Do you think they are "reading the entrails of chickens" with these dates? Do a google scholar search for that phrase if you don't know what I'm talking about.
Yes, take these divergence time with a huge grain of salt. Should go without saying. Here is the abstract of the 2003 TREE paper entitled "Reading the entrails of chickens: molecular timescales of evolution and the illusion of precision" by Graur and Martin, vol. 20: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).
So...we should paste "very roughly" on the front of all those numbers?:)) Still--very cool, and lots of fun to play around with! Thanks for the link!(OT but--are your boys wearing Jin Bei in that cute photo up there?)
Yes, all times are approximate. Can't really tell you how much so. If you go to their website, you can read about how the times are computed.(Yes, wearing jinbei during Tanabata.)
Are those numbers calibrated to fossil data at all? Or pure molecular clock? (if so, *shudder*)
Psi, the divergence times are based on results from a long list of articles. The results are all based on molecular data, and some (many) exclusively on molecular data.Why the shudder?
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