Why do we pee?

[shkrobius]

The textbook answer is that animals need to urinate in order to excrete extra salts and nitrogen metabolites from their blood. The ammonia in aquatic animals, insoluble uric acid in birds, diapsid reptiles, and insects, and soluble urea in amphibians and mammals are the means of disposing the N generated by transdeamination of unwanted amino acids

Comments

[shkrobius]

Here is your problem: you start from the assumption that altruism, chastity, and homosexualism cannot be compatible with fitness and reproductive success of individuals. If you measure this success in the fraction of the genome that is passed to the progeny and the quantity of offspring, it begins to make much sense. We've discussed altruism already; in a group that practices reciprocal altruism, being altrustic makes perfect sense in terms of fitness and reproductive success of each individual.

Now, consider chastity. Worker ants are more than chaste - they are sterile. The same goes for mole rat ants. The sterility makes sense if one's genes will be transferred by someone who shares a large chunk of your genome and to whom you consigned your reproductive rights. Then you do not have to worry about wasting time and energy for sex. Back to humans. Chastity makes Darwinian sense if the probability of childbirth fatality is very high. Then you would have higher probability of passing your genes delegating the childbirth to your blood relative and helping this kin to look after his or her children - than doing it all yourself, facing colossal odds. Actually, in rare cases natural selection can and will favor sterility. You can read about it here http://shkrobius.livejournal.com/96646.html

The genetics of homosexualism is poorly known, but consider the following scenario: suppose a gene that makes males homosexual when coupled to another gene makes them more fertile when it is coupled to a different gene. Or, alternatively, it makes their mothers more fertile. Then it makes perfect sense that a fraction of homosexual males will appear in each generation, because it bestows reproductive advantage over the rest of the population, including the parents of these males. That's hypothetical, but homosexuality is too common among animals
http://en.wikipedia.org/wiki/Homosexuality_in_animals
to strongly suspect that it has genetic basis.

You say there is a fundamental difference between people and the rest of the Creation. I agree, but the same can be said about any species, they are all unique. However, chastity, altruism, and homosexuality all have precedents in Nature. This is not what makes us unique. The many instances suggest that there is common mechanism by which such traits occur time and time again. Darwinian theory suggests such a mechanism. It falters in other respects, but it works pretty well regarding the concerns that preoccupy you.