Wikipedia:Reference desk/Archives/Science/2012 July 14

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July 14

Cognitive biases and predictions of the end of Moore's Law

Do any purely psychological explanations exist behind why the various forms and corrolaries of Moore's Law consistently continue for longer than experts predict, making it an exception to the usual optimistic bias of technology predictions? NeonMerlin 00:13, 14 July 2012 (UTC)

Are you asking why the experts are too pessimistic? Or are you asking whether Moore's Law is an illusion? I don't see how to make the question make sense if it doesn't mean one or the other. Looie496 (talk) 00:18, 14 July 2012 (UTC)

Judging by the word any I take it he means both. 203.27.72.5 (talk) 00:25, 14 July 2012 (UTC)

Because the serious limits don't start to become evident until 2016-2022? 71.212.249.178 (talk) 00:38, 14 July 2012 (UTC)

And the reason for that is intense competition pressure. To stay on top of the game, semiconductor companies continually make huge investment in research, so that each technical bottleneck is broken just in time to keep Moore's Law in place. The rate of Moore's Law is determined by the cost of research and time-to-market http://en.wikipedia.org/wiki/Time_to_market. Both are relatively constant, hence Moore's Law is fairly constant. The explanation is not psycological, its commercial. Ratbone124.182.22.24 (talk) 01:28, 14 July 2012 (UTC)

I think the point is that that's what they always say. The supposed end of Moore's law is always just around the corner when the "serious limits" start to kick in, yet in 50 odd years it's never actually happened. 203.27.72.5 (talk) 01:14, 14 July 2012 (UTC)

The optimistic bias in technological predictions is just a lack of imagination on our part. When asked to imagine what the world will look like in the future, we might say something like "cancer will no longer be a problem". If we're pressed as to how that will happen, it's usually the most obvious hyped up area of research today, like genetic thearpy or nano-robots or something like that. History has shown us that we will probably be blindsided by some unforseen breakthough and after that we'll think it was obvious and wonder why we didn't think of it sooner. We don't have the android technology seen in the 1979 film Alien, but in that film, the computers were all using a text based operating system and had tiny CRT monitors. It's easy to think of technology giving us stuff like interstellar travel and life-like robots, but thinking of the more subtle things that take incremental advances but improve our lives by so much requires more imagination than we have. The advances won't be the ones that we think they'll be, but they'll still be awesome, and that's reflected in genuine, objective measurements of technological advances, like with Moore's law. 203.27.72.5 (talk) 01:26, 14 July 2012 (UTC)

"in that film, the computers were all using a text based operating system and had tiny CRT monitors. " Not only that, but it made a sound each time a character appeared on the screen! And the speed was about 10-20 characters per second. Bubba73 ^{You talkin' to me?} 03:30, 14 July 2012 (UTC)

And no doubt the text was far larger than on any real screen. This is a common trope in movies and TV, as a person reading small, monochrome text on a screen, in silence, just isn't very interesting to watch. StuRat (talk) 04:32, 14 July 2012 (UTC)

And often the font on the screen would be OCR-A font, which makes no sense. Bubba73 ^{You talkin' to me?} 04:39, 14 July 2012 (UTC)

From memory StuRat, no it wasn't like that because it wasn't important that the viewer actually read the text, it was just lines of text scrolling over the screen much like an old execution of autoexec.bat on a 486 running windows 3.1. 203.27.72.5 (talk) 05:46, 14 July 2012 (UTC)

I can beat the Alien example. An original Outer Limits episode featured a future video phone, with a cord, and ... wait for it ... a rotary dial. :-) StuRat (talk) 02:15, 14 July 2012 (UTC)

Ha. That's hilarious. And realistically, how much has a video phone conversation changed our lives vs wireless telecommunications and reliable buttons? But no one is going to marvel at how much CGI went into making a futuristic button. Audiences wouldn't have even understood what was going on if they saw a movie that depicted the use of a modern mobile phone back when Outer limits was on TV.203.27.72.5 (talk) 02:24, 14 July 2012 (UTC)

I think they would have. After all, the Dick Tracy two-way wrist radio (introduced January 13, 1946, with video added in 1964) had buttons, going way back. StuRat (talk) 03:15, 14 July 2012 (UTC)

Did he get spammed by Jamba!, or MMS pictures of evidence to his client using the intergrated camera? Did it have a visible antenna? Did he lose reception in underground carparks, or have no coverage in a major metropolitan area? 203.27.72.5 (talk) 03:23, 14 July 2012 (UTC)

The D'Arsonval meter movement is rather funny: [1] (at the bottom). We still use that on car speedometers and gauges, though. The speaker also looks like something from a 1960's console TV. The screen does seem to use some type of flat screen technology, at least not a CRT. StuRat (talk) 04:02, 14 July 2012 (UTC)

Can Cannabis grow in the Colorado high country?

9000+ feet, Rocky Mountains. I was walking through an open meadow near a popular golf course and noticed Cannabis looking plants growing in bunches within a large circle of area. According to the rather confusing Cannabis article, "The leaves have a peculiar and diagnostic venation pattern that enables persons poorly familiar with the plant to distinguish a Cannabis leaf from unrelated species that have confusingly similar leaves (see illustration)"—first of all, what illustration?! Okay, next, the picture to the right of the paragraph sure looks like what I saw. What "unrelated species" are there that I may be confusing this with? If this is Cannabis, does that mean someone threw some seeds there as a joke or something? Thanks! Reflectionsinglass (talk) 02:58, 14 July 2012 (UTC)

Is this a real question or just a lead up to a Rocky Mountain High joke ? StuRat (talk) 03:17, 14 July 2012 (UTC)

In case it's meant as a serious Q, let me take a stab at it: Cannabis grows like a weed, hence the name. Not sure if it grows at that altitude, but, if so, maybe some hippie spilled some seeds out of his baggie, and that's all it took.

The illustration they meant was the one to the right. Here's the full-sized version: [2].

Doing some web searches, it does appear to grow at high altitudes, but 8750 feet is the highest point I saw listed explicitly. Here's a couple sites I found: [3], [4]. StuRat (talk) 04:11, 14 July 2012 (UTC)

Wild cannabis isn't that rare of a weed in NA, but no one cares because the weed version is worthless to smoke, just like the vast majority of plants we eat, plant breeders have dramatically improved the quality of cannabis that is cultivated. The "hippie" bit is uncalled for, please keep your stereotyping to yourself. Unique Ubiquitous (talk) 05:03, 14 July 2012 (UTC)

The wikipedia article must need a visit from the PC police too then, since it says that the movement is known for experimentation with drugs. 203.27.72.5 (talk) 05:37, 14 July 2012 (UTC)

Sure, but it does not follow that those who use or grow the drugs are hippies. It has never been the case that only hippies smoked pot, and the vast majority of pot smokers today are not hippies. I would be more worried that someone is intentionally growing them up there — which can be a dangerous thing to interact with depending on who is growing it. When you see a stand of marijuana growing, consider that that's somebodies money growing out there. --Mr.98 (talk) 15:15, 14 July 2012 (UTC)

Fair enough, but what's "NA". Namibia ? Netherlands Antilles ? StuRat (talk) 05:06, 14 July 2012 (UTC)

What's the reference to "grows like a weed, hence the name" about, Stu? The etymology has nothing to do with weeds, as far as I can see. -- ♬ Jack of Oz ♬ ^{[your turn]} 05:12, 14 July 2012 (UTC)

Do you not use the slang word "weed" in Australia, for cannabis ? StuRat (talk) 05:28, 14 July 2012 (UTC)

I'm pretty sure JoO is aware of the slang word, they're just saying the etymology of the slang word has nothing to do with cannabis growing like a weed. Whether or not this is true I can't say, I had trouble any reliable sources most appear to discuss othe things like the word marijuana or pot. Nil Einne (talk) 05:49, 14 July 2012 (UTC)

Sorry, of course I know it as "weed". I misinterpreted Stu's comment, which I read to mean that the name "cannabis" was from some presumably Latin or Greek word meaning "weed". My bad. But in checking out the etymology, I did discover it's cognate with the word "canvas". That had never occurred to me, but it makes a lot of sense. -- ♬ Jack of Oz ♬ ^{[your turn]} 06:24, 14 July 2012 (UTC)

