Books
arthritis, asthma, Alzheimer’s disease,
and endometriosis. He explores the
genetic and metabolic tradeoffs behind
our big brains, the origins of our relative hairlessness, the changes that produced light skin colors in European
populations, and much more. Looking
for a lesson in the evolution of gene
regulation? In Harris’s hands, there is
no better example than the story of
how widely scattered human populations separately developed the ability
to digest milk as adults.
To be sure, there are rough spots.
Some of the book’s lineage diagrams
are not clearly explained, and the
level of detail makes for rough going
in a few places. In his eagerness to
incorporate new concepts such as
“gene surfing” to account for certain
genetic disorders, Harris dismisses
other explanations, such as heterozygote advantage, with little explanation. Finally, some of the genomic
explanations for certain human characteristics are, as he admits, highly
speculative. Despite these minor
quibbles, readers looking for an upto-date, clearly written, and wellillustrated tour through the dynamics
of human evolution will find no better
guide than this compelling volume.
KENNETH R. MILLER
Kenneth R. Miller (kenneth_miller@
brown.edu) is a professor of biology at
Brown University, in Providence, Rhode
Island.
doi:10.1093/biosci/biv057
EVOLUTION’S EVER-CHANGING
ARMS RACE
Animal Weapons: The Evolution of
Battle. Douglas J. Emlen. Henry Holt
and Co., 2014. 288 pp., illus. $30.00
(ISBN: 0805094504 cloth).
M
ention dung beetles to most
people, and they think of insects
rolling balls of dung, usually somewhere in the tropics. If they have
watched a lot of nature documentaries or spent any time in sub-Saharan
730 BioScience • July 2015 / Vol. 65 No. 7
Africa, you might get a comment along
the lines of how surprisingly cute they
are for insects with such scatological
habits. But that is usually the limit of
any normal human being’s interest in
them. Doug Emlen, however, knows
more. Rather than rolling balls of
dung, many dung beetles simply bury
it directly under pats to lay eggs in, and
Emlen started his scientific career by
carrying out a series of groundbreaking studies on the shenanigans that
take place in this dark and odiferous world. For instance, male beetles
armed with a surprising variety of
horns, spikes, and plates fight for mating rights with the females, whereas
other males, often completely lacking weaponry, sneak around, avoiding aggression and enjoying fleeting
assignations with those same females,
all while the grandstanding bullies
remain oblivious, on guard at the tunnel entrances. Emlen has contributed
important work on the trade-offs that
the armed males must make in order
to grow their horns, on the diversity and high-speed evolution of these
weapons, and—more recently—on
how the insulin-like growth factor
­signaling pathway that controls much
of the growth of these animals also
provides a mechanism for maintaining
honest signaling, whereby a small and
feeble animal cannot cheat by growing
an extra large horn and pretending to
be something that he is not.
Emlen has now put some of his
understanding of how these animal
weapons work into this popular science book and has extended his ideas
by drawing an analogy between the
weapons that animals use—­especially
the hugely exaggerated weapons that
are carried by animals such as deer
and ­
rhinoceros beetles—and the
weapons that humans use. He draws
comparisons, for instance, between
­
male e­lephants’ contests for access to
females and the jousts of medieval
knights. He also likens the extinct giant
deer’s costly race to grow larger antlers
with that between the European ­powers
to build more and more battleships in
the years before the First World War.
All in all, the book is an entertaining
romp through the history of weapons
as used by animals and people, sprinkled with anecdotes from Emlen’s fieldwork in Central America and ending
on a more serious note with a discussion of the future of human weaponry
and the destabilizing effects of cheap
weapons of mass destruction.
The early chapters deal with subjects such as the weaponry used in
predation and the evolution of animal
armor and how this compares with the
history of armor used by humans. The
second part of the book introduces the
use of weapons in contests between
animals, and there is a particularly nice
explanation of the way that anisogamy
(the disparity in size between male and
female gametes) can be seen as driving
the evolution of many of the differences between male and female reproductive behaviors. There are ­sections
on the costs of animal weaponry, the
trade-offs that the animals that carry
large weapons have to make, and the
way that the condition dependence
of ­
animal weapons enforces honest
signaling. This then leads to a discussion of arms races and some interesting comparisons between those among
animals and those among humans,
either in terms of weapons technology
or in terms of investment of resources
into military forces. Those sneaky male
dung beetles make an appearance, and
there is a chapter comparing animal
fortifications, such as termite mounds,
with human fortifications and discussing the effects of siege weaponry, such
as trebuchets and then artillery, on the
design of fortifications.
http://bioscience.oxfordjournals.org
Books
Although the book is terrific overall, I did find that some parts worked
better than others did. The analogy
between animal and human weapons
is unconvincing in parts: It works well
in some instances, such as when considering the comparison between animal arms races and human military
spending, but it does not work as well
when considering weapons technology
per se, in my opinion. The weapons
that humans use in battle are usually built simply as tools to kill other
­people, whereas the extravagant animal
weapons that are the main focus of this
book are used in nonlethal contests
between males and have a function in
signaling male fighting ability that can
be considerably more important than
their utility as tools. For example, the
eyestalks of diopsid flies are discussed
in the book, but these are really pure
signaling structures and are not even
used when a pair of males have begun
actually fighting.
