2 Cultural Evolution
The concept of cultural evolution—the idea that culture
evolves and that useful parallels can be drawn between
biological and cultural change—has had a long and often
controversial history in the social sciences. Ever since the
publication of The Origin of Species in 1859, scholars
have attempted to use ideas from biology to understand
cultural change. Evolutionary approaches to culture have,
at different times over the past century and a half, been
both the dominant paradigm for understanding cultural
change and also deeply unpopular and virtually taboo.
There have also been several different theories of “cultural
evolution,” from nineteenth-century progressive
theories of cultural evolution to more recent fads such
as memetics. Not all of these bear much resemblance to
evolution as either Darwin, or modern biologists, would
recognize it. So it is crucial to specify exactly what is
meant by a theory of cultural evolution and also to show
that this theory is empirically supported.
While biology has undoubtedly changed in the 150
years since its publication, The Origin remains one of
the most compelling descriptions of biological evolution
ever written, and the basics of Darwin’s argument have
not considerably changed.1
A clearer picture of a theory
of cultural evolution can, I think, be achieved by going
back to this original source.2
Darwin famously described
C H A P T E R T W O 26
The Origin as “one long argument.” This argument can be seen as
comprising three elements, or preconditions: variation, competition,
and inheritance.3
First, individuals within a species vary in their characteristics.
For example, ﬁnches might vary in the size of their beaks,
with some ﬁnches having larger beaks than other ﬁnches. Second, there
is competition between individuals. This competition may be over
food, nesting space, mates, or any other limited resource. As a result,
not all individuals will have an equal chance of surviving and reproducing.
Moreover, an individual’s characteristics affect its success in
this competition to survive and reproduce. For example, ﬁnches with
larger-than-average beaks might be able to open a wider range of seeds
than ﬁnches with smaller-than-average beaks. These large-beaked
ﬁnches will get more food, thus increasing their chances of survival
to reproductive age and of successfully raising offspring compared to
small-beaked ﬁnches. We can say here that larger-beaked ﬁnches have
higher ﬁtness than smaller-beaked ﬁnches, where ﬁtness refers to the
success of an entity in reproducing. Finally, offspring inherit characteristics
from their parents. For example, large-beaked ﬁnches will, on
average, give birth to similarly large-beaked offspring. Over time, this
variation-competition-inheritance cycle results in evolutionary change,
deﬁned as a change in the frequency of a trait in a population over
time. Finches with larger beaks obtain more food and so have more
offspring on average than ﬁnches with small beaks. Because those offspring
inherit large beaks from their parents, the next generation will,
on average, have slightly larger beaks than the parental generation. The
same happens in the subsequent generation: larger-beaked ﬁnches will
have more offspring than smaller-beaked ﬁnches, and the third generation
will have slightly larger beaks again. Over successive generations,
beak size gradually increases. Indeed, this very process of ﬁnch beak
evolution was observed in the 1970s on the Galápagos Islands, when
a drought drastically reduced the number of seeds in the environment.
Large-beaked ﬁnches were able to open a wider range of seeds than
small-beaked ﬁnches, were more likely to survive and reproduce, and
so average beak size in the population increased.4
So this was Darwin’s basic idea—that all biological change can be
described in terms of just three basic preconditions: variation, competition,
and inheritance. If any of these cannot be demonstrated, then
evolution simply does not happen (indeed, this is an important and often
underappreciated point: that the theory of evolution is falsiﬁable).
Since The Origin, biologists have established without a shadow of a
doubt that Darwin’s theory is correct as applied to biological change.
C U L T U R A L E V O L U T I O N 27
Does Cultural Change Exhibit Darwin’s Three Preconditions?
But what about cultural change? Can we also show that culture exhibits
these three key preconditions speciﬁed by Darwin? If so, then this
would provide justiﬁcation for describing cultural change as a Darwinian
evolutionary process. Let’s take each in turn.
Precondition One: Variation. Darwin documented, in often excruciating
detail, the variation between individuals of several species, especially
pigeons:
The proportional width of the gape of mouth, the proportional
length of the eyelids, of the oriﬁce of the nostrils, of the tongue
(not always in strict correlation with the length of beak), the size
of the crop and of the upper part of the oesophagus; the development
and abortion of the oil-gland; the number of the primary
wing and caudal feathers; the relative length of wing and tail
to each other and to the body; the relative length of leg and of
the feet; the number of scutellae on the toes, the development
of skin between the toes, are all points of structure which are
variable.5
And this goes on for several pages. But Darwin had good reason to
go into such painstaking detail. If every individual were identical, then
there would be nothing for natural selection to select, and no meaningful
change could take place. As Darwin noted, “These individual
differences are highly important for us, as they afford materials for
natural selection to accumulate.”6
Since The Origin, biologists have conﬁrmed and quantiﬁed the extent
to which biological organisms vary. There are, for example, an estimated
1.8 million extant biological species, while in terms of withinspecies
variation, humans and mice have around 20,000–25,000
protein-coding genes, Drosophila have 13,000, and rice has 46,000.7
Biologists have also determined exactly how variation is generated, in
the form of genetic mutation and recombination, and established that
novel variation is blind with respect to ﬁtness (i.e., beneﬁcial mutations
are no more likely to arise when they are needed than when they are
not needed). The equivalent processes that are responsible for variation
in cultural evolution and the issue of blind variation will be discussed
later in this chapter. For now, let us stick with the direct comparison
with The Origin and, like Darwin, simply try to demonstrate that cul-
C H A P T E R T W O 28
ture varies and remain temporarily ignorant of the causes of this variation.
Indeed, this echoes the position of Darwin, who admitted that
“our ignorance of the laws of variation is profound.”8
That culture also varies is patently obvious. People vary in their
religious beliefs, in their political views, in their scientiﬁc knowledge,
in their skills, and so on. The manifestation or expression of these
mental aspects of culture also, as a result, varies, such as variation in
buildings and tools. But following Darwin’s lead, can we go beyond
informal observation and give documented examples of this variation?
And furthermore, can we in any way quantify this variation? Technology
provides a good source of data regarding cultural variation. Historian
Henry Petroski documents the variation found in forks of the late
1800s, each designed for a slightly different function, listing “oyster
fork-spoon, oyster forks (four styles), berry forks (four styles), terrapin,
lettuce and ramekin fork . . . large salad, small salad, child’s, lobster,
oyster, oyster-cocktail, fruit, terrapin, lobster, ﬁsh, and oyster-cocktail
fork . . . mango, berry, ice-cream, terrapin, lobster, oyster, pastry,
salad, ﬁsh, pie, dessert, and dinner fork.”9
These vary in the number of
tines, the dimensions (length, width, thickness), the shape of the tines,
the shape of the handle, the material used, and so on, reminiscent of
the minute variation documented by Darwin for pigeons.
The patent record provides a good way of measuring technological
variation on a grosser scale. A staggering 7.7 million patents were issued
in the United States alone between 1790 and 2006.10
Because a
successfully patented invention must, by law, be demonstrably different
to all existing patents, each of these 7.7 million patents describes
unique variation. Other databases do the same for other aspects of culture.
