The richness
of life
Stephen Jay Gould

The evolution of life
“Science can, and does, strive to grasp
nature’s factuality, but all science is socially
embedded, and all scientists record prevailing
“certainties”, however hard they may be
aiming for pure objectivity. Darwin himself, in
the closing lines of The Origin of Species,
expressed Victorian social preference more
than nature’s record in writing “All corporeal
and mental endowments will tend to
progress towards perfection”
2

“Our conventional [sic] desire to view history as
progressive, and to see humans as predictably
dominant, has grossly distorted our interpretation of
life’s pathway by falsely placing in the center of things
a relatively minor phenomenon that arises only as a
side consequence of a physically constrained starting
point. The most salient feature of life has been the
stability of its bacterial mode from the beginning of
the fossil record until today”
3

“Our impression that life evolves toward
greater complexity is probably only a bias
inspired by parochial focus on ourselves,
and consequent overattention to
complexifying creatures, while we ignore
just as many lineages adapting equally well
by becoming simpler in form”
4

The evolution of life
“Three billion years of unicellularity, followed by five million
years of intense creativity and then capped by more than 500
million years of variation on set anatomical themes can scarcely
be read as a predictable, inexorable or continuous trend toward
progress or increasing complexity.
We do not know why the Cambrian explosion could establish all
major anatomical designs so quickly”
5

“An external explanation based on ecology seems attractive:
the Cambrian explosion represents an initial filling of the
“ecological barrel” of niches for multicellular organisms, and any
experiment found a space. The barrel has never emptied since.
But an internal explanation based on genetics also seems
necessary as a complement: the earliest multicellular animals
may have maintained a flexibility for genetic change and
embryological transformation that became greatly reduced as
organisms “locked in” to a set of stable and successful designs”
6

Exaptation
“Strict adaptation entails a paradox for
students of evolutionary change. If all
structures are well designed for immediate
use, where is the flexibility for substantial
change in response to severely altered
environments?”
Preadaptation does not cover the large class
of structures that never were adaptations for
anything, but arose as the numerous
nonadaptive sequelae of primary adaptations”
7

“The major basis of flexibility must lie in
nonadaptation.
Increased complexity implies a vastly
greater range of nonadaptive sequelae for
any change, and hence a greatly enlarged
exaptive pool”
8

“The scheme of punctuated equilibrium: lineages
change little during most of their history, but events
of rapid speciation occasionally punctuate this
tranquility. Evolution is the differential survival and
deployment of these punctuations.
If gradualism is more a product of Western thought
than a fact of nature, then we should consider
alternate philosophies of change to enlarge our realm
of constraining prejudices”
9

“I make a simple plea for pluralism in
guiding philosophies, and for the
recognition that such philosophies,
however hidden and unarticulated,
constrain all our thought”
10

Punctuated equilibrium
“[In punctuated equilibrium], punctuation must be scaled
relative to the later duration of species in stasis, and we suggest
1 to 2 percent (analogous to human gestation vs. the length of
human life) as an upper bound. Punctuated equilibrium can be
distinguished by the criterion of ancestral survival following the
branching of a descendant”
12

Punctuated equilibrium
“Stasis is not defined as absolute phenotypic immobility, but as
fluctuation of means through time at a magnitude not statistically
broader than the range of geographic variation among modern
populations of similar species, and not directional in any preferred
way, especially not towards the phenotype of descendants.
Gradualism certainly can and does occur, but at very low relative
frequencies when all species of a fauna are tabulated, and when we
overcome our bias for studying only the small percentage of species
qualitatively recognized beforehand as having changed through
time”
13

The episodic nature of
evolutionary change
“Natura non facit saltum: Nature does not
make leaps. Darwin portrayed evolution as
a stately and orderly process, working at a
speed so slow that no person could hope
to observe it in a lifetime”. Huxley felt that
Darwin was digging a ditch for his own
theory. Natural selection required no
postulate about rates”
14

“On issues so fundamental as a general
philosophy of change, science and society
usually work hand in hand. The static
systems of European monarchies won
support from legions of scholars as the
embodiment of natural law”
15

