Or, Reading the entrails of chickens: molecular timescales of evolution and the illusion of precision. Pointed out to me by a palaentologist friend. There’s a pdf here. Nothing at all to do with climate, but an interesting tale nonetheless. Or so I assume: it seems sensible, and was recommended by someone sensible, but may have been superceeded since 2004 for all I know. But this is the first time I’ve heard this wonderful story, and as someone who occaisionally reads about molecular clocks in the papers and assumes its all kosher, this article was a surprise.
Whats up (its fairly clear from the paper, I think, so I won’t bother summarise it more than briefly) is that estimates of species divergence from genetic clocks have been made with spurious accuracy and extrapolated well beyond reasonable bounds to produce erroneous results.
So we start with For almost a decade now, a team of molecular evolutionists has produced a plethora of seemingly precise molecular clock estimates for divergence events ranging from the speciation of cats and dogs to lineage separations that might have occurred ,4 billion years ago. Because the appearance of accuracy has an irresistible allure, non-specialists frequently treat these estimates as factual. In this article, we show that all of these divergence-time estimates were generated through improper methodology on the basis of a single calibration point that has been unjustly denuded of error. The illusion of precision was achieved mainly through the conversion of statistical estimates (which by definition possess standard errors, ranges and confidence intervals) into errorless numbers. By employing such techniques successively, the time estimates of even the most ancient divergence events were made to look deceptively precise. For example, on the basis of just 15 genes, the arthropod-nematode divergence event was ‘calculated’ to have occurred 1167 +/- 83 million years ago (i.e. within a 95% confidence interval of ,350 million years). Were calibration and derivation uncertainties taken into proper consideration, the 95% confidence interval would have turned out to be at least 40 times larger (~ 14.2 billion years).
And the language is wonderful: The reason for the transformation of the secondary calibration date into a primary one, which is equivalent to blood becoming Cabernet Sauvignon… and In what will surely not be the last chapter in this story, a recent review in Trends in Genetics  contains four blood-curdling innovations involving statistical methodology, taxonomy, physics of time reversal and logic.
Sigh. I wish climate papers were written like that.