Take religious beliefs: the World Christian Encyclopedia estimates
that there are over 10,000 distinct religions worldwide.11
Within each
of these 10,000 religions there is further variation: Christianity can be
divided into 33,830 denominations, for example. Languages also vary:
there are an estimated 6,800 languages currently spoken worldwide.12
Again, within each language there is further variation: the Oxford
English Dictionary contains over 615,000 different words, with the
average person using 16,000 words every day.13
And just as dictionaries
contain a record of linguistic variation, encyclopedias contain a
record of general knowledge. In August 2009, the English-language
Wikipedia added its three-millionth page (it was about Beate Eriksen,
a Norwegian soap opera actor). The combined number of Wikipedia
entries across all languages is, at the time of writing, 9.25 million,
C U L T U R A L E V O L U T I O N 29
while even this is just a fraction of the more than 25 billion website
pages on the internet.14
There are, of course, caveats to these ﬁgures. Some might quibble
with the methods of data collection, or how the different units (words,
religions, technologies, web pages) are deﬁned. It also presupposes that
this variation is discrete and can be counted, rather than being continuous,
in which case there would be no discrete units (e.g., words,
patents) to count. Another important issue is the distinction between
variation of the same type of cultural trait (e.g., different types of fork),
analogous to within-species variation, versus variation between different
types of cultural trait (e.g., forks and tractors), analogous to
between-species variation. This is important because competition will
be most extreme in the former case, between similar traits that serve
the same purpose and so are competing for the same cultural “niche.”
These are all important issues, and no doubt methods for quantiﬁcation
can be improved. But it is reasonable to conclude that there is
huge variation in human culture, on the order of millions to billions
of variants, and that this variation can be documented and quantiﬁed.
We can therefore state with some certainty that the ﬁrst of Darwin’s
preconditions—variation—is present in culture.15
Precondition Two: Competition. Darwin talked about competition in terms
of a “struggle for existence,” asking rhetorically, “can we doubt (remembering
that many more individuals are born than can possibly
survive) that individuals having any advantage, however slight, over
others, would have the best chance of surviving and of procreating
their kind?”16
Inspired by the ideas of the economist and demographer Thomas
Malthus, Darwin argued that this struggle for existence results from
the fact that populations tend to increase in size exponentially, generating
inevitable shortages of ﬁnite resources such as food, living space,
and mates. There will therefore be competition for these limited resources,
with only a subset of the population likely to survive and reproduce.
This competition between individuals might be direct and
physical, such as when jackals ﬁght over a fresh carcass or when stags
lock antlers in order to impress onlooking females. However, Darwin
also stressed that competition need not be literal or direct. A single
individual can also be said to struggle for existence in the face of the
physical environment, such as when “a plant at the edge of a desert
is said to struggle for life against the drought.”17
Here, competition
C H A P T E R T W O 30
between different plants is indirect, with the plants best able to deal
with dry conditions more likely to survive and reproduce than less able
plants. This indirect competition is not what most people think of as
“competition,” and to avoid this confusion modern biologists tend to
use the phrase “differential ﬁtness” instead of “competition.”18
I will
continue to use the word “competition” because it is less cumbersome
and maintains the link with Darwin’s terminology in The Origin. But
really “competition” is shorthand for “differential ﬁtness,” which simply
says that some individuals are more likely to survive and reproduce
than other individuals, and these differences in survival and reproduction
are linked in some way to their characteristics.
Intuitively, there must be some form of competition in culture
given the extent of the variation observed even in such things as forks,
let alone religions and languages. It is surely impossible for any single
person to possess the knowledge and skills to manufacture 7.7 million
distinct inventions, or to learn every one of the 6,800 languages in
existence. And even if some linguistic genius could learn 6,800 languages,
they could only ever speak one language at any one time. This
highlights the ﬁnite resources that are acting upon culturally acquired
information: there are limitations on memory capacity and on the time
it takes to learn and express knowledge.
Evidence supports this intuitive reasoning. That technology and language
are subject to competition due to ﬁnite resources is highlighted
by the phenomenon of extinction, just as extinction of species is the
product of biological competition. The extinction of various forms of
technology has been documented by historians and anthropologists,
such as the loss of various technologies and practices from the islands
of Oceania (e.g., the canoe, pottery, the bow and arrow, and circumcision)
and the loss of artifacts such as bone tools and skills such as ﬁshing
in prehistoric Tasmania following isolation from mainland Aus-
tralia.19
There is also an extremely high extinction rate of languages
at present, much higher than the extinction rate of any biological spe-
cies.20
And within languages, it has been shown that numerous irregular
verbs have, throughout history, gradually been whittled down to
just a handful, based on how often those verbs are used.21
Irregular
verbs that are used often, such as “to go” with its irregular past tense
of “went,” are easier to remember, less likely to be regularized, and so
more likely to survive in the vocabulary. Indeed, this process in which
easily remembered words are more likely to survive was presaged by
Darwin himself:
C U L T U R A L E V O L U T I O N 31
A struggle for life is constantly going on amongst the words and
grammatical forms in each language. The better, the shorter,
the easier forms are constantly gaining the upper hand.22
Archaeologists, too, have documented many examples in which one
type of artifact or technology has increased in frequency over a speciﬁc
time period, while a different type of artifact or technology shows a
corresponding decrease over the same time period. This is consistent
with the former replacing the latter as a result of competition between
the types. Examples include painted pottery replacing corrugated pottery
in New Mexico or the replacement of spear-throwing technology
with bow-and-arrow technology in North America.23
At a more proximate level, evidence from experimental psychology
provides details of how different ideas compete for memory space.
Classic experiments have demonstrated the existence of “interference
effects” in memory.24
In these experiments, subjects are asked to read
and recall lists of words. Subjects show signiﬁcantly worse recall of
the words when they have to read another list of words while they are
trying to remember the ﬁrst list. This suggests that the second list is
interfering with recall of the ﬁrst. And if one cannot recall a word, one
cannot pass it on to another person, and the word declines in frequency
in the population as a whole. Interestingly, this interference is greater
when the distractor words are similar in meaning to the target words,
suggesting that, as Darwin noted, competition is greatest between similar
kinds, because they are competing for the same cultural niche:
[I]t is the most closely allied forms—varieties of the same species
and species of the same genus or of related genera—which,
from having nearly the same structure, constitution, and habits,
generally come into the severest competition with each
other.25
We therefore see competition in culture both at the psychological
level, in the form of competition for space in memory, and also the
effects of that competition, in the form of the extinction of various
cultural practices and forms. Cultural traits, like biological organisms,
take part in an endless struggle for existence.
Precondition Three: Inheritance. The third of Darwin’s preconditions for
evolution was inheritance, and he was direct about its importance:
C H A P T E R T W O 32
“Any variation which is not inherited is unimportant for us.”26
Darwin
noted that individuals that are more likely to survive and reproduce
during the struggle for existence will often pass on their traits or
characteristics to their offspring. If those characteristics were at least
partially responsible for the parents’ increased chances of survival and
reproduction, then there will be a gradual increase in ﬁtness and adaptation
to the local environment. Inheritance therefore allows beneﬁcial
traits to be preserved in successive generations. Without inheritance,
beneﬁcial traits are not preserved, and evolution cannot occur.
Although inheritance was necessary for Darwin’s argument, for
him “the laws governing inheritance are quite unknown”27
beyond
the basic observation that offspring resemble parents more than a randomly
chosen member of the species. It was not until the rediscovery
of Gregor Mendel’s pea-plant experiments, and further experiments
in the early twentieth century, that the details of genetic inheritance
were worked out. So for the moment let’s ignore the details of cultural
inheritance and simply ask whether cultural information can be successfully
reproduced, or transmitted, from one person to another.
As discussed in chapter 1, there is voluminous evidence from crosscultural
comparisons that people acquire beliefs, attitudes, skills, and
knowledge from other people via cultural transmission. Early immigrants
to the United States have passed values related to civic duty down
successive generations via cultural transmission, people in small-scale
societies transmit norms relating to fairness as evidenced by cultural
variation in the ultimatum game, and holistic and analytic thinking
styles have been transmitted from generation to generation in East Asia
and the West, respectively. Evidence from studies of contemporary immigrants
conﬁrms that this inheritance is cultural rather than genetic,
given that in only one or two generations the children of immigrants
are indistinguishable from long-term residents, rather than their more
immediate genetic ancestors.