“The history of most fossil species includes two features
particularly inconsistent with gradualism:
Stasis: Most species exhibit no directional change during their
tenure on earth. Morphological change is usually limited and
directionless.
Sudden appearance: In any local area, a species does not arise
gradually by the steady transformation of its ancestors, it
appears all at once and ‘fully formed’”
16

“Evolution proceeds in two major modes. In the first, phyletic
transformation, an entire population changes from one state to
another. [It] yields no increase in diversity. Since extinction is so
common, a biota with no mechanism for increasing diversity
would soon be wiped out. The second mode, speciation,
replenishes the earth. New species branch off from a persisting
parental stock.
Eldredge and I believe that speciation is responsible for almost
all evolutionary change. The way in occurs virtually guarantees
that sudden appearance and stasis shall dominate the fossil
record”
17

“All major theories of speciation maintain that
splitting takes place rapidly in very small populations.
The theory of geographic, or allopatric, speciation is
preferred by most evolutionists for most situations. A
new species can arise when a small segment of the
ancestral population is isolated at the periphery of the
ancestral range.
Large, stable central populations exert a strong
homogenizing influence. New and favorable
mutations are diluted by the sheer bulk of the
population through which they must spread”
18

“But small, peripherally isolated groups are cut off
from their parental stock. They live as tiny
populations in geographic corners of the ancestral
range. Selective pressures are usually intense
because peripheries mark the edge of ecological
tolerance for ancestral forms. Favorable variations
spread quickly. Small, peripheral isolates are a
laboratory of evolutionary change”
19

Betting on chance
“The most serious of all
misunderstandings between technical and
vernacular haunts the concepts of
probability and particularly the words
random and chance.
Ironically, the scientific sense of random
conveys… maximal simplicity, order, and
predictability –at least in the long run.”
20

“Stability is far more common than change at any
moment in the history of life. In its ordinary everyday
mode, natural selection must struggle to preserve
working combinations against a constant input of
deleterious mutations. Natural selection must usually
be “purifying” or “stabilizing”. Positive selection for
change must be a much rarer event than watchdog
selection for tossing out harmful variants and
preserving what works”
21

22
“I do not challenge the statement that the most
complex creature has tended to increase in
elaboration through time, but I fervently deny that
this limited little fact can provide an argument for
general progress as a defining thrust of life’s history.
Such a grandiose claim represents a ludicrous case of
the tail wagging the dog, or the invalid elevation of a
small and epiphenomenal consequence into a major
and controlling cause”

The ladder and the cone
“Scientists view our pictures only as ancillary
illustrations of what we defend by words. Few
scientists would view an image itself as
intrinsically ideological in content. Pictures, as
accurate mirrors of nature, just are.
Many of our pictures are incarnations of
concepts masquerading as neutral
descriptions of nature. These are the most
potent sources of conformity, since ideas
passing as descriptions lead us to equate the
tentative with the unambiguously factual.
Guesses and hunches become things”
23

The ladder and the cone
“The fatuous idea of a single order amidst the
multifarious diversity of modern life flows from
our conventional iconographies and the
prejudices that nurture them –the ladder of life
and the cone of increasing diversity. By the
ladder, horseshoe crabs are judged as simple; by
the cone, they are deemed old. And one implies
the other under the grand conflation discussed
above –down on the ladder also means old,
while low on the cone denotes simple”
25

“The familiar iconographies of evolution
are all directed –sometimes crudely,
sometimes subtly- toward reinforcing a
comfortable view of human inevitability
and superiority.
We now know that the vast majority of
“simpler” creatures are not human
ancestors or even prototypes, but only
collateral branches on life’s tree.”
26

27

Up against a wall
“It just feels ‘right’ to us that the very earliest art should be primitive.
Older in time should mean more and more rudimentary in mental
accomplishment. [But] most individual species don’t alter much during
their geological lifetimes. Large, widespread, and successful species tend
to be specially stable. Humans fall into this category, and the historical
record supports such a prediction. Human bodily form has not altered
appreciably in 100,000 years. Cro-Magnon cave painters are us –so
why should their mental capacity differ from ours? We don’t regard
Plato or King Tut as dumb, even though they lived a long time ago.”
28