NA = North America. What else, StuRat? OsmanRF34 (talk) 05:26, 14 July 2012 (UTC)

OK, a bit non-specific, though. I listed two possible more specific meanings. StuRat (talk) 05:28, 14 July 2012 (UTC)

Which of the three contains the region mentioned in the title of this section? —Tamfang (talk) 06:08, 14 July 2012 (UTC)

People often reply to questions on one part of the world with answers on how things work in their own part of the world. StuRat (talk) 06:30, 14 July 2012 (UTC)

In order that we may answer your questions within wwikipedia ref desk guidelines, please explain at the ref desk discussion board thread on this post why you cannot see the illustration in the article you searched to the right of the text you mentioned. Please upload an image there so we may help you identify the plant, although, do be aware that people have been shot for trespassing on someone's weed patch. Please explain there what evidence you have that someone has planted these plants as a joke so that we can evaluate it, rather than speculate and debate upon it. (Comment added by User:Medeis (μηδείς), who, by omitting their name, implies that their opinion is that of everyone here, when it is really only theirs. StuRat (talk) 05:09, 14 July 2012 (UTC))

From our article it appears that some people have described ditch weed as a separate species, though I haven't reviewed the evidence; whatever it is called, it was used fairly widely for routine purposes of landscaping and preventing erosion even during the early days of Prohibition. Apparently law enforcement still goes to great lengths to seek out and exterminate such plants, though they are suited for little but genuinely medicinal or perhaps textile use. Wnt (talk) 05:14, 14 July 2012 (UTC)

I do not believe it can grow there. Cannabis needs lots of warmth and light. OsmanRF34 (talk) 05:23, 14 July 2012 (UTC)

Light isn't a problem at elevation. If anything, they get more light, especially UV. Warmth could be a problem, though. StuRat (talk) 05:26, 14 July 2012 (UTC)

Perhaps I should have elaborated. "Ditch weed", according to our article, is Cannabis ruderalis, and is hardier than the other species. Wnt (talk) 11:10, 14 July 2012 (UTC)

How can law enforcement distinguish between wild useless cannabis and smokable cannabis? Do they look different enough? OsmanRF34 (talk) 05:33, 14 July 2012 (UTC)

I doubt if they bother, but just destroy anything that looks like it. StuRat (talk) 05:56, 14 July 2012 (UTC)

Cannabis sativa grows wild in the UK, and throughout Western Europe. According to my wild flowers book it is native and not introduced. I dare say it is a common escape from cultivation (hemp). It's said that the plants have little or no pharmacological content, not sure if that is because of the variety or because of the growing conditions. Illegal cultivators in the UK use greenhouses or artificial lighting. The UK police have no interest at all in wild hemp, as far as I know. Itsmejudith (talk) 17:08, 14 July 2012 (UTC)

Thanks to all the responses. The plant is growing on private property owned by a resort, which owns the golf course as well. So there's no fear of being shot. I also assume that a pot farm would look more like that scene in the film Without a Paddle, with lots of land dedicated to these plants than just the few bunches I found. I'll bring a plant inside and compare it to the photograph in the article. The way the sentence with the phrase "see illustration" is worded, I was looking for an illustration showing the different types of plants that can be confused with cannabis. I might post a photograph of these plants as well and post a link here. Reflectionsinglass (talk) 21:31, 14 July 2012 (UTC)

Question about Big Bang theory.

Transcluded from the Miscellaneous reference desk. 203.27.72.5 (talk) 06:05, 14 July 2012 (UTC)
the Big-Bang theory is telling that the universe was originated about 13.75 billion years ago from a tiny ball with infinite density and temperature when the ball blasted with a big bang. according to the theory the universe is expanding like a balloon. My questions are:-

1. where that 'tiny ball' was? kept over something? floating some where? or hanging over something?

2. where forom that 'tiny ball' came?

3. who had created that tiny ball?

4. how is it possible that a very 'tiny ball'had so much of matter that a universe of billion galaxies with billion stars are containing?

5. If the universe is expanding then there must be one starting point and one ending point or an edge, then what is there out of the edge?

— Preceding unsigned comment added by 117.201.102.48 (talk) 04:39, 14 July 2012 (UTC)

Wouldn't the Science Desk be a better place to ask science Q's like this ? StuRat (talk) 04:46, 14 July 2012 (UTC)

4) Since matter can have an infinite density, as in the singularity in a black hole, there's no reason the entire universe couldn't fit into a tiny point. StuRat (talk) 04:48, 14 July 2012 (UTC)

You might enjoy Ned Wright's cosmology tutorial.

There was probably never a time of infinity density and temperature; big bang cosmology doesn't require that, and it doesn't seem very likely. Cosmic inflation is the best known attempt to explain the origin of the initial very dense state, but there isn't enough evidence to be sure that it's right. It isn't necessary for the expanding region to have an edge, though it could. Other than that, the answer to the questions is "nobody knows (yet)". -- BenRG (talk) 06:31, 14 July 2012 (UTC)

Your questions make assumptions that the universe "before" the big bang and "outside" it have properties like the universe we know today. But depending on the particular theory, these assumptions may be false (which is why I have put those words in quotes). For example, one common theory about the Big Bang (famously presented by Stephen Hawking is that "before the Big Bang" is like "South of the South Pole". So our experience is that wherever we are on the planet there is something to the South of us; but if we go to the South Pole, our experience (our assumption) breaks down: there is no "South" there. In the same way, Hawking suggests, at the Big Bang there is no "before". On that theory, your questions 2 and 3 do not make sense, as they contain erroneous presumptions. --ColinFine (talk) 08:42, 14 July 2012 (UTC)

(ec) I thought the idea was that since all of space was contained within the big bang--there was no "place" outside it. So it makes no sense to ask "where" it happened. It happened "everywhere". Isn't this supposedly why the Cosmic microwave background radiation is found everywhere? And, perhaps I'm wrong, but isn't the big bang also supposed to be the origin of time itself? If so it would make no sense to ask about "before" or "what caused" it, right? Pfly (talk) 08:45, 14 July 2012 (UTC)

(5) An expansion does not imply that there will not be a contraction. In other words, the expansion may go on forever - or it may not. It may contract. It may oscillate between expansion and contraction. We simply don't know. Our universe may be a bubble in an even bigger universe - or it may not. I'm reminded of one of Haldane's quotes: "The universe is not only stranger than we imagine, it is stranger than we can imagine". We can gather information and see what that information leads us to, but to suggest that we know the answers to your questions is arrogant at this point in time. Doesn't stop us theorising, of course, and shouldn't stop you asking! --TammyMoet (talk) 08:53, 14 July 2012 (UTC)

Blood test after getting infected by HIV....

I had only oral sex with a prostitute before 3 months but now I fear that it might have infected me from HIV as I had some rashes on my genitals and perhaps she also had bleeding gums........ Now I want to clear my doubt that either I got infected or not. I heard somewhere that HIV will not show up in blood test so early after getting infected, so what is right time for blood test. — Preceding unsigned comment added by 14.140.235.82 (talk) 06:19, 14 July 2012 (UTC)

Wikipedia does not give medical advice. See a doctor, or other appropriate medical practitioner. AndyTheGrump (talk) 06:22, 14 July 2012 (UTC)

See a physician. If you can not afford a physician, is there a free clinic in your area? Furthermore, Diagnosis of HIV/AIDS#Rapid or point-of-care tests also does not constitute medical advice. 71.212.249.178 (talk) 06:33, 14 July 2012 (UTC)

The OP has not asked for medical advice regarding us diagnosing or treating his condition. He has asked how soon a positive HIV test shows up after infection. The answer is that it may take very little time or more than a year. See HIV_test#Window_period. μηδείς (talk) 05:39, 15 July 2012 (UTC)

I agree with your interpretation, but that article says more than six months is extremely rare. Diagnosis of HIV/AIDS#Window period has more detail. 71.212.249.178 (talk) 22:14, 15 July 2012 (UTC)

See a doctor as soon as possible, how long you have to wait before HIV is detectable is completely irrelavant if you are already presenting symptoms. Time is of the essence, the sooner you get yourself diagnosed and treated the better. Vespine (talk) 22:55, 15 July 2012 (UTC)

Do Sounds Played at the Same Time Add?

