Chapter 20
Cultural and
Social Evolution
Figure CO: A lion and her cubs
© George Lamson/ShutterStock, Inc.
• Unlike most other animals, humans transfer
information from generation to generation
through genes and culture
• Animal Behavior – Ethology – Sociobiology
– All organisms exhibit behaviors, not just animals
• Human language abilities
• Social Darwinism – a discredited social
• Biological and cultural evolution interact
– Eugenics, genetic engineering and cloning
Animal Behavior
• Animal behavior is the scientific study the behavioral
relationships of animals to their physical environment as well
as to other organisms, and includes such topics as how
animals find and defend resources, avoid predators, choose
mates and reproduce, and care for their young
• The study of animal behavior is concerned with understanding
the causes, functions, development, and evolution of
• The causes of behavior include both the external stimuli that
affect behavior, and the internal hormonal and neural
mechanisms that control behavior
• The functions of behavior include its immediate effects on
animals and its adaptive value in helping animals to survive or
reproduce successfully in a particular environment
Animal Behavior
• The development of behavior pertains to the ways in which
behavior changes over the lifetime of an animal, and how
these changes are affected by both genes and experience.
• The evolution of behavior relates to the origins of behavior
patterns and how these change over generations
• This discipline was founded by American biologists and
psychologists, primarily after WWII, and included
considerable emphasis on laboratory experimentation
• Many behavioral psychologists emphasized the study of
learned behaviors
– Ivan Pavlov (1849-1936) and his dog studies is the classic
• Ethology is the scientific study of animal behavior, and a
sub-topic of zoology
• The modern discipline of ethology begun during the 1930s
in Europe and parallel to but rather independent of the
Modern Synthesis
• Ethology is a combination of laboratory and field science,
with a strong relation to certain other disciplines — e.g.,
neuroanatomy, ecology, evolution
• Ethologists are typically interested in a behavioral process
rather than in a particular animal group and often study
one type of behavior (e.g. aggression) in a number of
unrelated animals — a comparative approach
The Nobel Prize in Physiology or
Medicine 1973
• Karl von Frisch, Konrad Lorenz, and Nikolaas Tinbergen "for
their discoveries concerning organization and elicitation of
individual and social behavior patterns“
• A rare prize for evolutionary biologists for the founders of
modern Ethology from the Nobel Committee
Karl von Frisch (1886 - 1982)
• Austrian entomologist who
studied insect communication
• Made major contributions to the
study of honey bees, their ability
to communicate to hive mates
about food sources with the
waggle dance, use of
pheromones, and their ability to
see in color and in ultravioltet and
polarized light.
• Wrote Dancing Bees, A Biologists
Remembers, Animal Architecture,
and other works
Konrad Lorenz (1903 - 1989)
• Austrian ornithologist
and ethologist
• Studied instincts and
fixed action patterns in
birds, and later became
interested in human
• Wrote many books
including King
Solomon’s Ring and On
Nikolaas Tinbergen (1907 - 1988)
• Dutch zoologists who studied
fish, birds and insects in nature
and the laboratory, and later
• A better experimentalist than
Lorenz, the theoretician
• Wrote The Study of Instinct,
The Herring Gull’s World, Social
Behavior in Animals, Curious
Naturalists, etc.
effect ↑
Robert Hinde (1923 - )
• British zoologist who studied birds,
then primates, and later humans
• Wrote Animal Behaviour: A Synthesis
of Ethology and Comparative
Psychology (1966), a classic work that
helped integrate research in
psychology and ethology, Biological
Bases of Human Social Behaviour
(1974), Individuals, Relationships and
Culture (1987), Towards
Understanding Relationships (1979),
and Why Gods Persist (1999), etc.
Desmond Morris (1928 - )
• British ethologist,
popularizer of science,
and surrealist painter.
