Wikipedia:Reference desk/Archives/Science/2017 March 9

= March 9 =

How did Mammuthus spp. die out but Homo sapiens survive?
During the last Ice Age, how did Homo sapiens survive? Shouldn't Homo sapiens be extinct too because of climate change that killed the food supply? 166.216.159.20 (talk) 03:20, 9 March 2017 (UTC)


 * Your question is based on a false premise - the scientific community has not agreed on a cause for the extinction of mammoths, see Mammoth. Climate change is suspected to be a major component, but not the sole cause. Even if we did assume food supply as a cause, the human diet is much broader than the Mammoth diet, as you're comparing an omnivore to an herbivore. Someguy1221 (talk) 03:33, 9 March 2017 (UTC)


 * Wikipedia has an article on said extinctions of megafauna. See Quaternary extinction event.  As noted by Someguy, you'll not find a "here's what we know caused it" type answer, but rather "here's a half-dozen possible things that caused it, and some or all of these may have contributed to some degree".  -- Jayron 32 03:40, 9 March 2017 (UTC)
 * The distinction between omnivores and herbivores raises another issue that would've contributed to mammoth extinction while helping humans survive. Ian.thomson (talk) 03:47, 9 March 2017 (UTC)
 * Indeed. In simple terms, humans could eat mammoths but mammoths couldn't eat humans. Gandalf61 (talk) 09:03, 9 March 2017 (UTC)
 * Isn't it true in more than one way -- i.e. that overhunting by cavemen contributed to the mammoths' extinction? 2601:646:8E01:7E0B:9031:2E93:E491:EE2 (talk) 10:58, 9 March 2017 (UTC)
 * Do any of you have some reading on any of this, or are we just making it up as we go along? -- Jayron 32 11:24, 9 March 2017 (UTC)
 * "Mammoths were herbivores so were very dependent on gaining all the nutrients they needed to survive from the plants that they ate... a poor habitat as a result of climate change, combined with increased contact and hunting by humans as they increasingly entered their areas of habitat led to their eventual extinction" Why Did The Wooly Mammoth Die Out, National Geographic. Gandalf61 (talk) 21:49, 9 March 2017 (UTC)
 * Additionally to what others have said, the extinction of one species, even in the course of a mass extinction event, does not mean that all other species must go extinct. If it did, life itself would not have survived the Cretaceous–Paleogene extinction event that killed the non-avian dinosaurs, or the many other extinction events over time. Life, of course, has survived mass extinction events. Some species survive, others fail, for reasons of natural selection and fitness to their changing environment or flexibility to adapt to it. --OuroborosCobra (talk) 15:58, 9 March 2017 (UTC)
 * Moreover, humans have an obvious adaptibility advantage, other than being able to vary the diet and to more efficiently disperse heat. Intelligence, allowing to pass knowledge from generation to the next through culture, map and mark territory, invent and build tools and traps, create or adapt shelters, create and wear clothing, use fire, carry water, manage resources, establish concurrent social roles (infant protection and raising vs education vs hunting and fighting) etc.  PaleoNeonate (talk) 18:20, 9 March 2017 (UTC)
 * I forgot to mention it, but an important factor for survival is also the metabolic rate; despite our energy-hungry brain, humans do not have to actively feed all-day to meet its nutritional requirements. PaleoNeonate (talk) 18:27, 9 March 2017 (UTC)

I'd like to speak to the premise of the question (I don't think there's an agreed upon answer for the actual question beyond the fact that humans were clearly more in charge of their environment than other animals at that point - fire is a great ally). Mammoths and mastodons (and others) went extinct and a handful of elephant species survived to modern times. Erectus and Neanderthalensis (and others) went extinct and Homo sapiens survived to modern times. Both families seem to have enduring the same kind of 'pruning', but you're comparing apples and oranges, so to speak, and wondering why they're different. Mammoths and humans occupied very different ecological niches and habitats so comparing them is always going to be problematic. A better question is to compare within a niche or clade or geographical area and examine differential survival rates. Incidentally, humans and elephants are by no means unique in this regard. Old school attempts to force evolutionary history into a straight line obscures that - and leads people to make the same kind of error the OP did. Rather unfortunately, our lead pic in evolution of the horse makes the same mistake, though the caption at least attempts to address the issue. Matt Deres (talk) 19:37, 9 March 2017 (UTC)

