Reports of the National Center for Science Education

Review: Darwinian Detectives

Darwinian Detectives: Revealing the Natural History of Genes and Genomes
Norman A Johnson
New York: Oxford University Press, 2007. 220 pages.
Reviewed by
Rebecca L Cann

Just about every topic under the
banner "why genetics is important
to understand and still amazing to
many professional biologists" is covered
in this compact book. What a
delight to read about some well-chosen
examples, glittering in succinct
detail and presented in a manner designed to
intrigue and captivate a general audience.
After all, where else can you find the forensic
details about how a dentist did in an ex-lover with an HIV infection,
what the chimpanzee genome
project could tell us about differences
between the sex lives of all
three chimpanzees, the true origins
of Akita dogs, or what red-haired
singers might have in common with
talking Neanderthals? Think of the
conversation starters at your next
sushi bar encounter, where you can
captivate an audience with details
about the genomes of smooth versus
spiny pufferfish! Then toss off a
few comments about the delta 32
mutation in CCR5 and the Black
Plague, followed by the link
between silaic acids and huge
brains, and you are sure to be voted
geek of the week. The amazing thing
is that Norman Johnson has been
able to show the scientific method
making sense of the world in all this
crazy detail.

A designed biota would not be
as messy, as haphazardly assembled,
or as truly jerryrigged as the
genetic systems cobbled together
in the last billion years of random
processes and presented here for
your total wonderment.

Johnson starts with the general,
boxing the math for readers to skip
over completely or come back to
later, and moves to the specific in
well-organized sections. The book
starts with a good exposition of the
methods scientists use to deduce
how genomes are organized and
how they got that way, that is, evolution.
His discussion on natural selection,
both positive and negative, is
clear and easy to follow. The focus
on how scientists are able to identify
cases of positive selection sets the
stage for discussions of how populations
(simple and complex, marine
and terrestrial) have changed over
time. In cases where morphological
shifts cannot be clearly linked to
environments undergoing directional
change, he also does a good job of
introducing a reader to the idea of
balancing selection. If you had an
hour to read a chapter a week, covering
this book would be like taking
a good college biology seminar in a
semester with your favorite teacher.
You come away with enough background
to critically dissect a too
facile news story, like the one for a
"language gene" or "killer male
gene". And if your interest runs to
recreational genetics as in ancestry
testing, you will learn enough here
to know that even a $1000 test fee is
going to give you a probability statement,
not an identity link.

There is one glaring error on
page 160 in the text, easily corrected,
but unfortunate because it concerns
dogs and how they changed
in their domestication from a wolflike
ancestor. Dogs have been bred
to diverse body shapes, colors, and
personalities, so much so that
behavioral geneticists are particularly
keen to unlock many secrets
about genes contributing to behavioral
patterns using the dog genome
as a model system. Because many
people have close relationships
with their pets and may have missed
early stages of behavioral development
with their own children, this
topic is close to a reader's heart and
important to get right. So, when
Johnson talks about the latest information
from large-scale nuclear
gene testing of 85 breeds of dogs
and suggests that dogs originated
from African stock, contradicting
previous mitochondrial DNA work,
he does so because he misidentifies
the basal breeds in the dog tree as
African, when in fact they are Asian.
Anthropologists can now note that I
am finally arguing for an Asian
ancestry of one species dear to

Another minor quibble is his failure
to include a good discussion of
superbugs, or bacteria resistant to
multiple antibiotics. Hospital
acquired infections are important
in an aging population undergoing
more intense medical care, and
while the latest statistics can be
scary for someone spending time
in an intensive care unit, it is also
clear that school gymnasium facilities
and hotel rooms with dirty
remote controls or bedspreads can
also be a problem. Herd immunity
assumed by parents in an attempt
to avoid autism risks, where failure
to vaccinate has contributed to
measles epidemics nationwide, is also a public health issue far more
immediate than a potential bird flu
mutation, yet these topics do not
appear. Instead, a final chapter on
genome evolution that attempts to
give the big picture falls flat, and
suffers from both over- and undersimplification,
especially in the discussion
of transposable elements
and gene regulation.

I hope that biology teachers
nationwide looking for evidence
of evolution to engage their students
with take a look at this book.
I also hope that physicians who
have a shaky understanding of evolutionary
processes feel inclined to
refresh how their practices can
contribute to or detract from the
general health of their patients.
This slim volume sparked many
discussions with airplane seatmates,
and clearly covers stories
that will resonate with a variety of
readers. If a paperback version
appears, it would also be a good
text for a non-majors biology or an
advanced placement high school
class. Armed with the right information,
these folks may themselves
become citizen scientists.

This version might differ slightly from the print publication.
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