• Happy to take
controversial positions
when advocating for
the biological basis of
human behaviors
• Wrote the bestsellers
The Naked Ape and The
Human Zoo, among
nearly eighty volumes
David P. Barash (1946 - )
• American psychologist and
• Barash has been named one of the
country's "101 Most Dangerous
Professors," by right-wing writer
David Horowitz, because of his
advocacy of peace and other
progressive causes, as well as his
avowed atheism and persistent
exploration of evolutionary biology
and its application to human
• Excellent writer and author of more
than 25 books
One of his most recent books is Natural Selections: selfish altruists,
honest liars and other realities of evolution (2007)
George B. Schaller (1933 - )
• Perhaps the world’s greatest living
field biologist and ethologist
• Preceded Dian Fossey with his 1959
study of the mountain gorilla
• Since has studied big cats, pandas,
African, Tibetan, Brazilian, Chinese and
Southeast Asian fauna
• Helped establish many national parks
in Asia
• Has won many awards and written
several dozen books, beginning with
The Mountain Gorilla – Ecology and
Behavior (1963), and, recently, A
Naturalist and Other Beasts: Tales
From a Life in the Field (2007)
Nature versus Nurture?
• Animal behavior is best explained by investigating
the contributions of both genes and environment
• Behaviors form a spectrum from innate behaviors
which exhibit little variation among members of a
species and appear at predictable times in
development to learned behaviors which require
exposure to various environmental stimuli to
develop, usually require trial-and-error repetition to
improve their efficiency and exhibit considerable
variation among members of a species
• In all cases, organisms with genes must interact with
their environment for behaviors to occur
• Relatively complex innate, predictable,
stereotypical behaviors which are present
in individuals, sometimes even from birth,
and performed completely without
requiring any experience
• The simplest are muscular and autonomic
reflexes such as pupil constriction in bright
light or a flexor reflex when the hand
touches a hot object
• More interesting are fixed action patterns,
e.g., courtship rituals in many animals, nest
building, predator defense behaviors, etc.
Filial Imprinting
• Konrad Lorenz himself raised
these greylag goslings from first
hatching, so it was to him that
they imprinted, expressing their
innate behavior of following their
• Imprinting behaviors usually
trigger at critical times in
• Now imprinting is used to
reintroduce captive-reared birds
to life in the wild
Biased Learning
• Biased learning is a restricted form of learning ―
the ability to learn and modify behavior from a
restricted set of environmental stimuli
• Lorenz, Tinbergen, and others demonstrated that
imprinting and other “innate” behaviors develop
from heritable “hard-wired” neurological programs
which may still be influenced by biased learning
– Following behavior in water birds, mate identification in
various birds, mating combat with rivals, etc.
Sexual Imprinting
• Male zebra finches select a
mate based on the color
pattern of the female that
rears them, regardless of
• On the other hand, their
courtship song and dance
require some learning
Reverse Sexual Imprinting
• When two people live in close domestic proximity
during the first few years in the life of either one,
both are desensitized to later close sexual attraction
• This phenomenon, known as the Westermarck
effect, was first described by Finnish anthropologist
Edvard Westermarck
• Documented in biological families, Iraeli kibbutz,
Chinese Shim-pua arranged child marriages, and
many other cultural setting
Genetic Sexual Attraction
• When a brother and sister are brought up
separately, never meeting, they may find each
other very sexually attractive as adults; first
cousins are also often highly attracted
– Charles Darwin and Emma Westwood were first
cousins, but did know each other during their
• This suggests that the Westermarck effect
evolved to inhibit inbreeding with its negative
genetic consequences
Inherited Behavior
in Lovebirds
Two species of lovebirds were interbred. Female
Fischer's lovebirds cut long strips of nesting
material, which are carried individually to the
nest. Female Peach-faced lovebirds cut short
strips and carry several at a time by tucking them
into her back feathers.
Hybrid females cut intermediate length strips
and tried, but failed, to transport them by
tucking into back feathers. They learned to carry
strips in their beaks, but never gave up all
tucking behavior.
Phenotypic differences in the behavior of the
two species are based on different genotypes.
Innate behavior can be modified by experience.
Learned behaviors are typically based upon
gene-determined neural systems that are
receptive to learning.
Genes vs. Environment
— Bird Song
a) Three calls of the male
meadowlark are shown, one
set produced by a free-living
individual and one produced
by a hand-reared male kept
isolated from ever hearing the
songs of another male. The
meadowlark’s genetic
program is sufficient to
produce normal songs.
