Transcript Evolution and Human Survival

Evolution and Human Survival
Lecture 4
PSY391S
John Yeomans
Diversity of Life Forms
• Categorization by phenotypes.
• Linneaus: Species, genus, family, order
class, phylum, kingdom.
• Which features are most important in
making groups?
• Can the same principles be used to make
other groups?
• How were these groups formed?
Diversity of Ancient Life
• Geology: Older fossil forms in deeper
sediments.
• Changes in size, structure and design
imply family histories. Evolution.
• Variety of habitats and fossils. Beagle.
• How did species evolve over millions of
years?
• Darwin: “Survival of Fittest”
Evidence for Theory
• Historical Record: Wars, famines, diseases,
habitat lossselection.
• Movement of species to new habitats
new structures, e.g. lungs, legs, hair.
• How did this happen in prehistory?
• Selective breeding of domestic animals-pigeons, cows, dogs.
Speciation
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Finches in Galapagos--Darwin and
Grants.
When do phenotype differences become
species differences?
How did humans diverge from primates?
Why did Neanderthals or other primates
die?
How to Survive?
• “We are the accumulation of mechanisms that
allowed our ancestors to survive and to
reproduce their genes” (Sagan)
• “Accumulation” includes functional and vestigial
systems. DNA also an accumulation.
• Who were our ancestors who managed to
survive and reproduce?
• The Selfish Gene: All our systems and strategies
are shells for helping our genes survive.
• Biological Purpose of Life?
Human Strategies
• Survival: Kill others genes and save your
own? Humans survive by social
cooperation rather than “dog eat dog”.
• Reproduction: Have the most offspring
possible? Humans have the fewest--single
births, long immature period--but highest
survival rate.
• Learning and specialization--Civilization.
• Aggression? Yes, but not to disrupt social
organization.
Classification and Gene
Lineages
Lecture 5
PSY391S
John Yeomans
Classification by Phenotype
• Which features are most important? Little
agreement.
• Principles of comparing different groups?
• Where is change from species to genus to
family etc, if evolution is continuous?
• Genes are more fundamental, in theory,
than any surface features.
• Quantitative rather than qualitative.
Classification by Genes
• Hybridization of DNA samples (Wilson).
• Complete sequences, genomes.
• Similarities in genes from flies to humans
imply common lineages.
• Reconstruction of family trees: Are all
bases equally important?
• Is DNA mutation rate constant?
• Genetic Clock~ 1%/5 million years.
Human Family History
• Females: Mitochondrial DNA is preserved
from mother to daughter. 16,569 bases.
• Trace human origins to Eve?
Neanderthals?
• Males: Y chromosome is preserved from
father to son. Trace family lineage.
• Trace DNA in all humans to extract
lineages around the globe.
Human Genes
• Which DNA makes us different from
primates? E.g. prodynorphin.
• Are some genes more important?
• Which genes affect hands, brain, speech?
• Could a few genes lead to larger brains?
CNS Evolution--Invertebrates
• Nerve nets: Action potentials, reflexes.
• Ganglia chains: Molluscs, worms,
arthropods.
• Giant neurons and axons--no myelin.
• Head ganglia are fused.
Lecture 6: Evolution of Brain
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Mammalian brain properties
Brain size vs. body weight
Ancient brains--when did they get bigger?
Human brains--when did they get bigger?
Vertebrate CNS
• Protected brain and spinal cord.
• Myelinated axons saves space for more
neurons.
• Shift from midbrain, cerebellum and
olfaction to limbic system then cerebral
cortex.
Brain Size and Body Weight
Equation
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Log Brain Weight=0.7(log Body Weight)+b
Or: Brain Weight = K(Body Wt)0.7
Power function linear on log-log plot.
Some mammals have extra brain size
(Humans and dolphins 8X extra)
• K = encephalization factor.
All Vertebrates
Ancient Vertebrates
• Brain weight from endocranial space.
• Body weight from leg bone diameter.
• Ancient reptiles same as modern reptiles,
except for Archeopteryx (bird-like
predator).
• Modern birds and mammals increased
brain capacity by 4X over ancient birds
and mammals (still 4X reptiles).
• Warm blood favors brain evolution?
Encephalization
Evolution of Human Brain
• Increased by 3X about 1-2 million years
ago.
• Most of change in frontal cortex.
• Neoteny: Do we sustain embryonic brain
growth for longer by keeping neonate
features?