Wikipedia:Reference desk/Archives/Science/2016 May 27

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May 27

Anti muscarinics

There are mACh receptors in the vomiting centre, but most antimuscarinics (like hyoscine) don't block all vomiting reflexes (instead, just motion sickness and gastric irritation, in the vestibular nuclei and nucleus of the solitary tract).

So, are there M3 receptors in the vomiting centre, and only M1 receptors in the vestibular nuclei and the nucleus of the solitary tract? Le Sanglier des Ardennes (talk) 21:51, 27 May 2016 (UTC)

I don't think so. As I understand it the nature of the cholingeric contribution to nausea is not very clearly understood. By the way the "vomiting centre" is the area postrema. Looie496 (talk) 22:40, 27 May 2016 (UTC)

Rare earth hypothesis and young earth creationists

Why do young earth creationists like the rare earth hypothesis? — Preceding unsigned comment added by 24.207.71.235 (talk) 17:52, 27 May 2016 (UTC)

Assuming that's a true statement, it could be because both ideas fit with their literalistic interpretation of Genesis. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:00, 27 May 2016 (UTC)

Rare Earth hypothesis. AllBestFaith (talk) 19:56, 27 May 2016 (UTC)

Conversely, Young Earth creationism. InedibleHulk (talk) 19:58, 27 May 2016 (UTC)

Assuming it's a false statement, they might dislike the way the rare Earthlings allow the planet to predate life by a ridiculously long time (in human years, anyway). InedibleHulk (talk) 19:57, 27 May 2016 (UTC)

• Not sure why there is such difficulty in answering the question. They like it because they believe the Earth in its current state could not have arisen by natural processes and must have been deliberately engineered. The less likely the current state of the Earth, the more plausible that argument is. Looie496 (talk) 22:19, 27 May 2016 (UTC)

Genetic change of people in africa

How much genetic change have people in Africa undergone compared to people on other continents? -- 24.186.172.52 (talk · contribs)

The pace of mutation is typically presumed to be constant (a molecular clock model generally assumes this to develop population genetics models). While individual traits may be under selective pressure, this varies by trait for each population, and I don't think the data on this point will be anything near comprehensive. Genetic drift, the fixation of alleles, will depend on effective population size. A paper like this is less than satisfying, though it addresses some of the issues. In general, the level of genetic diversity in humans has fallen fairly steadily with the degree of migration, so that there is relatively little variation among American Indians compared to quite great diversity in Africa. Yet as said at early human migration, there is still some uncertainty regarding pretty dramatic questions like Toba catastrophe theory - judging by ongoing research like [1], that still seems in fairly early days - and there have been relatively recent reports about Neanderthal and Denisovan hybridizations that really upended the existing models. Despite a much larger number of sequenced human genomes, I don't think we can make statements with any great confidence just yet, except in the very general sense that most differences between humans are shallow due to the relative youth of the species, and the others aren't particularly consistent in any given geographical population. Wnt (talk) 19:26, 27 May 2016 (UTC)

The user is a one-time poster from a proxy server. http://whatismyipaddress.com/ip/24.186.172.52 μηδείς (talk) 01:01, 28 May 2016 (UTC)

The question is actually quite legitimate, and even the racist question behind it is legitimate, though a racist answer is quite legitimately wrong. It is a surprising, I would even say a supernatural phenomenon that humans around the world are so fundamentally similar. I mean, there is one species on Earth that can work math, play organ music, build suicide bombs to blow itself up, or decree that rape is wrong. How on Earth is it that every single population on every single continent has all these same unique features, with not even a single ability from the list, however minor, however unselected for, being unique to one continent or absent from another? And now that we know that humans are not even all precisely the "same species", in the sense that some are (debatably) H. sapiens x H. neanderthalensis and some are something else, this becomes even more remarkable. This unity of humanity is something meaningful and important to us - that's why we decry racism - yet we can't even realize it exists if we don't let ourselves ask the underlying questions. Wnt (talk) 11:09, 28 May 2016 (UTC)

