8 June, 2009Issue 9.7Science

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Soufflé à la Darwin

Jacob Lemieux

toibinNick Lane
Life Ascending: The Ten Great Inventions of Evolution
Profile Books, 2009
288 Pages
ISBN 978-1861978486

A white wooden plaque hangs next to the door of Darwin’s original home in Shrewsbury. “Charles Darwin was born here in 1809”, the plaque reads, but the exhibit ends there. Visitors are not invited to enter. “The Mount”, as it was known to the Darwin family, who occupied it for the better part of the 19th century, has been converted into a government tax office.

The absence of any further mention of The Mount’s most famous inhabitant is especially remarkable this year, Darwin’s bicentennial. A few miles away, in downtown Shrewsbury, large banners proclaiming “Darwin 200” are concentrated in the main shopping plaza. Walk into Waterstones on the town’s High Street and you’ll find a torrent of titles whose publishers are hoping to ride the wave of worldwide “Darwinmania”. Life Ascending: The Ten Great Inventions of Evolution, by Nick Lane, is Profile Books’ attempt to get in on the game.

Lane, who earned a doctorate in biochemistry before becoming a full-time science writer, garnered high praise for clear exposition and bold ideas in his first two works, on oxygen and mitochondria, respectively. These books, aimed at non-specialists, succeeded in unconventional areas: neither diatomic molecules nor organelles are typical popular science fare, and that gave these ambitious books a certain panache.

A background in biochemistry lends itself to the molecular issues less frequently covered in popular books on evolution. The most interesting of these issues is the question of abiogenesis: how did life on Earth emerge from inanimate matter. In his most famous work, Darwin avoided speculation on this question (ironic for a book titled The Origin of Species), instead focusing on how life evolved once it existed. The curious, elegant last sentence of The Origin reads: “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 law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

This sentence—which leaves room for a creator who “originally breathed” life into the first organisms—was more a move of political expediency than scientific inference. Darwin knew the question of life’s genesis was intractable with current science, and though he was fully aware of the religious implications of his work, he was probably relieved to leave a place for a creator in his theory. Following publication of The Origin, Darwin never showed an interest in engaging in the religious debate it engendered, focusing his work on further scientific investigation (including eight years devoted to drafting the definitive study of barnacles) and defending his theory from scientific attack. The popular and religious debates he left to his friends and supporters, most notably Thomas Henry Huxley, who came to be known as “Darwin’s Bulldog”. Privately, however, he did muse about the origins of life. In a letter to his close friend Joseph Hooker, he wrote, “But if (and oh! what a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, &c., present, that a proteine (sic) compound was chemically formed ready to undergo still more complex changes, at the present day such matter would be instantly absorbed, which would not have been the case before living creatures were found.”

This speculation was put to the test in 1953 by the young Stanley Miller. Lane begins his discussion on the origins of life here, with the famous Miller-Urey experiment. Miller, then a graduate student at the University of Chicago, reacted a mixture of water, methane, ammonia, and hydrogen gas—then believed to be the contents of Earth’s early atmosphere—with electric sparks, meant to play the role of lightning. Within a few days, he found appreciable concentrations of most of the amino acids which form the building blocks of proteins. The notion of a “prebiotic soup” out of which life evolved came to dominate thinking about life’s origins for the next two decades. Miller’s findings, however, were perhaps too perfect. With the fluency of an adept biochemist, Lane masterfully deconstructs this appealing but flawed hypothesis. Given what we now know, the Miller-Urey soup recipe turns out not to be the correct one. More recent experiments have not reproduced Miller’s promising results. Lane then introduces us to two competing theories which account for the early evolution of life from deep ocean vents.

It is here that Lane is at his best, parsing competing theories with the command of a practitioner, yet cushioning the sharp edges of the technical details. He deftly employs metaphor, toeing the line between presenting the fully scientific details and sketching the larger picture. The old metaphorical stalwarts are there (thermodynamics is the science of “desire”, what atoms do and don’t “want” to do), but so are some new ones (the transfer of high-energy phosphate groups is a children’s game of tag).

But as Lane ascends the ladder of life—moving away from prebiotic chemistry onto topics such as sex, movement, sight, and “hot blood”—his comparative advantage as a biochemist fades. This area of evolutionary literature already has been covered extensively in popular format by biologists such as Richard Dawkins, Stephen Jay Gould, and EO Wilson. One wonders whether Lane would have been better off if he had remained on his native terrain.

Indeed, prebiotic chemistry is especially rich terrain in the immediate aftermath of last month’s announcement by University of Manchester researchers that they had synthesized RNA nucleotides in a laboratory setting using the ingredients that would have existed on early Earth. Proponents of the “RNA world hypothesis” argue that ribonucleic acid polymers—whose subunits are composed of a sugar, a base, and a phosphate group—could have given rise to life by encoding information (as DNA does) and catalysing replication (as proteins do). But no scientist had successfully shown how the initial RNA nucleotides could have emerged in high yield from appropriately prebiotic conditions—until now.

Last month, the University of Manchester’s John Sutherland and his team stunned the world of prebiotic chemistry with an announcement that they had synthesized RNA nucleotides under conditions similar to those that existed on the early Earth. Whereas other scientists had tried to put the sugar, base, and phosphate group together piece-by-piece, Sutherland’s team took a different approach. As Sutherland told reporters: “Basically, we took half a base, added that to half a sugar, added the other piece of base, and so on. The key turned out to be the order that the ingredients are added and the way you put them together — like making a soufflé.”

RNA synthesis could have occurred under “prebiotically plausible conditions“, Sutherland and his co-authors wrote in Nature. Or, as Sutherland subsequently said, “It’s consistent with a warm pond evaporating as the sun comes out”. In short, Darwin’s speculations in his letter to Hooker might have been correct after all.

For readers interested in learning more about prebiotic chemistry and early evolution, Lane’s Life Ascending provides a helpful primer (even if Sutherland’s findings mean that the recently released book is still not quite up-to-date). But ultimately, the cottage industry that has emerged around Darwin’s bicentennial pays little homage to his scientific legacy. After penning The Origin, Darwin dedicated his final years to filling its gaps, and published a further five editions. The most meaningful celebration of his life is the work of scientists such as Sutherland who continue to test his hypotheses—and who strengthen the theoretical framework that The Origin of Species left behind.

Jacob Lemieux is a DPhil student Clinical Medicine in the Molecular Parasitology Group at St. John’s College, Oxford.