Tiktaaliks, kangaroos and hairy apes

Welcome to the Rap Guide to Evolution Blog! We will be taking a closer look at the science behind the lyrics and hopefully intrigue you. This is an interactive discussion, so if you have a comment, idea, spot a mistake or just want to say ‘hello’ please do so.

Like gravity, evolution just ‘is’. There is no plan, no goal, no right or wrong.

Do your knees cause you agony? Have you got a shoddy ankle? Or maybe a back that gives out every time you try and pick a pencil up from the floor?

Well that’s bipedalism (walking on two legs) for you. All very well for covering long distances, but the basic body plan that probably preceded it, quadrupedalism (walking on four limbs – also witnessed in adult humans with Uner Tan Syndrome), mean that the mechanics of weight and force distribution were markedly different from the elongated upright form (floppy head with dodgy connection) we carry around with us today.

We are of course not alone in standing on two legs, birds do it and so do kangaroos. What makes us unusual from most other living monkeys and apes is that we can stand on our back legs effortlessly and without wasting lots of energy. Other primates will move bipedally, but only occasionally. Moving through mangrove swamps, proboscis monkeys frequently wade bipedally. Similarly bonobos will walk bipedally when carrying tools, however this is not their main form of locomotion.

Ostriches: one of the fastest living bipeds

Indeed bipedalism has become a defining trait of what it means to be human and arose in one of our early ancestors, Australopithecus, around four million years ago. But of course the true beginnings were much earlier yet, when land dwelling animals, like the Tiktaalik, first emerged with no notion that eventually hairy apes would be roaming the land.

It may not help that bad back, but at least you and your body are subject to the same forces as everything else on this planet. Selection only works within the constraints of the current environment. Your back, knees and ankles are a bit dodgy as the preceding hardware just wasn’t capable of being moulded into a ‘perfect’ shape – a CD may seem superior to a cassette tape, but if you only have a cassette player at hand, the tape is the only way forward.

Indeed, it is a truism to think of anything in the living world as ‘perfect’ – there simply is no such thing. Everything is constantly in flux. Species survive within certain limits. Maybe some behavioural flexiblity and cultural ingenuity helps us humans (remember your mom saying: “Put on a coat, it’s cold out!”), but we are no more or less ‘special’ than anything else out there. Having said that…I can’t think of any other animal which would be stupid enough to cripple itself picking up a pencil.

Fun Fact: There are other alternatives to bipedalism, you could walk around on two arms like octopuses occasionally do.

Octopus marginatus hiding between two shells from East Timor.

Images courtesy of: Nick Hobgood and Gary M Stolz via Wikimedia Commons and Morgue File

Written by: Djuke Veldhuis

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