Chapter 2: Evolution and Human Nature
• What binds us together is that we are all human beings.
• Unless we develop some sense of what we all have in common, we will never fully appreciate nor
understand diversity and individuality.
• The study of the person must begin with human nature.
• By virtue of the original sin, the Christian church has taught us that well are essentially bad,
• Hinduism, Buddhism, Judaism, Christianity, and Islam suggest that the natural state of the human
is fundamentally flawed and in need of a deliverance from that state.
• 18 Century French philosopher Jean-Jacques Rousseau and 19 Century romantic poets such as
Shelly and Keats described human nature as innocent and good.
• Rousseau suggested we are noble and good at birth but vulnerable to corruption because of
• 17 Century British philosopher John Locke suggested that human nature is a blank state.
o At birth people are ready to be shaped into any form that their environment can produce.
• Contemporary scientific understandings of human nature focus on human evolution.
o Human beings have evolved to survive and reproduce
• Evolution and human nature provide fundamental context for understanding human individuality.
• We are all products of human evolution.
On Human Nature: Our Evolutionary Heritage
Principles of Evolution
• A fundamental property of living things is that they propagate.
• All animals and plants reproduce.
• The origins of life on earth reside in the first instances of physical reproduction: Once upon a
time, a psychochemical phenomenon reproduced itself through some means, providing a jump-
start required for the evolution of life to begin.
• Cognitive scientist Steven Pinker (1997) tells the story of how evolutionary scientists believe the
earth began in How the Mind Works o In the beginning was a replicator. This molecule or crystal was a product not of natural selection
but of the laws of physics and chemistry. Replicators were wont to multiply, and a single one
multiplying unchecked would fill the universe with its great, great, … great grandcopies. But
replicators use up materials to make their copies and energy to power the replication. The world is
finite, so the replicators will compete for its resources. Because no copying process is one hundred
percent perfect, errors will crop up, and not all of the daughters will be exact duplication of the
copying errors will be changes for the worse, causing a less efficient uptake of energy and
materials or a slower rate or lower probability of replication. But by dumb luck a few errors will
be changes for the better, and the replicators bearing them will proliferate over the generations.
Their descendants will accumulate any subsequent errors that are changes for the better, including
that assemble protective covers and supports, manipulators, catalysts for chemical reactions, and
other features of what we call bodies. The resulting replicator with its apparently well-engineered
body is what we call an organism, (pp. 157-158)
• Pinker’s imagined scenario contains the essence of Charles Darwin’s insight about the evolution
• The more successful systems are those that produce more viable copies of themselves for the next
• A system must meet the demands of the environment wherein it resides.
• As environments change, designs of organisms change because some designs of organisms will
be more successful in promoting replication than others.
• Tooby and Cosmides (1992)
o Evolution “appears as a succession of designs, each a modification of the one preceding
it. Generation by generation, step-by-step, the designs of all the diverse organisms alive
today- from the redwoods and manta rays to humans and yeast- were permuted out of the
original, very simple, single-celled ancestor through an immensely long sequence of
• Darwin argued that all living things have evolved in response to their interactions with
• Facing scarce resources, organisms compete with one another for survival and replication and the
“fittest” designs win.
• Natural selection: a process whereby nature gradually selects those characteristics of organisms
that promote survival and reproductive success.
• Organisms within a species manifest wide variation in physical and behavioural characteristics.
Certain characteristics may promote the survival of the organism. • Organisms with advantageous characteristics should live longer and reproduce more than
organisms without them.
• The offspring of the organism with advantageous characteristics is more likely to posses them and
in turn live longer and reproduce more.
• Darwin did not understand the precise mechanism for biological transmission of characteristics
from parent to offspring.
• Now we know that genes are responsible for the inheritance of characteristics.
• Genes are segments of chromosomes found in every cell in the body and are composed of DNA
(a long, threadlike molecule well suited for passing on hereditary information).
• Through sexual reproduction, genes are passed down from one generation to the next.
• Sometimes genes may be transformed by accident. Genetic mutations may be advantageous.
• 9000 years ago, when the cattle were first domesticated and people started to consume milk,
natural selection would have favoured anybody with a mutation that kept the lactose gene
switched on after weaning.
o The mutation occurred in early cattle-raising people in north-central Europe 5000 years
o The mutation that afforded lactose tolerance was passed down and eventually spread to
other parts of Europe.
o Today almost all Dutch and 99% of Swedes are lactose tolerant. The mutation becomes
less common in Europeans who live at increased distances from where the mutation first
o The mutation promoted health and survival.
• In The Selfish Gene, Richard Dawkins (1976) made the famous idea that genes aim for one thing
o Persons are designed to engage in behaviours that ultimately make for the replication of
the genes that determine their design.
• Pinker (1997)
o “Genes ‘try’ to spread themselves by wiring animals’ brains so that animals love their kin
and try to keep them warm, fed, and safe.”
• Generate and promote one’s own biological offspring.
o Bearing and raising one’s own children.
• Promote the reproduction and well-being of those individuals who share the same genes.
o Through the offspring of kin. • William Hamilton (1964) elaborated the concept of inclusive fitness that a solution to the riddle
began to appear.
o Organism’s inclusive fitness is its overall (total, inclusive) ability to maximize the
replication of the genes that designed it. Part of that total includes the results of the
organism’s own reproductive success, but part also includes the reproductive success of
close relatives, with whom the organism shares genes.
The Environment of Evolutionary Adaptedness
• Scientific estimates propose that life on earth emerged about 3.5 billion years ago.
• 500 million years ago, multicellular organisms emerged.
• Dinosaurs became extinct 60 million years ago.
