A Swing of Opinion

Only a few years ago we were all being told barefoot running was the path to an enlightened and injury-free life. The work of Harvard paleoanthropologist Prof. Daniel Lieberman was popularised as his endurance running theory of human evolution struck many chords for those wanting a more active, simple and natural approach to movement and exercise. However, the barefoot running movement created as many arguments, shin-splints and inflammations as it solved and we are at threat of doing the same thing again with the rise of the ‘brachiation theory’.

A decade ago Crompton and colleagues published a landmark paper presenting considerable evidence that our knuckle-walking cousins (particularly chimps, bonobos and gorillas) developed their locomotion strategies independently and after their split from our branch of the family tree (Crompton et al, 2008). If chimps and gorillas developed knuckle-walking after the separation from our Homo lineage, it means that the earlier locomotion style of suspension is more representative of our primitive state and therefore closer to our evolutionary path. Slowly, the idea of our last common ancestor using overhead suspension rather than knuckle-walking has crept into some literature.

It may be that our more distant ape cousins, the gibbons and orangutans, with their suspensory anatomy and locomotor behaviour, resemble our primitive state more closely than gorillas, chimps and bonobos. With the current trend of evolutionary medicine, this leads to the obvious conclusion that we should ‘get back to basics’ and start swinging from the branches a little more. But, before you head of to find the closest monkey bars or think about cashing in by designing some barehand climbing gloves, there are a number of problems with this story.

The science is good, there are numerous factors that show we might have come down from the trees with bipedalism already reasonably well developed. It is easier to stand on two legs holding onto overhead branches as you walk along lower boughs. However this is not full-on brachiation, it is suspensory locomotion.

Brachiation is swinging from branch to branch, something the gibbons, our most distant ape cousin, specialise in. A gibbon can reach up to 30 miles per hour gliding effortlessly between hand supports. Sadly we can’t compete – we are not built the same way.

Humans and gibbons may have evolved from similar creatures that used suspensory behaviours of some form, but the anatomy of Homo has changed considerably in the 7 million years since we last shared the canopy with any of our cousins. Our arms are short relative to the rest of the body when compared to any other ape but especially to the gibbons and orangs. Likewise, our fingers are short but our thumbs are long giving us plenty of dexterity for manipulation. You might consider yourself great at catching and holding onto a branch but try finding a randomly oriented support at 30mph – wouldn’t it be great if your margin of error was a little higher? A gibbon’s long, curved phalanges adapt perfectly to grasping and their short thumb stays out of the way as the branch looms closer, while the ball and socket in the wrist joint can fine-tune to the angle of the branch.

Speaking of ball and socket joints, the human glenoid fossa orients almost directly laterally, with the spine of the scapula almost horizontal to the ground. This is in contrast to the scapulae of all other apes, which are elongated from inferior angle to the glenoid fossa and orient more superiorly; a convenience if you are either quadrupedal or suspensory and unnecessary for a biped.

Like barefoot running, brachiating is an attractive back-to-basics idea – ‘health and happiness comes from swinging in the trees because that’s where we came from and we are designed to brachiate’. However, it is just not quite true and we will lose medical and anatomical street-cred if we keep saying it.

I do not wish to be a killjoy – there are many benefits to getting out, being active and using our bodies in novel ways, and if it takes a ‘return to your roots’ story to motivate you then so be it. However, be aware there are concerns with suspending and not all of them are gravity related. Climbing and suspension are great exercises but they are just that – an exercise. Our skeletal alignment has evolved so that we are no longer aligned for brachiating. Concomitantly, our soft tissues have not adapted to a repeated overhead supporting role. Like barefoot running, we will have to build up tolerance and strength for the new stresses and we will have to ensure adequate range of motion in the scapula to orient the glenoid fossa upwards to prevent gleno-humeral impingement.