The human body is often likened to a high-performance machine.
But it is so much more than that. It works 24 hours a day for decades without (for the most part) needing regular servicing or the installation of spare parts.
It runs on water and a few organic compounds, is soft and rather lovely, reproduces itself with enthusiasm, makes jokes, feels affection and appreciates a red sunset.
How many machines do you know that can do any of that? There is no question about it. You are truly a wonder.
And how do we celebrate the glory of our existence? Well, for most of us by exercising minimally and eating maximally.
Think of all the junk you throw down your throat and how much of your life is spent in a near vegetative state in front of a glowing screen.
Yet in some kind and miraculous way our bodies look after us, extract nutrients from the miscellaneous foodstuffs we push into our faces and somehow hold us together.
Even when you do nearly everything wrong, your body maintains and preserves you. Most of us are testament to that in one way or another.
Five out of six smokers won’t get lung cancer. Most of the people who are prime candidates for heart attacks don’t get heart attacks.
Every day, it has been estimated, between one and five of your cells turns cancerous and your immune system captures and kills them. Think of that.
A couple of dozen times a week, well over 1,000 times a year, you get the most dreaded disease of our age, and each time your body saves you.
Our bodies are a universe of 37.2 trillion cells operating in more or less perfect concert more or less all the time.
An ache, a twinge of indigestion, the odd bruise or pimple is about all that in the normal course of things announces our imperfectability.
There are thousands of things that can kill us – slightly more than 8,000, according to the World Health Organisation – and we escape every one of them but one. For most of us, that’s not a bad deal.
‘Feel this,’ the doctor is saying to me. We are in the dissecting room at the University of Nottingham Medical School and Dr Ben Ollivere is directing my attention to a piece of detached tubing in the upper chest of a male body.
I am struck by a powerful thought. In the dissecting room, the human body is no longer a wondrous piece of precision engineering. It’s meat.
Ben instructs me to stick my gloved finger into the interior of the tube and feel it. It is stiff, like uncooked pasta.
I have no idea what it is. ‘The aorta,’ Ben says, with what seems like pride.
I am frankly amazed. ‘So that’s the heart?’ I say, indicating the shapeless lump beside it.
Ben nods. ‘And the liver, pancreas, kidneys, spleen,’ he says, pointing out the other organs of the abdomen in turn.
Ben is an old friend and a distinguished academic and trauma surgeon. There isn’t anything in the human body that doesn’t fascinate him.
‘Just consider all that the hand and wrist do,’ he says. He tugs gently on an exposed tendon in the cadaver’s forearm up near the elbow and, to my surprise, the little finger moves. Ben smiles at my startlement and explains that we have so much packed into a small space in the hand that a lot of the work has to be done remotely, like strings on a marionette.
‘The wrist is just a thing of beauty,’ he goes on. ‘Everything has to go through there – muscles, nerves, blood vessels, everything – and yet it has to be completely mobile at the same time.
‘Think of all the things your wrist has to do – take a lid off a jam jar, wave goodbye, turn a key in a lock, change a light bulb. It’s a magnificent piece of engineering.’
Ben’s field is orthopaedics, so he loves bones and tendons and cartilage the way other people love expensive cars or excellent wines. ‘See that?’ he says, tapping a small, smooth, very white obtrusion at the base of the thumb, which I take to be a bit of exposed bone.
‘No, it’s cartilage,’ he corrects. ‘Cartilage is remarkable, too. It is many times smoother than glass: it has a friction coefficient five times less than ice.
‘Imagine playing ice hockey on a surface so smooth that the skaters went 16 times as fast. That’s cartilage.
‘But unlike ice, it isn’t brittle. It doesn’t crack under pressure as ice would. And you grow it yourself. It’s a living thing.
‘None of this has been equalled in engineering or science. Most of the best technology that exists on Earth is right here inside us.’
Before we move on, Ben examines the wrist more closely for a moment. ‘You shouldn’t ever try to kill yourself by cutting your wrists, by the way,’ he says.
‘All of those things going in are wrapped in a protective band called a fascial sheath, which makes it really hard to get to the arteries.
‘Most people who cut their wrists fail to kill themselves, which is no doubt a good thing.’
He is briefly thoughtful. ‘We are designed not to die.’ This seems a slightly ironic thing to say in a big room full of dead bodies, but I take his point.
We tend to think of our bones as inert bits of scaffolding, but they are living tissue too. They grow bigger with exercise and use just as muscles do.
‘The bone in a professional tennis player’s serving arm may be 30 per cent thicker than in his other arm,’ Margy Pratten, an associate professor of anatomy told me – citing Rafael Nadal as an example.
Look at bone through a microscope and you will see an intricate array of productive cells just as in any other living thing. ‘Bone is stronger than reinforced concrete,’ says Ben, ‘yet light enough to allow us to sprint.’ All your bones together will weigh no more than about 20 lb (nine kilograms), yet most can withstand up to a ton of compression.
‘Bone is also the only tissue in the body that doesn’t scar,’ Ben adds. ‘If you break your leg, after it heals you cannot tell where the break was. There’s no practical benefit to that. Bone just seems to want to be perfect.’
Even more remarkably, bone will grow back and fill a void.
‘You can take up to 30 centimetres of bone out of a leg, and with an external frame and a kind of stretcher you can have it grow back,’ Ben says. ‘Nothing else in the body will do that.’ Bone, in short, is amazingly dynamic.
