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Our Ancient Diet Played A Part In Why Our Hands Look The Way They Do

W. Scott McGill/Shutterstock

W. Scott McGill/Shutterstock

It is the shape and dexterity of our hands that make it possible for us to write, paint, gesticulate and even take part in a fist fight. The common sense is that the nimble human hand evolved as our ancient ancestors started with using tools. However that might not be the whole story, according to a latest research released by the Journal of Human Evolution.

Compared with other primate species, our hands are very different from theirs, because our wrists are more flexible, our joints are larger, our thumbs are longer and more muscular, but our fingers are shorter. Such adaptions enable us to do some tasks like building a fire, throwing spears at woolly mammoths as well as making and using tools.

Scientists from Chatham University, Pennsylvania, and the University of Kent, UK, believe that some tool behaviors are more fundamental to the evolution of the human hand than others. They conclude from their study that although archaeological evidence shows that early hominins participated in different kinds of tool behaviors, it is not likely that all behaviors equally influenced modern human hand anatomy.

Of specific importance, they say, is weapon-making and our ancestors’ taste for the juicy and calorie-rich substance found in bones, aka bone marrow.

In order to further study their hypothesis, scientists recruited 39 volunteers to do some neolithic-era tasks, such as cracking a nut, wielding a hand axe, hammering flint with a stone, and hitting bones to extract bone marrow. While volunteers were doing all these work, they were equipped with a glove-like contraption to monitor manual pressure distributions.

The results demonstrate that using a stone to crack open nuts involved the least manual pressure and, therefore, nutcracking  isn’t a reason for us to evolve uniquely dextrous hands, Instead, it was using a hammerstone to collect marrow or make flakes of flint (to use as weapons) that required the most pressure. It is suggested from the study that these two behaviors had more of an influence on the anatomical and functional evolution of the human hand than the other 37 behaviors measured.

So, it is now quite clear that although the evolution of the human hand is a long and complicated process that cannot be explained by one or two neolithic activities, munching on bone marrow and carving stone tools might have been two of the decisive forces in this process.

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