PSYC 3102: Introduction to Behavioral Genetics
Lecture 1
History of Genetics
—Provides framework of where we are and where we’re going
Mankind has had implicit knowledge of genetics for a long time, but had no “hard
science” or explicit knowledge
- the first genetic engineering began 10-20,000 years ago in the form of
breeding plants and animals for desired traits
- wild onions, lentils, and ginger were engineered by humans, and replaced the
original progenitor plants
First known attempt to explain heredity—Hippocrates
Hippocrates’ theories:
 Bricks & mortar approach—thought sperm contained tiny body parts and
transferred them to ‘fertile ground’ of womb where the parts assembled and grew
 Believed in the inheritance of acquired characteristics—characteristics which parents
acquire prior to conception are past on to offspring
 Example: strong Olympic body builders pass on big biceps so their
offspring are born strong Olympic body builders
 Example: giraffes that stretched their necks to reach leaves had
offspring with longer necks
Aristotle:
 Generation or two after Hippocrates
 Criticized Hippocrates’ theories:
 On ‘bricks and mortar’ approach
 Mutilated parents can have normal children
 Example: father loses arm in war, but offspring has two arms
 On inheritance of acquired characteristics
 Parents can transmit traits they do not show at the time of conception
 Example: gray hair – offspring can go gray even though parents had dark
hair when offspring were conceived
 Aristotles’ Theory:
 What is inherited is information
 Building a house analogy—one inherits the blueprint of how to make the
house, not the actual bricks and mortar
 But was ignored, most people went with the bricks and mortar theory
Foundation of Modern Genetics
-- Science doesn’t develop in a vacuum, background and context is important
The 3 L’s:
-- Science tends to fit into a certain world view (bias, theoretical framework), and the
views of the 3 L’s created the world view/theoretical framework in which modern
genetics began to develop
1. Linnaeus (~1700) Developed classification system
Classification was:
 Heirarchical – implies species are related, genus - species concept
 Based on external morphology – similar looking = closely related
 Based on belief that species are fixed and immutable – creationist view/no
evolution
2. Lamark (~1800) First modern evolutionist
 Challenged belief of species being fixed and immutable
 Believed that species change over time in response to environmental
demand
 But, believed (falsely) in the inheritance of acquired characteristics theory
3. Lyell (~1830) founder of modern geology
 Challenged Creationism theory—the earth is far older than the bible says
(millions of years rather than thousands of years old)
 Earth as we know it is the result of physical changes occurring over long
periods of time, features have changed due to ice ages, erosion, etc.
 Darwin took Lyell’s book with him on the Beagle
Birth of Modern Genetics
-- Darwin, Mendel, Modern Cell Biology
Darwinian Trend
 Started out to become a physician, but couldn’t handle the sight of blood
 So, Darwin became naturalist on the Beagle (sailed for 5 years) in 1830’s\
 Keep in mind the context of the time—Linnaeus (species are related); Lamark
(species evolve); and Lyell (earth is millions of years old and has changed
throughout time)
 Darwin’s theory:
 Those animals best adapted to their environment are more likely to
reproduce than those less adapted to the environment
 Studied finches, similar but different from island to island
 Type of beak vs. food available (insects vs. seeds/nuts)
 Returned to England and obsessively, compulsively wrote for many years (want all
information and details to be perfect)
 Social circle included many top scientists at the time
 Push to publish…
 Alfred Wallace independently came up with the same theory
 Wallace went to Royal Society, but got pushed into background so Darwin
could publish first
 1859 – published “Origin of Species”
 Was a bestseller, sold out first edition before printed
 The theory enflamed the discord between physical geologists and biblical
creationists
 Genesis has two accounts of creation
 Creationists criticize—“Humans have evolved? No way”
 Side note: We are NOT descended from apes and chimpanzees, we share
common ancestors (cousins of sorts)
 Problems—Darwin’s book is internally inconsistent, he provides no theory of
inheritance!
 There MUST be variability
 He believed in “blending” inheritance (offspring is blended of both
parents)
 But with this theory, all variability would be lost after several generations
(mixing watercolors analogy)
 So, fudged theory, and supported theory of acquired characteristics,
claimed that this provided the necessary variability
 An unopened reprint from Mendel was found in his desk after his death, this was
the theory of inheritance that he need to incorporate
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Darwin also wrote the 1st evolutionary Psychology book
 Dealt with human and animal behavior
 Expression of emotion
 Facial expressions (blind children smile, not merely mimicking behavior)
Darwinian follower (and cousin) Francis Galton
 1st to establish psych lab that measured individual differences
 1st to propose the twin method
 1st to come up with regression theory (and draw a regression line)
 Coined term “Eugenics” (started movement in England)
 1st to do empirical work on behavioral genetics
 published book “Hereditary Genius” (1960s)
 Looked at “eminent” people in society (top in politics, arts, science)
 Then traced their family histories
 1st degree relatives (fathers, brothers, & sons); 20% are also eminent in
society
 2nd degree relatives (grandfathers, uncles & ½ brothers); 8% are eminent
 3rd degree relatives (male cousins); 2-3% eminent in society
 percent of relatives that are eminent in society increases with the degree of
relatedness
 “Genius must be inherited”
 Main criticism: (VERY IMPORTANT – WILL SEE ON TEST)
 Shared family resemblence can not distinguish the role of genes
from that of the environment
 Familial resemblance is a function of shared genes, shared
environment, and some combination of shared genes and shared
environment
 Family studies cannot elucidate the influence of genes from that of
the environment
 Twin and adoption studies are needed to distinguish the
effects of shared genes and the effects of shared environment
Examples of essay questions
Beware of statements such as “it runs in families, therefore…” Remember this
cannot be determined with family studies!!!
Ex: Fears and Phobias
Environmental: Watson, social
learning
Genetic: inherited traits of
anxiety, fear
Ex: Abuse
Environmental: social learning,
Genetic: inherited traits such as
aggression, etc.
Social Darwinism and Eugenics
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Eugenics—“well” “genetics”; better people through better breeding
Positive push: provide benefits to and encourage ‘desirable’ people to breed
Negative push: discourage ‘undesirable’ people to breed
Social Darwinism—application of Darwin’s principles to society at large
The seeds of this were established before Darwin ever published
Victorian Era England used this to justify colonialism by their politicians
Herbert Spencer (NOT DARWIN) coined the phrase “Survival of the Fittest”