Genes vs. Environment —
Bird Song
b) The free living male chaffinch
produces a complex song, but if
raised in song isolation, its song is
much different. If the chaffinch is
exposed to the song of a tree pipit,
then the chaffinch song picks up
some of this vocal culture. Not
only is the chaffinch genetic
program insufficient to produce
the normal song, but song culture
(exposure to the tree pipit) can
modify it.
Learned Behaviors
• Learning can be defined as a persistent change in
behavior that occurs as a result of experience
• In general, learned behaviors will always be:
– Nonheritable -- acquired only through observation or
– Extrinsic -- absent in animals raised in isolation from others
– Permutable -- pattern or sequence may change over time
– Adaptable -- capable of modification to suit changing
– Progressive -- subject to improvement or refinement
through practice
Learned Behaviors
• Learned behavior is more flexible and often
more complex than innate behavior
• The capacities for most behavioral traits, like
so many other adaptations, result from
evolutionary selective forces
• Most behaviors have instinctive and learned
components, a spectrum related to the size
and complexity of the animal’s nervous system
Learned Behaviors
Figure 01: Caledonian crow tool making
© Behavioural Ecology Research Group, University of Oxford
• Imo, the Japanese Snow
Monkey genius (Macaca
fuscata), learned to wash
yams in sea water and dip a
handful of rice and sand in
the water to remove the
sand grains
• Caledonian crows learn to
modify twigs to probe for
• Both are traditions that vary
among demes
Gene/Environment Interactions
• Behavioral geneticists interested in humans began with
twin and adoption studies
• Linking specific behaviors to specific genes is just beginning
to be possible and will rarely be as simple as a one geneone behavior model
• Human environment includes:
Prenatal experiences
Family upbringing and parental and sibling interactions
Extended family and peer interactions
Societal experiences, interaction with the educational system,
media, marketing, religious and political institutions
– Demographics: gender, age, geography, culture, language,
literacy, socio-economic status, etc.
Genes vs. Environment — Speech
Louis Leakey
Jomo Kenyatta
• Human language comes in a variety of dialects, here represented as
• In humans, genes provide a person with the innate ability to speak
language(s), but the culture into which the person is born provides
the particular language(s) learned
• The final behavior is an interaction between genes and culture
• Second language acquisition is easiest when exposure occurs before
12 years of age
Key Hominid Behavioral Trends
• Bipedal locomotion and an eventual habitat shift
beyond the tropical forest
• Altered reproductive strategy: continuous female
receptivity and no cues for maximum fertility
(ovulation); enlarged female breasts but no vulval
swelling; enlarged penis and glans though the testes
are medium-sized relative to body size for a primate
• Prolonged pair bonding - (serial) monogamy
• Enlarged brain, tool use and tool making
• More complex social systems and culture
• Language development
Learning, Society and Culture
• Intelligence — and our consequent ability to
learn from our own experience or from the
experiences of others
• Cultural transmission of learned behavior
eliminates the hazards encountered when an
individual must learn by trial and error to cope
with environmental variables
What Makes
Human Thinking Unique?
What is Language for?
• Language helps us to pass on and develop
technologies (how to make better spears)
• It helps us to coordinate activities (e.g.,
• We can communicate knowledge about
relevant aspects of the environment (e.g.,
there’s a big herd of buffalo behind the hill
where we camped 5 days ago)
What is Language for?
• Language helps us identify things with names
and descriptions.
• It helps us to express our emotions
• It helps us remember and utilize the past as
well as plan for the future
Could we achieve any of this without language?
Could we even think this without language?
Speech and Symbolic
a) Chimpanzee, adult. The
language of a signing chimp is
here translated into the English
b) Human, 21 months of age. The
spoken words are shown
c) Human, 6 months later than (b).
The actions or prompts of the
interrogators are not included
Can Animals Develop Languages?
• Allen and Beatrice Gardner (1969) ( )
– Chimpanzee – Washoe learned ASL; 160 word vocabulary
– Rules of language or Operant conditioning (Nim Chimpsky)?
• Penny Patterson & Koko (1971) ( )
– Koko the gorilla; understands 1,000 ASL signs & approx 2,000 spoken English
• Irene Peperberg – Alex the African Grey parrot (1975-2007).