If you play two sounds at the same time will the resulting sound wave be the sum of the two individual ones? I'm guessing no since a sound wave that is a constant would not sound like anything and you can add two sine waves to get this. Then again, going from the graph of a sound wave to what it sounds like has always been a point of confusion for me. Thank you for any help:-) 209.252.235.206 (talk) 09:02, 14 July 2012 (UTC)

Yes, they add (the wave equation governing sounds is a linear equation). You can have cancellation of sound waves (for example when you hear a beat). —Kusma (t·c) 09:09, 14 July 2012 (UTC)

Yes, if they are exactly the same sounds, in phase with each other, and both arrive at the listener at the same time, then, as you said "the sine waves will add". However, if they are out of phase, either from being produced at slightly different times, or being at different distances from the listener, they can actually cancel each other out (see noise cancellation). Note that when they do add, twice the amplitude of sound wave does not mean it's twice as loud. See decibel. StuRat (talk) 09:13, 14 July 2012 (UTC)

Thank you very much:-) 209.252.235.206 (talk) 09:39, 14 July 2012 (UTC)

You're welcome. I will mark this Q resolved. StuRat (talk) 09:59, 14 July 2012 (UTC)

Resolved

You marked it resolved prematurely, Stu. You have repeated a common fallacy. Consider two independent sound sources (meaning each has its own arbitary waveform and phase): One sound source imparts x watts of acoustic power to the environment and the other y watts. Since energy cannot be created or destoyed, there is x+y watts of acoustic power in the environment. However, the amplitude [the amount of air displacement, or the distance a freely suspended surface (a la a microphone diapham or an eardrum) will move] is proportional to the square root of the acoustic power, just as the voltage in an electric device is proportional to the square root of the power. Two sound sources being indentical in all respects except being out of phase cannot just cancel, as this would mean energy destroyed. What happens is cancellation occurs in some directions and reinforces to double strength in others, the directions being a function of the spacing and phase of the two sources. In other words, the sound becomes directional - analogous to the common use in radio broadcasting to use two or more carefully spaced antennas to provide directional coverage. This principle is also used in concert sound reinforcement - indentical loudspeakers fed with indentical program are "stacked" to beam the sound into the audience and not waste it to the sky. Complete cancellation can only occur if the two sound sources occupy the exact same point in space - a rather theoretical concept. Ratbone121.215.69.8 (talk) 10:12, 14 July 2012 (UTC)

That's consistent with what I said, where I mentioned them both adding and cancelling, listing cancelling due to "being at different distances from the listener". Obviously the two sources wouldn't be at different distances from all possible listeners, and there the sounds don't cancel. The noise cancellation article I linked to explains the details. As for the math, I linked to the decibel article, which explains the relationships between power level, volume, etc. StuRat (talk) 10:24, 14 July 2012 (UTC)

Transcluded to Ratbone's now created talk page. 203.27.72.5 (talk) 11:09, 14 July 2012 (UTC)

BTW, since you misspelled it 3 times in your post, let me point out that it's "identical" not "indentical". StuRat (talk) 10:24, 14 July 2012 (UTC)

You should know by now, Stu, that I do lnkow how to spoll, but I am a shockinkg typist. Ratbone121.215.29.47 (talk) 12:20, 14 July 2012 (UTC)

Either there's an error in your logic or you just weren't clear on what you meant Ratbone, but where you said "Two sound sources being indentical in all respects except being out of phase cannot just cancel, as this would mean energy destroyed" it sounds like you're saying that being in phase is an intrinsic property of the two sound sources. It's not the sources, but rather the waves that are either in or out of phase, and that depends on the location i.e. they're in phase at point A, out of phase at point C, and somewhere in the middle at point B. 203.27.72.5 (talk) 10:29, 14 July 2012 (UTC)

This is probably just a comment on my english, but the wording I used is entirely standard in electronics and acoustics. Engineers talk of sources being "in phase", "out of phase" etc, without implying that waves will be the same relative phase everywhere in space, a phenomena which you have clearly appreciated. Ratbone121.215.29.47 (talk) 12:20, 14 July 2012 (UTC)

Ah, yes, well I'm not an accoustics engineer, so I wouldn't know about their standard technical jargon. Thanks for clearing that for me. 203.27.72.5 (talk) 13:06, 14 July 2012 (UTC)

"Two sound sources being indentical in all respects except being out of phase cannot just cancel, as this would mean energy destroyed": well, they'd have to be in exactly the same place, and the energy will be zero at all times since no wave is actually emitted. —Kusma (t·c) 10:33, 14 July 2012 (UTC)

Correct. Ratbone121.215.29.47 (talk) 12:20, 14 July 2012 (UTC)

Two sources producing the same sounds in phase would be indentical, 180^o out of phase, outdentical. Everything else would be inbetweenical. Clarityfiend (talk) 22:37, 14 July 2012 (UTC)

Back to the OP's question, yes, the sound wave will be the sum of the component waves at the point considered. But the perceived sound will depend on the context and history, see Helmholtz's On the Sensations of Tone as a Physiological Basis for the Theory of Music. μηδείς (talk) 05:49, 15 July 2012 (UTC)

Black Holes and Dark Energy/Matter

If I'm not mistaken, I believe that the existence of black holes was early in the 20th century without the involvement of either dark energy or dark matter. Likewise, the more recent 'proof' that black holes actually exist (based on the velocity of stars orbiting around the unseen black hole) is not dependent on dark matter or energy either.

How does the existence of dark energy and dark matter effect our understanding of black holes?Honeyman2010 (talk) 11:01, 14 July 2012 (UTC)

There is theory about objects called MACHOs that could include black holes and is meant to explain dark matter. It's essentially been disproven though. Dark matter and black holes are believed to be unrelated. 203.27.72.5 (talk) 11:06, 14 July 2012 (UTC)

Agreed; there is no close relation or connection between the three concepts. Black holes were known to be a theoretical consequence of general relativity long before any evidence of their actual existence was found, and indeed the observational evidence for black holes is still somewhat indirect and not totally conclusive. Dark matter and dark energy are names for possible mechanisms explaining puzzling astronomical observations (the galaxy rotation problem and the accelerating universe respectively), but the details of these mechanisms are not completely understood. The similarity in names, each involving black/dark, is partly coincidence and partly lack of imagination on the part of physicists/cosmologists. Gandalf61 (talk) 11:23, 14 July 2012 (UTC)

Thanks for the answers, but my confusion does not stem from the similarity of the words "black" and "dark". My question seems logical since black holes represent infinite gravity, and dark matter and dark energy are thought to comprise perhaps 80% of the matter in the universe. Surely some interaction cannot be so summarily dismissed. Also, would the recent discovery of the Higgs (a scalar) and dark energy (thought to be a scalar) not suggest the possibility of a link? And, finally, if Unification is ever realized through String Theory (perhaps pushed along now with the Higgs), or some other preocess, would that bear on my question? Thanks Honeyman2010 (talk) 12:16, 14 July 2012 (UTC)

The article on MACHOs explains why it is unlikely that dark matter has anything to do with black holes. Also, you should read the article on black holes, as you seem to have some misconceptions about them. They do not have infinite gravity. According to general relativity they contain a point called a singularity that has infinite density. Their mass is finite and they may have other characteristics that define them (see no hair theorem). 203.27.72.5 (talk) 12:44, 14 July 2012 (UTC)

Please see Talk:Dark matter#Draft table. 71.212.249.178 (talk) 21:51, 14 July 2012 (UTC)

Your table has nothing to do with the question. Please quit spamming the link.

The original question was, "do the existence of dark energy and dark matter change the way black holes work?". The short answer is "no, not really". The long answer is, "dark matter is absorbed like any other matter, and dark energy presumably gives a repulsive force as it does in any volume of space, but one that's far too weak to be relevant". --Christopher Thomas (talk) 02:43, 17 July 2012 (UTC)

I believe that the blue lines in Figure 2 on p. L70 of Lacki and Beacom (2010) impose constraints which bear on the answer to this question, but I have been told I am not interpreting that paper correctly, although the reasons why are elusive. I welcome others' opinions. 71.212.249.178 (talk) 05:05, 17 July 2012 (UTC)

Polyvinyl fluoride and PubChem name. A little confusion.

