I recently offered some commentary on a scientific paper, “Life before Earth,” written by a couple of geneticists, Alexei Sharov of the National Institute on Aging in Baltimore, and Richard Gordon of the Gulf Specimen Marine Laboratory in Florida, who suggest that the rate at which evolution advances necessitates that life must be much older than the Earth and may trace back to within the first 2 billion years of the universe’s existence.
Sharov and Gordon base their analysis on the claim that genetic complexity advances exponentially and they draw a comparison with Moore’s law which, though not actually a law, describes the fact that roughly every two years semiconductor manufacturers are able to double the number of transistors that can be crammed onto a microprocessor. Sharov and Gordon say that genetic complexity doubles every 376 million years.
The idea that life began long before the existence of our planet is certainly a view well outside orthodox views of evolution. And science is inherently conservative in its approach to radical new ideas. So, the fact that Sharov and Gordon’s paper has either been ignored or dismissed does not in and of itself indicate it is worthless.
However, I’m not a geneticist, so I’m not in a position to provide any critical analysis on what they wrote. Massimo Pigliucci, on the other hand, is a rare combination: he’s both a geneticist and a philosopher. So, unlike some other scientists, he doesn’t contemptuously dismiss the paper, but he does have the wherewithal to pick it apart.
[T]he first highly questionable statement … is that “the core of the macroevolutionary process … is the increase of functional complexity of organisms.” No, it isn’t. Stephen Gould long ago persuasively argued that there is no necessary direction of increased complexity throughout evolution. The only reason why complexity historically follows simplicity is because life had to start simple, so it only had “more complex” as a direction of (stochastic, not directed) movement. It’s a so-called “left wall” effect: if you start walking (randomly, even) from near a wall, the place you end up is away from the wall. And of course, as Gould again pointed out, life on earth was (relatively) simple and bacterial for a long, long time — and none the worse for it either. Moreover, the most complex organism on earth — us — though very successful in certain respects, is actually a member of a very small and often struggling group of large brained social animals. Measured by criteria such as biomass, bacteria still beat the crap out of us “superior” beings.
But the real problems begin for the Sharov and Gordon paper when they finally get to the business at hand: correlating genomic complexity with time of origin of the respective organisms, and then extrapolating back in time. [As a commenter on my Twitter stream pointed out, they could just as “reasonably” have extrapolated into the far future, arriving at the conclusion that the entire universe will eventually be made of DNA…]
The authors realize that simple genome length won’t cut it, because what matters is functional complexity, and there are some portions of the genomes of various organisms that are redundant and possibly without function. Nonetheless, they end up plotting the log-10 of genome size against time, which is how they arrive at the figure of 9.7 billion years ago for the origin of life. As PZ Myers quickly pointed out, however, even if we accept the procedure at face value, they simply cherry picked the data: plenty of organisms that don’t show up on the graph (plants and fungi, for instance) would completely scramble the results. Make no mistake about it: this is a fatal blow to the entire enterprise, and one that the authors ought to have thought about well before posting the paper. [Continue reading…]