Intro to biological anthro f 2011 owen elephants and

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Intro to Biological Anthro F 2011 / Owen: Elephants and epistemology p. 2 - Today, in areas outside of Uganda where the elephants are effectively protected, still “only 2% of the animals are tuskless.” - that is, where they are protected from poaching, little has changed - But today, in areas of severe poaching: - “Research at the Queen Elizabeth National Park, Uganda, showed that 15% of female elephants and 9% of males in the park were born without tusks” - A survey of elephants in Zambia’s North Luangwa National Park in 1997 found that over 38% of the elephants there have no tusks - what is going on here? - Before heavy poaching, tusks were favored by selection - they are useful for digging for food and water - for scraping the edible bark and cambium layer off trees - for self defense - and attracting mates - “Conservationists say an elephant without tusks is a crippled elephant.” - But because poachers kill elephants to get their tusks, selection against elephants with tusks is now severe - so the few tuskless individuals that are born each generation survive and breed without being bothered by poachers - a tuskless elephant is much more likely to survive long enough to leave offspring than a normal elephant with tusks - “…being tuskless is better than being dead…” - in other words, the selection pressure favoring tusklessness is very strong - The “tuskless” trait has gone from 1% or 2% to over 38% in Zambia in 70 years! - and this is in a species with very long generations - elephants don’t mate until they are 15 or 16 years old - so the “tuskless” trait has become 19 times more common in fewer than five generations! - recall that we were impressed by the finches’ beaks evolving at about 2% per generation - (each generation is 1 year, so 2% per year) - the frequency of tusklessness in these elephants is evolving at about 80% per generation! - (each generation is about 16 years, so about 4.4% per year) - this is rapid evolution, caught in the act. - and the change in environment (that is, heavy poaching for ivory) has been lasting, so the evolutionary effect is adding up - 70 years at 4.4% change per year accumulates to about 1900% (19 times)! - a similar trend was reported in 2005 for Asian elephants in China - if this continues, some wild populations of elephants may be virtually all tuskless within our lifetimes, or our children’s - while others in protected areas still almost all have tusks - since tusks are involved in attracting mates, - members of the tusked populations may tend not to mate with the tuskless ones -
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