Holding Hands

We use them every day, yet we do not realize how much we rely on them. Hands are a wonderful thing. They help us feel the world, take things, prepare food, create tools, build houses, feed ourselves, communicate and express love or dislike with a slap.

Michel de Montaigne expressed it very well when he wrote: “Behold the hands, how they promise, conjure, appeal, menace, pray, supplicate, refuse, beckon, interrogate, admire, confess, cringe, instruct, command, mock and what not besides, with a variation and multiplication of variation which makes the tongue envious.”

Many expressions used in common language refer to them - such as: "healing hands", "he's putty in her hands", "a show of hands", "in good hands", "to give a hand", "helping hands" to list but a few.

They are mentioned in songs, like in this old French one from Charles Trenet: "Place your hand in my hand, your heart against my heart and tell me if there is any more charming way of being happy...).  Not to mention the Beatles' hit "I Wanna Hold Your Hand" famous the world over.


This is why I want to spend a few minutes writing about hands and the differences between human and non-human primate hands.

Looking at the pictures below, you will notice that humans have a much longer thumb than most primates and our feet (of which we are not going to speak about today) have lost the opposability of the big toe, which in turns provides for more stability - an adaptation to bipedal locomotion.

The use of our hands and the evolution of two typical human handgrips, identified by JR Napier, are believed to have played an important role in the survival of our species.  These are the "precision grip" (most useful for throwing objects) and the "power grip" (most useful for hitting with clubs).  (Journal of Anatony, 2003 - Richard W. Young - "Evolution of the Human Hand: The Role of Throwing and Clubbing")

Human hands have the most mobile thumb of all primates (you can touch the tip of your thumb to the tip of your auricular finger) - this is what enables us to have "precision grip".

Humans have straighter fingers compared to primates.  Chimpanzees have hands (probably very similar to those of our early ancestors) with a short relatively weak immobile thumb, elongated carpal and metacarpal bones.  The third and fourth metacarpal are very strong and used for knuckle walking.  The proximal and middle phalanges are curved toward the palm, which is useful for arboreal locomotion.  Their fingertips are cone-shaped.

As a matter of fact, primate hands and feet evolved differently for different primates.  If you look at the hands and feet of baboons, for instance, they look kind of similar. Their hands and feet share many functions for grasping and propulsion.  Gibbons have hands and feet most adapted to suspensory behavior and vertical climbing.  Spider monkeys have an underdeveloped (quasi non-existent) thumb and long curved fingers. Their hands are most adapted to brachiation. They are not as dexterous as capuchin monkeys whose hands are close to ours.

All monkeys have nails instead of claws (except the lemur who still has a toilet claw on its feet).  This enhances their sense of touch.

"The primate hand is a remarkable invention and one that helped forge a new relationship between the animal and its environment.... The baboons' nimble fingers were into everything, plucking grass blades, digging up roots, selecting the tiniest herb pecking out of the ground cover... Their hands had both power and precision; the opposability of the thumb and fingers was as essential here on the savannah as it had been millions of years ago when tiny ancestral primates climbed into the forest canopy.  Some foods had to be excavated from rock-hard ground, others had to be peeled or seeded."  ("Almost Humans - A Journey Into the World of Baboons" - Shirley C. Strum)  

Much like us, non-human primates use their hands to accomplish a multitude of tasks - locomotion, feeding, changing the shape of objects to create tools (the use of a rock to crack a nut), scratching, grabbing, slapping (lemurs are big slappers), grooming.

Grooming is extremely important, it is the social glue in primate societies (including ours - who doesn't like a good massage?) Grooming helps individuals reconcile, form alliances, develop friendships.  Females groom a new mother in the hope of being granted the right to hold her infant.  It is used for courtship, to cement bonds between family and clan/group members, as well as soothing a grieving member.  All this would not be as efficient without hands.

Finally, hands are essential for humans and non-human primates to communicate with each other.  In the 1960s, baby chimps were trained to use sign language; Koko is famous for pointing at symbols on a board and expressing her thoughts and desire pretty clearly to her human team.  This is not surprising, since many studies show that sensory information travels from the hands to the brain.  This is why some researchers, like Virginia Berninger, professor of educational psychology at the University of Washington, are big advocates of handwriting for children as well as aging folks.  When we hold a pen, large regions of the brain involved in thinking, language and memory are activated.  When a young chimp learns how to hold a twig to fish out termites, the same regions light up.  

So, next time you hold a hammer, make sure to keep your fingers out of the way.   Love your hands!