Wikipedia:Reference desk/Archives/Science/2014 December 13

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December 13

how does evolutoin come up with CRAZY stuff like, "I'll wrap my tongue all the way around my head and through my nostrils"?

So, I'm wondering. How does evolution come up with CRAZY stuff like the woodpecker deciding in gestation that it will extend its tongue ALL the way around its head and through its notsrils - to help protect its brain as it's pecking. It's a fine design idea. But you can't get "halfway there" - I mean, you can't just like, wrap your tongue HALFWAY around your head and protect it. You have no other reason to have a tongue THAT long. So, from one generation to the next, evolution must have said, "all right now I'll make DNA that encodes a reeeeeeeeeeeeally long tongue, makes it go around and through a nostril, and protect the wodpecker brain". Huh?

How do REALLY complicated things like this happen evolutionarily? It just seems kind of crazy. 212.96.61.236 (talk) 16:09, 13 December 2014 (UTC)

This page explains it pretty well.

It does get halfway there. The part of the tongue that extends past the skull are actually the horns of the hyoid bone. In humans, the hyoid bone has been reduced to a small bone on the upper throat, but in birds they are still very much a part of their tongues.

They are also already quite elongated in most birds. The chicken's hyoid bone for example, already extends halfway around the back of the skull. That is because this is the only space where the bone can slide back when the tongue is retracted. When birds extend their tongues, the bone slides forward along with the tongue muscles, jabbing at whatever it is they're eating. So tongues wrapping around the back of the skull is normal in birds.

It thus follows that if you wanted a longer tongue, you will also need a longer hyoid bone. And a longer hyoid bone means it needs to extend further up behind the skull when retracted. Woodpeckers which eat grubs from deep holes in trees will positively select for longer tongues. Given that it evolved in conjunction with their drilling behavior, the tongue also began to develop a secondary function. And voilà, crazy stuff.

Again, this is only a secondary function. The original reason why it extends to their nostrils is not because woodpeckers decided they needed shock absorbers, but because they needed a longer tongue to reach grubs deep inside the trees. It also does not "develop from gestation". Young woodpeckers who rely on being fed by their parents or woodpeckers which do not eat grubs from tree holes have short tongues and normal-length hyoid bones (that is, they also extend behind the skull, but not to the nostrils).

And this is not unique to woodpeckers. Some hummingbirds which also need long tongues for reaching into flowers also have massively elongated hyoid bones. See here and here. They too reach behind the skull and almost touch the eyes actually. Though they don't protect the hummbird's braincase, they themselves have their own unique adaptation. Rolls of tissue that hold the nectar in.

And despite what creationists are saying, it actually still only confirms evolution in the sense that this structure isn't just magically there. It is derived from a preexisting anatomical feature shoehorned into that function by the requirements of survival. It's a less-than-elegant solution that got retained and magnified for the very simple reason that it worked. -- OBSIDIAN†SOUL 17:03, 13 December 2014 (UTC)

Can animals without a prefrontal cortex have anxiety disorders?

Doesn't anxiety involve the ability to think about the future and involve the concept of the self? I am aware that dogs can manifest depression-like signs. Dogs may view their human owners as members of the pack, so when the owner/master dies, the dog may refuse to eat. Does the behavior have to do with the existence of the prefrontal cortex? 71.79.234.132 (talk) 17:28, 13 December 2014 (UTC)

Depression and anxiety are quite separate cases:

1) Anxiety could be caused by continual release of adrenalin, which should normally only be released during emergency situations. It's quite possible something might go wrong biologically, causing adrenalin to be released continually, although worrying about the future isn't likely to be a cause in most animals. Some species of animals which are constantly in danger also naturally have a high anxiety level in order to keep them alert.