Such cross-cultural studies are complemented by more direct experimental
studies that demonstrate person-to-person cultural transmission
of behavior, attitudes, and opinions. Classic experiments conducted
by social psychologist Albert Bandura in the 1960s showed that
children will readily imitate the behavior of adult demonstrators.28
Children who saw an adult acting aggressively toward a large inﬂatable
“Bobo” doll themselves later showed more aggressive actions toward
the doll than children who did not see any aggressive actions, or who
saw an adult behaving nonaggressively. Other classic experiments conducted
by social psychologist Solomon Asch show how adults readily
C U L T U R A L E V O L U T I O N 33
adopt the opinion of others in simple tasks, such as matching a line
to one of a set of other lines of varying length, even when the other
people’s answers (actually stooges of the experimenter) are patently
false.29
These experimental studies are complemented by questionnaire
studies showing strong parent-offspring correlations in traits that are
unlikely to be entirely genetic, such as religious beliefs and hobbies,
as well as similarly high correlations between unrelated peers in such
traits, which cannot be genetic.30
In a sense, however, mere person-to-person transmission of information
is not enough for a fully Darwinian cultural evolution. Darwin
famously described biological evolution as “descent with modiﬁcation.”
By this he meant that for biological evolution to work, minor
modiﬁcations must not merely be inherited from parent to offspring
in a one-to-one fashion, inheritance must be faithful enough such that
the modiﬁcations are preserved over several successive generations and
potentially combined with other beneﬁcial traits. Only then can we
explain the complex adaptations involving several functionally interrelated
parts, such as eyes or wings, that are the result of the accumulation
of numerous separate modiﬁcations over countless generations.
We can similarly demonstrate the gradual accumulation of modiﬁcations
in culture. Historians have repeatedly shown how technological
artifacts rarely, if ever, spring from nothing. Instead, successful
innovations are always slight modiﬁcations of what went before, or
the combination of previously separate innovations. Historian George
Basalla gives the example of the steam engine.31
Rather than suddenly
emerging fully formed from James Watt’s inventive mind, as suggested
by some popular accounts, Watt’s steam engine was actually a modiﬁed
version of the preexisting Newcomen steam engine, with which
Watt had had extensive experience, and which in turn was a modiﬁcation
of a previous model, and so on back through history. Bodies of
knowledge also accumulate gradually in the same way that technological
artifacts do. Mathematics, for example, has evolved through
the accumulation of successive innovations by different individuals in
different societies over vast periods of time, with each new innovation
paving the way for the next. Even the basic base-10 decimal system
took over 4,000 years to emerge. Only after the Sumerians began to
use written symbols to represent numbers in around 2400 BC could the
Babylonians invent the place value system, in which the position of a
digit with respect to the decimal place determines its value. This then
allowed the Hindus and Mayans to invent a written symbol for zero,
which in turn made calculations easier. This accumulation of directly
C H A P T E R T W O 34
related successive inventions proceeded for centuries, with major additions
from the Greeks (e.g., geometry), Arabs (e.g., algebra), and Europeans
(e.g., calculus), through to present-day mathematics.32
Human culture therefore also exhibits the last of Darwin’s three preconditions
for evolution, inheritance. Cultural variants can be passed
faithfully from one individual to another, just as genes are passed from
parent to offspring in biological evolution. Moreover, this cultural inheritance
is of sufﬁciently high ﬁdelity that it can successfully support
the gradual accumulation of modiﬁcations, just as Darwin observed
for lineages of biological organisms.
Further Parallels
As well as demonstrating the existence of these three key characteristics
of Darwinian evolution—variation, competition, and inheritance—
Darwin also showed that these characteristics can explain the hitherto
mysterious biological phenomena that had puzzled naturalists for
centuries. Three such phenomena are adaptation, maladaptation, and
convergence. So if culture is Darwinian, then we should expect to see
these emergent phenomena in culture also.
Adaptation. One of Darwin’s greatest achievements was to provide a
scientiﬁc explanation for the often striking ﬁt between organisms and
their environments, in the form of adaptations:
We see these beautiful co-adaptations . . . in the structure of
the beetle which dives through the water; in the plumed seed
which is wafted by the gentlest breeze; in short, we see beautiful
adaptations everywhere and in every part of the organic
world.33
Natural selection provides a scientiﬁc explanation for this organismenvironment
ﬁt. Over successive generations, individuals that are better
at interacting with and gaining resources from their environments—
individuals that are faster or more efﬁcient at swimming through water,
for example—are more likely to survive and reproduce than less
effective individuals. We see the outcome of this gradual selection process
in the form of, for example, streamlined body shapes that make
swimming faster and more efﬁcient. More complex adaptations, such
as the eye, may have multiple working parts all interacting with one
another in a precise manner. These can equally be shown to be the
C U L T U R A L E V O L U T I O N 35
product of gradual natural selection through the accumulation of successive
beneﬁcial modiﬁcations, from concave pits of photosensitive
cells to adjustable lenses, each of which improved an organism’s ability
to sense light and movement in their environments.
We can also observe cultural adaptations that are exquisitely designed
for a particular purpose or for use in a particular environment
but that are the result of cultural rather than biological evolution. An
example might be the bow and arrow, which features multiple working
parts all interacting with one another in a precise manner. For
example, the San people of Botswana have 1-meter-long bows with
strings made of animal tendons, arrow shafts made of reeds, arrowheads
of ostrich bone (or more recently, barbed wire) that are poisoned
using beetle larva, and quivers made of tree roots.34
These components
together form a “beautiful co-adaptation” that is highly suited to its
function and features many functionally interrelated parts. The examples
of cumulative cultural evolution given above, such as modern
mathematics or the steam engine, also constitute cultural adaptations.
Indeed, these examples highlight the power of cultural processes in
generating adaptations that single individuals could never have come
up with on their own.
Maladaptation. While it was important for Darwin to demonstrate that
his theory could explain adaptations, it was equally important to demonstrate
that species are not perfectly adapted to their environments.
Perfect adaptation would, after all, be consistent with the action of
an omniscient creator designing every species to a perfect standard.
To counter this view, Darwin gave examples of maladaptation, where
a species is ill ﬁtted to its environment. This might occur when the
environment in which a species lives changes in some way, or when a
species moves into a new environment. Although drastic mismatches
between the species and the new environment are likely to lead to extinction,
when the mismatch is not so drastic then minor remnants of
adaptations to the previous environment may often persist despite no
longer serving any purpose. Examples include the small and functionless
skeletal hind limbs of whales and snakes that have been preserved
from their quadrupedal ancestors but which no longer serve any function.
Vestigial organs such as these provide evidence for descent, and
therefore for Darwinian evolution.
Aspects of culture can also be described as vestigial, where onceadaptive
cultural adaptations become maladaptive when environments
change. A familiar example is the QWERTY keyboard, which com-
C H A P T E R T W O 36
prises a conﬁguration of keys designed to make typing as slow and
awkward as possible. In the context in which it emerged, the QWERTY
keyboard was highly functional because fast typing caused early typewriter
keyboards to jam. Modern keyboards no longer have this limitation,
yet the suboptimal QWERTY keyboard conﬁguration remains.35
Vestigial features are also common in technological artifacts, especially
when new raw materials become available. Indeed, George Basalla
notes that such cases are common enough to merit their own label,
namely, a “skeuomorph,” which is deﬁned as an “element of design or
structure that serves little or no purpose in the artifact fashioned from
the new material but [which] was essential to the object made from
the original material.”36
Stone columns, for example, often retain the
masonry joints of their wooden precursors, despite no longer serving
a function.