– ( )
– Could identify fifty different objects and recognize quantities up to six; could
distinguish seven colors and five shapes; had a vocabulary of about 150 words
(operant conditioning?)
• Sue Savage-Rumbaugh
( )
– Bonobo chimpanzee – Kanzi (the Einstein of chimps?)
– Used symbols that represented language
– Receptive language – 72% of 660 requests
When Did Language Evolve?
5-8 million years ago
Australopithecus africanus
common ancestor
Australopithecus robustus
Australopithecus afarensis
Homo habilis
Homo erectus
common chimpanzees
Archaic Homo sapiens sapiens
Language Gradually Evolved
We hunt
Many buffalo
Don’t attack
until I say
Let’s take the kill
back to the others
I have seen herds of
antelope over the hill. I
think we should move
Let’s spend the winter
here. It’s more
sheltered and there
are many animals to
Because out language skills
got better we survived
better. But it all happened
slowly and gradually.
Why Is Language So Interesting?
• Because everybody knows that only humans
talk although other animals may understand a
number of words
• Language makes long-term cumulative
cultural evolution possible
• A novel type of inheritance system with
unlimited hereditary potential
What Is So Special
About Human Language?
• Basically, it is the fact that we make sentences using
• Languages are translatable into one another with good
• Some capacity for language acquisition seems to be
• The “Holy Grail” is the emergence of Syntax
• A system of rules for arranging words into sentences
Different rules for different languages
A sentence must have a noun phrase and a verb phrase
Language Defined
Language: symbols that convey meaning, plus rules for
combining those symbols so that they can be combined
to generate infinite variety of messages
3 - Properties of Language
– Symbolic: represents objects, actions, events & ideas
(ex: car = class of objects that have certain properties)
– Generative: limited number of symbols can generate infinite
array of novel messages (there is always something novel)
– Structured: infinite variety is structured in a limited number
of ways (Rules govern the arrangement of words into phrases
and sentences)
Understanding Language
Evolution Is Difficult
Gossiping Hypothesis
• 2/3’s of all conversation is
about social relationships
– Both in developed countries and
for hunter-gatherers
• Does this kind of language use
have any effect on our fitness?
• Does it help our survival rate?
• Does it increase our
reproductive success?
Substitute for
• Monkeys and Apes are
very social
• They maintain complex
• Grooming is their main
form of social
Increasing Group Size Hypothesis
• Largest group size for non-human primates is
50-55 (chimpanzees and baboons)
• For modern hunter-gatherers it is about 150
• Primates spend up to 20% of their days
• Humans would need to spend 40% of their
time to cover such a large group
 Language is ‘vocal grooming’
Genetic Origin of Language
• Early hominids probably began using gestures to communicate
intentions within a social setting.
• FOXP2 gene: Language or Speech gene responsible for major
inherited speech disorder (KE family studied)
– Over 3 generations, half the family afflicted
– Inability to form intelligible speech
– Defects in processing words according to rules
– Caused by a single nucleotide mutation on exon 14 of
chromosome 7
– Very conserved gene – 1 change in 75 million years before the
divergence of chimps & humans and 2 in the 6 million years
since that divergence
– Mutation occurred 10,000 – 100,000 years ago and may be
critical for the development of modern human speech
Evolution of FOXP2
75 Mya
Grey boxes mark single amino acid mutations
0 mutations in 75 million years for chimps
1 for mice
2 for humans in last 6 million years
This suggests Neandertals have the same human
Vocal Anatomy Gradually Evolved
Vocal Anatomy
Figure B02: Views of how adult humans produce three
vowel sounds by positioning the tongue
Figure B01A: Upper respiratory system
of humans adult
Adapted from Aiello, L., and C. Dean. An Introduction to
Human Evolutionary Anatomy. Academic Press, 1990.
Figure B01B: Upper respiratory
systems of chimpanzee
Figure B01C: Upper respiratory
systems of human infant
Figure B01D: Upper respiratory systems of
Adapted from Conroy, G. C., G. B. Weber, H. Seidler, P. V. Tobias, et al., Science 280 (1998): 1730-1731; and
Lieberman, P. The Biology and Evolution of Language. Harvard University Press, 1984; and Lieberman, P.
Uniquely Human: The Evolution of Speech, Thought, and Selfless Behavior. Harvard University Press, 1991.