See here: "Woolly mammoths (Mammuthus primigenius) populated Siberia, Beringia, and North America during the Pleistocene and early Holocene. Recent breakthroughs in ancient DNA sequencing have allowed for complete genome sequencing for two specimens of woolly mammoths (Palkopoulou et al. 2015). One mammoth specimen is from a mainland population 45,000 years ago when mammoths were plentiful. The second, a 4300 yr old specimen, is derived from an isolated population on Wrangel island where mammoths subsisted with small effective population size more than 43-fold lower than previous populations. These extreme differences in effective population size offer a rare opportunity to test nearly neutral models of genome architecture evolution within a single species. Using these previously published mammoth sequences, we identify deletions, retrogenes, and non-functionalizing point mutations. In the Wrangel island mammoth, we identify a greater number of deletions, a larger proportion of deletions affecting gene sequences, a greater number of candidate retrogenes, and an increased number of premature stop codons. This accumulation of detrimental mutations is consistent with genomic meltdown in response to low effective population sizes in the dwindling mammoth population on Wrangel island. In addition, we observe high rates of loss of olfactory receptors and urinary proteins, either because these loci are non-essential or because they were favored by divergent selective pressures in island environments. Finally, at the locus of FOXQ1 we observe two independent loss-of-function mutations, which would confer a satin coat phenotype in this island woolly mammoth." Count Iblis (talk) 20:11, 9 March 2017 (UTC)


 * Mammoths aren't extinct. They are just waiting for us to clone them back into existence. :-) StuRat (talk) 21:49, 10 March 2017 (UTC)

Feeding boogers to tropical fish
I must ask, is it okay for children to regularly feed boogers to a tank of tropical fish? Anna Frodesiak (talk) 12:51, 9 March 2017 (UTC)

See also:

Anna Frodesiak (talk) 12:53, 9 March 2017 (UTC)
 * There is nothing here I'd call a reliable source, but the question has been asked before on some forums, and there are some answers you can go with. I'd be shocked if a scholarly journal ever addressed the issue, beyond the Annals of Improbable Research.  -- Jayron 32 14:51, 9 March 2017 (UTC)


 * Way back in the commit-log, I think I was an early contributor to the Wikipedia article on benthic macrofauna detritivores... that's a lot of pseudolatin scientific mumbo-jumbo for fishy-things that eat booger-y things. Gross!
 * There is an entire area of biological and ecological research about organisms that live under water and eat detritus that falls from above. It's yucky, but it's scientifically interesting from an ecological perspective, and even from a standpoint of pure thermodynamics.  Ecologies based entirely on detritus have even been featured in documentaries including BBC's Planet Earth.  We surface-dwellers don't often notice it, but our waste-organic-matter is something else's food - for example, whale falls spawn entire civilizations of organisms!  It's a great reminder that our planet's biotic zone is a lot larger than the two-meter-wide, almost-spherical shell that we humans are familiar with.  It's also great perspective: entire species evolve to survive by feeding on some more important organism's rotted garbage.  You've landed a truly opportune teaching moment for the youth of today!
 * I'm not sure if any research specifically calls out boogers - let alone fish in captivity - but surely one of our avid enthusiasts can be tasked to looking into the topic. If you use the scientific terms "detritus" and "detritivore," you'll probably find better results than searching the web for fish-boogers at large.
 * Seasonally varying impact of detritivorous fishes on the benthic ecology of a tropical floodplain river (2017) ....
 * Growth response of a benthic detritivore to organic matter composition in sediments (2002) ....
 * Nimur (talk) 17:47, 9 March 2017 (UTC)
 * Wikipedia offers a word for fish eating mucus ("mucophagy") and an article on humans eating nasal mucus (boogers). The main concerns are more about a child possibly damaging its nasal septum or social disapproval of its habit than about the health of the fish. Blooteuth (talk) 19:06, 9 March 2017 (UTC)
 * Thank you, Blooteuth. Anna Frodesiak (talk) 01:46, 10 March 2017 (UTC)
 * Hi Nimur. Thank you for the thoughtful reply. Gross, but thoughtful. :) Anna Frodesiak (talk) 01:46, 10 March 2017 (UTC)
 * Hi Jayron32. I'm afraid I can't access google where I am. I see nothing at Bing, but will look harder. Best, Anna Frodesiak (talk) 01:46, 10 March 2017 (UTC)