Convergence. Finally, Darwin observed that isolated species could evolve
similar traits due to convergent evolution to similar environments. He
himself drew a cultural analogy here:
[I]n nearly the same way as two men have sometimes independently
hit on the very same invention, so natural selection . . .
has sometimes modiﬁed in very nearly the same manner two
parts in two organic beings, which owe but little of their structure
in common to inheritance from the same ancestor.37
Familiar examples of convergence in biological evolution include the
independent evolution of wings in bats, birds, and insects, or streamlined
body forms in ﬁsh and cetaceans. Indeed, convergence is now
considered to be one of the strongest forms of evidence for natural
selection, given the unlikelihood that similar forms would evolve independently
in unrelated lineages unless they are adaptations to similar
environments.
In culture, Darwin famously conﬁrmed the ﬁrst part of his observation
above when both he and Alfred Russel Wallace came up with
the theory of natural selection at the same time. Other examples of
parallel inventions or discoveries in culture include writing, which was
invented independently by the Sumerians around 3000 BC, the Chinese
around 1300 BC, and the Mexican Indians around 600 BC.38
Convergent cultural evolution may also produce artifacts that perform
the same function but do so in different ways, such as knives
C U L T U R A L E V O L U T I O N 37
and forks in Europe and chopsticks in China, both used to handle hot
food.39
Darwinian versus Spencerian Theories of Cultural Evolution
Given the many parallels outlined above between biological and cultural
change, including several parallels pointed out by Darwin himself,
it is not surprising that theories of cultural evolution began to
appear not long after the publication of The Origin of Species. Many
of these were proposed by inﬂuential early anthropologists such as Edward
Burnett Tylor in Britain and Lewis Henry Morgan in the United
States.40
Unfortunately, the evolutionary theory that they applied to
culture bore little resemblance to Darwin’s theory and more closely resembled
the rather un-Darwinian “progressive” evolutionary ideas of
Darwin’s contemporary, Herbert Spencer.41
Spencer saw evolution as
embodying a process of inevitable progress along a ladder of increasing
complexity, from simple microorganisms, to more complex plants and
animals, and ultimately to humans. Following Spencer, Tylor and Morgan
saw cultural evolution as also embodying some form of inevitable
progress. For them, cultural change could be described as the movement
of societies along ﬁxed stages of ever-increasing complexity. For
example, Morgan presented seven stages through which every human
society supposedly has passed or will pass in the future: lower, middle,
and upper savagery, then lower, middle, and upper barbarism, and ﬁnally
civilization. According to Morgan, each of these periods “has a
distinct culture and exhibits a mode of life more or less special and peculiar
to itself.”42
For example, “lower barbarism” begins with the appearance
of speech and ends with the invention of ﬁre, while “middle
barbarism” begins with the domestication of animals and ends with
the appearance of iron smelting. (For computer game enthusiasts, it’s
a lot like the ﬁxed stages of technological advancement seen in Sid
Meier’s Civilization games.) Morgan then goes on to classify contemporary
societies as each having advanced to one of these levels. Australian
aborigines, for example, he classiﬁed as having achieved “middle
savagery,” while Central American “Village Indians” were placed at
“middle barbarism.” European societies, and their recent colonial offshoots
such as the United States, were placed at the top of this cultural
ladder, and non-European societies were explicitly compared with
ancestral stages of European societies. For example, contemporary (to
Morgan) Central American “Village Indians” had reached the same
C H A P T E R T W O 38
stage as ancient Britons, and had not yet achieved the stage attained by
“Italian tribes shortly before the founding of Rome.”43
There are many problems with these early “progress” theories of
cultural evolution. First, they are rather tainted by the racist and colonialist
social views of the Victorian societies in which they emerged.
The idea that non-Western societies were “less evolved” than contemporary
Britain or America provided an attractive “scientiﬁc” justiﬁcation
for what today are considered to be rather distasteful social and
political attitudes. Beyond their political implications, however, it is
crucial to recognize that these progress theories bear little resemblance
to the evolutionary theory that Darwin proposed in The Origin, nor to
what modern-day biologists understand by evolution, and nor, indeed,
to the theory of cultural evolution presented in this book. As the biologist
Stephen Jay Gould has repeatedly argued, biological evolution is
explicitly nonprogressive.44
Species do not progress along ﬁxed stages
from simple microorganisms to more complex plants and animals. Humans
are not at the top of the evolutionary ladder, because there is
no ladder of which to be at the top. There is only local adaptation to
local environments, which does not necessarily translate into global
increases in ﬁtness, and does not result in inevitable and entirely predictable
evolutionary change along a prespeciﬁed course.
Similarly, as argued in the 1920s by anthropologists such as Franz
Boas and his followers, there is little historical or ethnographic evidence
that different societies pass through exactly the same stages in
the same order, and contemporary non-Western societies cannot be
meaningfully equated with ancient European societies.45
More fundamentally,
societies do not constitute self-contained wholes in the form
of distinct stages. Ideas, technologies, and people can move from one
society to another, such that different societies may share some aspects
of culture and differ in others. Finally, progressive theories are inadequate
because they do not specify the processes that are responsible
for this supposed cultural progression. It seems that societies somehow
magically jump from one stage to the next once they have accumulated
the necessary inventions (e.g., the use of ﬁre or pottery).46
Unfortunately, while progress theories of biological evolution
were quickly purged from biology, progress theories of cultural evolution
persisted well into the twentieth century.47
To this day, many
anthropologists and sociologists are wary of modern theories of cultural
evolution because of their (unfounded) association with politically
motivated and scientiﬁcally dubious nineteenth-century progress
theories of cultural evolution. It is crucial to recognize, therefore, that
C U L T U R A L E V O L U T I O N 39
the progressive Spencerian theory of evolution is fundamentally different
to Darwin’s population-based theory of evolution. This difference
is illustrated in ﬁgure 2.1. Spencer’s theory views species as a group
of homogenous individuals that all share the same essential qualities.
Evolutionary change occurs when one species abruptly steps up to the
next rung of the evolutionary ladder to become a new, more “complex”
species. The same was true of Spencerian theories of cultural
evolution, except instead of species there are societies that move up a
stagelike ladder. Darwin’s theory, on the other hand, focuses instead
on the variation within populations (e.g., in beak size) and how this
variation gradually changes over time. Given enough time, a population
might change enough to warrant being called a new species, but
this change is internally driven by selection and other processes acting
on the individuals within the population, rather than propelled by
an externally triggered shift. This change in thinking, from essentialist,
ladderlike thinking to variation-focused, Darwinian “population”
thinking, has been described as one of Darwin’s major contributions
F I G U R E 2 .1 The conceptual differences between Spencerian and Darwinian evolution. (a) Spencerian
evolution involves movement up a ladder of increasing complexity, from simple to more complex
stages. The inset shows how populations (e.g., species or societies) are considered to be homogenous
types. (b) Darwinian evolution is treelike rather than ladderlike. There is no inevitable increase
in complexity, and many branches go extinct. The inset shows how variation within populations
(e.g., species or societies) gradually changes over time.
C H A P T E R T W O 40
to science.48
Furthermore, Darwinian evolution does not require that
species increase in complexity over time. Traits may be lost, and species
frequently go extinct (the dead-end branches in ﬁgure 2.1b). This
makes Darwinian evolution more treelike than ladderlike, as lineages
branch off from one another in a haphazard, nonlinear manner. The
theory of cultural evolution discussed in this book is Darwinian, not
Spencerian.
