“Gosto das suas costas” – anonymous
I stepped out onto the street, still in a daze with those dreamy Portuguese words dancing in my head. A keychain dangled around my neck, the glittery ‘A’ bouncing off my stomach in a steady rhythm. A Sainsbury’s trolley full of bones dragged behind me as I marched towards the British Museum. Latte in hand and a smile on my face, I said: “I’m here. Where do I set up?”
It was London Anthropology Day. This was my first workshop.
I felt the blood rush towards my head. Everything was upside down. I adjusted my hands according to yoga instructions I had been given many years ago – “you have a very long back” I had been told. I tilted my head to the side to meet 50 pairs of very confused eyes staring intently at me… I was, after all, doing downward dog in a Paleoanthropology workshop.
“So you see, you really get the sense of how much longer our legs are in relation to our arms when you get on all fours. Apes on all fours don’t look this silly. And all of this because we are bipedal.” I said.
A human in downward dog and chimpanzee on all fours
I stacked my body back onto my legs, turning the room right side up again. My heels landed at the bottom of their multicoloured boots, in a painful reminder of the missing left insole, and as the weight of my torso came bearing down on my feet, my spine adjusted sorely over my uneven legs. With a supernumerary lumbar vertebra that gives my back its extra length, and a left leg 9 mm shorter than the right that gives my spine a slight sideways bend, my backbone is both a beauty and a torment. Concealing the discomfort from my audience, I secretly cursed this human condition as my lower back begged for downward dog again.
Like 24 little doughnuts piled one on top of the other, the human vertebral column, the hallmark of our species, remains among the most problematic structure of the human body. The lower back, in particular, which plays a key role in keeping the trunk erect and in equilibrium with minimal force, has both been described as an ‘evolutionary failure’ and as a ‘highly sophisticated gear system’. Stacked into a solid but bendable formation like a sturdy flower stem, the five lumbar vertebrae (or six…) are wedged into a lordotic curve that allow for both stability and flexibility in withstanding the forces generated by the weight of a heavy head and large torso over two stilt-like legs – a compromise achieved by a mechanism of interlocking facets, that just like a jointed toy snake, allow movement between the vertebrae in some directions while preventing it from moving in others.
The human S-shape vertebral column has two main curvatures, the thoracic kyphosis and the lumbar lordosis
But our locomotor repertoire of choice means we subject our lower backs to a great deal of bending stress throughout life – the most dangerous kind of stress for bony tissue – and because we can’t spend our lives in downward dog… we must pay the price in pain.
In fact, low back pain, or lumbago, is the most common type of back pain. It affects 80% of people at some point in their lives and accounts for more sick leave and disability than any other medical condition. In the U.S., lower back pain competes with the common cold as the leading reason why people see a physician; it is the number one cause of disability in workers under age 45 and is responsible for an estimated $20 to $50 billion annual expenditure in medical treatments and disability payments. Yet, in the UK, 19 in 20 cases of low back pain are classed as ‘non-specific’, because it is usually not clear what is actually causing the pain, and only about 1% are ever found to have severe causes.
The human lower back anatomy allows for a great deal of flexibility
A pain that has no cause, no cure, is not due to any physical abnormality yet plagues the whole of humanity? It is no surprise that lower back pain is described by the more spiritual as a part of our trial on earth, a burden we must endure in this physical life, only to be alleviated in the next celestial one.
But relief would have to wait for now. At least until I could locate my left insole.
“Was he bipedal?” asked a student while holding up an Australopithecus africanus skull. The room was now hot like an overcrowded yoga studio. I readjusted my back, and as I took the skull in my hands I wondered if ‘he’ had ever felt this way too…
And as it appears, he may very well have. It is likely that early hominids evolved a human-like lumbar lordosis around 3 million years ago, and they are even regularly quoted as having had six lumbar vertebrae – it was looking like, as far as my backbone was concerned, I had more in common with the africanus in my hand, than with the undergraduate opposite me.
However, individuals with six lumbar segments have only been observed in some gibbons and modern humans where they occur with a frequency of 2-8% in different populations, whereas great apes have only four or even three segments. The hominid axial skeleton shows many derived adaptations for bipedalism including an elongated lower back, both in number of vertebrae and in length; this stabilizes the upper body over the lower limbs by positioning the trunk’s centre of mass above the hip. In this case, the long lumbar spine of early hominids would have to be explained by the incorporation of a sixth vertebra during evolution, whereas the primitive condition of the common ancestor of great apes and humans is thought to be either five or four. However, this explanation requires us to accept the appearance and subsequent disappearance of lumbar vertebrae during our evolution – an unsavory explanation as far as the rules of evolution and parsimony go.
So much for my connection with africanus, my sixth vertebra was sounding more like a ‘fail’ than a ‘sophistication’… But at least there was yoga, and a very helpful 9mm thick insole to level me back.
I stepped back onto the streets, energized from the excitement of the workshop. The steady sound of the trolley wheels behind me, eating their way through the London pavement. As I moved away from the museum gates, the cheerful clinking of the shiny keychain ricochetted against my belly, to the pace of my slightly lopsided gait.
“Gosto das suas costas” I heard again.
I couldn’t tell where it was coming from, and its meaning was lost to me, but I smiled anyway. I slipped into a daze, under the welcoming July sunlight. The trolley’s wheels grew silent behind me as did the clinking of the keychain. I felt my feet float away from the ground and the weight of the world being lifted from my every vertebrae, until my back no longer hurt. I heard it again, this time in English, the same exact blurred sentence playing in a loop: “I like your back.” My whole body drifted away from the concrete floor as the city noises grew distant beneath my multicoloured boots. I closed my eyes and let myself go. My head was spinning under the spell of those hazy words that now multiplied below me: “I like your back. I like your back.” From one came many, faster and faster, louder and louder, like the beating of a drum, thumping away until I could not longer ignore them. My body suspended over the cityscape, I finally opened my eyes to meet the voices now shouting at me…
Underneath me there was London, a warm and sunny London, spreading like an enormous worn straw mat, and on that straw mat there were people, a crowd, no, many crowds, countless crowds expanding as far as the eye could see, all coming together into a friendly cohort of toy soldiers calling my name and chanting in unison…
“Welcome back! Welcome back!”
Author’s note: scientific facts aside, much of the account has been heavily fictionalised.