Darwin's little tree

by Martín Bonfil Olivera
Published in Milenio Diario, April 1, 2009

In 1837, returning from his five-year travel on board of theHMS Beagle, and starting the two decades he would spend thinking about the "transmutation of species", Charles Darwin wrote in his notebook the phrase "I think", and then he drew a little branched outline: the first evolutionary tree.

In 1859 he published The origin of species, and the only illustration he included was a more elaborate tree. Since then, the tree is evolution's dominant metaphor: a ramified process in which new species appear from pre-existent ones.

But attacking Darwin is a hobby few can resist, from fanatics that try to banish it to restless biologists that pretend to jump into fame by proving that some of his ideas are wrong.

And of course, there are a lot of aspects in which Darwin was wrong (his theory of heredity, for example, was way out of line). With time, the Darwinian theory of evolution by natural selection has been corrected, completed and fine tuned. Still, it remains as the backbone of modern evolutionary thinking.

Recently, New Scientist magazine published an article that caused an upstir, because it declared that the discovery of "horizontal gene transfer" (not from parents to descendants, but like that which occurs when two bacteria exchange antibiotic resistance genes, or when a virus injects genes from another species into us, as has happened lots of times in human evolution) is the downfall of the image of evolution as a tree.

But gene evolution is not the same as species evolution. Of course, evolution is not as simple as Darwin thought, and in some aspects it looks more like a confusing web than a tidy tree. There are branches that are weirdly connected one with another (like when some bacteria entered old cells to become our mitochondria and chloroplasts). Maybe the tree has more than one root (there is evidence for several "origins of life" that later became connected).

Maybe the tree metaphor will change, or will be substituted by a web. But from that to proclaiming "the end of Darwin" or biology's next great revolution, there's a long way to go.

(translated by Adrián Robles Benavides)

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Posthumous experiment

by Martín Bonfil Olivera
Published on Milenio Diario, October 22, 2008

Rarely does a scientific discovery drastically change the contents of school books. Normally, the advances of science, with their slow but constant refining and their very rare revolutions, take years to be reflected in books.

But the discovery that the team leaded by Jeffrey Bada, from Scripps Institution, which involves the participation of Mexican biologist Antonio Lazcano, from UNAM (Science, October 17), will surely change Biology books.

It deals with, as reported by MILENIO Diario, the re-analysis of the results from the classical experiment about the origins of life performed by Stanley Miller in 1953. It consisted of the introduction, into a very simple apparatus, of water and several of the gases that, back then, were supposed to have formed the atmosphere of the primitive earth (methane, hydrogen and ammonia), around four billion years ago. This mixture was boiled and re-circulated for several days and also exposed to electric discharges . After that, the mixture was analyzed with the methods current in those days; in it, five amino acids (units that form the proteins, essential molecules for living beings) were found.

What Bada's team found when checking the samples stored by Miller together with his laboratory log was that, apart from the classic experiment, there were two variants that were not reported. In one of them, the gases, instead of simply circulating, were injected in a jet to the chamber where the electric discharge was occurring.

It is today's belief that the primitive atmosphere did not have the composition that Miller thought. But the jet apparatus simulates the conditions of a volcano, where these gases are indeed found. And a lot of times, the eruptions are accompanied by lightning. In the "volcanic" experiment, with today's modern methods, twenty two amino acids were found. With this, we now have a new option to explain the appearance of molecules that formed the living beings.

But, why study the origins of life? Not only to know our history; also because if simple chemical process like these occurred on Earth, they could also be present in other worlds. The booming science of Astrobiology is a granddaughter of Miller's experiment, today again, surprisingly current. Good science is always full of surprises.

(translated by Adrián Robles Benavides)

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