Hello, I looked up polyvinyl fluoride in PubChem Compound and got struck. For polymers, PubChem Compound shows only the monomers. However in this case it shows fluoroacetylene instead of fluoroethylene. (i.e; fluoroethyne instead of fluoroethene). Why? And in Pubchem Substance, it is more confusing to me. Can you help me please? Your comments are always welcome. They have got it almost right for polyvinyl chloride. (For reference you may look CAS and CHEBI:)Vanischenu m^Talk 12:34, 14 July 2012 (UTC)

I don't think the answer is too exciting. It looks like they're just plain old wrong. Should be an alkene, not an alkyne. 203.27.72.5 (talk) 13:01, 14 July 2012 (UTC)

It's quite unfortunate that this occurred at a trusted site. Thank you for your kind reply. I will mark this question as resolved then.

Resolved

Vanischenu m^Talk 19:26, 14 July 2012 (UTC)

Genetic difference between Africans

Is it true that the genetic difference between two different ethnic groups in Africa like say the Hutu and the Zulu people is comparable or even greater than the genetic difference between a given black guy and a given white guy? ScienceApe (talk) 16:07, 14 July 2012 (UTC)

I found this:

Interestingly, both autosomal and X-linked sequence data show higher DNA variation within Africans than between Africans and Eurasians, contrary to the general observation of lower within-population than between-population differences in population genetics. This finding implies that Africans differ on average more among themselves than from Eurasians. Thus, with the exception of many minor unique variants, the nucleotide diversity in Eurasians is essentially a subset of that in Africans, as suggested by the observation that both Y-linked and autosomal haplotypes found outside of Africa were often a subset of the collection of haplotypes found in Africa. Our finding is more in agreement with the out of Africa model of human evolution than with the multiregional model because it is consistent with the view that modern humans originated in Africa and that a smaller subset of this population later migrated to other parts of the world. During and after the migration some variants would have been lost and, as the separation time is still short, non-Africans have not yet acquired many high-frequency variants, though they might have derived some variants from indigenous archaic populations in Asia and Europe. For these reasons, the genetic differences between non-Africans and Africans are on average smaller than the genetic differences within Africans.
(Yu et al. (2002). "Larger Genetic Differences Within Africans Than Between Africans and Eurasians". Genetics. 161, 269-274)

Which basically means yes. I don't know specifically about Hutu or Zulu genetic differences, but the latter study includes several Bantu peoples (of which the Hutu are genetically very close to) and the Zulu people. However, it also includes the !Kung, which belong to the Khoisan-speaking peoples; and two of the African pygymy peoples, the Aka of the Mbenga group and an unspecified member of the Mbuti group. The latter peoples are the most genetically diverse of the human populations on the planet, so depending on what you mean by "African" it can be skewed one way or another. Most people tend to separate the Khoisan group and the pygmies from other African populations, which in turn are separated from the more recent ethnic Arabs in North Africa (not included in study). Also note that "Eurasians" in this case refers to European (both Western and Eastern) and Middle Eastern human populations, though the sample group for them is composed purely of Europeans.-- OBSIDIAN†SOUL 17:29, 14 July 2012 (UTC)

This should not be surprising, under the the recent African origin of modern humans theory. (It is only surprising if you are fooled into thinking that superficial differences like skin color, hair type, and eye folds are actually indicative of deep genetic differences.) Imagine Africa as a big pool of genetic diversity. Spurs are flung out of it relatively recently in human history. These spurs migrate all over the place. But they are still just spurs of some initial African population — by and large, the initial Africans stay in Africa. So there would still be more diversity there than elsewhere. See also, Founder effect: populations that leave necessarily have less genetic diversity than the place they left. Such is my quite lay understanding of it, anyway. --Mr.98 (talk) 17:36, 14 July 2012 (UTC)

On an interesting note, given the historic trends of racism. The non-African population genetically closest to African populations are Eurasians. The farthest are the dark-skinned and curly-haired Melanesian Oceanians and Australian Aborigines. Just goes to show how phenotypes can be quite misleading.-- OBSIDIAN†SOUL 17:40, 14 July 2012 (UTC)

On the example of Hutu and Zulu, both groups have origins in the Bantu expansion, so that might not be the best example to use. Of course the genetic difference between two individuals depends on the specific individuals. "A given black guy and a given white guy" is too vague to be very meaningful. Pfly (talk) 03:34, 15 July 2012 (UTC)

Name for numbers in chemical notation?

Is there an overarching, dedicated name for the numbers in chemical notation indicating quantity of atoms in a molecule. For example it would refer to the numbers, collectively as a class, in water and ozone: the 2 in H₂O, and the 3 in O₃?--108.46.98.134 (talk) 16:47, 14 July 2012 (UTC)

I just looked quickly at some of our articles on formulas. They don't seem to name them though. They are just a ratio of the moles of the elements I think. Scholars may have named them at one point. If they haven't then I move that they be called 'Canoe ratio integers'.--Canoe1967 (talk) 17:50, 14 July 2012 (UTC)

Chemical formula is one link. There are more links in the article.--Canoe1967 (talk) 18:02, 14 July 2012 (UTC)

Ha! It feels like they should have a name. I want to use it in a sentence in something I am writing but I can make do. However, I'll check back for further answers.--108.46.98.134 (talk) 18:02, 14 July 2012 (UTC)

Stoichiometric_coefficient#Stoichiometric_coefficient seems to be it. I was wrong as usual.--Canoe1967 (talk) 18:04, 14 July 2012 (UTC)

Nope. That is the big number in front to count the number of molecules in a reaction.--Canoe1967 (talk) 18:09, 14 July 2012 (UTC)

Maybe not but "stoichiometric" is a great word to know.--108.46.98.134 (talk) 18:18, 14 July 2012 (UTC)

I think the numbers (and symbols) surrounding chemical symbols are informally known as "indices" (sing. "index", of course). See this. The number specifying the number of atoms of an element seems to be rather unimaginatively known as the "right subscript" from its relative position (see Chemical symbol).

Then there's also the Greek numerical prefixes (which must be differentiated from the Latin numerical prefixes used for temporarily naming new elements), mono-, di-, tri-, tetra-, penta-, etc. (e.g. H₂O (water) is dihydrogen monoxide; O₂ (molecular oxygen) is dioxygen; O₃ (ozone) is trioxygen)

And lastly, there's the terms monatomic, diatomic, triatomic, etc. But these refer to the number of atoms in a molecule, not the number of atoms of an element in a molecule (e.g. H₂O is triatomic, so is CO₂)-- OBSIDIAN†SOUL 18:25, 14 July 2012 (UTC)

Could it safely be called the 'proportional integer suffix' type thing?--Canoe1967 (talk) 18:33, 14 July 2012 (UTC)

A single Oxygen atom is roughly more than twice the radius of a Hydrogen atom. And Hydrogen is 1/16th the relative atomic mass of Oxygen of course... so "proportional" doesn't exactly fit. :P How about just "number of atoms of an element in a molecule", heh.-- OBSIDIAN†SOUL 18:52, 14 July 2012 (UTC)

'quantitative integer suffix'? I am just trying to think of a ten dollar phrase for a 2 bit number is all.--Canoe1967 (talk) 19:00, 14 July 2012 (UTC)

What's wrong with just calling it the "subscript" ? StuRat (talk) 19:05, 14 July 2012 (UTC)

I was assuming the OP wanted a fancier term is all.--Canoe1967 (talk) 19:47, 14 July 2012 (UTC)

"atomic quantity subscripts" 71.212.249.178 (talk) 21:53, 14 July 2012 (UTC)

Even IUPAC called it just as subscripts at the very sacred Golden book, the Gold Book (online version). See empirical formula. You will be disappointed to see molecular formula.
Simply, it represents the number of an atom or a species in one molecule of the compound under consideration. This is really an amazing question! Vanischenu m^Talk 23:48, 14 July 2012 (UTC)

Our Chemical formula calls them quantity subscripts. 71.212.249.178 (talk) 02:33, 15 July 2012 (UTC)