The skeleton is, of course, only one part of the vital infrastructure that keeps you upright and mobile. The bulk of you, no matter how modestly built you are, is muscle.
You have more than 600 muscles altogether. We tend to notice our muscles only when they ache, but of course they are constantly at our service in 1,000 unappreciated ways – puckering our lips, blinking our eyelids, moving food through the digestive tract.
You need a dozen to move your eyes over the words you are reading now. The simplest movement of the hand – a twitch of the thumb, say – can involve ten muscles. Many of our muscles we don’t even think of as muscles – our tongue and heart, for instance.
Altogether, you are about 40 per cent muscle if you are a reasonably slender man, slightly less if you are a proportionately similar woman, and just keeping that mass of muscle uses up 40 per cent of your energy allowance when you are at rest and much more when you are active. Because muscle is so expensive to maintain, we sacrifice muscle tone really quickly when we are not using it.
Studies by Nasa have shown that astronauts – even on short missions, from five to 11 days – lose up to 20 per cent of muscle mass.
All of these things work together in a deft and splendid choreography. Nowhere is this better demonstrated than in your hands.
Inside each of them you have 29 bones, 17 muscles (plus 18 more that are in the forearm but control the hand), two main arteries, three major nerves (one of which, the ulnar nerve, is the one you feel in your elbow when you hit your ‘funny bone’) plus 45 other named nerves and 123 named ligaments, all of which must coordinate their every action with precision and delicacy. The hand is a marvellous creation without question, but not all its parts are equal.
If you curl your fingers into a fist, then try to straighten them out one at a time, you will find that the first two pop up obediently enough, but that the ring finger doesn’t seem to want to straighten out at all. Its position on the hand means that it can’t really contribute much to fine movement and so it has less in the way of discriminating musculature.
Nor, surprisingly, do we all possess the same component parts in our hands. About 14 per cent of us lack a muscle called the palmaris longus, which helps to keep the palm tensed.
It is rarely missing from top-ranked sportsmen and women who need a strong grip to perform, but is otherwise quite dispensable.
It is often noted that we have opposable thumbs (by which is meant that they can touch the other fingers, giving the capacity for a good grip) as if this were a uniquely human attribute.
In fact, most primates have opposable thumbs. Ours are just more pliant and mobile.
What we do have in our thumbs are three small but resplendently named muscles not found in any other animals, including chimps: the extensor pollicis brevis, the flexor pollicis longus, and the first volar interosseous of Henle.
Working together, these muscles in the thumb allow us to grasp and manipulate tools with sureness and delicacy. You may never have heard of them, but these three small muscles are at the heart of human civilisation. Take them away and our greatest collective achievement might be winkling ants out of their nests with sticks.
The feet, our other disproportionately bony outposts, receive a lot less praise and attention when it comes to discussing the features that make us special, but in fact the feet are pretty marvellous, too.
The foot has to be three different things: shock absorber, platform and pushing organ. With every step you take – and in the course of a lifetime you will take probably something in the region of 200 million of them – you execute those three functions in that order.
Our feet were designed to grasp, which is why you have an abundance of bones in them. They were not designed to support a lot of weight, which is one reason they ache at the end of a long day of standing or walking. Ostriches have eliminated this problem by fusing the bones of their feet and ankle – but then ostriches have had 250 million years to adjust to upright walking – roughly 40 times as long as we have had.
The miracle of human life is not that we are endowed with some frailties, but that we aren’t swamped with them.
As we have seen, our genes come from ancestors who most of the time weren’t even human. Some of them were fish. Lots more were tiny and furry and lived in burrows. You are the product of three billion years of evolutionary tweaks.
We would all be a lot better off if we could just start afresh and give ourselves bodies built for our particular human needs: to walk upright without wrecking our knees and backs, to swallow without the heightened risk of choking, to dispense babies as if from a vending machine.
As modern-day humans, we pass our existence within this miraculous, warm wobble of flesh and yet take it almost entirely for granted. How many among us know even roughly where the spleen is or what it does? Or what our lymph nodes are up to?
How many times a day do you suppose you blink? Five hundred? A thousand? You’ve no idea, of course. Well, you blink 14,000 times a day – so many that your eyes are shut for 23 minutes of every waking day.
Yet you never have to think about it, because every second of every day your body undertakes an unquantifiable number of tasks – a quadrillion, a nonillion, a quindecillion, a vigintillion (these are actual measures); at all events some number vastly beyond imagining – without requiring an instant of your attention.
In the second or so since you started this sentence, your body has made a million red blood cells. They are already speeding around you, coursing through your veins, keeping you alive.
Each of those red blood cells will rattle around you about 150,000 times, repeatedly delivering oxygen to your cells, and then, battered and useless, will present itself to other cells to be quietly killed off for the greater good of you.
Altogether it takes seven billion billion billion (that’s 7,000,000,000, 000,000,000,000,000,000, or seven octillion) atoms to make you. No one can say why those seven billion billion billion atoms have such an urgent desire to be you.
But your atoms are just building blocks, and are not themselves alive. Where life begins precisely is not so easy to say.
The basic unit of life is the cell – everyone is agreed on that. The cell is full of busy things – ribosomes and proteins, DNA, RNA, mitochondria and much other microscopic arcana – but none of those are themselves alive. The cell itself is just a compartment – a kind of little room to contain them, and of itself is as non-living as any other room.
Yet somehow when all of these things are brought together, you have life. That is the part that eludes science. I kind of hope it always will.