2) Depression can also have a purely chemical cause, and this may not have any non-biological cause. However, animals with strong social bonds may suffer from depression as a result of separation from others they have bonded to (whether the same species or not). Some birds and mammals are the most likely to have such strong social bonds. StuRat (talk) 19:05, 13 December 2014 (UTC)

Your first point suggests that high anxiety level keeps some animals alert. If it's evolutionarily advantageous and adds to the species fitness, then does that still count as a "disorder" that impairs functioning? Your second point does not explain how social bonds are relevant to the pre-frontal cortex. 71.79.234.132 (talk) 19:17, 13 December 2014 (UTC)

No, I wouldn't call it a disorder if they are normally that way. StuRat (talk) 23:43, 13 December 2014 (UTC)

• Recent studies of the bird brain show it is not wired the same as the mammalian brain, and direct comparisons are not necessarily applicable. We don't actually have an article on the bird brain, which is embarrassing. See HVC (avian brain region) for the best article I am aware of. In any case, by definition, if an animal cannot for some reason (injury to, or simple lack of the appropriate brain region) anticipate future dangers it is not going to suffer anxiety in the human sense. Both pet birds and mammals are known to suffer "psychological" pathologies, but "pet bird anxiety" is not ungooglable. μηδείς (talk) 20:32, 13 December 2014 (UTC)

See also, Avian Brain Nomenclature Consortium for its external links and Avian pallium. μηδείς (talk) 20:52, 13 December 2014 (UTC)

I'm having trouble finding the references right now, but I've seen studies that fish which are frequently frightened / harassed by people or other animals can become skittish and antisocial. Such work drew parallels with some forms of anxiety disorders in humans as a kind of conditioned behavior. I'm not sure how accurate such analogies really are, but fish certainly don't have a prefrontal cortex and if people are willing to interpret their behaviors as anxiety, then presumably it isn't required. Dragons flight (talk) 23:55, 13 December 2014 (UTC)

I think this highlights a difference between medicine and biology. In medicine, something is a "disease" if a patient comes to you saying it's a problem and he needs it fixed. In a few cases (homosexuality, people with an amputation fetish, people seeking sex reassignment surgery...) this may be controversial. By contrast, in biology, the question is whether it helps them survive and reproduce. As explained in anxiety, well, it can reduce the number of accidents. And depression likewise seems like a fairly adaptive reaction to the presence of predators, or a world where most people would love to lock you in a stress position and torture you for years on end if they can collect a salary from it. Wnt (talk) 01:09, 14 December 2014 (UTC)

Does GPS need satellites?

Couldn't you measure your distance from 3 radio stations?--Noopolo (talk) 17:49, 13 December 2014 (UTC)

Satellites provide a more 'global' coverage. Yet many cheap devices (like cell-phones) do use multilateration to provide fixes from comparing signals from near by cell-phone towers. Which is why they don't work in the middle of nowhere.--Aspro (talk) 18:05, 13 December 2014 (UTC)

Yes, you could. See LORAN, Decca Navigator System, and Omega (navigation system). -- ToE 18:10, 13 December 2014 (UTC)

What is the relation between green foods and vitamin k?

The vitamin k creates the green or something like that? 149.78.233.188 (talk) 20:00, 13 December 2014 (UTC)

Your intuition is close. If you read Vitamin K it explains that vitamin K₁, found in plants, is highly available in leafy green vegetables, especially of the genus Brassica; kale, spinach, broccoli, etc. If you read the article on vitamin K₁'s chemical name, mentioned in the first article, it will explain why you will see it in plants. If you find this difficult on your own we can guide you more explicitly. μηδείς (talk) 20:11, 13 December 2014 (UTC)

Vitamin K itself does not create the green, no. --OuroborosCobra (talk) 21:22, 13 December 2014 (UTC)

This article explains that vitamin k found in highest amounts in green leafy vegetables because it is directly involved in photosynthesis. But I don't understand it because the other vegetables -in other colors- are also involved in photosynthesis. 149.78.233.188 (talk) 21:34, 13 December 2014 (UTC)

You have to read more than just the lede: "Vitamin K1, the precursor of most vitamin K in nature, is a steroisomer of phylloquinone, an important chemical in green plants, where it functions as an electron acceptor in photosystem I during photosynthesis." Short Brigade Harvester Boris (talk) 21:38, 13 December 2014 (UTC)

Thank you deeply! for both of you.149.78.233.188 (talk) 22:07, 13 December 2014 (UTC)

How would we observe wormholes?

