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Thread: re: homeostasis
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Old 05-18-2015, 01:32 PM   #73 (permalink)
Guybrush
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I'm just gonna nitpick a little bit.

Natural selection selects for fitness, not altruism. Altruism, in the strict sense, would be selected against - weeded out. Hence, no organism gives up reproduction for its population or its species if that implies altruism. The only reason an organism would evolve to give up reproduction was if this was part of a fitness raising strategy. I'm fairly sure you know this, but I just want to point it out because I see you write "in order for the species to survive" which reads to me like a fallacy. Species and population has little to do with it. How genetically alike the individual who gives up reproduction is to the individuals he or she can help raise the fitness of, that's what matters.

So the more related you are to your nieces and nephews, the more a "gay uncle theory" becomes valid. Giving up reproduction is common with f.ex social bees and I'm sorry if this seems a little long winded, but I can quickly explain why (if you don't already know).

In a bee hive, the queen makes haploid clones with only one set of chromosomes. These become males. The queen has sex with one male and he will father all the female worker bees. The worker bees will have two sets of chromosomes, one from father and one from mother. Because father bee is haploid, all his sperm carry the same set of chromosomes. His sperm are genetically identical. That means that all worker bees are basically guaranteed to be 50% alike genetically which is the half that comes from dad. Then they will receive one set of chromosomes from mom, who has two to pass on. On average, two worker bees should have half of the genetic contribution from mom in common. This means that two worker bees, on average, share 75% of their genes, 50% from dad and an extra 25% in common from mom.

Now, if a worker bee was to have sex with a male, any offspring she could get would have 50% of her genes. The other 50% would come from the male. However, every new sister she gets would be 75% (on average) related. In other words, getting a new sister raises fitness more than having her own child. Giving her own life in order to help ward off a predator becomes a no-brainer.

So if you're a social bee, it probably makes sense to give up your own reproduction in order to ensure the continued birthing of new sisters. After all, they will be more related to you than your own children.


But how related are human uncles or aunts to their nieces or nephews? Just looking at it in the simplest way - with a regular sibling, you are about 50% related on average. You each have one of two possible sets of chromosomes from each parent. Then your siblings children will be further watered down. On average, they'd be 25% related to you. Since your own children are 50% related to you, it seems you would have to raise twice as many nephews or nieces as your own children in order to have the same fitness.

There's no doubt that we do many sorts of kin selection, but generally speaking, I don't think we do it to the point where we give up our own reproduction in order to further the genes of nieces and nephews. I could be wrong, but the basic maths of it just don't look right to me. Humans already lived in family groups in the more recent part of our evolutionary history. Wouldn't it be better to just be "altruistic" (kin selection actually) and cooperate with raising both your own and your siblings children? For men in particular, the price of having a kid can become pretty cheap - you could basically impregnate someone and never see them again and she could raise the kid on her own or in her family group - so why evolve abstinence from reproductive sex?
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Last edited by Guybrush; 05-18-2015 at 02:03 PM.
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