Wikipedia:Reference desk/Archives/Science/2021 January 14

= January 14 =

obese people to lie down on their sides
What's the scientific explanation for the fact it's difficult for obese people to lie down on their sides? Is it just about turning the body or also because of some physiological mechanical issues that don't enable them to lie down on their sides?ThePupil (talk) 00:13, 14 January 2021 (UTC)
 * What's the basis of your premise? ←Baseball Bugs What's up, Doc? carrots→ 03:15, 14 January 2021 (UTC)


 * I don't know if this is an alleged fact or a common recommendation or what. I have seen, with some amazement, that COVID-19 patients who have serious breathing problems are better off when turned on their bellies. I guess this has experimentally been proven to help (and not just in theory), but doesn't a prostrate position make breathing harder for obese patients? --Lambiam 11:01, 14 January 2021 (UTC)


 * It is a proven and practiced manoeuvre. See here, not specifically Covid19 patients but discusses the advantages of nursing obese patients in the prone position. Richard Avery (talk) 12:23, 14 January 2021 (UTC)
 * If they're quite heavy, as with the OP's question, wouldn't lying on their bellies inhibit breathing? ←Baseball Bugs What's up, Doc? carrots→ 20:51, 14 January 2021 (UTC)
 * Did you read the paper linked to? --Lambiam 12:03, 15 January 2021 (UTC)

Animals with Milk Production at Upper end of Torso rather than Lower.
For Humans, breasts are at the "Upper" end of the Milk line (closest to the head) and for Cows (and I guess most other Mammals), the udder (with at least two sets of active nipples) is at the lower end of the Milk line at the udder. Two questions. 1) Does milk production at the upper end of the Milk Line correspond to Mammals with hands (like the other apes) so that the babies can be carried and nursed? 2) Are there any animals where the Milk production is at the upper end of the body but it is standard to have more than one active nipple on each side? (seems like standard is either one set of nipples close to the head or at least two sets close to the groin) Naraht (talk) 14:21, 14 January 2021 (UTC)


 * Elephants have breast and it's located at the fore part of their torso, at a chest. --CiaPan (talk) 14:44, 14 January 2021 (UTC)


 * I'm not sure there is any strict pattern, but there may be based on some large grouping (i.e. specific class or family or grouping of genuses or something like that). For example, cats and pigs have teats that are fairly centrally located; I would describe neither as "upper" (as in humans) or lower (as in cattle), and other than being "mammals" I can't think of any commonality between cats and pigs in terms of taxonomy.  -- Jayron 32 14:50, 14 January 2021 (UTC)


 * Litter size? Cats and pigs tend to have larger litters than people (or cattle), though that could simply be coincidence. In very broad terms, it seems like it should be logistically easier to nurse a litter if the teats are not tucked at one end. Matt Deres (talk) 15:16, 14 January 2021 (UTC)
 * Possibly, but that still doesn't explain why cattle nurse near the back legs and elephants nurse near the front legs. -- Jayron 32 15:35, 14 January 2021 (UTC)
 * You are assuming that there is a reason. Both variants are obviously functional, which one developed in which lineage of mammals may be more or less random. Obviously, once established, the pattern is unlikely to virtually the point of impossibility to reverse itself. For example, descendants of modern humans are unlikely to switch to udders at or near the waist. --Khajidha (talk) 15:47, 14 January 2021 (UTC)
 * If you're using the word "you" to refer to myself, then quite the contrary. I've been arguing very hard that there is no reason, by providing counterexamples and the like.  Perhaps you were confused when I stated "I'm not sure there is any strict pattern."  You see, what I meant by that was that I wasn't sure there is any strict pattern.  I hope that clarifies things for you.  -- Jayron 32 15:54, 14 January 2021 (UTC)
 * No, I just got confused because I didn't notice that the same poster (you) had said both "I'm not sure there is any strict pattern" and "that still doesn't explain why cattle nurse near the back legs and elephants nurse near the front legs". --Khajidha (talk) 16:50, 14 January 2021 (UTC)
 * (EC) Broadly agree, but if lactation only evolved in mammals once (closest article seems to be this and links from it, but it doesn't address this point directly) then mammals have switched strategies. I don't think it's crazy to assume that this happened due to evolutionary pressure, but we'd just be guessing as to what those pressures might be. Litter size may play a part, but so could overall body shape, locomotion method, and other factors. There are probably several. I threw out litter size in my reply to Jayron only in answer to what cats and pigs have in common that people and cows don't and even that came with a question mark. Matt Deres (talk) 16:58, 14 January 2021 (UTC)
 * Somewhat obviously, delivering a large litter size has an energy cost, which would be wasted if half the litter dies for lack of teats to feed them, but an excess of milk-producing teats also has its cost, so evolutionary pressure will tend to correlate the number of milk-delivering teats with litter sizes. --Lambiam 11:49, 15 January 2021 (UTC)
 * Yes, lactation evolved once, but that is not what is at question here. The earliest mammals would have had multiple teats all along the milk line. In various lineages some of these teats have been "lost". Humans simply no longer regularly develop mammary glands and nipples further down the torso and cows no longer regularly develop nipples closer to the head. --Khajidha (talk) 17:30, 14 January 2021 (UTC)
 * Humans occasionally develop supernumerary nipples further down the torso; if there were any evolutionary advantage to these, they might catch on. Alansplodge (talk) 12:19, 15 January 2021 (UTC)
 * If it evolved once, that implies that something drove it to be expressed differently in different groups. It doesn't have to be due to pressures, of course, but if the ancestor mammal developed, say, mid-torso lactation, then it's not unreasonable to assume that evolutionary pressures caused later lineages to deviate from that. Matt Deres (talk) 12:52, 16 January 2021 (UTC)
 * Well, yes, but that's not what you seemed to be saying earlier. You previously mentioned switching strategies, which I took to mean switching from front lactation to rear lactation (or vice versa). What you are now describing (and what I was saying) is the specialization from lactation along the torso generally to localizing lactation in the front (or rear). Some lineages specialized one way, some the other. And some retained nipples all along the torso. No switching, only specialization. --Khajidha (talk) 20:45, 17 January 2021 (UTC)

Cows, horses, sheep, etc (with udders between their rear legs)seem to be able to lick their babies while they suckle, elephants have a much less flexible body so they can only fondle their babies with their trunks while the babies are suckling from the nipples in their "armpits" 49.197.29.242 (talk) 07:10, 17 January 2021 (UTC)

Mask with Ag+
I've bought a face mask with Ag+ ions for antimicrobial properties (at least per its description) and after about 25 minutes of wearing started to feel a slight salty taste in the mouth, as if saliva became mildly salty. Is it because of those silver ions or sort of a placebo-like illusion? 212.180.235.46 (talk) 22:07, 14 January 2021 (UTC)
 * One of the reasons that silver cutlery is useful is because although antimicrobial, it has no taste. See Silver. I can't explain your specific experience. Mike Turnbull (talk) 13:21, 15 January 2021 (UTC)