Environment-dependent dependent expression of a genotype

Phenotypes are not always a direct reflection of genotypes Temperature-sensitive alleles: Siamese color pattern Nutritional effects: phenylketonuria

Siamese or “Himalayan” Different allele of the C locus that causes albinism. Temperature sensitive.

Phenylketonuria Nutritional defect: can’t metabolize phenylalanine. Can lead to severe physical and mental disorders in children, but only if they consume phenylalanine. Disease phenotype can be avoided by eliminating phenylalanine from the diet

Modern Homo Sapiens Regional-Continuity Model (Milford Wolpoff, UMich) –Humans evolved more or less simultaneously across the entire Old World from several ancestral populations. Rapid-Replacement Model (Chris Stringer, NHM London) –Humans evolved only once--in Africa from H. heidelbergensis ancestors--and then migrated throughout the Old World, replacing their archaic predecessors. Also called the “Out of Africa” and “Killer Ape” hypothesis.

Hunters and Gatherers Prior to 11,000 BC all peoples on all continents were hunter-gatherers. 11,000 BC AD different rates of development on each continent. The spread of humans around the world. How do we know? Archaeology

Mammalian Candidates for Domestication EurasiaSub-Saharan Africa AmericasAustralia Candidates Domesticated species Percentage of candidates domesticated 18%0%4%0% Why some animals were not domesticated: Diet, bad feed conversion or carnivores. Growth rate too slow. Problems with captive breeding. Nasty disposition. Tendency to panic.

Domestication of Animals Species Dates B.C. Place Dog 10,000Southwest Asia, China, North America Sheep8,000Southwest Asia Goat8,000Southwest Asia Pig8,000China, Southwest Asia Cow6,000Southwest Asia, India Horse4,000Ukraine Donkey4,000Egypt Water buffalo4,000China Llama / alpaca3,500Andes Bactrian camel 2,500Central Asia Arabian camel2,500Arabia

Fertile Crescent Civilization; cities, writing, empires, and agriculture. –Mediterranean climate. –Easily domesticated plants. –Most of the plants pollinate themselves.

Mediterranean Climate

Why farm? Decline in the availability of wild foods. Depletion of wild game less rewarding, easier to gather grains. Increased technology for collecting, processing, and storing wild foods. Increasing population, increase food production, better diet. Adopt food production or die at the hand of those who have. (soldiers & germs)

Domestic Mammals Meat production plus! –milk –transportation –plowing –wool –hides Evolution with humans –immunity to diseases (measles, tuberculosis, smallpox, flu, pertussis, malaria)

Major axes of the continents