• In the chimpanzee and
Austrlopithecine, the pharynx is
short and the soft palate and
epiglottis meet to separate the oral
cavity from the pharynx while
• In the human, the pharynx is
longer, the oral cavity is taller, and
the tongue is shorter and has more
room to change size and shape to
form the sounds of speech
Vocal Anatomy
Various investigators have suggested that the Neandertal vocal anatomy is
intermediate and, perhaps, less efficient for making the variety of sounds of
modern human speech
Vocal Anatomy
The modern human palate is arched which gives greater
variety to tongue shapes to articulate speech
Humans Have a Distinct Chin
The attachment of the
tongue behind the chin
allows for more varied
tongue movements
necessary to articulate
speech sounds
Paranasal Sinuses
Act as resonating chambers,
giving distinct timbre to
each human voice
Perhaps the most important synapomorphy in all of human evolution!
One Perspective on Human
Language Families
Another Perspective on Human
Language Families
Human Society and Culture
• Humans have two hereditary systems:
– a genetic system, which transfers biological
information from biological parent to offspring
through the coding properties of DNA
– a cultural system, which transfers cultural
information, ideas from speaker to listener, from
writer to reader, from performer to spectator through
social interactions coded in language and custom, and
embodied in records and traditions
• Richard Dawkins compared the two in his classic
The Selfish Gene (1976) in which he coined the
term “meme” for the unit of cultural inheritance
or cultural evolution, an idea or concept
Human Society and Culture
• The entire tradition of the Liberal Arts is an
effort to describe and understand human
society and culture
– Anthropology and Archaeology
– History and Sociology
– Languages and Literature and the other Arts
– Psychology and Philosophy
• The scientific disciplines went their own way
in studying the causes of human behaviors in
the first century after Darwin
Human Society and Culture
• If we look back to the Victorian era, Darwin’s concept
of natural selection both captivated and frightened
many of his contemporaries
• The power of the process of natural selection, the
“struggle for existence,” caused many individuals
from disciplines outside of the biological sciences to
apply Darwinian-type explanations and analogies to
other fields of study to help justify their positions in
disciplines outside of biology: sociology, politics,
ethics, jurisprudence, aesthetics and economics, etc.
The Two Cultures
• The Two Cultures is the title of an
influential 1959 Rede Lecture by
British scientist and novelist C. P.
• Its thesis was that the breakdown of
communication between the "two
cultures" of modern society — the
sciences and the humanities — was a
major obstacle to solving the world's
Social Darwinism
• Historians looking back at these efforts to
justify social hypotheses by analogy to natural
selection term the phenomenon “Social
• The term was not coined until 1877 by a
German and did not become a widespread
term for this phenomenon in the English
speaking world until after WW II
• It is generally used to discredit the social
hypotheses under discussion
Social Darwinists
• Herbert Spencer, who coined the term the Struggle
for Existence was a sociologist who saw human
societies evolving and increasing in complexity
• Freidrich Nietzsche and Sigmund Freud borrowed
concepts to apply to the development of the human
• Frederich Engels and Karl Marx (co-founders of
Marxist communism) saw their theory as
evolutionary, “a basis of struggle in history”
– Karl Marx wrote to Darwin for permission to
dedicate his book Das Capital to him, but Darwin
declined the “honor“
Social Darwinists
• Adolph Hitler and Benito Mussolini relied on Darwinian
justifications for their fascism
• In America, laissez faire capitalists, the Rockefellers and van
der Bilts, etc., and author Ayn Rand justified their economic
philosophy, in part, by analogy to the “survival of the fittest,”
but in their view, to be rich was to be fit
• This is just the short list of some of the most famous of the
Social Darwinists; there are still Social Darwinists today,
though they wouldn’t use that term themselves
“Are there no workhouses? Are there no
prisons...then let them die and decrease the
surplus population.“ — Ebenezer Scrooge
Social Darwinism
• Not everyone agreed that biological concepts should be
extended to society, even though nature and culture share
similar evolutionary mechanisms, especially natural selection
• Thomas Huxley – Evolution and Ethics (1893)
• Julian Huxley – Evolutionary Ethics (1943)
• The naturalistic fallacy described by British philosopher G. E.
