‘She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity—A Review


Gregory Cochran
Gregory Cochran
6 min read

A review of She Has Her Mother’s Laugh: The Powers, Perversions, and Potential of Heredity by Carl Zimmer. Dutton (May 2018) 656 pages.

In this book, Carl Zimmer tries to lay out how our ideas and knowledge of genetics have developed over time, and where we are today. He mixes in discussion of the social impact of these ideas. Some of those discussions are reasonable, some are not.

He covers a very wide range of topics, from contagious cancers in clams to recent developments in genetic engineering.

Before I go any further – Zimmer is wordy. He has things to say, but he never uses one word when ten will do. The facts are always part of some long-winded human-interest story. If you like that sort of thing, you may like this book. I cannot say that I did.


For example, he dislikes Francis Galton, and mocks him for his poor results in mathematics at Cambridge, a subject Galton really wanted to excel in. Galton hired brilliant tutors, but he just couldn’t hack math — interesting, since he later helped develop key concepts in statistics such as correlation and regression to the mean. It’s as if all the special prep in the world won’t compensate for a lack of innate talent (a commonplace observation, unless you’re Malcolm Gladwell) — but that, of course, supports Galton’s central thesis, namely, that intelligence is largely determined by hereditary factors. At this point, things have become sufficiently meta that I can’t tell whether Zimmer even knows whether he’s dissing Galton or agreeing with him.

Maybe math blindness ran in the family. Darwin, Galton’s half-cousin, said:


Another example: Zimmer talks about Cyril Burt, a British psychologist and hereditarian who did twin studies of intelligence. In particular, studies of identical twins separated early in life, a good way of testing the strength of genetic influences on intelligence and other traits. Burt claimed that heredity had a very strong influence on intelligence. He also believed that there were class differences in intelligence — that the children of barristers and boffins outscore, on average, those of navvies and knackers, partly for genetic reasons. Which is the case, of course.

Leon Kamin, then a psychologist at Princeton, detected errors in Burt’s publications and concluded that Burt’s work was fraudulent. Kamin argued that genes had zero influence on intelligence — which would suggest that dogs really can play poker. But other people (Thomas Bouchard) have done their own studies of separated identical twins and gotten the same results as Burt. It appears that Burt got old and careless, republishing earlier work. Genome-based estimates give similar results. And nobody now believes Kamin’s claim of zero heritability.






Look, there’s a standard quantity, the fixation index, Fst, that measures the genetic difference between two populations. Fst = 0.0 means the two populations are identical, Fst = 1.0 means they have nothing in common. For example, the genetic distance between the HapMap sample of Europeans and their African sample is 0.153.

But the genetic distance between North American wolves and coyotes is also 0.153. Am I supposed to believe that wolves and coyotes are really just the same or that the species known as canis lupis is a social construct? It’s possible for two populations with that degree of genetic differences to be profoundly different — because wolves and coyotes are profoundly different. Two populations can be very different even if they generally share the same genetic variants, as long as those variants have different frequencies. This is especially so if there is a systematic shift — for example, if most of the variants that increase height (plus variants) are more common in one group, while the minus variants have higher frequencies in the other.

In dogs, there is more within-breed genetic variation than between-breed variation: about 70% is within-breed. For humans, about 85% is within-population.

According to Lewontin’s argument, which has been pulled apart by A.W.F. Edwards and numerous others, dog breeds must not really be very different. Great Danes can’t really be very different from teacup Chihuahuas. Pit bulls can’t really have different personalities than Labrador retrievers. What do you think?



David Reich (who is NOT an English major) knows that the clusters that emerge from genetic analysis correspond fairly closely to old-fashioned racial classifications. He mentions Lewontin’s argument in Who We Are and How We Got Here — but as an example of obfuscation. “This carefully worded formulation is deliberately masking the possibility of substantial average differences in biological traits across populations,” he writes. On the other hand, having once been a physics major does not make you infallible: Reich and Zimmer both say a real race has to be very old. It doesn’t count if it was created by admixture of earlier populations several thousand years ago. So since they are the result of a mix of Anatolian-origin farmers and Indo-European pastoralists about five thousand years, Europeans cannot be a real ‘race’. So Mexicans, ‘la raza’, are imaginary, like elves and Eskimos. While German Shepherds, created in 1899, are just a bad dream — albeit a dream with teeth.

Some other reviews have neglected to mention Zimmer’s embrace of complete nonsense on a number of questions about human genetic variation — it’s common nonsense, politically correct and (really) politically required nonsense. The New York Times is the Alamut of political correctness: if you don’t smoke the dope, out you go.

This book is up-to-date and covers a very wide range of topics in a low-intensity way. Most readers will learn a lot. Carl Zimmer deserves some thanks for a decent account of scientific progress in a field that he evidently finds deeply disquieting.

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Gregory Cochran

Gregory Cochran is the co-author of The 10,000 Year Explosion: How Civilization Accelerated Human Evolution.