It should be noted though that there are two subscripts. The left subscript is the atomic number (number of protons), while the right subscript refers to the number of atoms of that element in a molecule.-- OBSIDIAN†SOUL 23:07, 16 July 2012 (UTC)

Making graphite out of wood

How can you make it? Is that technically too difficult? What happens to wood if you just put a lot of pressure into it? OsmanRF34 (talk) 17:35, 14 July 2012 (UTC)

Can you make graphite out of wood? You can certainly make charcoal out of wood, which is another form of carbon, but isn't strictly speaking graphite. Synthetic graphite is not made from wood. --Mr.98 (talk) 17:44, 14 July 2012 (UTC)

Graphite#Uses_of_synthetic_graphite has methods. That is a sub-section of the graphite article above. I would think it is more a matter of cost than difficulty. They may use it to get purer forms as well.--Canoe1967 (talk) 17:57, 14 July 2012 (UTC)

My reading of that section led me to conclude that synthetic graphite is made of Silicon carbide, not wood. --Mr.98 (talk) 18:20, 14 July 2012 (UTC)

The natural creation section says "....a result of the reduction of sedimentary carbon compounds during metamorphism." I would assume some of that was wood. It could possibly be made from wood in a lab but would probably involve more steps?--Canoe1967 (talk) 18:43, 14 July 2012 (UTC)

Right, but doesn't that probably take like millions of years? --Mr.98 (talk) 19:36, 14 July 2012 (UTC)

Yes it would probably have to be a generation lab then?--Canoe1967 (talk) 19:50, 14 July 2012 (UTC)

Wood is a very complex substance made largely of cellulose, a sugar, when dry. Charcoal is what is made be heating wood in a reducing environment, not graphite, which is made of sheets of carbon, not amorphous carbon. μηδείς (talk) 02:19, 15 July 2012 (UTC)

When I was about 10, I was given a chemistry set (something you don't see nowadays). This led me, as it did with a lot of boys, to figure out how to make gunpowder and other sorts of explosives. I aslo had a burner that used alchohol as a fuel, burning it via a wick. I found that placing a cold plate (thin pice of metal) in the top part of the flame produced copious quantities of very pure graphite in powder form adhering to the cold plate. It works on test tubes containing water too. Keit58.169.240.198 (talk) 02:16, 15 July 2012 (UTC)

That's called soot. It's not graphite. μηδείς (talk) 02:51, 15 July 2012 (UTC)

Actually, your method (or the approximate reaction scheme behind it anyway) sounds like what these researchers are doing. 203.27.72.5 (talk) 02:50, 15 July 2012 (UTC)

Well, there you go; you could make graphite from wood by first destructively distilling it to make wood alcohol, burning it and reducing the hot CO/CO₂ with a metal. Not too efficient, but there you go. 203.27.72.5 (talk) 02:27, 15 July 2012 (UTC)

Hey wait, I didn't read that part about it working on (presumably glass) test tubes. Medeis is right. It was just soot. 203.27.72.5 (talk) 03:17, 15 July 2012 (UTC)

Yes, the black stuff on the cold plate is soot. But what is soot? In this case, almost entirely carbon with a bit of hydrocarbon. Not the same as soot from other sources such as wood. What's carbon precipitated when not heated to sublimation? Why, graphite! Keit121.221.5.163 (talk) 04:02, 15 July 2012 (UTC)

What is soot, you ask? Well, it's a mixture of hydrocarbons and amorphous carbon. Amorphous carbon is a bit of a misnomer because it's actually a mixture of graphitic and diamond-like carbon. There's no reason to think that the soot you made when you were 10 had a particularly high graphite content. Why do you think the hydrocarbon and diamond-like carbon content was low? 203.27.72.5 (talk) 04:49, 15 July 2012 (UTC)

Why did I think it had no significant hydrocarbon? - because it was a dry powder with no smell. While amorphous carbon produced by other means may have traces or significant amounts of diamond-like material, anything diamond like from this source doesn't sound very likely. Amorphous carbon is relatively quite reactive compared to graphite - the stuff I made behaved as I expected it to. Keit60.230.195.6 (talk) 13:44, 15 July 2012 (UTC)

You could just make charcoal as per above and then heat that to ~3000°C to make graphite, as is mentioned under Graphite#Electrodes. 203.27.72.5 (talk) 03:20, 15 July 2012 (UTC)

How to get graphite out of wood: Buy a bunch of pencils, split them open, and take out the graphite "leads". :-) StuRat (talk) 02:35, 15 July 2012 (UTC)

Nope - that's part graphite and part clay. Keit121.221.5.163 (talk) 04:02, 15 July 2012 (UTC)

Do algae like or even need darkness once in a while?

If algae (in my case I'm very interested in growing Spirulina) are grown in a Photobioreactor using artificial light instead of direct sunlight, it seems obvious you'd have the highest yield when the light is always on. Evolutionary, though, algae are used to having at least a few hours of "rest" during the night. If you'd supply 24/7 light, could you be halting some important processes from happening? Joepnl (talk) 21:15, 14 July 2012 (UTC)

Yes and no. Please see photosynthesis. 71.212.249.178 (talk) 21:57, 14 July 2012 (UTC)

Judging by how close to the poles algae are known to thrive, I think the assumption that in nature they wouldn't be exposed to light 24/7 is incorrect. 203.27.72.5 (talk) 22:17, 14 July 2012 (UTC)

Ok, some algae (or may be all) possibly like 24/7 light. But to be more precise: I'm only referring to algae (like Spirulina) that only survive in high temperature areas and so have had millions of years of being able to "sleep" at least 6 hours a day and possibly have developed some good or even vital use for that period.

@71.212.249.178 from that article I can't see the reason why algae would or could need darkness? Joepnl (talk) 22:49, 14 July 2012 (UTC)

I was guessing yes on "like" and no on "need" for the tropical varieties you are interested in, but μηδείς's answer below is better, especially if you judge "like" strictly by growth rate. 24/7 sunlight for tropical algae isn't likely to cause enough metabolic stress on them to make their growth rate much less than twice that of 12 hours per day sunlight. 71.212.249.178 (talk) 02:25, 15 July 2012 (UTC)

Some higher plants need a period of darkness or red light to bloom. See photoperiodicity. There are photosynthetic reactions that proceed in the dark, see dark reactions. I am unaware of any metabolic need for darkness. μηδείς (talk)

dark reactions: "Despite its name, this process occurs only when light is available." photoperiodicity is about seasons whereas growing algae is about "seasons" with a duration of perhaps 24 hours or even less. What I'm looking for is research that says "Spirulina (dietary supplement) contains a lot less beta-carotene in a 24/7 light situation, compared to Spirulina that had 20 minutes / hour darkness. Joepnl (talk) 13:18, 15 July 2012 (UTC)

Are you implying that you believe this to be true because you have come across it before, and are looking for help finding a ref you know exists? μηδείς (talk) 16:42, 15 July 2012 (UTC)

Sorry, that was a bit unclear. I was trying to give an example of what kind of conclusion might come from such research, but I don't know if it has been done or did get to a conclusion like that. I can just very well imagine that algae use daylight to gather as much energy as possible, and switch to making complicated molecules during the night. If it's always "day", they might not make that switch resulting in a worse end product. My new hobby is to grow Spirulina, using artificial light, and I obviously don't want to torture the poor cells :) Joepnl (talk) 17:37, 15 July 2012 (UTC)

I doubt you would have any change in composition beyond an increased concentration of malic acid, which wouldn't change other things enough to bother turning off the lights for part of the time. But there is only one way to find out! Run an experiment. 71.212.249.178 (talk) 08:00, 16 July 2012 (UTC)

This poster from a recent conference may be relevant: [5]. Unfortunately, I can only find the abstract online. If you can track down an e-mail address for the presenter you might be able to get a copy of the poster or a preprint of the paper. --Amble (talk) 15:27, 16 July 2012 (UTC)

Thank you! I'll try to contact them. I also found a book on growing spirulina which says "Growth only takes place in light (photosynthesis), but illumination 24 hours a day is not recommended. During dark periods, chemical reactions take place within spirulina, like synthesis of proteins and respiration." That makes the results of your find extra interesting.

