Wikipedia:Reference desk/Archives/Science/2017 May 28

= May 28 =

If babies are never weaned, then will they be able to digest lactose at later ages?
I know babies are weaned from breastmilk. But what happens if they are never weaned? Will babies continue to feed on breastmilk and be able to digest breastmilk at later ages? 50.4.236.254 (talk) 02:07, 28 May 2017 (UTC)
 * Most people can digest milk their entire lives. Why would this matter?  --DHeyward (talk) 02:28, 28 May 2017 (UTC)
 * It may be true in D's country, but it is not true in general that "most people can digest milk their entire lives". --69.159.60.50 (talk) 02:40, 28 May 2017 (UTC)
 * Agreed. Most people of the world live in Asia, and Asians, with exceptions of North Asians, are largely lactose-intolerant. 50.4.236.254 (talk) 03:22, 28 May 2017 (UTC)
 * Fine, but the question seems to be, if they never stop drinking milk, can they avoid the onset of lactose intolerance? I think the answer is "no", but I'm not really sure, and it's an interesting question. --Trovatore (talk) 03:39, 28 May 2017 (UTC)
 * I agree I think the answer is no. First, I don't see any reason to think breast milk will make a difference so without ruling it out, I'll let someone else look for any evidence about that. While I couldn't find a source specific places specifically commenting on the issue, remember in plenty of places cow milk consumption is fairly common from weaning or before. Most sources like  discussing lactose intolerence refer to differing ages of onset etc. They don't say anything about how people can avoid it if they make sure they always consume milk. Note that although people who regularly consume milk may have less symptoms of lactose intolerance, according to  which is from the dairy industry of Canada, there's no evidence that this is due to increased lactase production and actually they acknowledge they don't know for sure why there seems to be this adaptation, but just that there is evidence does. This doesn't rule out a higher level of lactase production in people who have always consumed milk (nor for that matter that there really is no increased production in people who start to later regularly consume milk even if they lack the various known lactase persistence alleles), still it makes it seem less likely. Nil Einne (talk) 04:26, 28 May 2017 (UTC) 07:04, 28 May 2017 (UTC)


 * If I'm reading your question right, you're not talking about any old milk (like from cows or goats) but from human breastmilk. ←Baseball Bugs What's up, Doc? carrots→ 09:46, 28 May 2017 (UTC)


 * There is a specific gene (MCM6) which has the role of switching off lactase production after weaning: it generally kicks in when the child is about four, and had an evolutionary advantage, in that it prevented the older child from hogging the mother's milk, and let the next baby get its share. The mutation which changed Europeans, and some other populations, means that this gene does not work: we continue to produce lactase, so can continue to digest lactose. Without that mutation, the gene is going to switch of lactase production: a child will stop wanting to breast feed because it will start getting bad tummy aches. Wymspen (talk) 10:26, 28 May 2017 (UTC)


 * Actually re: my answer above, I intentionally didn't link to or check out our articles because I assumed the OP had read them. It seems this was a mistake and I'm now assuming they didn't. While Lactose intolerance isn't that helpful (that I noticed), we also have an article Lactase persistence which specifically covers the issue "While a variety of genetic, as well as nutritional, factors determine lactase expression, no evidence has been found for adaptive alteration of lactase expression within an individual in response to changes in lactose consumption levels.[1]". I haven't checked the source, so I'm not sure if it specifically comments on continuous lactose consumption, I think the evidence is now fairly strong that it's unlikely it will ward of the development of lactose malabsorption/intolerance. About your comment, I believe we covered the question of why lactase nonpersistence is the norm recently. While it's possible it did provide an evolutionary advantage in some species including humans, for the reasons you stated, I would be careful about assuming that this is a significant factor. Lactase nonpersistence seems to be the norm in most mammal species so it's not clear that preventing older offspring from hogging the milk would be a significant factor.  Nil Einne (talk) 11:32, 28 May 2017 (UTC)
 * Reading a bit more, I see I missed this part:
 * "Multiple studies indicate that the presence of the two phenotypes "lactase persistent" (derived phenotype) and "lactase nonpersistent (hypolactasia)" is genetically programmed, and that lactase persistence is not necessarily conditioned by the consumption of lactose after the suckling period.[11][12]"


 * Nil Einne (talk) 11:36, 28 May 2017 (UTC)
 * Decades ago I read a book about a European's life among the Inuit. It may well have been "Arctic Adventure" by Peter Freuchen. In it the author told of a custom among the local Inuit of mothers continuing to breastfeed their offspring into adulthood, such that a grown man would proudly take a suck from his old mother's breast. I wonder if lactose intolerance is common among the Inuit? (PS) I found the actual passage, confirming what was stored in my memory from 50 years ago! . Edison (talk) 13:09, 28 May 2017 (UTC)
 * Hmmmm... I may have contributed to confusion here before. I went on recently about lactase being inducible in humans, being sure I'd read something to that effect, yet now as you say there are sources being cited to the contrary.  Looking at it this time, I ran across a curious bit of data:   says that "The mean level of lactase activity among subjects with C/C-13910 genotype was 6.86 ± 0.35 U/g, with C/T-13910 genotype 37.8 ± 1.4 U/g, and with T/T-13910 genotype 57.6 ± 2.4 U/g protein"  So at this key genetic locus, it is less than a ten-fold difference in level - and homozygotes and heterozygotes, differing by 2-fold, are taken to be essentially the same.  That paper also concludes that lactase levels have to be less than 10 U/g for lactase intolerance to occur.  Now that strikes me as a really small difference in enzyme activity, when we consider that some of us are afraid to put milk in coffee and others of us will kill an entire container of ice cream in no time!  I also ran across an indication that intestinal flora contribute to lactase levels in rats  but haven't looked into this further.  There's something I don't understand here... Wnt (talk) 00:10, 29 May 2017 (UTC)

