and his team of researchers also believe that the faces of our human ancestors evolved to withstand punches, while more recent faces have become more sensitive in response to our lessened reliance on brute force violence.
Despite the evidence that Carrier presents, members of the evolutionary community are not convinced and believe that the support for his hypothesis is not strong enough to prove it definitively.
The study was published in the Journal of Experimental Biology.