Darwinian versus Neo-Darwinian Theories of Cultural Evolution
Another important distinction to make is between Darwinian theories
of cultural evolution and neo-Darwinian theories of cultural evolution.
The evidence reviewed above demonstrates that cultural change
is Darwinian in that it exhibits those properties of variation, competition,
and inheritance that Darwin outlined in The Origin. Yet Darwin
often had little idea—and in some cases was dead wrong—about exactly
how these processes worked at a microlevel: where new variation
comes from and how it is generated, the precise forms of competition
that act to sort different variants, and the mechanisms by which traits
are inherited from parent to offspring. In the decades following publication
of The Origin, a group of biologists known as experimental
geneticists conducted a series of ingenious breeding experiments in order
to work out these “microevolutionary” details. Microevolution describes
those small-scale, individual-level processes that act to change
trait frequencies within a single population, and can be contrasted with
macroevolution, which describes large-scale patterns and trends above
the species level, such as the emergence and diversiﬁcation of new species
due to adaptation.
The microevolutionary details worked out by experimental geneticists
include the ﬁndings that genetic inheritance is particulate (it involves
the transmission of discrete units of information in an all-ornothing
manner) and non-Lamarckian (changes to an organism during
its lifetime, such as the loss of a limb or the overuse of a muscle,
are not directly transmitted to offspring), and that genetic mutation is
blind with respect to selection (genetic mutations are no more likely to
arise when they are needed than when they are not needed). Adding
these microevolutionary details to the basic theory of Darwinian evolution
gave rise to what became known as the neo-Darwinian theory
of evolution.
Several researchers have subsequently argued that these neoDarwinian
details also apply to cultural evolution: that cultural trans-
C U L T U R A L E V O L U T I O N 41
mission is particulate, cultural evolution is strictly non-Lamarckian,
and cultural mutation is blind with respect to selection. However,
many social scientists have argued that these neo-Darwinian details do
not apply to cultural change. In many cases these criticisms appear to
be valid, or at least potentially valid. The following sections examine
in more detail these three neo-Darwinian principles ﬁrst as applied
to biological evolution and then whether they also apply to cultural
evolution.
Is Cultural Transmission Particulate? A common observation by animal
and plant breeders of Darwin’s day was that traits appear to blend
when they are inherited: a large pigeon and a small pigeon would have
intermediately sized offspring, for example. This suggested to many
early biologists, Darwin included, that biological inheritance is a process
of blending, where offspring take an intermediate form between
their two parents. However, Austrian monk Gregor Mendel showed
through breeding experiments with pea plants that this blending is just
superﬁcial, and at a microlevel biological inheritance is in fact particulate
not blending. In other words, biological inheritance involves
the transmission of discrete units of inheritance (called genes) that are
transmitted in an all-or-nothing fashion. We either inherit one version
(or allele) of a gene or another version, and these discrete units do not
blend together to produce an intermediate allele halfway between our
two parents’ alleles. Eye color is the classic example, where the child
of a brown-eyed parent and a blue-eyed parent will have either brown
or blue eyes, not a mixture of brown and blue. While other traits such
as height or skin color do appear to blend and take on any value on a
continuum, such cases are now known to be caused by lots of discrete
underlying alleles jointly determining such characters. For example,
in 2009 a team of researchers showed that the striking variation in
the coats of different dog breeds, from shaggy-coated bearded collies
to smooth-coated Chihuahuas, is controlled by just three discrete
genes.49
Does cultural inheritance similarly involve the particulate, all-ornothing
transmission of discrete units of cultural information? This is
a central assumption of the neo-Darwinian theory of cultural evolution
called memetics. Memetics originated in the ﬁnal chapter of Richard
Dawkins’s hugely inﬂuential book The Selﬁsh Gene, where he coined
the term “meme” to describe a discrete unit of cultural inheritance, or
cultural replicator, that operates within human culture.50
He described
this as the cultural equivalent of the biological replicator, the gene, such
C H A P T E R T W O 42
that the differential selection and transmission of these memes would
make cultural change an evolutionary process. Although Dawkins primarily
intended the meme concept to be a way of highlighting how his
replicator-centered theory of evolution was not limited to just genes,
others such as philosopher Dan Dennett and psychologist Susan Blackmore
have developed the meme concept into a full theory of memet-
ics.51
Memetics makes the neo-Darwinian assumption that culture can
be divided into discrete units that are inherited in a particulate fashion,
like genes. It also assumes that memes are transmitted with high ﬁdelity,
this being one of the deﬁning characteristics of a replicator according
to Dawkins.
However, whereas genetic inheritance is particulate, cultural inheritance
in many cases appears to be nonparticulate. As anthropologist
Maurice Bloch puts it, “culture simply does not normally divide
up into naturally discernable bits.”52
Think of political beliefs, which
vary on a continuum from extreme left-wing to extreme right-wing, or
archaeological artifacts such as arrowheads, which vary continuously
in their length and width. There is also evidence that cultural traits
blend when transmitted. During language acquisition, children appear
to blend the speech sounds of their parents and their peers, resulting
in a shift toward the average pronunciation of several people.53
Social
psychologists have similarly found that people adopt the blended average
of other people’s judgments of ambiguous stimuli, such as the
extent to which a small point of light appears to be moving in a pitchblack
room.54
Now, a limitation of such studies is that they might be at entirely
the wrong level of analysis: artifacts, speech sounds, and stated beliefs
are the outward behavioral expressions of information stored in
the brain and as such are the cultural equivalents of phenotypic traits
such as height or skin color. As we saw for the biological case, even
though phenotypic traits such as height may vary continuously and
appear to blend in offspring, they are nevertheless determined by discrete
underlying units of inheritance (genes). In the same way, it may
be that continuous, blending cultural traits such as speech sounds and
expressed political values are determined at the neural level by discrete
cultural units of transmission. This is ultimately an issue for neuroscientists
studying how information is represented in the brain and how
it is transmitted from one brain to another. Given our current lack
of understanding of such issues, it is impossible to say with certainty
whether cultural transmission, at the neural level, is particulate or
nonparticulate. Without this evidence, a cautious working assumption
C U L T U R A L E V O L U T I O N 43
should be that cultural variation may, in some cases, be continuous,
and that cultural transmission may, in some cases, be blending.55
Is Cultural Evolution Lamarckian? Another common belief of early biologists,
including Darwin, was that changes that occurred to an organism
in its lifetime were directly (i.e., genetically) transmitted to its offspring.
This inheritance of acquired characteristics is often called “Lamarckian”
after the eighteenth-century French biologist Jean-Baptiste La-
marck.56
The textbook example of Lamarckian inheritance involves
giraffes: a Lamarckian explanation of long giraffe necks is that giraffes
in one generation stretch to get leaves on high tree branches; their neck
muscles stretch and lengthen slightly as a result of this stretching, and
their offspring directly inherit these elongated neck muscles. Successive
generations of stretching resulted in the long necks we see today. The
alternative to this Lamarckian explanation instead invokes selection:
some giraffes happen to have been born with long necks, some with
short necks; those with longer necks can reach higher branches, get
more food, and have more offspring; those offspring inherit the long
necks of their parents, and so long-neck genes gradually spread in the
population.