I was really think about whether or not the fish will be harmed, nourished, or what. I hate to say this but the fish really seem to like them and fight over them. Folks here think it's terribly funny. But it's not going to kill the fish, is it? I'm quite fond of them and fear that boogers may contain some sort of bad ingredients. They are, after all, waste, right? Anna Frodesiak (talk) 01:46, 10 March 2017 (UTC)


 * No, it's not really waste - we consume about a liter of it every day by recycling it (see mucus, which also mentions that it's rich in glycoproteins, among other nutrients). And even if it was waste, that doesn't mean that it would necessarily be bad for the fish. At this point, I'm going to invoke our medical disclaimer, though. All the editors on Wikipedia are actually dogs and are therefore unfit to provide veterinary advice. You're obviously concerned about this; my advice to you is to get advice from someone qualified to dispense it. Matt Deres (talk) 03:11, 10 March 2017 (UTC)
 * Matt Deres, thank you. Okay, if we consume it, it can't be too terrible. I will not consider any of the above "medical advice", and since there is nobody around here who knows, I'll let it continue and take a chance. Heck, it can't be worse than those dreadful fish food flakes. They seem to encourage disease, and definitely make the water yellow. Suspicious that the same company sells products to get rid of yellow water and fish diseases. Best, Anna Frodesiak (talk) 03:38, 10 March 2017 (UTC)

Cattle population historical chart
Does anyone know where I can find a chart of the cattle population in the world since domestication, showing how it has increased (and possibly sometimes, reduced) from century to century? --Lgriot (talk) 13:56, 9 March 2017 (UTC)


 * I don't think the Romans kept track of their cattle. A few latest years are here. --AboutFace 22 (talk) 21:40, 9 March 2017 (UTC)
 * Any approximation would be fine, I don't need the numbers from a statistical government department, just any historian's / archeologue's / biologist's estimate would do. --Lgriot (talk) 16:18, 10 March 2017 (UTC)
 * Might be possible to estimate through atmospheric methane, if the other major sources could be corrected. Probably not possible post-industrial revolution by this method. Klbrain (talk) 00:53, 12 March 2017 (UTC)
 * That is an interesting idea, although it will also include other natural sources of methane production than cattle (Methanogenesis) and even possibly methane of non-organic origin when going far back enough (abiotic methane, Abiogenic_petroleum_origin). PaleoNeonate (talk) 05:05, 12 March 2017 (UTC)

Press and hold to turn on electronic device
A friend is building some type of battery-powered electronic device and has asked me general questions about breadboarding. Having got the device to work, he would like to add a pushbutton which would require a long press (say 2 seconds) to turn on the device. I've see smart phones and meters with such a feature: presumably there is a very low-current-draw circuit which monitors the on switch, the powers up the main device(perhaps with a small microcomputer in it) which has a much higher current draw. This would prevent accidental turn-on and provide longer battery life than if the device were always at high current draw but muted. Any suggestions as to where to find coverage of this? Edison (talk) 19:50, 9 March 2017 (UTC)


 * Without a CPU the way I think your friend can do it is simply with a circuit where by a capacitor can be charged until it switches on a transistor which activates the device. The time delay being the value of the resistor between the power rail (connected by depressing the switch) and the capacitor value. Not being able to see the circuit diagram can't advise any better. Yes, it is doable very simply.--Aspro (talk) 20:14, 9 March 2017 (UTC)


 * You can email me the circuit diagram if you like (as I only charge $90 an hour consultancy fees). Yet, from this your friend can grasp the basic principle and adapt it.--Aspro (talk) 20:25, 9 March 2017 (UTC)


 * Search for "delay timer circuit" - for example this one. Gandalf61 (talk) 21:37, 9 March 2017 (UTC)


 * Yep. That ticks the box. Note: it shows an electrolytic capacitor and so did my example. This is a must.--Aspro (talk) 23:14, 9 March 2017 (UTC)