• Primates made their appearance on earth 55 million years ago and humans 2 to 4 million years
ago probably in the heart of Africa.
• Humans gradually migrated in all directions of the planet.
• The period in which human beings emerged and evolved to their current form is called the
Pleistocene epoch of earth history (1.6 million years ago to 10 000 years ago) making the end of
the last ice age.
• Environment of evolutionary adaptedness (EEA): the hypothesized world of the Pleistocene
epoch during which human beings evolved and human nature was forged. It is believed that
humans evolved over 2 to 4 million year span as hunters and gatherers living in small, migratory
• Humans could better defend themselves against predators and other threats by living together in
collectives, looking out for one another in times of danger, and consolidating resources, skills,
and strength to meet the many challenges they were likely to face, including threats from other
groups of humans.
• Hunters could work in groups.
• Human beings are by nature social animals because social life proved to me most propitious
strategy for survival and reproductive success in the EEA.
• Natural selection designed humans to want to be together in groups.
• Those few individuals who do not seem to share this social sense (e.g. hermits, autistic children)
stand out as oddities, often eliciting from others reactions fear, pity, or bafflement.
• Social life entailed competition and conflict as much as cooperation and care. • deWaal (1996) points out, the “greatest disadvantage [of group life] is that one is continuously
surrounded by individuals searching for the same food and attracted to the same mates. Groups
are breeding grounds for strife and competition, which ironically also pose the strongest threat to
• Human groups tend to be organized in hierarchical ways.
• Humans honed a set of characteristics that set them apart from all other species on the planet.
o Humans stood up right, on 2 feet, freeing their fingers and opposable thumbs for a wide
variety of complex and finely tuned motor tasks.
o Manufactured and depended on a great many tools.
o Lived longer than other apes and bore helpless infants who required many years of care.
o Kin negotiated mating relations.
o Relationships between brothers and sisters were discouraged.
o Sexual intercourse was not limited to particular times of the month for females but could
occur at any time.
o Females cooperated in the care of children and in gathering fruits and vegetables for the
o Communicated with one another through language and used language, as well as other
symbol systems, to disseminate information, pass on traditions, accumulate knowledge
and adaptative wisdom, and create culture.
• Theory of mind: a basic understanding that other people have minds filled with desires and
beliefs, and that people act upon those desires and beliefs.
• Different human groups developed different cultures.
• Universals found across cultures: Athletic sports, bodily adornment, cooperative labor, courtship,
dancing, education systems, etiquette, family feasting, folklore, food taboos, funeral rites, games,
gift giving, incest taboos, inheritance rites, law, marriage, medicine, penal sanctions, personal
names, property rights, puberty customs, religious rituals, soul weather controls.
• Religious rituals can be found in all cultures.
• E.O. Wilson (1978) argues that each of these universal patters can be traced back to hunting-and-
The Adapted Mind
• Adaptive characteristics are passed on to subsequent generations (eg. Giraffe’s long neck made it
easier to obtain food that was elevated above the ground) • Retooling of the human skeleton and posture over evolutionary time leading to human beings
walking efficiently on two feet.
• Way in which the human brain has evolved producing complex behavioural patterns and mental
• Human beings survived and reproduced with felicity in the EEA because they were smarter.
• Cognitive niche: the particular position that human beings have evolved to occupy in the
evolutionary landscape, whereby their main adaptive advantages center on the computational
powers of the human mind. The human mind has evolved to enable human beings to adapt to the
many threats and challenges faced in the environment through mental manipulations of situations,
innovative strategies for attaining goals, analysis, reasoning, language, and so on.
• Adaptive mind may be organized in into many different functional modules.
• Buss (1997) analogizes the human mind to a carpenter’s tool kit:
o Having many specialized tools, each designed to perform a particular function.
• Darwin (1859) identified many of the survival problems under the heading of “hostile forces of
o Food shortages, harsh climate, disease, parasites, predators, and natural hazards.
• Reproductive problems are more social in quality and therefore, more centrally implicated in
• Buss (1991) lists eight classes of reproductive problems:
o Successful intrasexual competition:
individual must win out over competitors in gaining access to desirable members
of the opposite sex so that sexual reproduction can occur.
o Mate selection:
selecting mates with greatest reproductive value.
o Successful competition:
the individual must engage in the necessary social and sexual behaviours to
fertilize a mate or become fertilized by a mate.
o Mate retention:
the individual must retain the mate, preventing the encroachment of intrasexual
competitors as well as preventing the mate’s defection or desertion. More acute
among species and individuals who pursue long-term mating strategies.
o Reciprocal dyadic alliance formation:
must develop a relationship with the mate characterized by a certain degree of
cooperation and reciprocity o Coalition building and maintenance:
Must cooperate with others whose interests are aligned with his or her own.
o Parental care and socialization:
Ensuring the survival and reproductive success of his or her own offspring.
o Extraparental kin investment:
Must sacrifice his or her own self-interests to promote the survival and
reproductive success of nondescendant genetic relatives.
• Humans formulate goal-directed tactics and strategies that aim to ensure our survival and
• Evolution has shaped sexual activity to be extraordinarily pleasurable so that people will engage
in it often, ensuring that offspring will eventually be produced.
• The distal (evolutionary) reason for human sexual activity is to replicate the genes, but the
proximate (individual) motivation for engaging in it is that it feels good.
• Behaviour in terms of proximate causes is to appeal to the immediate environmental,
physiological and cognitive mechanisms that determine a person’s behaviour.
• Distal explanations consider the significance of behavioural patterns in the ultimate terms of
evolution and inclusive fitness.
• For the male, it is to his advantage to impregnate as many females as possible to ensure the