Transcript 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.

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”
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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 -1500 AD
different rates of
development on
The spread of humans around the world. each continent.
How do we know? Archaeology
Mammalian Candidates for Domestication
Eurasia
Sub-Saharan
Africa
Americas
Australia
Candidates
72
51
24
1
Domesticated
species
13
0
1
0
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
10,000
Southwest Asia, China, North America
Sheep
8,000
Southwest Asia
Goat
8,000
Southwest Asia
Pig
8,000
China, Southwest Asia
Cow
6,000
Southwest Asia, India
Horse
4,000
Ukraine
Donkey
4,000
Egypt
Water buffalo
4,000
China
Llama / alpaca
3,500
Andes
Bactrian
camel
2,500
Central Asia
Arabian camel
2,500
Arabia
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