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

[vdinets]

Very interesting!
Of course, desert mammals have been under intense pressure to produce more and more concentrated urine - and the result is that even a few drops of cat urine will give your carpet its smell forever...
But the purpose of bladder is pretty obvious. The alternative would be passing urine constantly - just laying a perfect scent trail for predators.

[shkrobius]

So that's why... It may be obvious to you, but it did not occur to me. I guess you are right, though it is not too clear to me, why mammalian predators would retain their bladders and how flightless birds go around this problem. On the other hand, that would explain why flying birds do not care. I still wonder if the function is mainly chemical communication. Amazingly, there is almost no literature on the evolution of urinary bladder - and there are thousands of papers on swim bladders and kidneys.

Do you know whether other animals than mammals use urine for (1) territory marking and (2) estrus communication? I cannot find anything, and this looks very odd. Are these unique mammalian traits?

[vdinets]

Mammalian predators start their lives as small and vulnerable. Besides, constant passing of urine, especially during sleep, would interfere with thermoregulation. Birds don't pass urine constantly, either. I wonder if u. bladders of whales show any sign of reduction (I should know that, but I don't).
I'm not aware of any other animals having estrus in mammalian sense, but I suspect terrestrial amphibians (lungless salamanders, poison-dart frogs etc.) could use urine for scent marking. No idea if they really do.

[shkrobius]

They do not. I got your point, but I am not sure about thermoregulation. I gotta check this out.

ot

[eta_ta]

Need your assistance here.
I refuse to adhere to the author's view that development of morality is contradictory to theory of evolution; still, can't provide coherent reasoning. I think you wrote something on the subject in the past - or is it tooo broad for you?

Re: ot

[shkrobius]

It is a bit too broad, but I can suggest you a book where you will find the arguments you need to strengthen your case. It is "The origin of virtue" by M. Ridley
http://www.amazon.com/Origin-Virtue-Matt-Ridley/dp/0670863572
Ridley reviews various evolutionary theories of altruism, co-operation, and conformism. I think you will enjoy this book; it is exceptionally well written and goes over a lot of different theories; it is also thin and it has no technical slang in it. The "burning house" situation is explicitly examined there. Perhaps your opponent might be interested in reading it, too.

Re: ot

[eta_ta]

many thanks

Re: ot

[eta_ta]

'eta-ta', not quite as pretty as your other name, but anyway, you might also like to try Ridley's "The Red Queen: Sex and the Evolution of Human Nature". A fascinating book which I will now have to re-read so that I am ready for your criticisms. However, I should warn you that the neo-Darwinist arguments used to explain altruism are almost painful to behold in their extreme contortions! Anyway, if Richard Dawkins says that morality does not exist in a Darwinian world, who am I to argue?

"Be warned that if you wish, as I do, to build a society in which individuals cooperate generously and unselfishly towards a common good, you can expect little help from biological nature. Let us try to *teach* generosity and altruism, because we are born selfish." 'The Selfish Gene', ch.1, p.3.

David Duff - http://duffandnonsense.typepad.com

[anonymous]

eta-ta: I share your suspicion of anyone who urges *others* to indulge in altruism, but the word covers a huge variety of actions and no doubt some of them prove beneficial, others not. However, the point is that altruism exists, and thus requires an explanation

[shkrobius]

David, the problem with this argument is that I can furnish exactly the same kind of reasoning about humans, e.g. you. I'd argue that you do what you do and your actions have little to do with what you call your self-knowledge, and that the latter, including morality, is ad hoc rationalization of what you are doing anyway that is supplied by your cortex. Prove me wrong. As for the "microbes," the amoebas that form the fruiting body of the slime mold have their choice of joining the others or not; it is free choice, and many decide not to join and try their own luck. You deny them self-awareness, but I do not know on which grounds. Their genomes are 5-10 times larger than ours; we simply do know what are they capable of, and in some ways they are more complex than us. They can recognize each other, they can communicate with each other, so they de-facto behave as if they have the concept of the self. I can be no more certain about them having no self-awareness as about you. It is not written on your forehead that you are self-aware; it

[anonymous]

shkrobius: Oh dear! It's difficult enough arguing the pros and cons of human 'free will' without worrying about amoebas

[shkrobius]

Not only I cannot say it about amoeba, I cannot say it about you. Moreover, I cannot say it about the hero who saved a child from a burning house. It is not difficult to represent this act as yet another instance of reciprocal altruism, kin selection, groupishness, status enhancement, etc. Morality does not belong to a Darwinian world only in a sense that it does not belong to the world, period. It exists in our heads and serves as rationalization of our altruistic acts. What causes these acts may not have anything to do with their rationalizations. The hero might be convinced that he had freely chosen the right thing to do, but he would be utterly unable to explain, clearly and logically, why is it the right thing to do. The more you ask, the more declarative answers you'll hear. Our self-awareness is shallow and it does not go to the core issue of why people behave altrustically. The fact is that they do act this way, and so an explanation is due. If evolutionary theory explains it that's fine; if not, we still need a theory to

[eta_ta]

Heh. Is all I'll say.

[eta_ta]

No time this evening but I hope to return to this fascinating conversation tomorrow.

Eta_ta: "Heh"? I wish all women could be as brief as that! :)

David

[eta_ta]

shshsh! You're lucky that Memsahib isn't listening.

[eta_ta]

Sorry for the delay