REVISED AND EXPANDED EDITION 41
who have written on the history of mental testing, because they do
not have expertise in this vital subject, and I do. I am an evolutionary
biologist by training. Variation is the focal subject of evolutionary
biology. In Darwinian theory, evolution occurs (to put the point
technically for a moment) by the conversion of variation within pop-
ulations into differences between populations. That is (and now
more simply), individuals differ, and some of this variation has a
genetic basis. Natural selection works by differentially preserving
the variation that confers better adaptation in changing local envi-
ronments. As a caricature, for example, hairier elephants will do
better as ice sheets advance over Siberia, and woolly mammoths will
eventually evolve as selection, acting statistically and not absolutely,
preserves more hirsute elephants generation after generation. In
other words, variation within a population (some elephants hairier
than others at any moment) becomes converted into differences
through time (woolly mammoths as descendants of elephants with
ordinary amounts of hair).
Now consider the subjects of this mix: genetically based variation
within populations, and development of differences between popu-
lations—and what do you have? Voila: the subject of the The Mismea-
sure of Man. My book is about the measurement of supposedly
genetically based variation in intelligence among members of a pop-
ulation (the aim of IQ testers assessing all the kids in a classroom, or
of nineteenth-century craniometricians measuring the heads of all
the workers in a factory, or weighing the brains of their dead aca-
demic colleagues). My book is also about the putative reasons for
measured differences between groups (racial in white vs. black, or
class-based in rich vs. poor, for example). If I know the technical
basis of any subject, I understand this material best (and many psy-
chologists don't because they have not had training in a profession
like evolutionary biology that regards the measurement of geneti-
cally based variation as central to its being).
For my second specific rebuttal, I entered paleontology in the
mid 1960s, at an interesting time in the profession's history, when
traditions of subjective and idiosyncratic description were begin-
ning to yield to calls for more quantitative, generalized, and theoret-
ically based approaches to fossil organisms. (I am, by the way, no
longer so beguiled by the lure of quantification, but I was so trained
and was once a true believer.) We young Turks of this movement