@71.212.249.178, I would if I happened to have a lab handy. Joepnl (talk) 18:45, 16 July 2012 (UTC)

Well if it's your new hobby, maybe you want to start looking for labs where you can do basic assays like this. 71.212.249.178 (talk) 19:46, 16 July 2012 (UTC)

Not sure about the US, but it's not a $30 thing here to go to a lab and say "Hi, can I use your machine to test my sample for protein (or maybe something poisonous I haven't even heard of) content, and btw I'll be back every thursday with new samples". I'm happy to start playing with algae to try different lights, temperatures, agitation, alkalinity, water levels, nutritients, etc myself and I hope the real scientists, who have all the machines, may be able to tell me if 24/7 daylight is a bad idea and I should have a mechanism for 6/24 hours darkness. Or more. Or less. Or maybe 15 min/hr instead. Joepnl (talk) 00:13, 18 July 2012 (UTC)

I was suggesting labs where you can mail food samples for standard nutritional analysis assays which support agriculture. If there is a farm economy near you, there should be an assay lab for farmers which does mail work. 75.166.200.250 (talk) 06:49, 18 July 2012 (UTC)

Ok, that's true. I'll look for one. Thanks! Joepnl (talk) 21:06, 18 July 2012 (UTC)

What color skin did the earliest humans have?

I know of the theory stating that ancient humans migrated out of Africa, but there's something about it I don't quite understand. Would the earliest humans have had black or white skin? I'm just trying to figure out if Europeans descended from black humans, or if the black skin tone was something that evolved later in Africans to cope with the sunlight. I'm just trying to understand this better. Thank you for any and all information. InforManiac (talk) 23:18, 14 July 2012 (UTC)

Black skin would have come first, as this is important to living in Africa, or any place with bright sunlight, without getting skin cancer (clothes, hats, sunscreen, and spending most of our time indoors now serve that purpose). Europeans and (north) Asians later developed lighter skin, since, with less sunlight, skin cancer was less of a concern, and lack of UV light to synthesize vitamin D became more of an issue (vitamin D supplements now lessen this concern). StuRat (talk) 23:22, 14 July 2012 (UTC)

Thank you. That's kind of what I assumed, but I just wanted to double check. Thanks again. InforManiac (talk) 23:25, 14 July 2012 (UTC)

OK, I will mark this Q resolved. StuRat (talk) 23:27, 14 July 2012 (UTC)

Actually, the idea that skin color derived as an adaptation to protect against sunlight is an outdated but still common misconception held in increasingly low regard by researchers. Rather, like most phenotypical variation between the races, it is believed to have been (at least much more) the result of sexual selection, rather than natural selection. However, Stu is correct that the original Homo Sapiens sapiens were dark skinned. For the OP, I know of a couple of very good resources on this subject (and the general outwardly physical divergences of the races that are very accessible to even non-experts, if you're interested. Note: I've removed the resolved tag since I do not believe an accurate and full answer was given and expect further discussion to be forthcoming. Snow (talk) 00:28, 15 July 2012 (UTC)

I don't understand. Why would people in tropical climates prefer dark-skinned mates, people in temperate climates prefer medium-skinned mates, and people in arctic climates prefer light-skinned mates ? StuRat (talk) 00:58, 15 July 2012 (UTC)

They don't; it's an incremental process; people tend to prefer (but not necessarily to exclusion) mates who look like those they grew up around. This does not just apply to skin color; when you look at married couples, you find they tend to have very similar characteristics in the shape and relative size of many facial features which are counter-intuitive when you look at the overall span of human variation (things like the length of the earlobe, the width of the bridge of the nose, ect.). This and a whole ton of other well evidenced mechanisms have led a strong consensus that the differentiation of light-skinned people (and different phenotypes in general) started from random mutations (as all adaptions do, whether based in natural or sexual selection) which developed slowly thereafter. That's a cursory explanation that needs a lot more extension, I know, and I hate to bring it up and then dash out just when I got your curiosity up, but as I'm short on time and it will have to wait until later -- will comment further by tomorrow at latest, my apologies! Snow (talk) 01:16, 15 July 2012 (UTC)

That seems to just be saying that people with ancestors in hot climates having dark skin and those in cold climates having white skin is complete coincidence. That's not a very compelling argument. StuRat (talk) 02:14, 15 July 2012 (UTC)

No Snow, that's incorrect, StuRat is right. Melanin which is the pigment that produces dark skin, is well known to protect against UV radiation. ScienceApe (talk) 21:40, 15 July 2012 (UTC)

comment: The primary driving factor for dark skin was probably not skin cancer, which likely wouldn't affect you until after you had children, but the fact that UV destroys folic acid (vitamin B9) in the blood, leading to spinal bifida in pregnant women. That is, an inappropriate level of melanin in either direction leads to deformities in children.

Also, chimps have pale or at least blotchy skin. Black skin wouldn't be necessary as long as we had hair or lived in the forest, but the earliest common ancestor to humans most likely did not live in the forest, and was very likely much less hairy than modern Europeans. — kwami (talk) 23:53, 14 July 2012 (UTC)

Why would the earliest common ancestor to humans be "very likely much less hairy than modern Europeans" ? --Demiurge1000 (talk) 00:50, 15 July 2012 (UTC)

See aquatic ape hypothesis. 203.27.72.5 (talk) 01:25, 15 July 2012 (UTC)

Europeans seem to be an outlier. Looking across the most divergent genetic lineages, most have very little body hair. The other famous outlier are the Ainu, also a northern (= cold, and not the environment of our common ancestors) people. — kwami (talk) 02:49, 15 July 2012 (UTC)

The primary driving factor for dark skin was its protective properties against UV radiation which cause skin cancer and other diseases. What you're saying is true, but it seems likely that it was a combination of factors. Suffice to say, having light skin in Africa and other sunny environments confers no benefit and is harmful, thus would be selected against. Aside from our head, human hair is too fine to provide much protection from the UV light on the rest of our bodies. Human populations in Africa lived in a multitude of environments, forests, deserts, jungles. It seems fairly obvious that they had dark skin. Our non-sapiens (homo) ancestors probably had dark skin as well. ScienceApe (talk) 22:04, 15 July 2012 (UTC)

I don't think this can be answered without speculation. No harm in that, so long as what is written comes from good scientific thinking, and preferably excellent sources. Has this been studied and written about by notable, suitably qualified anthropologists or similar? We also need to moderate the original question, and suggest that black and white are not the only, diametrically opposed options. There's a lot of other shades out there. HiLo48 (talk)

Of course there a lot of other shades out there. I'm just trying to figure out, generally speaking, how humanity's skin tone started and where along the line things changed. I mean, when humanity was starting in Africa, was skin tone dark and subsequently got lighter in other areas? Or did humanity's skin start out lighter, but got darker in Africa as time progressed? I thought StuRat provided me with a good answer, and I still think his answer maybe very good. I am a little confused by the conflicting opinions though. In regards to the other shades that you mentioned, File:Homo_heidelbergensis_(10233446).jpg is one of them. I just want to get a loose understanding of what happened. InforManiac (talk) 03:47, 15 July 2012 (UTC)

As far as accessible and widely well-regarded sources go, Jared Diamond wrote extensively on this subject matter in the The Third Chimpanzee, I seem to recall. That's an excellent book, by the way, that I recommend to anyone who is looking for a primer on early human prehistory and development, especially as regards animal precursors to our uniquely human traits and our later differentiations as a species. As for more technical sources, I will add some a bit later, as well as a deeper discussion of why the "trait that evolved to protect against sunlight" hypothesis is considered dubious by contemporary researchers -- would do it now but afraid I'm just out the door! Snow (talk) 00:54, 15 July 2012 (UTC)

One bad case of sunburn in Africa would make you lion fodder. The evolution of pale skin, blond hair, and blue eyes can be attributed to sexual selection. There is a pretty universal trend for females to be paler than males. μηδείς (talk) 02:13, 15 July 2012 (UTC)

