In a recent post I mentioned that there was an error in Jobling, Hurles and Tyler-Smith’s (generally very good) book on Human Evolutionary Genetics. Discussing an important measure of genetic distance (Nei’s D), the authors state that D varies between 0 and 1. I was fairly sure that this was wrong, as D is minus the log of a fraction, and the fraction can vary between 1 and 0, so it therefore seems that D can vary from 0 to infinity (that is, it increases without limit as the fraction approaches 0). I was a bit nervous about pointing this out, as I don’t like to disagree with those more expert than myself, so I was pleased to find my belief confirmed in another book, Speciation, (2004) by Jerry Coyne and Allen Orr, who say clearly (page 73) that D can range from 0 to ∞.

This isn’t by any means the first time I’ve noticed an error in a textbook. It is particularly annoying to find mathematical errors in a book aimed at students and other non-specialist readers. An expert in the field will probably be able to see immediately that something puzzling is just a careless slip or printing error, whereas a student may spend a long time trying to make sense of it, and worrying that they are missing something. I suggest that textbook authors and publishers should be fined $1,000 for every error of this kind!

Addendum from Razib: AJHG has a review of the Jobling, Hurles and Tyler-Smith book, as does Henry Harpending. I enjoyed it a great deal, though advanced readers might find it more interesting as a lead/source for a wide range of papers and texts on topics that pique their curiousity as opposed to a nuts & bolts primer. If you want something more technical, I recommend Genetics of Human Populations by Bodmer and Cavalli-Sforza, the data is out of date, but the equations are all good (and the price is really phat if you get it used).