Class 12 - Gene Culture Coevolution

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University of California - Berkeley
Integrative Biology
Leslea Hlusko

10/10/13  Evolution: changes in allele frequencies over time  4 forces of evolution o Mutation (only source of new variation) o Selection (acts to diverge populations directionally) o Drift (act to diverge populations randomly) o Migration (acts like genetic glue)  Epidemiology: the science of disease occurrence and transmission  Human babies drink mama’s milk for the first 6 months o Babies drink milk but adults don’t  Ex: cats. Meow.  Basic primitive condition: adult mammals are lactose intolerant  This is because there needs to be a point where the babies stop drinking their mothers milk  Lactose: milk sugar  Lactase: enzyme that digests lactose into usable parts  Lactose intolerant: “normal” for humans but the derived trait is lactase persistent o Aka: mutated allele (lactase persistent (+)) lactose tolerant. Can digest milk. All babies are this. o Vs normal allele (lactase (-)) lactose intolerant. Body can’t digest milk and the bacteria digests it instead.  Ex: Asians, blacks, Native Americans – high % of people are lactose intolerant  Why are there hotspots?  Migration? No! Look at a map. Random peaks and stuff. Don’t match migration patterns.  Drift? No!  Sexual selection? No! Don’t wana mate with someone who can drink milk.  Natural selection? YEA! Food value, water content, more calcium intake o Can do better than others o BUT what environment would favor ability to digest milk  Pastoralism: Economy that relies on cattle, sheep, goal, CAMEL, etc. o Get milk, meat, blood from them (mainly milk and blood) o Even if you can’t drink their milk it’s still super helpful o Helpful for places with little water o Kids take animals in the morning, take care of them, then bring them back at night  Sheep: little boys and little girls take them out  Cattle: teen guys  Camel: young men o ANIMALS ARE EVERYTHING TO THEM :D  Ex: Hlusko in Ethiopia, Tanzania  Lactase persistence = around world based on selection o Only in Europe?  Because of rickets? Need milk to help deficiency – nahhh o If you don’t live around animals who produce milk then there is no selection for lactase persistence o Lactose intolerance is the natural condition of most adults  the culture of the society is the thing that naturally selected for this gene  LCT gene – o Perfect correlation between lactase persistence and having at least 1 alleles for this  Some people can digest milk better than others (homo vs hetero, this gene is “dominant”) o 9-10kya there was a cultural environment to select for this  People focused in Europe but Africa too! (4-5kya) o There are different mutations that lead to the same thing o Convergent evolution! :D o 19% more offspring for people who are lactase persistent  Inherit 2 kinds of information from ancestors: genetic & cultural o Ex: more people with larger brains because there are complex social
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