Dark skin in a sunless climate causes rickets. That's a strong selective force. Since we tan, you wouldn't get bad sunburn in Africa with pale skin, you'd just get really leathery as you age. AFAIK, the preference for pale skin is a product of hierarchical societies, and presumably would not apply to foraging populations like our common ancestors: pale skin means you spend time indoors and therefore have not had a peasant's life of outdoor labor. (Men don't want to be dark for the same reason; ditto the preference for long fingernails.) I'd like to see a study that women are actually paler than men, accounting for time spent in the sun. — kwami (talk) 02:47, 15 July 2012 (UTC)

There's Sex_differences_in_humans#Skin_and_hair and at google. μηδείς (talk) 03:00, 15 July 2012 (UTC)

No kwami, dark skin in a sunless climate does not directly cause rickets, vitamin D deficiency can lead to certain diseases involving weak bones like rickets. Having dark skin means you synthesize vitamin D from the sun at a much slower rate, but if the individual is consuming a diet rich in vitamin D, it's not a problem. But yes, there was a selective force for lighter skinned individuals in Europe and northern Asia for this reason. The preponderance for getting a sunburn or a suntan for a light skinned person depends on a number of factors. Genetics is a big factor. Some light skinned individuals simply burn more easily than others. If I were to guess, light skinned people whose ancestry traces to Mediterranean countries have better protection from the sun than say... people from Poland. ScienceApe (talk) 21:51, 15 July 2012 (UTC)

@InfoManiac: Anatomically modern humans would have started out with the dark skin typical of Africans, Dravidians, Negritos, Melanesians (New Guineans) and Australian aborigines. Whites and Orientals show different mutations in the melanin genes leading to differently pale yellow and pink skins. From Race_(human_classification): "Scientists discovered a skin-lighting mutation that partially accounts for the appearance of Light skin in humans (people who migrated out of Africa northward into what is now Europe) which they estimate occurred 20,000 to 50,000 years ago. The East Asians owe their relatively light skin to different mutations.[62]"μηδείς (talk) 04:16, 15 July 2012 (UTC)

Thank you. I was just thinking about that. About a year or so ago, I was reading a news article about an African family, and a couple of the children had a certain albino mutation. I understand that there is more than one kind of albinism in humanity. But anyway, a few children of black Africans looked as European as could be. I don't remember the eye color, but instead of the hair being white, it was light blond. InforManiac (talk) 04:29, 15 July 2012 (UTC)

What color skin did the earliest humans have? arbitrary break 1

The Washington Post article cited for that claim basically backs up what StuRat said in the beginning about the vitamin D (but just makes hints about black skin being a defense from the sun). It also mentions potential sexual selection, so maybe there's not really a consensus on that part of the issue. 203.27.72.5 (talk) 04:35, 15 July 2012 (UTC)

Nautrally brown and blond hair also occurs among Melanesians and some Australian aborigines (though the allele responsible is different to that of Europeans). And both groups as well as the now mostly extinct Ainu are among the hairiest of the human populations. Same with epicanthic folds which actually also exist natively in Scandinavian, Northern Slavic, and Celtic Europeans as well as Khoisan-speakers of Africa. Nasal bridges vary considerably as well, being predominantly low in East Asians but high in most Native Americans, despite being descendants of the latter. And neanderthals were about as phenotypically varied as modern humans in terms of hair color at least.-- OBSIDIAN†SOUL 07:20, 15 July 2012 (UTC)

I'd like to see a ref that aborigines can have naturally blonde hair. I really can't imagine that. 203.27.72.5 (talk) 07:55, 15 July 2012 (UTC)

Picture of a Vanuatu Melanesian kid at right. And here's an Indigenous Australian young man with reddish blond hair and a kid with brown hair. Plenty more pictures on the net if you want. And here's an online article by Canadian anthropologist Peter Frost which mentions it: "Why Do Europeans Have So Many Hair and Eye Colors?" (note: Frost is the most famous proponent of the sexual selection origin of modern human phenotypes mentioned by Snow earlier); and one study: Abbie & Adey (1953). "Pigmentation in a central Australian tribe with special reference to fair-headedness". American Journal of Physical Anthropology. 13, 3:339–360. -- OBSIDIAN†SOUL 12:02, 15 July 2012 (UTC)

As a (white) Australian who has thru work met a large number of aborigines, I'm very skeptical of this. Meeting a full blood aboriginal with blond hair has not happened. The photo Obsidian posted is of Rowan McNamarra, a noted Australian child actor. In the movie Sampson & Delila, he appeared with blond hair, and in all movie promotional photos and movie associated pics he has blond hair. But in other photos he appears to have black or dark brown hair. Its worth noting that the film was about folk living with no hope. It is very common for such people to be mixed race. Full bloods tend to have more pride and self-worth - it may be that the film people had his hair dyed for that reason - the film, light on dialog as the character portrayed by Rowan is severely brain damaged from gasoline sniffing, is full of visual cues and symbology probably completely lost on non-Australians, and mostly lost on Australian white audiences. The text is a very old text. In my State, Western Australia, there is a group originating from the Carnarvon area amomgst whom blond hair is very common, and their facial appearance is a little different to other aboriginal groups. It was only recently (~20 years ago as I recall) that it was proved that a Dutch ship was wrecked on the coast about 300 years before white settlement, and surviving sailors were accepted by the locals and intermarried. That's where the blond hair came from. Samson & Delila, a low budget film acted, directed, and produced almost entirely by aboriginals was an absolutely excellent film by the way. Wickwack124.178.177.175 (talk) 13:17, 15 July 2012 (UTC)

Stick my IP into a geolocate site and see why I'm so sceptical of this. I'm in the middle of nowhere in the NT, I work with the indigenous here on a daily basis and I've never seen nor heard of anything like this. I won't rule out that one individual tribe in central Australia has a blonde trait, but it must be very rare. W203.27.72.5 (talk) 22:38, 15 July 2012 (UTC)

Do click the links. Like mentioned below, take a look at the frequency map of the blond hair trait. The areas where it is near universal in occurrence is in central (eastern) Western Australia, gradually tapering off to the coasts of the state. The northern areas of Western Australia and NT are excluded (0% occurrence). Also note that it's a sexually dimorphic and paedomorphic trait, i.e. it's more prevalent among women and children and will usually darken after puberty (again like European blonds as mentioned below). Besides the only other explanations really is that either the pictures are a massive photoshop conspiracy, several scientists have somehow confused Australia with Austria, or hair bleaching has just become a massive fad among Australian Aborigines of all ages. :P -- OBSIDIAN†SOUL 23:29, 15 July 2012 (UTC)

Just to clarify, I did click the links. The paper about an Aboriginal tribe that had blondism is convincing. That's why I said I won't rule out that there is one tribe like that. But it's not wide spread in the NT which is in agreement with your map. Also, Alice Springs is in the NT, so if there is a tribe near there with blondism, then there can't be 0% occurrence in the NT. And there is a bit of a fad for younger aborigines of both genders to bleach their hair (it's not restricted to them either), which I think is more likely the origin of some photos of young, blond indigenous Australians. W203.27.72.5 (talk) 02:19, 16 July 2012 (UTC)

It's a study, not anecdotes. Take that in consideration. The study records blondism in central Australian Aborigines, notably among the Warlpiri around Alice Springs (AFAIK, Rowan McNamara is Warlpiri. the movie itself was about them). As an Australian I think you already know too that hair color in Australian Aborigines darken with age, and the same is true even in Europeans where most blond-haired children grow up to be brown-haired adults. And lastly, see this map of its frequency among Australian Aborigines, and note that it's less common the nearer you are to the coast.

The Carnarvon shipwreck story is also actually quite old, not 20 years ago. Though the wrecks of Batavia, Zuytdorp, and Vergulde Draeck were indeed only found in the mid-20th century, they have long been known to have sunk there. It was already a folk explanation for the occurence of blond or light-skinned Aborigines even in the 19th century in Western Australia. While intermarriage between natives and survivors is indeed quite plausible (though AFAIK, no DNA tests have proven this yet as of 2012), that does not mean that it's the cause of blondism, as it's also present elsewhere where there are no wrecked European ships, much less shipwrecked Europeans.

The Melanesians are the closest genetically to Australian Aborigines. As mentioned, the blond hair common in some Melanesian groups has been genetically proven to be native and to be caused by a different mechanism than in European blondism.