I don't see how it's very surprising. Humans are all the same species, descended from the same ancestors; you generally expect similar behaviors from members of the same species. Behavioral modernity is only about 50,000 years old, which is nothing on the time scale of the universe. That's not long enough for speciation to occur to any real extent, absent very strong evolutionary pressures. The problem of course is that our minds aren't good at conceiving of time scales longer than about a human lifetime, so anything longer than that all just blurs into "forever". --71.110.8.102 (talk) 21:35, 28 May 2016 (UTC)

Well ... if behavioral modernity evolved 50,000 years ago, then how did populations that separated 100,000 years ago end up with the same kind of behavioral modernity? Even assuming it didn't evolve then, but somehow was cryptically encoded in the genomes waiting around for tens of thousands of years or longer (even millions) for culture to develop that suddenly 'activated' it, why aren't there differences in which populations could support all its features at the genetic level? To me this doesn't seem like a trivial mystery, but a real call to arms to think about the 'human soul' as a real thing and not just a myth. Wnt (talk) 00:52, 29 May 2016 (UTC)

Yes, read between the lines, obvious troll question. Delete.68.48.241.158 (talk) 03:01, 28 May 2016 (UTC)

In this instance, he hasn't said anything overtly racist yet. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:49, 28 May 2016 (UTC)

This question implicates false information and racism.
The Cradle of Humankind shows in what direction the epi genetic change has gone.
The causes of any epigenetic change was some what else like climate, sun exposure on the planet or food situation.
The human intelligence is withcaused by brain size which is neccessary to rise the own children.
Compared to lots of animals human babies are really helpless and partents need to care more which
requires a minmum of intelligence of their parents. --Hans Haase (有问题吗) 12:30, 28 May 2016 (UTC)

climate, sun exposure on the planet or food situation led to actual genetic differences, not only epigenetic changes. Rmhermen (talk) 02:03, 29 May 2016 (UTC)

Here's what reads like a study guide to this subject, coming from a university in New Zealand, which looks like it bears working through. --TammyMoet (talk) 14:13, 28 May 2016 (UTC)

Human populations in Sub-Saharan African have the most genetic diversity of all human populations. This is in line with a general principle in evolutionary biology that genetic variation in a species is usually highest closest to the geographical origin of that species. --71.110.8.102 (talk) 21:35, 28 May 2016 (UTC)

Plate tectonics, kinematics, dynamics

Geologists use the familiar term "plate tectonics", which refers to the movement of continental plates, as our article says. They also use the term "plate kinematics", which sounds like it ought to mean the same thing, and "plate dynamics", which sounds like it ought to mean the same thing again. How are these terms different in meaning?

I'm faced with an article, Eclogitization, containing the words "... which leads to a change in plate kinematics, and plate motion of subduction zones." I'd like to remove some jargon from this article. It seems to have been created by a geology student and then reviewed (on the talk page) by other geology students from the same university, who treated it like a paper - and, like a paper, possibly in an attempt to look more academic, it's filled with jargon (which, when I examine the history, seems to have been progressively edited into the article over time, making it steadily denser and more abysmal in a process not unlike Eclogitization itself).

So is "plate kinematics" mere humbug that can be replaced with "the motion of tectonic plates", and then removed entirely since this duplicates "plate motion", or does it have a more specific meaning? If I'm going to clarify it with a parenthetical explanation as per MOS:JARGON, what should that explanation say?  Card Zero  (talk) 23:43, 27 May 2016 (UTC)

First, it's forum shopping to come here to get support for changing the article. You should have this discussion on the talk page. Second, the plain meanings of kinematics and dynamics are different. Kinematics deals with motion. Dynamics is broader, and might involve things like rifting or buckling. @Mikenorton: μηδείς (talk) 00:58, 28 May 2016 (UTC)

