In fact, the more we have learned in recent years the more complicated matters have tended to become. Even thinking, it turns out, affects the ways genes work. How fast a man’s beard grows, for instance, is partly a function of how much he thinks about sex (because thinking about sex produces a testosterone surge). In the early 1990s, scientists made an even more profound discovery when they found they could knock out supposedly vital genes from embryonic mice, and the mice were not only often born healthy, but sometimes were actually fitter than their brothers and sisters who had not been tampered with. When certain important genes were destroyed, it turned out, others were stepping in to fill the breach. This was excellent news for us as organisms, but not so good for our understanding of how cells work since it introduced an extra layer of complexity to something that we had barely begun to understand anyway.

It is largely because of these complicating factors that cracking the human genome became seen almost at once as only a beginning. The genome, as Eric Lander of MIT has put it, is like a parts list for the human body: it tells us what we are made of, but says nothing about how we work. What’s needed now is the operating manual-instructions for how to make it go. We are not close to that point yet.

So now the quest is to crack the human proteome-a concept so novel that the term proteome didn’t even exist a decade ago. The proteome is the library of information that creates proteins. “Unfortunately,” observed Scientific American in the spring of 2002, “the proteome is much more complicated than the genome.”

That’s putting it mildly. Proteins, you will remember, are the workhorses of all living systems; as many as a hundred million of them may be busy in any cell at any moment. That’s a lot of activity to try to figure out. Worse, proteins’ behavior and functions are based not simply on their chemistry, as with genes, but also on their shapes. To function, a protein must not only have the necessary chemical components, properly assembled, but then must also be folded into an extremely specific shape. “Folding” is the term that’s used, but it’s a misleading one as it suggests a geometrical tidiness that doesn’t in fact apply. Proteins loop and coil and crinkle into shapes that are at once extravagant and complex. They are more like furiously mangled coat hangers than folded towels.

Moreover, proteins are (if I may be permitted to use a handy archaism) the swingers of the biological world. Depending on mood and metabolic circumstance, they will allow themselves to be phosphorylated, glycosylated, acetylated, ubiquitinated, farneysylated, sulfated, and linked to glycophosphatidylinositol anchors, among rather a lot else. Often it takes relatively little to get them going, it appears. Drink a glass of wine, as Scientific American notes, and you materially alter the number and types of proteins at large in your system. This is a pleasant feature for drinkers, but not nearly so helpful for geneticists who are trying to understand what is going on.

It can all begin to seem impossibly complicated, and in some ways it is impossibly complicated. But there is an underlying simplicity in all this, too, owing to an equally elemental underlying unity in the way life works. All the tiny, deft chemical processes that animate cells-the cooperative efforts of nucleotides, the transcription of DNA into RNA-evolved just once and have stayed pretty well fixed ever since across the whole of nature. As the late French geneticist Jacques Monod put it, only half in jest: “Anything that is true of E. coli must be true of elephants, except more so.”

Every living thing is an elaboration on a single original plan. As humans we are mere increments-each of us a musty archive of adjustments, adaptations, modifications, and providential tinkerings stretching back 3.8 billion years. Remarkably, we are even quite closely related to fruit and vegetables. About half the chemical functions that take place in a banana are fundamentally the same as the chemical functions that take place in you.

It cannot be said too often: all life is one. That is, and I suspect will forever prove to be, the most profound true statement there is.

PART VI THE ROAD TO US

Descended from the apes! My dear, let us hope that it is not true, but if it is, let us pray that it will not become generally known.

Remark attributed to the wife of the Bishop of Worcester after Darwin's theory of evolution was explained to her

27 ICE TIME

I had a dream, which was not all a dream.

The bright sun was extinguish’d, and the stars

Did wander . . .

– Byron, “Darkness”

IN 1815 on the island of Sumbawa in Indonesia, a handsome and long-quiescent mountain named Tambora exploded spectacularly, killing a hundred thousand people with its blast and associated tsunamis. It was the biggest volcanic explosion in ten thousand years-150 times the size of Mount St. Helens, equivalent to sixty thousand Hiroshima-sized atom bombs.

News didn’t travel terribly fast in those days. In London, The Times ran a small story-actually a letter from a merchant-seven months after the event. But by this time Tambora’s effects were already being felt. Thirty-six cubic miles of smoky ash, dust, and grit had diffused through the atmosphere, obscuring the Sun’s rays and causing the Earth to cool. Sunsets were unusually but blearily colorful, an effect memorably captured by the artist J. M. W. Turner, who could not have been happier, but mostly the world existed under an oppressive, dusky pall. It was this deathly dimness that inspired the Byron lines above.

Spring never came and summer never warmed: 1816 became known as the year without summer. Crops everywhere failed to grow. In Ireland a famine and associated typhoid epidemic killed sixty-five thousand people. In New England, the year became popularly known as Eighteen Hundred and Froze to Death. Morning frosts continued until June and almost no planted seed would grow. Short of fodder, livestock died or had to be prematurely slaughtered. In every way it was a dreadful year-almost certainly the worst for farmers in modern times. Yet globally the temperature fell by only about 1.5 degrees Fahrenheit. Earth’s natural thermostat, as scientists would learn, is an exceedingly delicate instrument.

The nineteenth century was already a chilly time. For two hundred years Europe and North America in particular had experienced a Little Ice Age, as it has become known, which permitted all kinds of wintry events-frost fairs on the Thames, ice-skating races along Dutch canals-that are mostly impossible now. It was a period, in other words, when frigidity was much on people’s minds. So we may perhaps excuse nineteenth-century geologists for being slow to realize that the world they lived in was in fact balmy compared with former epochs, and that much of the land around them had been shaped by crushing glaciers and cold that would wreck even a frost fair.

They knew there was something odd about the past. The European landscape was littered with inexplicable anomalies-the bones of arctic reindeer in the warm south of France, huge rocks stranded in improbable places-and they often came up with inventive but not terribly plausible explanations. One French naturalist named de Luc, trying to explain how granite boulders had come to rest high up on the limestone flanks of the Jura Mountains, suggested that perhaps they had been shot there by compressed air in caverns, like corks out of a popgun. The term for a displaced boulder is an erratic, but in the nineteenth century the expression seemed to apply more often to the theories than to the rocks.