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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?

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Evolution and human survival l.jpg

Evolution and Human Survival

Lecture 4

PSY391S

John Yeomans


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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?


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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”


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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.


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Speciation

  • 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?


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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?


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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.


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Classification and Gene Lineages

Lecture 5

PSY391S

John Yeomans


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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.


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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.


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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.


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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?


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CNS Evolution--Invertebrates

  • Nerve nets: Action potentials, reflexes.

  • Ganglia chains: Molluscs, worms, arthropods.

  • Giant neurons and axons--no myelin.

  • Head ganglia are fused.


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Lecture 6: Evolution of Brain

  • Mammalian brain properties

  • Brain size vs. body weight

  • Ancient brains--when did they get bigger?

  • Human brains--when did they get bigger?


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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.


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Brain Size and Body Weight


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Equation

  • 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.


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All Vertebrates


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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?


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Encephalization


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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?


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