Wikipedia:Reference desk/Archives/Science/2017 February 24

= February 24 =

Blood meal
The blood meal article says that the substance is useful for repelling garden pests such as rabbits. How does that work? Using Google, I found nothing more scholarly than http://creekbed.org/bandh/pest.html, which claims that rabbits smell the blood and are repelled by its scent. Nyttend (talk) 01:01, 24 February 2017 (UTC)


 * Right, I also find lots of ads and patents, but not much in the way of true scientific discourse. I did ultimately find this review of animal repellent studies, which includes a couple of studies that found "intermediate effectiveness" for blood meal as a deer repellent. Someguy1221 (talk) 01:16, 24 February 2017 (UTC)


 * One possible mechanism would be if the smell of blood indicates the possible presence of a predator nearby, and those prey animals which avoid such areas are more likely to survive and pass on those genes. StuRat (talk) 05:59, 24 February 2017 (UTC)


 * Let me let you in on a secret. I don't have any references right now. I'm also not sure what the mechanism is. I don't know the answer, but I'm a smart person, and I have some ideas. But I'm not going to post anything. Let me do a little work, and I'll be back when I have references to share. SemanticMantis (talk) 20:35, 24 February 2017 (UTC)
 * Ok, I'm back. I searched google scholar, starting with /"blood meal" pest deterrent/. That search wasn't all that useful, because "blood meal" is also what they call it when a mosquito or bedbug gets a meal of blood, and there is tons of research on that stuff that has nothing to do with vertebrate pest repellent. So I though maybe putting a vertebrate in would help, and also maybe "pest". Take out the quotes on blood meal since that means a thing I don't want. So I searched /blood pest deter deer/, which led me to three very good references, which together will give OP access to a lot of real scientific findings about if and how this works. SemanticMantis (talk) 20:49, 24 February 2017 (UTC)
 * And now I've skimmed the articles, pulled out some quotes, and added a few wikilinks. The post below has a few key features:1) it took me more than thirty seconds to do. In fact it probably took me at least twenty minutes, not counting this explanatory text and some other things I was up to in the intervening interval. 2) it contains relevant references both external reliable sources, and also to wikipedia. 3) It gives OP plenty of directions to go if they want to learn more 4) I offer no opinions.
 * Now, I'm not saying that you or anyone else has to do all this. In fact, nobody has to post here at all. However, I hope that by explaining my process, people can learn how to provide helpful and well-referenced responses here, because that is what this desk is for. While posting of opinions and memories and hazy recollections and possibilities and the-way-that-one-guy-thinks-things-work are all very different, all well-referenced posts here are ultimately very similar, in that they share the four traits that I outlined above. SemanticMantis (talk) 21:13, 24 February 2017 (UTC)


 * Here is a freely accessible comparative study, from 2010 . It says "While urine  and  blood-based  repellents  were  somewhat  effective in short-term pen studies, they were less effective in field  studies." So maybe not the best stuff, but blood does have some beneficial effect against deer.
 * For mechanism, this study tested "Four repellents representing different modes of action (neophobia, irritation, conditioned aversion, and flavor modification)". The experimental "data support previous studies indicating that habituation to odor limits the effectiveness of repellents that are not applied directly to food, while topically-applied irritants and animal-based products produce significant avoidance. The paper discusses mechanisms in several places, with additional references. Finally, this short work is all about the concepts of how vertebrate repellents work, and is definitely worth a read: Vertebrate repellents: mechanisms, practical applications, possibilities. . SemanticMantis (talk) 21:03, 24 February 2017 (UTC)

How much vitamin b12 fortified foods must be eaten as a replacement for animal products?
Drinking fortified plant milk at every meal? How long can a human live healthfully without them? 107.77.194.188 (talk) 16:50, 24 February 2017 (UTC)


 * US RDA of B12 for non-lactating non-pregnant adults is 2.4 micrograms per day. The German RDA is 3 micrograms per day. You would need to look at how much B12 there is in a serving of the milk you're drinking, and calculate accordingly.    Vegans suggest that 3 servings of fortified foods per day usually gets you the RDA. - Nunh-huh 17:21, 24 February 2017 (UTC)
 * Or, the simple solution is to just take a B12 supplement. As our article on Vitamin B12 discusses, it's impossible to give a one-size-fits-all answer to "How long can a human live healthfully without them?", because the body can store a good deal of B12, so it depends on diet, genetics, history, etc. Obviously, if you have or suspect you have a B12 deficiency, consult a medical professional; deficiency can be caused by things other than lack of B12 in the diet, in which case oral supplementation often won't do anything to treat the deficiency. --47.138.163.230 (talk) 21:35, 24 February 2017 (UTC)