Are humans really grass eaters?
By grass, I mean members of the Poaceae family - rice, wheat, maize, and rye. Those are also staple food, which means they compose the majority of the diet because of high energy density. Does that mean that humans in temperate climates are primarily herbivorous omnivores, eating mostly various types of grass as a staple food? 66.213.29.17 (talk) 20:35, 9 March 2017 (UTC)
 * Most of us don't eat grass, we eat the grain or its products. ←Baseball Bugs What's up, Doc? carrots→ 21:13, 9 March 2017 (UTC)
 * See staple food. A staple food is that from which a population gets the most of its food energy (calories).  And the biggest staples are either grains or root vegetables, depending on the climate.  Of the top ten staples, #1, 2, 3, and 9 are grains, #4, 7, and 8 are roots, 6 is a legume, and 10 is a fruit.  Cereal grains are all botanically grasses.  -- Jayron 32 21:25, 9 March 2017 (UTC)
 * There is a trick in the nomenclature here. When you use the term 'grass eater', it strongly implies the eating of the plant itself (i.e. graminivore) rather than just a particular part (i.e. granivore). Humans by and large do not 'eat grass' in that sense; we would get very little nutrient from the indigestible fibre the grass leaves are composed of. It would be like asking 'Are humans really tree eaters?' because apples are popular. Grass eating men is something very very different. Matt Deres (talk) 22:33, 9 March 2017 (UTC)
 * Indeed, and our teeth are not adapted for large scale or long term grass eating (compare to File:Crâne_cheval.jpg for instance). PaleoNeonate (talk) 23:20, 9 March 2017 (UTC)
 * Sugar is usually made from grass: sugar cane in many places or corn in USA. Graeme Bartlett (talk) 12:29, 10 March 2017 (UTC)
 * ... or Sugar beet.   D b f i r s   14:25, 10 March 2017 (UTC)
 * That is not a grass though! It accounts for 20% of world production. So grass has 80% share. Graeme Bartlett (talk) 05:56, 11 March 2017 (UTC)
 * See edibles. --Trovatore (talk) 21:01, 12 March 2017 (UTC)

Quorn question
According to this per 100g it has 2g of fat, 0.5g of saturates, 4.5g of carbs, 0.6g of sugar, 5.5g of fibre, 0.3g of salt, and 14.5g of protein. That's only 27.9g. What is the remaining 72.1g made of? — Preceding unsigned comment added by 177.2.64.216 (talk) 20:38, 9 March 2017 (UTC)


 * Water.--Aspro (talk) 21:05, 9 March 2017 (UTC)
 * Yes -- in case a ref is needed, this site shows water content of various mushrooms, which are in the same ballpark. HenryFlower 21:08, 9 March 2017 (UTC)


 * Rather eat any of those various mushrooms than quorn, which I find horrid -even if it is cheap. --Aspro (talk) 21:37, 9 March 2017 (UTC)

For those who, like me, had no idea what Quorn was, here's a convenience link. --Trovatore (talk) 09:08, 10 March 2017 (UTC)
 * Thank you. Judging by the header (before I read the question), I figured it was an SA question, since I've only ever encountered "Quorn" in the Rain follows the plow article.  Nyttend (talk) 05:32, 11 March 2017 (UTC)

Trickshots
Due to some impossible physics (particularly at 2:06, 2:11, 2:15 and 2:38) are those some kind of remotely guided balls? Sifting thru comments, trickshot and google was not particularly helpful. Brandmeistertalk  21:38, 9 March 2017 (UTC)


 * Those are most likely real and for certain possible.--TMCk (talk) 21:50, 9 March 2017 (UTC)


 * I see nothing to indicate those are impossible physics. See Glossary of cue sports terms.  Enough practice and those shots can be made by anyone.  -- Jayron 32 21:53, 9 March 2017 (UTC)
 * Glossary of cue sports terms is also relevant. PrimeHunter (talk) 00:05, 10 March 2017 (UTC)
 * Yes, they all look natural, (if very, very difficult) to me. (I watch a lot of snooker, though with my eyesight I can no longer play.) You may notice that the demonstrator is using a white ball with spots, so that you can see the imparted spin which causes the arcing trajectories, reversals etc. Bear in mind that for each shot you're only seeing the take where it worked, not the possibly dozens of takes where it didn't. {The poster formerly known as 87.81.230.195} 90.202.209.145 (talk) 22:38, 9 March 2017 (UTC)