Sunday, February 5, 2012

Improbable evolution: how life beats the odds - John Rennie - SmartPlanet

In the 1993 film Jurassic Park, the mathematician character Ian Malcolm, so scene-stealingly played by Jeff Goldblum, rants about science quite a bit, often to poor effect. His references to chaos theory are an utter hash, for example, making it sound indistinguishable from Murphy’s Law. And in the speech that summarizes the central conflict of the rampaging dinosaur plot, he insists “life finds a way”:

“If there is one thing the history of evolution has taught us, it’s that life will not be contained. Life breaks free, expands to new territories, and crashes through barriers, painfully, maybe even dangerously, but, ah, well, there it is.”

The florid, unqualified sentiment of Malcolm’s quote probably made many biologists in the audience cringe, in keeping with what is described as the character’s “deplorable excess of personality.” (Again, thank you, Jeff Goldblum!) Malcolm’s unwavering fatalism toward biology going rogue may be shared by many opponents of genetic engineering who can never be reassured that their specific fears may be groundless. That’s most unfortunate.

Nevertheless, Ian Malcolm wasn’t entirely wrong. Time and again, organisms have shown themselves to be adept at evolving around seemingly insurmountable obstacles to their spread and survival. Evolutionary adaptation isn’t perfect and inevitable, but it allowed some ancient fish to become four-legged land dwellers, for instance, and some microorganisms to thrive in boiling hot sulfur springs and radioactive pools. Unwavering fatalism about biology going rogue, however, can also breed hysteria over genetic engineering and pandemics.

Biologists have therefore long wanted to understand better the evolutionary mechanisms that enable species to occupy previously forbidden ecological niches — and the limitations on those mechanisms. Several recent discoveries highlight the importance of that work and provide at least some of the answers.

Fatal flu and viruses that never say die

The most prominent of that work is the much-publicized recent research by independent labs in the Netherlands and Wisconsin on the adaptability of the H5N1 bird flu virus. As I’ve discussed previously, those scientists discovered that combinations of just five simple mutations in the bird flu’s DNA — which appeared repeatedly during their experiments — allowed the virus to become a highly infectious, frequently deadly flu in mammals. The work reinforced concerns that the bird flu virus might have the potential to evolve with disturbing ease into the cause of a global pandemic among humans. Indeed, the results were so troubling that flu researchers have elected to impose a temporary moratorium on similar experiments while they consider whether the benefits would compensate for any dangers of the mutant viruses maybe getting loose.

For a pathogen to jump from one host species to another might seem statistically impossible if multiple mutations are needed to effect the transition: if each of those mutations was individually a one-in-a-million shot, the odds of all five occurring spontaneously in one organism would be one in a million trillion trillion (10 to the 30th power). Creationists often make exactly that kind of argument to argue the impossibility of evolution. The flaw in that argument, however, is that it ignores how those mutations can arise as part of a process that makes them collectively more”

A great insight into exactly that process now comes from a study by Justin R. Meyer and others in the laboratory of Richard E. Lenski of Michigan State University, as published recently in Science. They found a clever way to investigate how organisms can leap past obstacles to their survival by looking at coevolution in the lab between the common bacterium E. coli and the lambda virus that infects it.

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