How to Make a Human Being: A Body of Evidence. Christopher Potter
chemical bonds and radiant heat.3 The tree is the water absorbed at its roots, it is all the water that has transpired from its leaves and been absorbed into the air, all the oxygen and carbon dioxide exchanged. It is the wind that has shaped it, and the parasites that live in its bark, that have mottled its leaves, the cankers and the mistletoe.4 It is the birds that nest in it and the birds that have nested in it, even the birds and insects that have briefly landed on its leaves and branches. It is the cows that have rubbed against it, and the initials lovers have carved on its trunk. It is the roots that stretch underground and join the roots of other trees. It is everyone who has ever sat in its shade. Whatever the tree is, it is you who decides where it begins and ends. There are no separate things, only what we make so. And so our investigations of the world begin as conscious human acts of separation made by observers. They begin in subjectivity, that, once the boundaries of our objects are decided upon, we call objectivity. You can say what a tree is and what it means to you, but from the point of view of the world, the world is of a piece and there is no tree.
And then snow descends and unifies the tree into the landscape. Snow unifies the suited tree to the field, even strident modern houses and factories and cars are reclaimed as natural forms, softened and smudged in. Gentle, muffling snow reminds us that the world is one.
The tree is as it is seen and painted by the artist. No one can draw a tree without in some measure becoming that tree, a painter once told Emerson. In a Gainsborough portrait the feathers in the woman’s hat have the same featheriness as the leaves on the tree.
The sunlight measures the tree, as does the wind passing through its branches, and you absorb the sunlight and the sounds and you measure the tree to your own ends. Or at night you make out the tree in a different fashion out of starlight. Even without the sun and stars you might – in theory – be able to measure the tree out of its relation to the particles coming into and out of existence in the vacuum. If the vacuum were truly empty there would be no tree. Yet you are conscious of the tree as a tree, as a unified thing. This is a profound problem.
1 | Physicists’ seeming obsession with fundamental descriptions takes them as far away from the human condition as it is possible to go, to the beginnings of the universe. Even though they often pretend otherwise – affecting to disdain philosophy – physicists care what the fundamentals are: what the material is that reality is woven out of; whether it is space that is real and time the illusion, or vice versa; whether or not there really are causes and effects; how the world can be all of a piece and yet have things in it. If we are ever to make a human being we will have to abandon these concerns and move closer to our own scale. In this evolving, expanding universe in which we find ourselves we might take everything to be equally existent no matter when it first appeared, or at what scale. Time may be an illusion from a reductive physical point of view, but it is no less real now at this point in the evolution of the universe. There are causes and effects in the human world. Things happen, and we make things. We might take the universe as read and wonder instead how the universe evolved human beings as things in time.
Who’s there?
The opening words of Hamlet
Darwin gives courage to the rest of science that we shall end up understanding literally everything, springing from almost nothing – a thought extremely hard to comprehend and believe.
Richard Dawkins
1 | These days evolution is invoked to describe not only the evolution of life, but the evolution of the whole universe. Evolution is the story of what happened, in an expanding universe, to those first particles created at the Big Bang.
There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
Charles Darwin, On the Origin of Species
If superior creatures from space ever visit earth, the first question they will ask, in order to assess the level of our civilisation, is ‘Have they discovered evolution yet?’
Richard Dawkins
2 | For reasons not entirely understood, a patch of energy escapes the eternally inflating quantum landscape and expands into a universe of space and time. The energy evolves into energy of different kinds. An array of different kinds of particles come into existence spontaneously and randomly out of nothing, among them quarks, gluons and photons. As the universe expands the particles evolve into other kinds of partlcles. Under gravity the first light atoms – hydrogen and helium mostly – are drawn together as quasars and stars. Gravity arranges the stars as galaxies and galaxy superclusters. The stars catch fire as great furnaces that transmute light atoms into heavier atoms. When some of the stars of the right size die and explode the first heavy atoms are spewed into space. Gravity acts on the light atoms and the newly forged heavier atoms to make a second generation of stars. Some of these stars of the right size explode and release even heavier atoms into space. And repeat. Simple compounds like water, carbon dioxide and some amino acids are also produced. How the simple compounds evolve into DNA is not yet known (it may never be known), but few doubt that evolution is how it happened. Human beings tell a plausible, if patchy, tale of how hydrogen was woven into flesh. It may be the same tale aliens tell. Assuming that aliens are made of flesh. And tell stories.
3 | Physicists used to criticise biology for being too descriptive and not testable. All that changed with the advent of genetics and molecular biology. Less than a century ago natural selection alone could not account for the complexity of living forms, but genetic theory turned natural selection into a rigorously testable theory.
4 | Life used to distinguish biology from physics. For centuries, biology was plagued with the notion of vitalism, a mysterious – perhaps even mystical – force that was invoked to account for the seemingly unbridgeable gap between living and non-living forms. In his book What is Life? (1944) Erwin Schrödinger wondered if life might emerge out of some simple physics of self-replication and a single molecule. His book influenced many biologists. Francis Crick swapped physics for biology when he read it.
Genetics killed vitalism. Once we could explain how genes determine biological function, vitalism was redundant. The golden age of molecular biology was ushered in. The discovery of the gene revealed the astonishing relatedness of all living forms. It came as a great shock to biologists to discover how much genetic information is conserved across all life forms. Our gene sequences are 95 per cent identical to those of yeast. The difference between yeast and a human being is largely a matter of organisation. We share 50 per cent of our genetic code with a banana. Sixty per cent of genes in humans that are associated with disease have a homologous gene – i.e. the same gene making the same proteins and doing a similar job – in the fly. The Krebs cycle – a vital part of the metabolic process – is common to all forms of life, from single-celled bacteria to flies and kangaroos. Within the Krebs cycle is a tiny epicycle that generates ATP, the chemical that powers muscle contraction and nerve impulse. ‘Where there is life,’ writes chemist P.W. Atkins, ‘there is ATP.’ These observations can be proclaimed either derisively or with wonder. Do we have more in common with flies and bananas than we have allowed ourselves to imagine, or do genes only take us so far? Or both?