Careful experiments conducted by geneticists such as August Weismann
in the 1890s showed that the former Lamarckian mechanism
does not operate in biological evolution. Weismann and others showed,
for example, that rats who had their tails cut off gave birth to offspring
with fully intact tails, indicating that acquired changes are not transmitted
genetically. This led to a distinction between the genotype, the
genetic information inherited by offspring, and the phenotype, the expression
of the genotype in the form of anatomical and physiological
structures. Changes to the phenotype are not directly transmitted to
the genotype; they cannot pass what became known as “Weismann’s
barrier.” In neo-Darwinian evolutionary theory, therefore, selection is
the main process that causes biological change, and Lamarckian inheritance
is strictly absent.57
Is cultural evolution Lamarckian? Obviously it is not literally Lamarckian
in the sense that the knowledge and skills we learn during
our lifetimes, such as how to play the violin or do differential calculus,
are not transmitted genetically to our offspring. But several researchers
have argued that cultural evolution is Lamarckian in the sense that the
knowledge and skills that we learn can be directly transmitted to others
culturally, rather than genetically. As Stephen Jay Gould put it, “cultural
evolution is direct and Lamarckian in form: The achievements
C H A P T E R T W O 44
of one generation are passed by education and publication directly to
descendants.”58
Others, such as economists Geoffrey Hodgson and
Thorbjørn Knudsen, maintain that cultural evolution, like biological
evolution, is strictly non-Lamarckian even in this sense. Still others,
such as philosopher David Hull, have argued that the term “Larmarckian”
cannot be meaningfully applied to cultural evolution.59
Clearly
much disagreement exists over this issue.
Whether cultural evolution can properly be described as Lamarckian
depends on how one deﬁnes the equivalent of the genotypephenotype
distinction in culture. The ideational deﬁnition of culture
given in chapter 1 implies that the cultural equivalent of the genotype
is the information stored in people’s brains that represents their
beliefs, attitudes, values, skills, knowledge, and so on. The cultural
equivalent of the phenotype is the expression of that information in the
form of behavior, speech, and artifacts. It is the latter—the phenotype
equivalent—that is copied during cultural transmission: we do not directly
acquire neural patterns of activation in people’s brains; we copy
people’s behavior, we listen to what they say, and we read what they
write. If we then modify the acquired beliefs, knowledge, and skills in
some way before transmitting them to someone else, we can be said to
be engaging in Lamarckian cultural inheritance.
The history books are full of apparent examples of the inheritance
of acquired cultural change, where single inventors have individually
modiﬁed an existing technology that has then spread to other members
of society. For example, in the 1760s James Watt dismantled and
tinkered with the workings of the preexisting Newcomen steam en-
gine.60
The Newcomen engine uses the condensation of steam to create
a vacuum underneath a piston. The greater pressure acting from
above then forces the piston down. Over the next two decades Watt
made several modiﬁcations to this preexisting design, such as having
a separate compartment for condensing the steam, which allowed the
piston chamber to remain hot continuously. Watt’s improved steam
engine, which ﬁrst appeared in 1784, diffused across the world and
dominated engine design for the next ﬁfty years. So here we have one
individual (Watt) acquiring information from another (Newcomen, via
his engine), modifying it in some way, and transmitting the modiﬁed
information to others, in a manner that can be described as Lamarckian.
So given the assumptions made earlier, we can say that cultural
evolution can be described as Lamarckian, and the neo-Darwinian requirement
that inheritance is strictly non-Lamarckian does not apply
to cultural evolution.
C U L T U R A L E V O L U T I O N 45
Is Cultural Evolution Blind? A third neo-Darwinian assumption is that
mutation is blind or undirected, such that novel genetic mutations are
no more likely to arise when they are needed (i.e., when they will confer
a ﬁtness beneﬁt on their bearer) than when they are not needed. This
was demonstrated deﬁnitively in the 1940s in experiments conducted
by Salvador Luria and Max Delbrück.61
In these experiments, different
colonies of initially genetically identical bacteria were exposed to a
virus. Luria and Delbrück reasoned that if mutations that conferred resistance
to the virus occurred randomly, then different colonies would
vary in their level of resistance, as only some colonies would happen
to have these beneﬁcial mutations. If, on the other hand, mutations
conferring resistance appeared nonrandomly and were triggered by the
presence of the virus, then all colonies should have the same level of
resistance. The former was found, indicating that beneﬁcial mutations
occur randomly and not in response to a particular adaptive problem.
This ﬁnding that genetic mutation is blind with respect to ﬁtness reinforces
the notion that biological evolution is undirected or unguided by
any kind of foresight.
A neo-Darwinian theory of cultural evolution that incorporates
the principle of blind variation is psychologist Donald T. Campbell’s
“blind-variation-and-selective-retention” (BVSR) theory.62
Campbell
argued that blindly generated cultural variants are subject to consistent
selection criteria, and the positively selected variants are preserved.
One of the key assumptions of BVSR theory, as its name suggests, is
that new cultural variation arises blindly, with no foresight directing
the course of cultural evolution. This resembles the neo-Darwinian
assumption of blind, or nonadaptive, mutation as established by Luria
and Delbrück for genetic variation. Consequently, BVSR theorists such
as psychologist Dean Keith Simonton have conducted extensive historical
studies of creativity and discovery in order to test this blind variation
hypothesis.63
Is cultural evolution blind? On the face of it, no: cultural evolution
appears to be guided by the intentional actions of people who possess
at least some degree of foresight, potentially increasing the likelihood
of adaptive cultural mutations. Inventors and scientists strive to solve a
particular problem, military commanders plot the course of a coming
engagement, and advertisers plan marketing campaigns, for example.
This is a point frequently made by social scientists. Sociologist Ted
Benton remarks that “Darwin’s mechanism of natural selection assumes
that mutations are random with respect to the selective pressures
which affect their chances of replication. In the case of the ac-
C H A P T E R T W O 46
tivities which lead to social change . . . human agents act intentionally
to produce anticipated outcomes: they are not ‘blind watchmakers.’”64
On the other hand, historical analyses of scientiﬁc and technological
change suggest that cultural change is not quite so directed, and foresight
not quite as accurate, as commonly assumed.65
Historical ﬁgures
often claim retrospectively to have guided cultural change in particular
directions, yet such claims may have the beneﬁt of hindsight and be
self-servingly exaggerated.66
However, there is a general lack of systematic
evidence regarding this issue, at least compared to the careful
experiments conducted by Luria and Delbrück in biology. We should
therefore be prepared to accept that cultural evolution may, at least in
some instances, be directed rather than blind and that there is a valid
difference here between cultural and biological evolution.
Cultural Evolution Is Darwinian, But Not Neo-Darwinian. This lack of correspondence
between neo-Darwinian evolutionary theory and cultural
change has often led to the wholesale rejection of any kind of evolutionary
theory of culture. Stephen Jay Gould, for example, argued on
the basis of the aforementioned differences that “biological evolution
is a bad analogue for cultural change,”67
while John Maynard Smith,
one of the most highly regarded biologists of the twentieth century,
argued that the
explanatory power of evolutionary theory rests largely on three
assumptions: that mutation is nonadaptive, that acquired characters
are not inherited, and that inheritance is Mendelian—
that is, it is atomic, and we inherit atoms, or genes, equally
from our two parents, and from no one else. In the cultural
analogy, none of these things is true. This must severely limit
the ability of a theory of cultural inheritance to say what can
happen and, most importantly, what cannot happen.68
This wholesale rejection of the application of evolutionary theory to
culture is unfounded once we make a distinction between Darwinian
and neo-Darwinian evolution. Whereas cultural evolution does not
appear to resemble neo-Darwinian evolution, with its strict assumptions
of blind mutation and particulate, non-Lamarckian inheritance,
cultural evolution can still be described as Darwinian, given the evidence
reviewed above that it exhibits the basic Darwinian properties of
variation, competition, and inheritance.69
Variation that is nonrandom
is still variation, and inheritance that is Lamarckian and nonparticu-
C U L T U R A L E V O L U T I O N 47
late is still inheritance. Indeed, it is an interesting historical point that
Darwin himself held distinctly non-neo-Darwinian beliefs concerning
biological evolution, such as in blending and Lamarckian inheritance.
