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 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 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 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?