Pervasive influence: Racism
“The primitive-as-child argument stood second to none in the
arsenal of racist arguments supplied by science to justify slavery
and imperialism. I do not think that most scientists who upheld
this argument intended to promote racism. They merely
expressed their allegiance to the prevailing views of white
intellectuals and leaders of European society.
Biological arguments based on innate inferiority spread rapidly
after evolutionary theory permitted a literal equation of modern
“lower” races with ancestral stages of higher forms”
29

30
“Biological arguments for racism may have
been common before 1859, but they increased
by orders of magnitude following the
acceptance of evolutionary theory. The litany is
familiar: cold, dispassionate, objective, modern
science shows us that races can be ranked on a
scale of superiority”

“Ultra-Darwinism… a conviction that natural
selection regulates everything of any importance in
evolution, and that adaptation emerges as a universal
result and ultimate test of selection’s ubiquity.
The irony is twofold. First, Darwin himself opposed
the ultras of his own day. Second, the invigoration of
modern evolutionary biology with exciting non-
selectionist and non-adaptationist data makes our
pre-millennial decade an especially unpropitious time
for Darwinian fundamentalism”
31

“But selection cannot suffice as a full explanation for
many aspects of evolution: for other types and styles
of causes become relevant, or even prevalent, in
domains both far above and far below the traditional
Darwinian locus of the organism. These additional
principles are as directionless, non-teleological and
materialistic as natural selection itself –but they
operate differently”
32

“How can we possibly know in detail what
small bands on hunter-gatherers did in
Africa two million years ago? These
ancestors left some tools and bones. But
how can we possibly obtain the key
information that would be required to
show the validity of adaptive tales: relations
of kinship, social structures and sizes of
groups, activities of males and females…
and a hundred other central aspects of
human life that cannot be traced in fossils?”
33
More things in heaven & earth

Spandrels
“Spandrels are the tapering triangular spaces formed by
the intersection of two rounded arches at right angles.
They are necessary architectural by-products of mounting
a dome on rounded arches. Such architectural constraints
abound and we find them easy to understand because
we do not impose our biological biases upon them…
Since the spaces must exist, they are often used for
ingenious ornamental effect.
The internal error of adaptationism arises from a failure to
recognize that even the strictest operation of pure
natural selection builds organisms full of nonadaptive
parts and behaviors. Non-adaptations arise for many
reasons in Darwinian systems, but consider only my
favorite principle of ‘spandrels’”
34

35
“Many, if not most, universal behaviors are probably spandrels,
often co-opted later in human history for important secondary
functions. The human brain is the most complicated device for
reasoning and calculating, and for expressing emotion, ever
evolved on earth. Natural selection made the human brain big,
but most of our mental properties and potentials may be
spandrels –that is, non-adaptive side consequences of building
a device with such structural complexity”

“We live in a world of enormous complexity in organic
design and diversity –a world where some features of
organisms evolved by an algorithmic form of natural
selection, some by an equally algorithmic theory of
unselected neutrality, some by the vagaries of history’s
contingency, and some as by-products of other processes.
Why should such a complex and various world yield to one
narrowly construed cause?
36

Posture maketh the man
“Upright posture frees the hands
from locomotion and for
manipulation. For the first time, tools
and weapons can be fashioned and
used with ease. Increased intelligence
is largely a response to the enormous
potential inherent in free hands for
manufacture”
37

The most unkindest cut of all
“Claptrap and bogus Darwinian formulations have
been used to justify every form of social exploitation
–rich over poor, technologically complex over
traditional, imperialist over aborigine, conqueror over
defeated in war. Every evolutionist knows this history
only too well, and we bear some measure of
collective responsibility for the uncritical fascination
that many of us have shown for such unjustified
extensions”
38

Excerpts by Ricardo Sosa
ricardo.sosa@monash.edu