If we move away from traits that
have a signaling function and look at
the animal traits that are most similar in function to an assault rifle or a
longbow, we find that these are often
quite boring and similar to each other.
Want to kill another animal? A set of
medium-length sharp canines seems
to do the trick for many mammals,
and although the diversity of weapons
used by predatory insects and fish is
somewhat wider, there is little suggestion of the diversity of forms found
in the structures used in nonlethal
combat. Human weapon designs are
often similarly conformist: The basic
design of the assault rifle was settled
on in the 1940s and 1950s, and these
weapons have changed little since then.
Although sights, calibers, and barrel
lengths have been refined, modern
soldiers use rifles that are fundamentally the same as those used half a century ago—not really much of an arms
race going on there, I think. There are
examples of arms races between predator and prey, of course, such as those
between shelled animals that evolve
thicker armor and shell-crushing predators who evolve larger and more muscular jaws or claws, and I think that it is
http://bioscience.oxfordjournals.org
a bit of a shame that these are not really
mentioned in the book or compared
with analogous situations in human
weaponry—the increase in the thickness of tank armor and the simultaneous increase in the power of antitank
guns, infantry portable antitank weapons, and tank guns themselves during
the Second World War, for example.
There are also some errors in the
book, most of which will be spotted
only by ancient and medieval history enthusiasts. Following a misspent
youth working on assorted archaeological sites, culminating in a particularly strange week spent by accident
in Switzerland with a Roman Army
reenactment group sometime in the
early 1990s, I have a surprisingly good
knowledge of ancient Roman arms
and armor (including some especially
strong memories of how heavy it all
is). The illustration of the Roman
­soldier clearly shows someone wearing
lorica segmentata, the classic “banded”
armor as worn by the hapless legionaries in the Asterix books, whereas
the accompanying text seems to be
describing the lorica squamata, which
was made of overlapping metal scales.
There is a picture of what is described
as a ballista that does not show a
large bolt-throwing device but instead
what looks to me to be an onager,
also a Roman weapon very similar to
a medieval catapult. Finally, from a
British perspective, the description of
the medieval longbow as not requiring
much training causes a bit of a wince.
As is known by pub bores from Dover
to Cardiff, the longbows that were
used at Crécy and Agincourt required
constant training from a young age,
and the remains of medieval archers
can be distinguished by the effects
this training had on their skeletons.
Indeed, there are few modern archers
who can even draw a full-size replica of the 6-foot-plus bows that were
retrieved from the wreck of the Mary
Rose. The longbow has near-mythical
status in England and Wales, and you
trivialize it at your peril.
Are these caveats and errors something that should really concern only
specialists and those concerned with
the Latin names of different types of
Roman armor or the penetrating power
of a 1944 bazooka versus a 1939 antitank rifle? I think so, and I do not think
they are anywhere near important
enough to worry the general reader,
at whom this book is squarely aimed.
I enjoyed it a lot, I learned some things
I did not know before, and it really
made me think about the connection
between animal and human weapons
in a way I had not before. I also fieldtested the book on my 13-year-old
daughter, who absolutely loved it, and
on that basis, I can do nothing but recommend Animal Weapons to all.
ROB KNELL
Rob Knell ([email protected]) is with
the School of Biological and Chemical
Sciences at Queen Mary University of
London.
doi:10.1093/biosci/biv067
BETTING ON DISPARATE VISIONS
The Bet: Paul Ehrlich, Julian Simon,
and Our Gamble over Earth’s Future.
Paul Sabin. Yale University Press,
2013. 304 pp., illus. $18.00 (ISBN
9780300198973).
O
ne does not need to stray far
when studying contentious ideas
to understand that egos often create
more problems than solutions, and the
history of the environmental movement is no different. In this timely,
interesting, and insightful work, Paul
Sabin provides us with a history lesson
through the lives of two bullish protagonists who were at extreme ideological
odds with each other. The juxtaposition of the two men, Paul Ehrlich
and Julian Simon, and their disparate
visions for the future of humanity
and humanity’s role on the planet is
a symbol of the differing directions
of American society and may help
explain the currently entrenched divisions we have in American politics.
Sabin’s thesis is therefore a wonderful
July 2015 / Vol. 65 No. 7 • BioScience 731