Moore in his Principia Ethica (1903)
– Moore stated that a naturalistic fallacy is committed whenever a
philosopher attempts to prove a claim about ethics by appealing to a
definition of the term "good" in terms of one or more natural
properties (such as "pleasant", "more evolved", "desired", etc.)
• Human traits and human populations could be
improved by guiding their evolution through
selective breeding
• First advocated by Darwin’s cousin, Sir Francis
Galton in 1883
• Positive Eugenics: increase the frequency of
beneficial alleles
• Negative Eugenics: decrease the frequency of
harmful alleles
• Initially eugenics was simply proposals
to encourage or discourage marriages
based on phenotypes
• Even at the outset, this was
impractical and it was difficult to
identify superior or inferior
phenotypes in an impartial scientific
• Originally it was well-meaning,
progressive, and based on the good
science of the day
• Idealized for its lofty goals for half a century and supported
by many prominent thinkers, it fell into disfavor when
abused by the Nazis
• Simultaneously, advances in genetics, i.e., the Modern
Synthesis, showed that harmful alleles cannot be
eliminated by controlling breeding, since most harmful
alleles exist in phenotypically normal heterozygotes, and
that with multigenic and pleiotropic effects, it is difficult to
determine which alleles are truly harmful at the population
• We may be entering a new age of molecular eugenics
thanks to the Human Genome Project, etc.
Harmful Eugenics Policies
• Restrictions on immigration and marriage
• Racial segregation, including bans in the United States on
marriage between whites and African Americans, was
overturned by the Supreme Court in 1967
• Compulsory sterilization of the “feebleminded,” certain
criminals, and others deemed unfit
• Forced abortions
• In Germany under the Nazis, genocide of those (especially
Jews) regarded as racially inferior and thus a threat to the
“purity” of the Aryan race
• Among many other examples . . .
Deleterious Alleles
• Despite improvements in medical care, alleles
that have obvious deleterious effects still
affect human populations (genetic load)
• Some arise as new mutations
• Some are preserved by heterozygote
advantage or hybrid vigor
• Others are preserved because public health,
sanitation, and medical science reduce the
effect of natural selection, but add to our
genetic load
Nature versus Nurture?
• This false dichotomy has been debated since before
Darwin’s day
• At times it pitted biologists against psychologists and
other social scientists
• Few biologists ever doubted that it was the
combination of genotype and environment
interacting that produced the phenotype, whether at
the molecular, cellular, organismal, or species level
• E. O. Wilson, Sociobiology: The New
Synthesis, 1975, launched a new field of
science which offered a way to solve the
contradictions by placing humans, as
Darwin had, within the tree of life
– Animal behavior is shaped by natural
– Human behavior is determined in part by
natural and sexual selection, but also by
cultural forces which have no equivalent in
animal societies
– Start with the constraints from the genotype
and then see how environment can shape
development from that foundation
Jared Diamond (1937- )
• American physiologist, ornithologist,
biogeographer and evolutionary
• Became interested in human cultures
and history while studying birds in
New Guinea
• Books include The Third Chimpanzee;
Why Is Sex Fun: The Evolution of
Human Sexuality; Guns, Germs, and
Steel: The Fates of Human Societies;
and Collapse: How Societies Choose to
Fail or Succeed.
Why Is Sex Fun?
