Thus, in the Babylonian Poem of Creation, it is related how man was fashioned from clay mixed with the blood of a god:
‘Let him be made of clay animated by blood’.2
Although, today, it is easy to dismiss these myths, they are in reality man’s earliest attempts to find answers to the questions still plaguing us – they are the first theories of everything. Today we know where the sun goes at night and why spring follows winter. But much of our knowledge is received wisdom and this wisdom of ages was hard-won. How many of us would be able to prove that the Earth revolves around the sun, when any fool can see the sun rise in the morning, travel across the sky and descend below the horizon at night?
The dawn of the rational approach to understanding our world is usually attributed to the intellectual revolution of the sixth and fifth centuries BC which gave rise to the ancient Greek civilization. One of the earliest philosophers was Thales (born about 600BC). Although his writings have been lost, several of his sayings have survived, including, ‘the lodestone has life, or soul, as it is able to move iron’. This short phrase implies a complex set of beliefs. Firstly, that the ability to initiate movement is a key attribute of life. This is a concept we will return to as, in modern molecular interpretation, it forms a cornerstone of this book. Secondly, that this ability to make movement betrays the presence of a ‘soul’. Like the mythmakers before him, Thales considered that the phenomenon of life pointed to the presence of supernatural forces. Finally, the equation: ability to initiate movement = life = soul, has been taken to the extreme of attributing the property of life to a variety of inanimate objects, such as a magnet (lodestone). This reflects a widespread tradition of pantheism in the ancient world. As the third-century Roman chronicler, Diogenes Laertius put it, ‘the world was animate and full of divinities’.
The ancient world’s greatest biologist was undoubtedly Aristotle. Sadly, our received image of him is frozen by those chalk-white busts of venerable bearded philosophers who seem to stare into a perfect world of spheres and equilateral triangles. But Aristotle’s vision was far more earth-bound than that. Like his predecessor, Heraclitus, he believed that ‘knowledge enters through the door of the senses’, and as a young man he spent several years living on Lesbos, studying marine life. His biological writings betray the acute observation and attention to detail which is the hallmark of all great naturalists.
‘Animals also which fly and those which swim, fly by straightening and bending their wings and swim with their fins, some fish having four fins and others, mainly those which are of a more elongated form (eels for example), having two fins. The latter accomplish the rest of their movement by bending themselves in the rest of their body, as a substitute for the second pair of fins. Flatfish use their two fins and the flat part of their body, instead of the second pair.3
Instead of the venerable sage, we should imagine a younger Aristotle diving into the Aegean’s clear waters to retrieve starfish, crabs and anemones, to study their form or observe their behaviour.
‘The sea-urchin has a better defence system than any of them: he has a good thick shell all round him fortified by a palisade of spine.’4
Any lover of rock-pools will recognize an ally in Aristotle’s writing. But the scientist in Aristotle was not content to describe nature; he needed to explain it. Perhaps, later in the day, he would set light to driftwood to cook his catch and ponder on the ephemeral quality he roasted out of the living flesh. Like Thales, Aristotle considered that the essential quality of living creatures was that they possessed their own internal will and this allowed creatures to initiate independent movement.
‘For nature is in the same genus as potency, for it is a principle of movement – not however in something else but the thing itself.’5
To Aristotle, living creatures were made distinct by their ability to move themselves. His concept of movement was more subtle than simple locomotion. The shoreline of Lesbos, had taught him that clams, anemones, or indeed simple seaweed moved very little (except when pulled by the waves and the tide), but were still very much alive. To Aristotle, there were six forms of movement: generation, destruction, increase, diminution, alteration and change of place. This broader conception of movement actually reflects a more general meaning to the verb, to move, than our modern usage, one that remains apparent when we say that we found a particular piece of music to be deeply moving, or when a motion is passed by a debating society. Our modern usage is rooted in Newtonian mechanics, and a better translation of Aristotle’s concept of movement would be the term action, a word with a precise, useful meaning in modern physics, to which we will return. The essential point of Aristotle’s argument is that all living organisms possess an internal will that allows them to initiate and perform actions such as growth, regeneration, procreation and movement. Aristotle, like Thales, ascribed this internal will – the cause of independent action – to the eidos, the soul or psyche: ‘The soul creates movement’.6
It would be mistaken to equate Aristotle’s eidos too closely with the Christian soul. He believed all animals and plants were endowed with a ‘soul’ capable of initiating movement. To Aristotle, this soul was clearly a much more functional entity than the Christian moral guardian. However, only man possessed the highest form of soul: the source of reasoning and moral judgement.
Aristotle’s writings, lost and then found by the Arabs and passed from them to mediaeval Europe, were to form the basis of Western thinking throughout the Middle Ages. The Aristotelian concept of a soul was translated into the vitalist approach to biology. To the vitalists, life possessed a mysterious property, the élan vital, or living spirit, whose nature lay beyond the realms of science. In the words of Joyce Kilmer:
Poems are made by fools like me
But only God can make a tree.
The vitalist tradition survived until the twentieth century in many biological writings. I remember biology textbooks that described the mysterious living protoplasm inside cells with the same awe and mystery that mystics describe the aura. However, the concept has been in retreat since the dawn of the Age of Reason in the seventeenth and eighteenth centuries, and no serious scientist subscribes to it today. The opposing camp, the Mechanists, were inspired by the machines that were, by then, revolutionizing the world; and they believed that life, like machines, could be understood in terms of the laws of chemistry and physics. They rejected the vitalist argument that life required special laws beyond conventional science. René Descartes (1596–1650) was a founding figure who proposed that animals were mere automata, in principle no different from the clockwork figures which played music or danced at fairgrounds. Descartes was however unwilling to accept the full implications of mechanism and reserved man a special place amongst God’s creations. He considered man’s intellectual capabilities, his reasoning power, betrayed the presence of an immortal soul. Mechanists had to wait for another century before books such as La Mettrie’s L’Homme Machine (Man the Machine) (1748) laid bare the full force of the mechanist manifesto. La Mettrie agreed that animals were no different from machines but argued that man differed from animals only in complexity. The way was now open for science to delve into the very substance of life.
Technical advances in analytical chemistry and microscopy naturally drove the life sciences towards reductionism – the belief that complex systems can be considered as the sum of their parts. Nineteenth- and twentieth-century scientists began a reductionist dissection of the chemistry of life. In 1853, the Lille brewing industry hired Louis Pasteur to discover why their wines soured. At that time, fermentation was considered purely a chemical reaction. Brewer’s yeast was thought to be a chemical catalyst facilitating the conversion of the grape-sugars to alcohol: yeast was not recognized as a living organism (which is not so strange when you examine it in its powdery form). The brewers’ hiring of the brilliant young chemist was, thus, hardly surprising.
Pasteur had made his name demonstrating that tartaric acid crystals came in two forms,