And I'm curious, why is it so hard to accept that blond hair is not exclusive to Europeans? Claims of European admixture as a reason for European features in natives (and vice versa, e.g Scandinavian epicanthic folds, most famously Björk's) based on hearsay accounts of shipwrecks or early intermarriages lost to history is common but unless substantiated by genetic studies, most if not all of it, is bullshit. Those kinds of explanations were very prevalent in the years of scientific racism (late 19th to early 20th century, pre-Hitler). Similar shipwreck stories were also used to explain some light-haired and blue/gray-eyed Mandan of North Dakota and "Blond Eskimos" in the same time period. And their existence has been used to "prove" everything from Greenlandic Viking settlers (despite the "Blond Eskimos" actually being in western Canada) to the Mormon lost tribes simply because Europeans colonists could not accept that such traits may be present in other human populations. It has since been genetically proven in 2003 that the fair-haired Kitlinermiut individuals are not descendants of early Viking explorers of Greenland.-- OBSIDIAN†SOUL 15:44, 15 July 2012 (UTC)

Yes, I was already aware. I myself first had blond hair, according to my parents, but it was dark brown by the time of the oldest photo of myself I have - age 3. I can recall being shown an aboriginal baby by its proud parents - she had light coloured hair. They told me they fully expected it to darken.

You are quite correct - the story is old. As I recall, Carnarvon area aborigines have always told whowever would listen that they had a partly white ancestry - but nobody of academic significance listened. I don't know about modern DNA test specifically, but it was proved about 20 years ago as follows: It happens that they have an inherited blood disease extremely rare elsewhere - in fact for a long time they were the only group in teh world known to have it. The disease isn't of much consequence for most of their life, as I understand, but does shorten their life a bit. A doctor researching it became aware, or already knew, of a closely similar disease confined to the descendents of a particular africaaner family in South Africa. Blood samples were obtained from SA and it turned out the disease was identical. Dutch ship crew records were then checked and it was found that a ship called at South Africa and took on some africaaners from that same family as repalcement crew. The ship was wrecked on the Carnarvon coast. For those who are unaware, Africaaners are people resident in South Africa since the 16th century, descended from Dutch pioneers. Wickwack58.170.163.160 (talk) 16:32, 15 July 2012 (UTC)

I'm guessing you meant the occurrence of variegate porphyria (common in Afrikaners) and Ellis-van Creveld syndrome (most notably documented among the Amish who were from Holland) in Western Australian Aborigines. The conclusions of both studies were actually negative. The three (possibly four) cases of variegate porphyria documented in Aborigines (out of six documented cases overall in Australia in the span of 20 years) were the result of different mutations from the South African one. And the Ellis-van Creveld syndrome is not exclusive to the Dutch, but is common in founder populations (particularly small groups of humans with little to no contact with other populations for long periods of time). See [6] and [7] for the actual studies.-- OBSIDIAN†SOUL 17:09, 15 July 2012 (UTC)

P.S. Please don't split your posts. :P It makes it confusing to determine who wrote what. -- OBSIDIAN†SOUL 17:11, 15 July 2012 (UTC)

What parts have been split up? I don't want to mix up who wrote what. Thanks. InforManiac (talk) 19:48, 15 July 2012 (UTC)

Sorry that was meant for 120.145.151.40. Disregard it. -- OBSIDIAN†SOUL 23:29, 15 July 2012 (UTC)

H'mmm... Your references support your statements, but as I recall, they traced it to a specific SA family - the newspaper article gave the Afikaner names. It could be that it was a different disease, or it could be that the researcher who gave the conclusion I reported simply got it wrong. Wickwack120.145.151.40 (talk) 18:06, 15 July 2012 (UTC)

I think they were actually simply reporting that Western Australian Aborigines seem to share two relatively rare genetic diseases that were also prevalent in other Dutch-descended populations. And they are quite correct in that. It was that connection, after all, that prompted the latter two studies which eventually proved that it was incorrect. Kind of a false positive in other words - seemingly damning evidence at first glance, but falls apart at closer inspection. Happens a lot in scientific hypotheses actually. -- OBSIDIAN†SOUL 18:23, 15 July 2012 (UTC)

Yes, especially in the medical field. Wickwack120.145.134.211 (talk) 02:34, 16 July 2012 (UTC)

@StuRat, Arctic dwelling people, Inuit and Eskimo are not light skinned. For the most part they are slightly darker than the average European. In the spring, for obvious reasons, the face and arms, if exposed, tend to get very dark. CambridgeBayWeather (talk) 12:10, 15 July 2012 (UTC)

They look rather light-skinned to me: [8], [9], [10]. However, if darker skinned, than, say, Nordic people, that might be explained by them having relatively recently migrated from more Southern portions of Asia. StuRat (talk) 19:57, 15 July 2012 (UTC)

The source you provide is wrong, StuRat. The ancestors of the Eskaleuts are ultimately derived from the Lake Baikal area. See Michael Fortescue's Language Relations Across the Bering Strait. They traditionally got their full compliment of vitamins A and D from fish oil and raw sea-mammal liver. μηδείς (talk) 21:34, 15 July 2012 (UTC)

And where did those in the Lake Baikal region come from ? Eventually they must have had ancestors from a more southerly climate, it's just a question of if it's far enough back to have allowed for major changes in skin color since then. StuRat (talk) 21:45, 15 July 2012 (UTC)

By your 'reasoning' here, StuRat, the fact that Eskimos evolved from reptiles far enough back explains why they are green. But you seem to have inadvertently omitted your source. μηδείς (talk) 21:58, 15 July 2012 (UTC)

Even you must realize that a few hundred million years is long enough for skin color to change, while a few thousand might not be. StuRat (talk) 02:39, 16 July 2012 (UTC)

Actually mammals did not evolve from reptiles, they evolved from therapsids. Eskimos and Inuit don't have dark skin, I suppose they have darker skin than individuals from say, Norway. I can't tell if they have skin darker than people whose ancestry is from China though. ScienceApe (talk) 22:26, 15 July 2012 (UTC)

Saying mammals evolved from therapsids, not modern reptiles is, of course, the usual gotchalism you will find on the ref desk. But therapsids have long been characterized as reptiles, it depends on how you wish to define the term, and you are quite aware of the point being made. These are the synapsids you say are not reptiles:

Synapsida	†Caseasauria Eupelycosauria †Varanopidae †Ophiacodontidae †Edaphosauridae Sphenacodontia †Sphenacodontidae Therapsida †Biarmosuchia Eutherapsida †Dinocephalia Neotherapsida †Anomodontia Theriodontia †Gorgonopsia Eutheriodontia †Therocephalia Cynodontia † Cynognathia Probainognathia Mammaliaformes Mammalia

As for the Eskaleuts, there is no evidence whatsoever that they evolved from South Asians, if you define that as India, China, and the land between. Here is a comment from an actual source:

He had brown eyes, dark skin, thick blackish hair and type A blood.

This eskimo, who lived about 4000 years ago in Greenland, also had dry earwax, shovel-like front teeth, an increased risk of going bald and the metabolism of a person who could survive in a cold climate.

And his ancestors were, to the surprise of scientists, ancient people in east Siberia rather than neighbouring Native Americans or Inuits.

All this detailed information about the long dead man has come from a study of a small clump of his hair, preserved for thousands of years in the Arctic permafrost.

Given the name Inuk, he will go down in history as the first ancient person to have had his full DNA code, or genome, sequenced. http://au.news.yahoo.com/thewest/a/-/world/6788814/genetic-time-machine-unmasks-eskimo-dna/

μηδείς (talk) 23:11, 15 July 2012 (UTC)

And posting massive charts to further a debate about whether mammals evolved from therapsids or reptiles in response to a question about human skin colour is of course the usual of off-topic grandstanding that is frequently found here too. W203.27.72.5 (talk) 01:19, 16 July 2012 (UTC)

I never actually said they were dark skinned, except in the spring of course, but that they were slightly darker as can be seen in the following. File:Inuk 1995-06-13.jpg, File:Inuit Amautiq 1995-06-15.jpg, File:Inuit Family 1995-06-15.jpg, File:Seal Hunter 1995-06-11.jpg, File:Greenland kayak seal hunter 2006.jpg CambridgeBayWeather (talk) 01:16, 16 July 2012 (UTC)