is confirmed by several related ex- 
amples. Female spider monkeys also 
have an enlarged clitoris and a false 
scrotum produced by overgrowth of 
the labial folds. Although their levels 
of androgen have not been measured 
(to my knowledge), they do use their 
enlarged clitoris in a male form of 
genital display and dominance. Better 
examples arise from unusual patterns 
of development within our own spe- 
cies. The adrenal glands also secrete 
androgens, usually in small amounts. 
In some genetic females, adrenals are 
abnormally enlarged and produce high 
levels of androgens. These baby girls 
are born with a penis and false scro- 
tum. Several years ago a drug was 
placed on the market to prevent mis- 
carriages. It had the unfortunate side 
effect of mimicking the action of nat- 
ural androgens. Female babies were 
born with a greatly enlarged clitoris 
and an empty scrotal sac formed from 
the fused labia. 
I believe that these facts of devel- 
opmental anatomy must force a re- 
vision in the usual interpretation of 
male mimicry in female spotted hy- 
enas. Evolutionary biologists have too 
often slipped into a seductively ap- 
pealing mode of argument about the 
phenomenon of adaptation. We tend 
to view every structure as designed 
for a definite purpose, thus building 
(in our imagination) a world of perfect 
design not much different from that 
concocted by eighteenth-century nat- 
ural theologians who “proved” God’s 
existence by the perfect architecture 
of organisms. Adaptationists might al- 
low a little flexibility for tiny and ap- 
parently inconsequential structures, 
but surely anything big, complex, and 
obviously useful must be built directly 
by natural selection. Indeed, previous 
literature on spotted hyenas has as- 
sumed that female sexual organs 
evolved directly for a definite func- 
tion — as in Kruuk’s speculation about 
the adaptive advantages of conspicu- 
ous external genitalia for recognition 
in the meeting ceremony. 
But another scenario is possible and 
strikes me as more likely. I don’t doubt 
that the basic peculiarity of hyena 
social organization — the larger size 
and dominance of females — is an ad- 
aptation to something. The easiest 
pathway to such an adaptation would 
be a marked rise in the production 
of androgenic hormones by females 
(these exist in small amounts in all 
mammalian females). High levels of 
androgens would entail complex sec- 
ondary effects as automatic conse- 
quences — among them, a peniform cli- 
toris and a false scrotum (we cannot, 
after all, label the very same condition 
in some abnormal human baby girls 
as an adaptation). Once they are pres- 
ent, some use might be evolved for 
them — as ip the meeting ceremony. 
But their current utility does not imply 
that they were built directly by natural 
selection for the purpose they now 
serve. (Yes, I know that my scenario 
might be run in reverse: conspicuous 
female genitalia are required for the 
meeting ceremony, are evolved by en- 
hanced androgen levels, thus yielding 
large female size and dominance as 
a consequence. I do, however, point 
out that under our usual preferences 
for seeing direct adaptation every- 
where, my scenario would not even 
be considered. Indeed, it wasn’t in the 
major works on spotted hyenas.) 
My columns have the nasty habit 
of discoursing on funny facts of nat- 
ural history, and then, only at the end, 
reaching the general argument that 
inspired the disquisition. This article 
is no exception, for I designed it to 
make a point about adaptation and 
the evolutionary analysis of form, not 
as a treatise on hyena penises. 
We do not inhabit a perfected world 
in which natural selection ruthlessly 
scrutinizes all organic structures and 
then molds them for optimal utility. 
Organisms inherit a body form and 
a style of embryonic development; 
these impose constraints upon future 
change and adaptation. In many cases, 
the direction that evolution takes is 
more a result of inherited patterns 
than of current environmental de- 
mands. These inheritances constrain, 
but they also provide opportunity. A 
potentially minor genetic change — a 
rise in androgen level in this case — 
entails a host of complex, nonadaptive 
consequences. The primary flexibility 
of evolution may arise from nonadap- 
tive byproducts that occasionally per- 
mit organisms to strike out in new 
and unpredictable directions. What 
“play” would evolution have if each 
structure were built for a restricted 
purpose and could be used for nothing 
else? How could humans learn to write 
if our brain had evolved for hunting, 
social cohesion, or whatever, and could 
not transcend the adaptive boundaries 
of its original purpose? 
In the second show of his Cosmos 
series, Carl Sagan told the tale of a 
Japanese crab that carries a portrait 
of a samurai warrior on its back. He 
argued that humans have built this 
face after their own image because 
local fisherman have been throwing 
back the most facelike crabs for cen- 
turies, thus imposing strong selection 
pressure for samurai look-alikes (the 
others get eaten). He used this ex- 
ample as his lead-in for a rapturous 
discourse on the pervasive power of 
natural selection. 
I doubt this story very much and 
suspect that the conventional expla- 
nation is correct — that the resem- 
blance is accidental and, at best, only 
slightly strengthened by human inter- 
vention. But even if Sagan were right, 
I believe that he is marveling at the 
wrong item (or at least failing to give 
equal time to another remarkable as- 
pect of the case). I am most impressed 
by a crab’s ability to do such an un- 
crablike thing in the first place — just 
as the capacity of an inherited de- 
velopmental system to produce (and 
so easily) such marked changes in the 
sexual anatomy of female hyenas 
grabs me far more than any putative 
adaptive significance for the change. 
The capacity of crabs to produce 
a face can have nothing to do with 
any selective value such a face might 
have since crabs do not routinely use 
this latent ability. It arises from sev- 
eral facts of crab biology: the bilateral 
symmetry of the carapace (corre- 
sponding by analogy with the bilateral 
symmetry of the human face), and 
the fact that many crabs are orna- 
mented by creases along the midline 
(where a “nose” might form) and per- 
pendicular to it (where “eyes” and 
“mouths” might be constructed). 
The (probably accidental) produc- 
tion of a human portrait represents 
a stunning example of the evolutionary 
flexibility arising from nonadaptive 
consequences of an inherited design. 
Organic material is not putty and nat- 
ural selection is not omnipotent. Each 
organic design is pregnant with evo- 
lutionary possibilities, but restricted 
in its paths of potential change. Fish- 
ermen might throw back selected 
starfishes with their five-part symme- 
try, or snails with their spiral design, 
for tens of millions of years and never 
carve a samurai into their hard parts. 
Peter Medawar has described sci- 
ence as the “art of the soluble.” Evo- 
lution might be labeled “the trans- 
formation of the possible.” 
Stephen Jay Gould teaches biology, 
geology, and the history of science 
at Harvard University. 
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