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Pierre Desrochers

Lecture 7 GGR329 2. Background From traditional historical interpretation… - Brutal European conquest of Native America To “virgin soil” epidemics Native Americans - No experience with many Europeans diseases - Immunologically unprepared Key point: Germs killed 90-95% of Americas’ population Early Accounts (Brief Mentions) Small pox “This scourge of the human race, totally unknown hitherto in the new world” From medical specialists… Several early contributors, most notably A.E. Stearn (The Effect of Smallpox on the Destiny of the Amerindian) So how many Native Americans in 1491? Before “virgin soil” theory - 1.15 M in north America (James Mooney, 1910) After “virgin soil” theory - 112 M in Americas - 18 M North America – more recent o Europe at the time Lecture 7 GGR329 - Still very controversial…. Peruvian Calamaties - 1525: small pox - 1546 typhus (probably) - 1558 Dobyns Key argument: Diseases - Swept from coastlines - To inland areas First Europeans would often have encountered depopulated areas. But considerable uncertainty… Other problems: 1. Small pox spreads a. Slowly b. Not very far (victim cannot move) 2. Different strains of small pox. In Americas, perhaps not a. Deadliest b. Most contagious 3. Early accounts not written by first-hand witnesses a. Link smallpox to 10 plagues of Egypt (punishment for sins?) 4. Local (American) diseases? Lecture 7 GGR329 a. Cocolitzli plagues i. Descriptions ii. Spread Do not fit any recognizable epidemiological paradigms like hemorrhagic fever? Epidemics and millions died, but Diseases: - Cannot explain first stages of conquests - Took several decades to have an impact 3. Lethal Gift of Livestock Food production is ultimate cause But there were more proximate causes - Denser populations - Nastier germs - Better technology (including weapons) - More centralized authority Diseases always have been biggest killers of people, Often major reason for death Microbes’ Perspective - Evolutionary benefits from making us sick? o Genital sores Lecture 7 GGR329 o Diarrhea - Why kill us? Answers: Microbes evolved like other species. Best = most effective at - Producing babies - Helping them spread to suitable places Microbes modify our bodies / behavior in order to spread microbes… How do microbes spread? 1. Wait for their host to be eaten by another host a. Salmonella bacteria in i. Eggs ii. Meat b. Worms in meat 2. Hitchhiking Insects to Humans - In saliva of insect that bites old host - And flies off to find a new host o Malaria o Plague o Typhus o Sleeping sickness - From mother to fetus o Syphilis Lecture 7 GGR329 o Rubella o AIDS 3. Modify anatomy/habits of hosts to facilitate transmission - Genital sores  syphilis - Skin lesions  smallpox (through blankets) - Cough/sneezing  influenza and common cold - Diarrhea  cholera - Biting frenzy  rabies 4. Attack directly the host - Hookworms - Schistosomes But why should a germ evolve the apparently self-defeating strategy of killing its host? Answer: - Unintended by-product of host symptoms promoting efficient transmission of microbes. - Providing each victim infects on average > 1 new victims, still winning evolutionary strategy. How do humans cope with germs? 1. Fever a. Attempt to bake germs to death 2. Immune system White blood cells and other cells - Some immune effects are o Temporary Lecture 7 GGR329 o Permanent (vaccination efficient) - Problem: o Some germs evolve not to be recognized by immune system through their antigens 3. Natural selection
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