01:185:253 Lecture 1: Human Nature & Diversity (Lectures 1 up to Thursday 2/8)
1/25/18
Mating (=sex, love and parenting)
There are dramatic sex differences in sexual behavior and preferences (at least in our culture)
Psychological differences between men and women→ which are part of human nature
What explains these differences?
1.) Are they a product of contemporary American culture, or do they reflect something
deep and important about human nature?
2.) According to the (relatively) new science of Evolutionary Psychology (EP) these
differences are human universals.
A component of human nature to be explained by the importantly different ways in
which natural selection has shaped male and female psychology
Is this true?
In order to answer that question, we need to understand what EP is
Since EP combines ideas from evolutionary biology and from cognitive science, so we must
1.) Review some important ideas from evolutionary biology
2.) Explain some of the central ideas of contemporary cognitive science
I. Evolution
A. For our purposes, the theory of evolution can be viewed as the claim that over
many generations, organic forms(= microorganisms, plant and animals)
change, and that the distant ancestors of most contemporary organisms were
very different
1. So some of your distant ancestors were ape-like creatures that were also
ancestors of modern chimps and gorillas… and some of your more
distant ancestors were single celled organisms
B. Though there is no serious scientific debate about this claim, surveys indicate
that more than 50% of Americans do not believe in evolution
1. Some people do not think that humans are descended from ape-like
creatures (and further back from creatures that were very different from
humans)
D. Darwin did not create the theory of evolution. Many earlier thinkers had claimed
that species evolved into other species. (common idea)
E. Darwin’s contribution was to propose a theory about the causal process that drives
evolution (why did this happen) : The Theory of Natural Selection (also simultaneously
proposed independently by Alfred Russell Wallace)
II. The Theory of Natural Selection
1. Artificial Selection practiced by plant and animal breeders
2. Thomas Malthus’ obvious observation about limits on the size of populations
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1.) Artificial Selection (darwin didn’t come up with natural selection but first to explain it)
a.) DNA evidence suggests that about 130,000 years ago the ancestors of all
modern dogs looked like wolves
b.) BUT largely as the result of human intervention, some of the descendants now
look dramatically different
c.) In order for these changes to occur, 3 factor were required
i.) Variation in Population: The organisms in a population must VARY (in
size, shape, strength, intelligence, fighting ability, docility, etc.)
ii.) Inheritance: some of these variations are reliably passed down from
parent to offspring
iii.) Human induced selection: humans help animals with some heritable
traits to have more offspring (choose which ones to mate)
But, most selection is not mediated by humans
So, on Darwin’s theory of natural selection, natural processes like starvation, predation,
disease, and competition for mates plays the role that humans play in artificial selection.
2.) NATURAL Selection
a. Malthus
b. Malthus noted that organisms reproduce “geometrically” - more and more and
more over time (however, most animals die before reproducing)
c. Which organisms get to survive and reproduce depends to a large extent on
their traits
d. And to the extent that the successful traits are inherited, they will spread thru the
population
III. The theory of Natural Selection
C. Darwin did not know the mechanism underlying inheritance
1. Mendel who did (discovered genes), may have send Darwin his paper, but
Darwin never read it!
2. Darwin thought that inheritance was a “blending” of the traits of the 2 parents
a. If this was true it would be bad news for Darwin b/c there’d be no room for
variation (blending gets rid of variation)- blending drives out variation after
a few generations
3. Darwin didn’t have any satisfactory account of the origin of variation
D. Modern genetics, which began with the rediscovery of Mendel’s work at the beginning
of the 20th century, addressed both these issues
1. We now know that genes are responsible for inherited traits, and that the genes
of the parents do not “blend” in their offspring
2. We also know that mutation- change in the chemical structure of genes- is
constantly introducing new variations into natural populations
a. While most mutations produce unhelpful (or maladaptive) traits,
some produce traits that enable the organisms that have them to do a
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better job of finding food, resisting parasites, fighting competitors,
avoiding disease, attracting mates, etc.
b. Those traits, and the genes that cause them, will (likely) spread through
a population, displacing other, less “adaptive” traits and the genes that
cause those less adaptive traits
1/29/18
E. The Focus on Genes
1. About 50 years ago, W.D. Hamilton added a major new element to the theory of
natural selection by noting that natural selection will favor traits that cause
copies of an organism’s genes to spread thru a population (how fast running
zebras evolved)
a. One way to get lots of copies of your genes into the population in the
future is to have lots of children and grandchildren
b. Another way is to do things that help your kin to reproduce since your kin
have copies of your genes (siblings)- get them food, help them survive
c. So, a gene that leads an organism to sacrifice itself when doing so will
save the life of 2 or more siblings (or 8 cousins) will spread thru the
population (kin selection)
i. There is a sense in which that gene is not beneficial to the
organism that has it, since it leads to the death of the organism
ii. This led Richard Dawkins to propose the colorful metaphor of
“The Selfish Gene”- natural selection will lead to the spread of
genes that do a good job of ensuring that copies of themselves
survive and replicate, even if they must sacrifice their “owner” to
do it (even if copies of genes come from kin and not you)
iii. As Evolutionary Psychologists who adopt the selfish gene
prospective often emphasize, you have the genes you do, NOT
because they lead to traits that will make you happy, and NOT
because they lead to traits that will help YOU survive and
reproduce
Rather, they lead to traits that have helped THEM to reproduce
(the genes)
ex.) social insects (bees) sting intruders despite dying after stinging
IV. The Origins of Evolutionary Psychology
A. Evolutionary Psychology emerged in the early 1990’s when a number of researchers
combined ideas from contemporary evolutionary biology with ideas from the fast
developing field of cognitive science
B. What IS cognitive science? (philosophy, psychology, computer science, linguistics,
neuroscience, evolutionary biology, anthropology… interdisciplinary)
1. In the 1960’s researchers in a number of disciplines realized that they could use
the methods, findings and theories of the other disciplines to help them answer
questions about the mind
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Document Summary
There are dramatic sex differences in sexual behavior and preferences (at least in our culture) Psychological differences between men and women which are part of human nature. According to the (relatively) new science of evolutionary psychology (ep) these differences are human universals. A component of human nature to be explained by the importantly different ways in which natural selection has shaped male and female psychology. In order to answer that question, we need to understand what ep is. Since ep combines ideas from evolutionary biology and from cognitive science, so we must. Explain some of the central ideas of contemporary cognitive science. D. darwin did not create the theory of evolution. Many earlier thinkers had claimed that species evolved into other species. (common idea) E. darwin"s contribution was to propose a theory about the causal process that drives evolution (why did this happen) : the theory of natural selection (also simultaneously proposed independently by alfred russell wallace)