What is needed is a theory of Darwinian cultural evolution that explicitly
incorporates non-neo-Darwinian microevolutionary processes
such as blending inheritance, Lamarckian inheritance of acquired characteristics,
and nonrandom variation, as well as other processes that
may have no parallel whatsoever in biological microevolution. Such a
theory is presented in chapter 3. However, further examination of the
history of biology suggests that simply having the correct microevolutionary
processes in place was not enough to make every biologist
agree on a single, unifying theoretical framework. It is instructive for
the social sciences to examine why not.
Bridging the Micro-Macro Divide
The Micro-Macro Problem in Early Biology. Even after experimental geneticists
such as Mendel and Weismann had established the neo-Darwinian
microevolutionary principles of particulate, non-Lamarckian inheritance
and random variation, these microevolutionary principles were
not readily accepted by other biologists studying macroevolution, such
as naturalists documenting spatial macroevolutionary patterns by
comparing the species found in different regions and paleontologists
documenting temporal macroevolutionary trends in the fossil record.
As biologist Ernst Mayr notes:
Through the ﬁrst third of the twentieth century the gap between
the experimental geneticists and the naturalists seemed
so deep and wide that it looked as if nothing would be able
to bridge it . . . The members of the two camps continued to
talk different languages, to ask different questions, to adhere
to different conceptions.70
One particularly ﬁerce argument raged over Lamarckian inheritance
and the strength of selection.71
Naturalists had by this time documented
immense diversity in living species as a result of expeditions
such as Darwin’s own voyage on the Beagle, as well as equally diverse
forms found in the fossil record, such as the many dinosaur species uncovered
in the late nineteenth century. The only process that is strong
enough to generate such diversity, the naturalists reasoned, was Lamarckian
inheritance. After all, if an organism could directly transmit
C H A P T E R T W O 48
beneﬁcial changes to its offspring, then meaningful change could occur
in just a single generation and myriad diverse forms could rapidly
emerge. The non-Lamarckian alternative, natural selection, seemed to
the naturalists to be far too weak to generate the diversity that they
had documented. Selection, they thought, was severely limited because
it relied on the chance occurrence of beneﬁcial mutations. And even
when a beneﬁcial mutation did happen to arise, it must spread gradually
over the course of several generations as those individuals that
possessed the beneﬁcial mutation had more offspring than those that
didn’t possess the beneﬁcial trait. This advocacy of Lamarckian inheritance
over selection put the naturalists in direct conﬂict with experimental
geneticists such as Weismann who, as we saw above, had shown
experimentally that inheritance is strictly non-Lamarckian.
A second division between the experimental geneticists and the
naturalists concerned particulate inheritance and gradualism.72
Experimental
geneticists such as Mendel had shown that biological inheritance
involves the all-or-nothing transmission of discrete units (genes),
with evolutionary change occurring when one of these discrete units
mutates into a different version. Several experimental geneticists, most
notably Richard Goldschmidt, saw this as inconsistent with Darwin’s
assertion in The Origin that biological change is gradual. Goldschmidt
and others instead advanced a saltationist theory of evolution, in which
major evolutionary change, such as the appearance of new species, occurs
in a sudden, single-generation leap, equivalent to a massive mutation.
While most of these mutants will be maladaptive, or nonviable, a
rare mutant (a “hopeful monster” as Goldschmidt put it) might happen
to be adaptive, and thus an entirely new species is born. Naturalists and
paleontologists, on the other hand, saw saltationist theories of evolution
as entirely inconsistent with their observations of macroevolution.
The fossil record, rather than showing sudden jumps, generally records
gradual change in species over time. Rather than birds evolving from
dinosaurs in a single dramatic mutation, paleontologists were ﬁnding
transitionary forms such as Archaeopteryx that indicated gradual, incremental
evolutionary change. The same applied to geographical variation
in species, which tended to be gradual rather than abrupt. The
ﬁnch species found by Darwin on the Galápagos, for example, while
being measurably different in beak size and shape, were nevertheless
all minor variations on the same design (i.e., the common ancestor).
The Evolutionary Synthesis in Biology: The Beneﬁts of Formal Models. These
disagreements between the experimentalists and the naturalists were
C U L T U R A L E V O L U T I O N 49
caused largely by ﬂawed, informal reasoning on both sides regarding
the relationship between micro- and macroevolution: the naturalists’
informal intuition that selection (a microevolutionary process) is too
weak to generate the rich species diversity they had observed (a macroevolutionary
pattern), and the experimentalists’ intuition that particulate
inheritance (a microevolutionary process) was incompatible
with gradual change (a macroevolutionary trend). What was needed
was a way to more precisely test these intuitions regarding the macroevolutionary
consequences of different microevolutionary processes.
In the 1920s and 1930s a group of mathematically inclined biologists,
primarily R. A. Fisher and J. B. S. Haldane in the United Kingdom and
Sewell Wright in the United States, developed a set of mathematical
tools, known as population genetic models, that allowed these informal
intuitions to be tested far more precisely than is possible with informal,
verbal arguments and thought experiments.73
These population genetic
models can be seen as methods of evolutionary “bookkeeping.” Just as
a bookkeeper compiles a record of all of the ﬁnancial transactions that
act to change a company’s stock levels or proﬁt margin, so a population
geneticist compiles a record of all of the natural processes that act to
change gene frequencies in a population over time. The modeler speciﬁes
a set of alternative genes (or alternative versions of a gene, known
as alleles) in a population. Then they specify a set of processes (e.g.,
mutation or different kinds of selection) that change the variation in
genes in the population in a single generation. Mathematical modeling
techniques are then used to predict the long-term changes in genetic
variation over time, identifying, for example, whether one allele will
entirely replace another allele, or whether the two alleles will coexist at
some stable equilibrium.74
In the 1920s and 1930s, Fisher, Haldane, Wright, and others used
population genetic models to resolve the disagreements that separated
the naturalists and experimentalists. They showed mathematically
that selection, far from being the weak, insigniﬁcant force assumed by
the naturalists, was in fact an extremely potent force.75
Their models
showed, for example, that a gene that conferred an advantage of just 1
percent (i.e., its bearers were 1 percent more likely to reproduce than
individuals without the gene) could spread to half of a population in
just 100 generations. Although quite long in terms of human generations,
for most species 100 generations is quite short. And compared
to the complete history of life on earth, it is but the blink of an eye.
Fisher and Haldane therefore showed that the naturalists’ assumption
that selection was too weak to effect meaningful biological change
C H A P T E R T W O 50
was incorrect and that recourse to Lamarckian inheritance was unnecessary.
Once the naturalists accepted this, reconciliation with the
anti-Lamarckian experimentalists soon followed. Fisher also showed
mathematically that continuous phenotypic variation, like that seen
in height or skin color, could arise from the combined action of multiple
discrete genetic characters, each of which has a small individual
effect. This reinforced Mendel’s experimental demonstration that biological
inheritance is particulate. He then showed that gradual phenotypic
change could occur as mutations appear in just a subset of the
underlying discrete characters. Because each discrete character has a
small individual effect, this does not result in the massive phenotypic
mutations envisioned by the experimental geneticists who advocated
saltationism. Thus the experimental geneticists’ informal intuition
that particulate inheritance inevitably leads to abrupt, discontinuous
change became untenable; they abandoned saltationism and accepted
the gradualism of the naturalists.
