_X = 100

Distribution of IQ scores

Low High

How much of this variation is due to genotypicdifferences among individuals? What is theheritability ?

Maze learning in rats: selection for maze “bright” and “dull” strains of rats(R.C. Tryon 1942)

1. Used a 17 unit (multiple “T”) maze

2. Counted up the number of errors made across multiple trials in the maze (19 trials)

3. Errors were counted as number of entries ina blind alley

4. Rats making the fewest errors were mated among themselves; rats making the most

errors were mated among themselves

Number of errors in maze test

MB

MB MD

MD

Number of errors in maze test

10 54 190

Generation 0

Generation 4

Generation 8

The response to directional selection formaze learning indicates that the heritabilityof maze learning is above zero

What is the mode of inheritance of individual differences in maze learning?

MB MD

10 54 190

10 54 190

10 54 190

F1 rats

F2 rats

Maze learning appears to exhibit typicalcomplex or polygenic inheritance

Are the maze “bright” and maze “dull” rats good and bad, respectively, at other tasks? In other wordsis their “intelligence” general or specific?

In three out of five different measures of learning ability,rats of the “dull” strain performed at levels equal to or Superior to rats from the “bright” strain.

_X = 100

Distribution of IQ scores

Low High

Mental retardation

MENTAL RETARDATIONDSM4 (Diagnostic and Statistical Manual for PsychiatricDisorders, American Psychiatric Association)

1. Score of 70 or below on a standard IQ (intelligencequotient) test

2. Adaptive functioning: how well the individual meetsage and culture specific standards

3. Age of onset before 18

Degrees of severity:Mild: 55-70Moderate: 35-55Severe: 20-35Profound: below 20

Genetic abnormalities and mental retardation

SINGLE GENE DISORDERS:1. Phenylketonuria (PKU) used to be the leading

single cause of mental retardation2. X-linked (GDI1, PAK3,Oligophrenin, FMR2)3. Angelman syndrome4. Fragile-X syndrome5. Duchenne muscular dystrophy6. Picks disease7. Galactosemia

CHROMOSOMAL DISORDERS1. Downs syndrome: trisomy 212. Turner syndrome: XO3. Klinefelter syndrome: XXY, XXXY4. Triplo X syndrome: XXX

Genetic abnormalities and mental retardation

SINGLE GENE DISORDERS:1. Phenylketonuria (PKU) used to be the leading

single cause of mental retardation2. X-linked (GDI1, PAK3,Oligophrenin, FMR2)3. Angelman syndrome4. Fragile-X syndrome5. Duchenne muscular dystrophy6. Picks disease7. Galactosemia

CHROMOSOMAL DISORDERS1. Downs syndrome: trisomy 212. Turner syndrome: XO3. Klinefelter syndrome: XXY, XXXY4. Triplo X syndrome: XXX

Evidence that genetics influences intelligence in man

1. Genetic abnormalities: single gene and chromosomalaberrations are associated with impairments inintelligence

2. Normal variation in intelligence:Similarities between relatives ?

Demonstrating a genetic component to behavior

1. Family studies: Examine similarities between family members. The closer the genetic relationship,the more similar family members are predicted to be

2. Adoption Studies: Compares biological with adoptedfamily members. Biologically related individuals arepredicted to be more similar than adopted relatives.

3. Twin studies: Identical twins compared to fraternal twins.Identical twins predicted to be more similar

Study Adoptive Children

Biological children

Biological mothers and their children adopted by other parents

Fathers

Mothers Fathers Mothers

Minnesota 1

0.15 0.23 0.39 0.35

Minnesota 2

0.16 0.09 0.40 0.41

Texas 0.17 0.19 0.42 0.23 0.32

Parent-child correlations for IQ in three adoption studies

Conclusion: Despite variability among studies, biologicalrelatives are more similar than adoptive ones.

Test Twins Intra-pair Correlation

heritability

StanfordBinet IQ

MZS (19)MZT (50)DZT (50)

0.690.920.62

0.67 + 0.13

Otis IQ MZS (19)MST (50)DZT (50)

0.730.920.62

0.72 + 0.10

DominoesIQ

MZS (34)MZT (37)DZT (38)

0.730.750.69

0.74 + 0.07

MZS Monozygotic raised separatelyMZT Monozygotic raised togetherDZT Dizygotic raised together

HUMAN EVOLUTION

1. FOSSILS

2. GENETICS

Phrenology is the study of the structure of the skull to determine a person's character and mental capacity. The Viennese physician Franz-Joseph Gall (1758-1828)was an early phrenologist. Bumps and indentations on the skull, according to Gall, reflect specific areas of the brain that determine a person's emotional and intellectual functions. It remained popular, especially in the United States, throughout the 19th century and was highly praised by Ralph Waldo Emerson, Horace Mann, Thomas Edison, and Alfred Russell Wallace.

Where do we come from? Human origins

1. Relationships to other animal groups

2. Relationships to other primates

3. Early humans and their ancestors: Fossil history

4. Temporal and spatial aspects of human ancestors

Domain: Eukarya

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primates

Family: Hominidae

Genus: Homo

Species: sapiens

Australopithecus afarensisEthiopia 4-2.9 myaNo stone toolsSmall cranial capacity

Australopithecus africanus3-2.3 myaSouth AfricaNo stone tools

Australopithecus robustus2-1 myaSouthern AfricaNo stone tools

Australopithecus boiseiEast Africa2-1myaNo stone tools

Homo habilis2-1myaEast AfricaStone tools

Homo rudolfensis2-1myaEast AfricaStone tools

Homo erectusWidespread Africa, Asia

Homo neandertalensis1856 Neander Valley-Germany: various interpretations

such as a race before humans, a pathological specimen of man

Now known to be a specialized hominid restricted to Western Europe and Mediterranean, living in rock shelters and caves.

Homo sapiens

ChimpanzeeTeethBrowCranial sizeSagittal crest

Gorilla

Proposed history for the development of human language

6-7 million years ago Proto-hominids Simple hand gestures. Vocalizations of alarm, emotions, etc.

4-5 million years ago Australopithecine hominids. Advent of bipedalism: appearance of more sophisticated hand signalling

1-2 million years ago Homo habilis and Homo erectusHand gestures become fully syntactical, vocalizations start to become symbolical, stark increase in brain size

100,000 years ago Homo sapiens uses vocal language, zenith of brain development, hand gestures play secondary role

chimpanzee A. africanus H. sapiensH. erectus