OK, I posted this question to the talk page, but that page has seen no activity since 2012 (and the article itself is barely changed since that date - somebody copyedited one sentence and that's about all). So I don't really know who I'm talking to there. I'm not looking for support on a controversial decision, I'm just looking for technical information so I can edit the article correctly, which I thought was supposed to be a major purpose of the ref desks.  Card Zero  (talk) 01:23, 28 May 2016 (UTC)

please do the world a favor and ignore the absurd suggestion above that you've done something wrong..hopefully people will be along to help you out so that you can improve Wikipedia if it's indeed discovered that improvement is needed..68.48.241.158 (talk) 01:58, 28 May 2016 (UTC)

It is fair enough to post the question here, just leave the detail of the article changes proposed to its talk page. But the people who wrote it are long gone off Wikipedia. You may be able to email them though. The place to find the answer will be a geological dictionary. Graeme Bartlett (talk) 02:09, 28 May 2016 (UTC)

Anyone who needs to post advice to ignore others using an IP account should himself be ignored. User:Mikenorton is the best authority "I am a structural geologist based in the UK" I know who might help with your question. Other than kvetching, about my telling you the right way to handle this, I see absolutely no helpful answers. You can also post a WP:RfC on the relevant talk page. But simply conflating the terms would be wrong, since dynamics and kinematics are not the same thing:

"Dynamics is a branch of applied mathematics (specifically classical mechanics) concerned with the study of forces and torques and their effect on motion, as opposed to kinematics, which studies the motion of objects without reference to its causes."

μηδείς (talk) 04:08, 28 May 2016 (UTC)

note: if you plan on taking advice from anonymous strangers on the internet (whether one of them has concocted a "username" or not) indeed ignore the bad advice and go with the good..and thank you for looking into improving Wikipedia!68.48.241.158 (talk) 12:33, 28 May 2016 (UTC)

And one might as well refer to the definition for tectonics, which encompasses far more, in a narrow realm, than dynamics and kinematics. Personally I wouldn't get too worked up about it all, but hey, egos. Greglocock (talk) 05:52, 28 May 2016 (UTC)

For my part, I would tend to regard "plate dynamics" and "plate kinematics" as synonyms, both describing the motions of the plates. On the other hand, I would tend to construe "plate tectonics" more broadly to encompass not only the dynamics of the surface plates but also how their structures and compositions are influenced by those dynamics and the theories about processes in the mantle that help to drive and direct plate motions. Dragons flight (talk) 08:10, 28 May 2016 (UTC)

Strictly "plate kinematics" only decribes the direction and rate of plate motion, whereas dynamics would look more at the forces involved as Medeis had pointed out, but I accept that most geologists tend not to be dogmatic about these things. In the eclogitization article, it would be fair to say that it particularly affects the dynamics, by altering the forces on the pieces of crust involved. A better place to ask a question about an article that has an inactive talk page is at the relevant WikiProject, in this case Wikipedia talk:WikiProject Geology. Mikenorton (talk) 12:00, 28 May 2016 (UTC)

Yup, the WikiProject is probably the way to go with these sort of questions in future, when a suitable project is available. But while you're here ... my next question is whether I can turn the word "appears" (previously "the appearance of", previously "is observed", previously "is formed") back into "formed". Do geologists have some prejudice against "formed", perhaps reserving it for a special meaning which makes it inapplicable here? I'm puzzled because it was the article creator who made all those changes, as if they were improvements. "Formed" seems like the idiomatic word to use, to me.

Oh I see you replied on the talk page, too. Thank you.  Card Zero  (talk) 20:01, 28 May 2016 (UTC)

The original wording was better I think - "appears" is a little odd, sounds a bit like magic. Note that this article was created by a BSc student as part of a class and was definitely in need of some work. Mikenorton (talk) 20:36, 28 May 2016 (UTC)

Maybe it's because of wikt:facies! "Appearance", see?  Card Zero  (talk) 21:10, 28 May 2016 (UTC)