 * It's a matter of current research (i.e. no-one really knows) how important B12 is, and how frequently it needs to be administered. If you suffer from chronic fatigue, linked to a B12 deficiency, then you're likely to be prescribed a dietary supplement and if that doesn't have an effect, intramuscular B12 injections. Then opinions vary: there is some indication that some people (likely those suffering from the chronic fatigue) are unable to absorb B12 at the normal rate (and so the standard RDAs are too low for them) even if they're ostensibly getting an "adequate" supply. Also conventional models suggest intramuscular B12 at intervals of months, whereas those reporting the fatigue see a boost and tail off on a cycle of weeks, suggesting that more frequent doses are needed.
 * In general, B12 is available in a good diet in such quantities, and is only needed at such a low level, that there isn't a problem. But when there is a problem, this has been explained previously as a dietary shortage when there is now indication that it's also (and particularly so for the chronic fatigue cases) at least as much a metabolic issue of utilising what the diet does provide.
 * B12 is an obvious issue for vegans, and one of the very few real dietary issues for a decent Western vegan diet. Yet some doctors, particularly in the US, see this choice as tantamount to asking for poor health and will simply fail to engage with vegans, or tell them outright that a vegan diet is an inevitable cause of weakness and imminent death. The Vegan Society is a bit more balanced. https://www.vegansociety.com/resources/nutrition-and-health/vitamins-minerals-and-nutrients/vitamin-b12-your-key-facts/what-every-vegan-should-know-about-vitamin-b12  Andy Dingley (talk) 16:10, 25 February 2017 (UTC)

Why is human intention regarded as unnatural?
Natural selection is a different concept from artificial selection. Why are "natural" perceived as good, while unnatural is not good? Why are human culture and technology regarded as artificial while chimpanzee culture and technology are natural? Are the tools made by Homo erectus also artificial? Since everything made by humans stems from the human brain, and the brain is natural, shouldn't everything "artificial" or "synthetic" be natural? 107.77.192.233 (talk) 23:28, 24 February 2017 (UTC)


 * Venn A subset B.svg


 * One possible way to resolve the dilemma is if artificial selection is viewed as a proper subset of natural selection. In other words, whatever people do is both natural and artificial.  As to why they are normally considered to be mutually exclusive, remember that it's only quite recently (in terms of language development) that the Theory of Evolution was proposed, and it still is far from globally accepted. StuRat (talk) 23:39, 24 February 2017 (UTC)


 * It took natural selection 4 billion years to make humans. It took only 0.005 billion years for humans to surpass the natural record in many things like creature power, speed, game complexity, cause the Sixth Mass Extinction, almost cause a worse one (nuclear winter), terraform much of the surface and maybe disassemble most of the observable universe with grey goo (though they could only dismantle the galaxy by 0.0001 billion years AD due to the speed of light) Sagittarian Milky Way (talk) 00:08, 25 February 2017 (UTC)


 * Yes, technically speaking, everything humans do is part of nature, though we tend to set ourselves apart from the rest of the natural world for various reasons (nature is something to be conquered, humans are exceptional beings, etc.). There's a lot of discussion about why that is. Here's some further reading:, , . See also environmental philosophy. clpo13(talk) 00:12, 25 February 2017 (UTC)


 * (ec, or then again, someone here might just come through! Thanks Clpo13, looks interesting!)  This seems like a very important but very difficult philosophical question.  To some extent I would suspect it is cosmetic, but rooted in the tendency of life to optimize to a situation.  A barren volcanic flow or a meteor impact seems less "natural" than a jungle.  But to a large extent it might depend on the nature of free will itself, and its ability to create genuinely new things.  It might depend more simply on the ability of cognition to recognize and favor novelty, but I'm skeptical that's the full explanation.  You might have better luck (like properly referenced answers) on the Humanities desk, because this is the sort of thing Mephistopheles would say is not of his kingdom.  You need something past science, I think. Wnt (talk) 00:19, 25 February 2017 (UTC)


 * "Natural" does not inherently equate to "good". ←Baseball Bugs What's up, Doc? carrots→ 00:32, 25 February 2017 (UTC)


 * All-natural lava. Yummy! Sagittarian Milky Way (talk) 01:17, 25 February 2017 (UTC)


 * "Nature" in this context is a philosophical concept, it's an idea dreamed up by men. And "Nature" as used philosophically has several meanings. One of them is the inherent or defining properties of a thing. A thing (other than man) has inherent or defining properties not dependent on human action, so if one wants to know the "nature" of a thing one is necessarily studying that thing in the absence of human intervention. - Nunh-huh 01:31, 25 February 2017 (UTC)
 * Nature is neither good nor bad, it just is what it is. Woody Allen once described nature as "basically a gigantic restaurant." ←Baseball Bugs What's up, Doc? carrots→ 02:05, 25 February 2017 (UTC)