Once the population geneticists had used formal models to resolve
these disagreements, the two previously separate camps—experimental
geneticists studying microevolution and naturalists studying macroevolution—came
together during a short ten-year period from 1937
to 1947 in what is known as the evolutionary (or modern) synthesis to
form what we now recognize as evolutionary biology.76
Essentially this
synthesis represented a bridging of the micro-macro divide: macroevolutionary
patterns documented by naturalists, such as gradual change
and species diversity, were shown to be consistent with the microevolutionary
processes that had been demonstrated experimentally by the
geneticists, such as particulate and non-Lamarckian inheritance. As
Mayr put it:
The proponents of the synthetic theory maintain that all evolution
is due to the accumulation of small genetic changes,
guided by natural selection, and that transspeciﬁc evolution is
nothing but an extrapolation and magniﬁcation of the events
that take place within populations and species . . . it is misleading
to make a distinction between the causes of micro- and
macroevolution.77
Although this synthesis was by no means comprehensive and complete
(a major omission, for example, was development), the bridging of
the micro-macro divide within a common neo-Darwinian theoretical
C U L T U R A L E V O L U T I O N 51
framework set the stage for huge advances in the study of biological
evolution.
The Micro-Macro Divide in the Social Sciences. The micro-macro divide
that afﬂicted the biological sciences in the early twentieth century has
a striking parallel in the social sciences today. The divide in the social
sciences is between the microlevel, that is, those small-scale, individual-level
processes that act to change the frequency of culturally
transmitted traits within a single population, and the macrolevel, that
is, large-scale patterns and trends at or above the level of entire societies,
such as cross-cultural differences in civic duty or cognition,
or long-term historical trends such as the rise and fall of the Roman
empire or the diversiﬁcation of Indo-European languages. Just like the
geneticist-naturalist divide in presynthetic biology, these two levels
are often studied entirely separately, by different scholars in different
disciplines, and with little attempt to ensure that the ﬁndings at one
level are consistent with the other, or to use the ﬁndings of one to
explain observations at the other. Psychologists, for example, study
the behavior of single individuals (as in cognitive psychology), or at
most the behavior of individuals interacting within small groups (as
in social psychology), under controlled conditions in the laboratory.
Cultural anthropologists, meanwhile, often focus on macrolevel, societywide
cultural variation in customs and practices, and archaeologists
deal with macrolevel cultural change over time, such as the spread of
a particular arrowhead design over several centuries. Other disciplines
exhibit an internal micro-macro split. Economics is partitioned into
microeconomics, the study of individual-level processes such as how
the decisions of individual buyers and sellers affect supply and demand
for goods, and macroeconomics, the study of population-level variables
such as GDP and unemployment rates. Similarly, microsociology
is concerned with the analysis of individual behavior (or “agency”),
while macrosociology deals with population-level phenomena such as
social structure. Linguistics has microlevel branches such as psycholinguistics,
concerned with how individuals acquire and use language,
and macrolevel branches such as historical linguistics, concerned with
how entire languages change over hundreds or thousands of years.
This micro-macro divide is problematic for two reasons. First, macrolevel
researchers are often unwilling to explain macrolevel patterns
and trends that they document in terms of underlying individual-level
processes. This reluctance has its origin in the ideas of many inﬂuen-
C H A P T E R T W O 52
tial early social scientists. For example, cultural anthropologist Alfred
Kroeber saw culture as a “superorganic” phenomenon that cannot be
reduced to individual-level psychological (“mental”) processes:
Mental activity . . . proves nothing whatever as to social events.
Mentality relates to the individual. The social or cultural, on
the other hand, is in its very essence non-individual. Civilization,
as such, begins only where the individual ends.78
Similarly, one of the founders of sociology, Emile Durkheim, argued
that:
In no case can sociology simply borrow from psychology any
one of its principles in order to apply it, as such, to social facts.
Collective thought, in its form as in its matter, must be studied
in its entirety, in and for itself, with an understanding of its
peculiar nature.79
This unwillingness to reduce cultural phenomena down to individual
behavior persists to this day. While macrolevel disciplines such
as cultural anthropology, historical linguistics, history, and macrosociology
have documented patterns of cultural change, such as the rise
and fall of the Roman empire or the diversiﬁcation of Indo-European
languages, and patterns of cross-cultural variation in, for example,
supernatural and religious beliefs, marriage systems, or agricultural
methods, they have generally failed to explain these patterns of change
and variation in terms of the behavior and psychological processes of
the people who are responsible for those patterns. This reluctance to
reduce cultural phenomena to individual psychological processes may
have its roots in the mind-body dualism inherent in many of the nonscientiﬁc
approaches to culture such as social constructionism that were
discussed in chapter 1.80
Yet reductionism is a key tool of the scientiﬁc
method and is responsible for huge advances in the physical and natural
sciences, whether it is the reduction of matter to atoms and subatomic
particles in physics or, as we have seen in biology, the reduction
of macroevolutionary patterns such as adaptation and speciation to
microevolutionary processes such as natural selection and particulate
inheritance.
The second problem is the opposite of the ﬁrst: micro-level disciplines
such as psychology have failed to acknowledge the extent to
which macrolevel cultural processes shape individual behavior.81
Psy-
C U L T U R A L E V O L U T I O N 53
chologists, for example, tend to focus on single individuals and their
behavior in nonsocial experimental situations in the lab, or at most interactions
within small groups. Similarly, economists typically assume
that people make economic decisions in isolation from other people by
rationally assessing the costs and beneﬁts of different options. Yet as
reviewed in chapter 1, recent ﬁndings from cultural psychology have
demonstrated that culture shapes numerous aspects of human behavior
to a degree not hitherto suspected, from cooperative tendencies to basic
processes of attention and perception. Although these are signiﬁcant
ﬁndings, they are rather recent and have yet to permeate most of psychology.
A similar situation pertains to economics, in which the lack
of consideration of cultural processes such as conformity (sometimes
called “herd behavior”) has limited economists’ understanding of macroevolutionary
phenomena such as market bubbles and crashes.82
As
economist Herbert Gintis notes:
Sociology and anthropology recognize the importance of conformist
transmission but the notion is virtually absent from
economic theory. For instance, in economic theory consumers
maximize utility and ﬁrms maximize proﬁts by considering
only market prices and their own preference and production
functions. In fact, in the face of incomplete information and
the high cost of information-gathering, both consumers and
ﬁrms in the ﬁrst instance may simply imitate what appear to
be the successful practices of others.83
Microlevel disciplines such as psychology and microeconomics remain
largely divorced from the real-world patterns of cultural change and
variation documented by macrolevel disciplines such as cultural anthropology,
and archaeology. Without such links, the validity of microlevel
experiments and theories concerning human behavior remain
in doubt.
Conclusion: A Darwinian Theory of Culture Can Synthesize the
Social Sciences
Given that cultural change, like biological change, is Darwinian, perhaps
a similar evolutionary synthesis to that which occurred in the
biological sciences in the 1940s might be possible for the social sciences.
Just as the evolutionary synthesis in biology solved the micromacro
problem by showing, through the use of formal, quantitative
C H A P T E R T W O 54
models, how microevolutionary processes are consistent with, and indeed
explain, macroevolutionary patterns, an equivalent evolutionary
synthesis in the social sciences would use similar models to show how
cultural macroevolution, as studied by macroeconomists, macrosociologists,
historical linguists, historians, cultural anthropologists and
archaeologists, is consistent with, and indeed explicable from, microevolutionary
processes studied by microeconomists, microsociologists,
psycholinguists, neuroscientists, and psychologists. Yet it is crucial that
the differences between biological and cultural evolution are incorporated
into these models, given that cultural evolution does not exhibit
the same neo-Darwinian microevolutionary processes as does biological
evolution. The following chapter outlines the pioneering work of a
handful of scholars who in the 1970s and 1980s attempted to construct
a formal theory of Darwinian cultural evolution taking these differences
into account.