• Diamond speculates on the
evolutionary forces that shaped the
unique aspects of human sexuality:
– female menopause, males' role in society,
having sex in private, and, most unusual of
all, having sex for fun instead of for
• Diamond considers the lengthy period
of dependency of human infants, sex
for pleasure as the tie that helps bind a
mother and a father together, and
menopause as an evolutionary
advantage that, by ending the
childbearing years, allows females to
pass wisdom and knowledge on to
society and succeeding generations
The Third Chimpanzee
• Diamond argues that humans are just a
third species of chimpanzee but a
unique animal due to its capacity for
innovation, which caused a great leap
forward in hominid evolution
• After stressing the significance of
spoken language, along with art and
technology, Diamond focuses on the
self-destructive propensities of our
species to kill each other (genocide and
drug abuse) and to destroy the
environment (mass extinctions)
• He also discusses human sexuality,
geographic variability, and ramifications
of agriculture (metallurgy, cultivated
plants, and domesticated animals)
Guns, Germs, And Steel
Diamond proposes that the uninterrupted east/west
axis of Eurasia produced a wider variety of potential
crop plants and large, land-dwelling animals suitable
for sedentary food production
Agriculture gave rise to food surpluses, which
allowed for the specialization of labor, which
provided for the emergence of centralized
governments and bureaucracies
Farming and centralized government created the
necessity for writing, providing its possessors a far
more accurate way of recording and transmitting
data than oral language, which greatly increased the
military prowess of Eurasian “generals” by allowing
for better intelligence
Finally, these farming, centralized societies urbanized
Urbanization, combined with the domestication of
animals, subjected these denser human populations
to diseases, zoonoses from their livestock, diseases
to which these populations developed immunities
and which would one day kill off and weaken other
human populations when introduced around the
• Collapse is a catalog of case
studies of the deaths of past
civilizations, such as the
Mayans and Anasazi, as well as
contemporary societies, such as
Rwanda during the 1994
• In Collapse, Diamond argues
that past civilizations collapsed
for five reasons: environmental
damage, climate change, hostile
neighbors, friendly trade
partners, and societal
responses to environmental
The World Until Yesterday
• Diamond looks at the ways we have
evolved by comparing practices of
traditional societies and modern and
industrialized societies
• Diamond draws on his fieldwork in New
Guinea, the Amazon, Kalahari, and other
areas to compare the best and most
questionable customs and practices of
societies past and present
• Diamond does not idealize traditional
societies, with smaller populations and
more interest in maintaining group
harmony than modern societies organized
by governments seeking to maintain
order, but he does emphasize troubling
trends in declining health and fitness as
industrialization has spread to newly
developing nations
Human Control Over Our Own Evolution
• Although our lives have changed
immeasurably as a result of our advanced
technology, our genetic makeup has not
• Biological and cultural adaptations operate at
different rates
• A result of improvements in sanitation, diet,
and medical practice over the last century and
a half, natural selection now exerts relatively
little influence on our “fitness”
Human Control Over Our Own Evolution
Figure B03: Survival curves for populations of hunter-gatherers
versus citizens of a modern industrialized society
Adapted from May, R. M., Nature 327 (1987): 15-17
• Less than half the hunter
gatherers lived to age 20 so
they were unlikely to have
more than 3 or 4 offspring and
most of those died young too
• In technologically advanced
societies, most people live
past age 50 and can reach
their biological capacity of 12
to 15 offspring unless they
choose to limit family size
• As economic security
increases, they tend to limit
family size voluntarily
Cultural Evolution
Outpaces Biological Evolution
• One measure of how change continues
to affect us is the time it takes to double
our collective knowledge
• Human minds have become agents of a
novel selection mechanism by
consciously choosing among
alternatives because of their
consequences (rational decision
Clones and Cloning
• A clone is an organism
descended from and
genetically identical to
another organism
– All offspring produced by
asexual means
Figure 04: Nucleus in pipette
© Antonio Petrone/ShutterStock, Inc.
Dolly (1996 –2003) was a
female domestic sheep, and
the first mammal to be
cloned from an adult
somatic cell, using the
process of nuclear transfer
Reproductive Technology and Eugenics
• So, if almost everyone
now survives to have
children, and if our
children can be
protected from natural
selection so that they
too will have children,
will natural selection
continue to operate on
• Yes, but at a reduced
Figure 03A: Doctor retrieving eggs
from ovary using vaginal ultrasound
© Monkey Business Images/ShutterStock, Inc.
Figure 03B: Illustration of a 12
cell embryo within membrane
©Joe Mercier/
Figure 02: Ultrasound
© attem/ShutterStock, Inc.
Supreme Court Critical
of Patents on Human Genes
• The Supreme Court justices • Several justices said
said on Monday, April 15,
patents should not be
2013, they were highly
given for “products of
skeptical of the idea that a
nature,” whether they are
company or a scientist can
plant leaves that cure a
hold a patent on human
disease or tiny parts of the
genes and prevent others
human body
from testing or using them
Chapter 20

Chapter 20 Cultural and Social Evolution