There is no evidence that wormholes exist even though general relativity does not forbid them. However, how well have we looked? How close to Earth would they have to be for us to see them?--Goose Geyser (talk) 20:15, 13 December 2014 (UTC)

They seem to involve effectively infinite energies, nor am I sure what one would look for, or how anyone would manage to secure a grant to look for one. μηδείς (talk) 20:21, 13 December 2014 (UTC)

The version of a wormhole that seems most reasonable to me is that black hole is paired with a white hole somewhere else in time, space, or perhaps another universe. (Of course, if the matter falling into a black hole does go elsewhere, some explanation is needed for why the gravity associated with that mass remains in the singularity.) But, in that case, the black hole end can be detected by gravitational lensing or observing objects in orbit about it or by the radiation emitted as matter collides in the accretion disk.

An active white hole would be far more obvious, with matter streaming out of it (perhaps the Big Bang was one). Since we haven't seen those, that seems to imply they exist elsewhere, if at all, or that any white holes nearby have no matter currently arriving. Detecting an inactive white hole might be quite a challenge. One theory is that white holes only exist for an instant, and our article on them states that a 2011 "paper even proposed identifying a new group of gamma-ray bursts with white holes".StuRat (talk) 20:29, 13 December 2014 (UTC)

The problem with that speculation is that as far as theory goes, black holes accrete mass, they don't send it somewhere else. We certainly wouldn't have million solar mass black holes in the center of galaxies if the mass were being sent to the Delta Quadrant or E-Space. The "white hole" effect is Hawking radiation which leads to an energetic evaporation of the black whole itself where it is located in our universe. μηδείς (talk) 20:40, 13 December 2014 (UTC)

Perhaps the gravitational mass and inertial mass could theoretically be decoupled, with only the gravitational mass remaining in the black hole. I don't see any evidence this is actually the case, but it's enough of a possibility to at least make for good sci-fi. StuRat (talk) 20:44, 13 December 2014 (UTC)

That's crazeh talk. I remember when I took Physics for Science Majors and we got into calculations of the attraction between various masses with various charges and it occurred to me to ask, then why is gravitational mass equal to inertial mass? And the professor (who was German, which was just great) paused, and then said, "We don't know". But I suspect if they were decoupled the blackholes' orbits couldn't be calculated. μηδείς (talk) 21:02, 13 December 2014 (UTC)

According to this APS published paper [1] the shadows cast by stable wormholes are smaller than those of black holes, making these wormholes' detection possible if they exist. See [2] and [3]. -Modocc (talk) 15:55, 14 December 2014 (UTC)

Carbonylated dihydridoiron

Which is the best explanation for the exasperation of the weak Fe-H bonds in carbonylated dihydridoiron (cis-[Fe(CO)
₄H
₂]), the trans effect or the cis effect? Plasmic Physics (talk) 22:24, 13 December 2014 (UTC)

It's just tired of all the bullshit it has to put up with... --Jayron32 23:13, 13 December 2014 (UTC)

Ha. JIC it passed by anyone, I'm using the word referred to, in the sense of worsening. Plasmic Physics (talk) 00:47, 14 December 2014 (UTC)

Well Fe-H bonds are pretty weak compared with Fe-Fe bond. Do you know how the carbonyl hydride decomposes? Our article does not say. Graeme Bartlett (talk) 15:06, 14 December 2014 (UTC)

I think that the first step is reductive elimination of the two hydrogen atoms. Plasmic Physics (talk) 18:21, 14 December 2014 (UTC)