Genuine Puzzles In Biology?

Creationist nonsense apart, there are some things in nature which make you think: "Why in the world should it be like that?"The hairlessness of humans is one instance, there's been a lot of debate about that.Another thing which has long puzzled me is the conservation of cervical vertebra number in mammals. With only two-and-a-half exceptions, mammals have seven vertebrae in their necks, no matter how long or short their necks are. Now, this number varies wildly in other classes of vertebrates; and also in mammals themselves the number of other sorts of vertebrae are not fixed at all: the number of dorsal vertebra can even vary within a species. Why should the number of cervical vertebrae be so invariable?So would anyone like to add to the list? What is genuinely puzzling in biology --- what are the questions that need answers and don't yet have them?

Thanks for participating. But could you be a bit more detailed? For example, you list: "Why haven't plants closed the green gap?" Now let me speak for 999 out of 1000 people posting here when I say that I have no idea what you're talking about.Your post would be more useful if you spent a paragraph or two explaining what the question actually is, like I did with conservation of cervical vertebrae number in mammals. I explained what I was talking about, and I explained why it was puzzling to me. Could you do the same?Thanks.

Sir, I salute you.

Well, there are some complications with live kidney donation (hypertension, proteinuria, preeclampsia). But also donors are warned not to take part in rough sports such as American football and boxing, because they're in deep trouble if something happens to their remaining kidney. Which is OK if you live a sedentary Western lifestyle, but not so good if your lifestyle involves hunting antelope. It's hard to say what would happen in the long term to someone with only half a liver, because if you cut a bit off someone's liver it grows back. So I'm not sure on what basis we could say that you can do without it.It is also the case that sometimes the liver has more work to do than at others. Yes, half a liver might do for everyday use, but what happens if you're exposed to a lot of toxins? Unlike many other organs, the liver has an emergency function, for which extra capacity is required. The figure usually given is 10%, but it isn't true, it's just a popular myth. It seems to have originated with an advertisement for one of those firms that sells booklets on how to improve your memory.

Not on the inside, we're not, and in particular the kidneys aren't quite symmetrically placed --- the left kidney is somewhat higher in the abdomen.

Thank you.

Why should the order of Hox genes in chromosomes be the same as the head-to-tail order of the bits of the phenotype they control?

I remain to be convinced that the puzzle exists, or that any such mechanism is required.The models which suggest that there might be a puzzle rely on the premise that there is a practically infinite supply of deleterious mutations so tiny in their effect that even in largish populations they can be fixed by drift.Now, in our present state of understanding, if natural selection can't detect them, then nor can we: we can't just look at a genome and say: "Ah, yes, changing T to A here will incur a teensy-weensy disadvantage".(We may also note that since mutations are discrete there must for each species be a lower bound on how little harm a mutation can do without doing no harm at all.)So do these mutations even exist? No-one, to my knowledge, has actually shown this, or is in any position to do so. If they exist at all, there is the further question of how many of them there potentially are, which again has not been answered.Now if hypothesizing the existence of entities the existence of which has not been demonstrated leads us to a conclusion in conflict with reality, then the most obvious conclusion is simply that this hypothesis is false, not that there is an equally undetected mechanism which counteracts the first set of undetectable entities.

I didn't say that. But genetic meltdown models rely on a large supply of deleterious mutations too small to be detected.(They have other problems too. For example, saving computer time by using an "infinite alleles" model that rules out the possibility of back mutations; and assuming hard rather than soft selection, both features of the paper on human mitochondria.)I don't deny the possibility of fixation of deleterious alleles, but I have questions about how the concept is being applied. Apart from Muller's Ratchet? The Red Queen's Race.(Sometimes biological nomenclature is rather fun, isn't it?) I did some computer simulations of my own recently. Here's a typical result: (In real life we would suppose that fitness has an upper limit (and that the typical organism is nearly there) and that a sufficient decrease in fitness would lead to extinction.)Now, however one fiddles with the basic parameters, so long as beneficial mutations can happen at all it seems that there is a population size above which deleterious mutations will not manage to drive down fitness. If the real-life parameters are such that the critical population size is a quintillion, then there's a problem.Until someone is in a position to determine the parameters, the fact that not every species is extinct suggests that this is not the case.Edited by Dr Adequate, : No reason given.Edited by Dr Adequate, : No reason given.

We have relatively big heads, and our pelvises are adapted to walking upright. Well, it's useful. In order to be able to plan ahead, we have to be able to say to ourselves: "What would happen if I do such-and-such a thing?" This is not clear. For example, the following has been observed. A chimp is set a puzzle where the reward is bananas. She tries to solve it, and fails. She sits staring at it for a few minutes. Then she gives a great whoop, turns a backflip ... and then solves the puzzle and acquires the bananas.The point is, she knew that she had solved the puzzle before she actually got the bananas, because she was capable of thinking: if I do this, then bananas will ensue.

It does? Where?I do in fact believe in free will, but I don't see that my explanation of the practical value of the imagination contains anything that would perturb the strictest incompatibilist determinist.

No, hold on.It may be true that given any particular state of my brain, the result of exercising my imagination will be inevitable; and certain philosophers would conclude from this (wrongly, in my view, since I am a compatibilist) that I have no free will and have not really made a choice.But even if we grant all this, it does not follow that the non-choice I don't-really-make as a result of exercising the faculty of imagination is the same as the non-choice I'd have not-really-made if I lacked this faculty: because to possess and use that faculty is part of the brain-state which determines my actions.(By analogy, if I know that bleach is poisonous, it may be the case that I cannot choose to drink it; and a philosopher might tell me that I am suffering from a mere illusion of choosing not to drink bleach. But it does not follow that this knowledge is completely useless to me, because if I lacked that knowledge and thought instead that bleach was a tasty and refreshing beverage, then I might drink it. The knowledge is useful and not superfluous precisely because my actions are determined --- and that knowledge is one of the things that determines my actions.)And so, so long as I make superior non-choices with an imagination than without one, which I think is beyond doubt, then it is biologically advantageous to possess the faculty.

These are all excellent questions which I shall answer the moment I figure out how to read the mind of a crow.

Sure, I have a definitive and empirically justifiable opinion about that, because I am the greatest philosopher who ever lived, and my mighty brain allows me to resolve such questions because I am so fucking smart.NOW WORSHIP ME AS YOUR GOD.Seriously, I suppose that animals are conscious because they behave like they're conscious. The same reason I suppose that you are conscious. I might be wrong.

Your whining is noted. Now, did you have an actual question about biology, or did you merely want to display your capacity for self-pity?The title of this thread is "Genuine Puzzles In Biology", not "Creationists Blub And Cry About How Unfair It Is That People Exist Who Disagree With Them".