 * This is related to the fact that people don't see themselves as biological machines subject to the laws of physics, many people are skeptical that machines could ever have human level intelligence. These feelings are not based on reality, but we do feel as if we're not part of Nature but rather are above it and are able to manipulate Nature as a sort of God. Count Iblis (talk) 03:39, 25 February 2017 (UTC)

Related to the myth that "natural" (whatever that means) is good, see naturalistic fallacy and appeal to nature. Someguy1221 (talk) 04:28, 25 February 2017 (UTC)


 * If you're talking about evolution specifically, there are important differences between natural selection and artificial selection. Natural selection has no goal - mutations arise at random, and some survive for various reasons (helping a creature to survive or reproduce is the main one, but there are weird effects like sexual selection and genetic drift happening too), but there's no final destination and no deeper reason. Birds didn't evolve wings so they could fly - instead, they seem to have been creatures that lived in a forest with lots of trees to jump off, and they gradually evolved featherier arms and stronger chest muscles because creatures that had these were better at hunting and escaping predators, until one day this jumping and gliding became actual flight. Artificial selection however usually has a goal - to maximise the size of grains, maybe, or produce dogs that are loyal and intelligent. A bulldog has a squat face because this makes it easier to bite into the side of a large animal, and bulldogs were selected by breeders to have this feature. Maybe from a godlike perspective this is the same thing (bulldogs evolved squatter faces because the ones that didn't got castrated by a species of hairless ape), but when analysing evolution from a human perspective, this is an important ontological difference. Smurrayinchester 10:17, 25 February 2017 (UTC)
 * Artificial selection still operates within the "natural" genetics that the individuals already have. Compare that with genetically modified organisms, which involve really "playing God" by inserting genetic material that could never be there via cross-breeding within a species. That's an argument you'll see against GMO's vs. "conventional" breeding. ←Baseball Bugs What's up, Doc? carrots→ 11:14, 25 February 2017 (UTC)
 * Not really true. Artificial selection tends to be a key part of mutation breeding (including atomic gardening for example) where it's highly questionable to say you're referring to "natural" genetics the individual already have. I mean they have them sure, but only because you mutated the hell out of them to get it. Or to put it a different way, why is (taken from ) so natural but any GMO isn't? Note that artificial selection and conventional breeding are not the same thing. Artificial selection is part of conventional breeding, but artificial selection may also be used as part of producing a GMO. Also GMO tends to cover both cisgenesis and transgenesis. Finally even with transgenetic organisms, this doesn't mean the genetic material could never be there with edit: without GMO. Depending on the complexity of the change, it may be possible to produce this somehow, perhaps by mutagenesis or looking through a wide database. It has been suggested that GM could be used as proof of concept before you spend the incredible time and resources to produce the same thing via conventional breeding somehow. Technically there would still be some small differences, particularly if you a marker is still hanging around but this isn't what you referred to. Nil Einne (talk) 16:30, 25 February 2017 (UTC) edit: 15:13, 26 February 2017 (UTC)
 * How would you be able to get Bacillus thuringiensis genes into a maize embryo via conventional cross-breeding? ←Baseball Bugs What's up, Doc? carrots→ 22:26, 25 February 2017 (UTC)
 * I never said you could in any specific case, but if your maize or a close relative already has a close analogue of whatever gene you're trying to introduce then you just have to mutate the gene until you get the version you want and the breed into into the maize you want. Remembering also as molecular biology techniques improve it's getting possible to successful crossbreed more dissimilar plants. A gene is just a gene. If you're referring to a specific gene without a close analogue in any plausible relative, e.g. the cry gene, then yes it's probably very difficult as I said "Depending on the complexity of the change". Note I said complexity of the change rather then mentioning gene for a reason, if you just plan to introduce an antisense gene you could reduce activity of the gene in other ways in conventional breeding (e.g. mutating it until it doesn't work properly) then breed it back into your common variants until they seem to function as you want them to (maybe with various molecular biology techniques to help speed up the process by tracking your mutated gene without having to do much growing) and hope in the process you didn't also breed something undesirable that was also mutated and didn't notice because you don't have to really test safety or anything else. Nil Einne (talk) 15:18, 26 February 2017 (UTC)
 * You wait for a plant to pick up the genes from the bacteria on its own. --47.138.163.230 (talk) 00:45, 28 February 2017 (UTC)