Effect of bovine milk and human milk on human babies
Humans probably agree that human babies should be fed human milk. But in case the mother dies in childbirth, has HIV, or (A) just doesn't want to or can't breastfeed for some reason, (1) how good is unpasteurized, grass-fed, raw bovine milk as a replacement for human breast milk? (B) Human breast milk may be flavored with whatever food the mother eats. So, (2) does that mean if the mother eats crappy doughnuts and soda, the child will grow up to eat crappy doughnuts and soda? (C) And if the mother eats fruits and vegetables, then her veggie-flavored or fruit-flavored breast milk will cause the child to eat fruits and vegetables and reject crappy doughnuts and soda because they are too sweet to be palatable? (3) What about the breast milk of the biological mother compared with the breast milk of the adoptive mother or wet nurse? 50.4.236.254 (talk) 17:17, 28 May 2017 (UTC)
 * [I have lettered your premises and numbered your questions to facilitate others' who may wish to address them. Please be aware that (A) elides the fact that many mothers find themselves unable to breastfeed their infant(s), no matter how much they'd like to – glossing over this fact can cause offense and distress. {The poster formerly known as 87.91.230.195} 90.200.129.108 (talk) 20:07, 28 May 2017 (UTC)]
 * I made small adjustments by adding the word "can't". 50.4.236.254 (talk) 20:23, 28 May 2017 (UTC)
 * (1). Cow's milk compared to human breast milk contains too little iron, retinol, vitamin E, vitamin C, vitamin D, unsaturated fats or essential fatty acids for human babies. It also contains too much protein, sodium, potassium, phosphorus and chloride which may put a strain on an infant's immature kidneys. In addition, the proteins, fats and calcium in whole cow's milk are more difficult for an infant to digest and absorb than the ones in breast milk. United States Centers for Disease Control report 148 outbreaks, 2,384 illnesses (284 requiring hospitalizations) as well as 2 deaths due to unpasteurized dairy products between 1998 and 2011.
 * (2) There is no evidence of eating habits being inherited through breast milk.
 * (3) What about it? Wet nursing is not widely practiced now. A more acceptable substitute is screened, pasteurized, expressed milk (or especially colostrum) donated to milk banks, analogous to blood banks. Blooteuth (talk) 19:40, 29 May 2017 (UTC)

What does the word "refractory" in "refractory period" refer to?
I know what it means "refractory period" (both, absolute and relative) in the action potential graph, but I don't understand what the meaning of "refractory" in this context is. What is it refractory for? 93.126.88.30 (talk) 12:49, 28 May 2017 (UTC)
 * See refractory. Refractory is an adjective usually used around high-temperature resistant materials, indicating that they are unaffected by outside influences, such as heat. This is extended by analogy to physiology, to where there is a time period during the potential graph, during which this too is unaffected by further outside stimuli. Andy Dingley (talk) 13:07, 28 May 2017 (UTC)
 * Also see meaning 4 in the Wiktionary entry: refractory. Looie496 (talk) 14:05, 28 May 2017 (UTC)
 * Thank you. I found the answer here. "After repolarization there is a period during which a second action potential cannot be initiated, no matter how large a stimulus current is applied to the neuron. This is called the absolute refractory period, and it is followed by a relative refractory period, during which another action potential can be generated, but only by a greater stimulus current than that originally needed. This period is followed by the return of the neuronal properties to the threshold levels originally required for the initiation of action potentials." 93.126.88.30 (talk) 14:45, 28 May 2017 (UTC)


 * This is really a language question. The word "refractory" means "very difficult to change." See refractory (disambiguation) for several non-metallurgical examples.-Arch dude (talk) 22:45, 28 May 2017 (UTC)

Re: whale death due to ship strike. Why not attach a beeping horn to the ships bow to provide warning to whales in imminent danger?
Blue whale gets hit by big ship and dies. Question: Would some kind of underwater horn that emits a warning sound towards the area of travel help whales avoid getting hit by the ship? My guess is, this would have been tried already and found to be unhelpful. But I'd like to know why it wouldn't work?

Thanks, --InverseSubstance (talk) 15:48, 28 May 2017 (UTC)
 * I'm sure it has not been tried. Abductive  (reasoning) 17:49, 28 May 2017 (UTC)


 * Ships already make a large amount of noise, and whales not only have excellent hearing but also have natural sonar. The problem is that the whales make little or no attempt to avoid being hit by ships.. The currently favored technology to reduce whale strikes is a combination of reduced ship speed, routing shipping lanes away from where whales are most common, and sonar and other alarms so that the ships can avoid the whales. --Guy Macon (talk) 18:31, 28 May 2017 (UTC)


 * Whales evolved for tens of millions of years in an environment which did not include large, hard, fast counter-current-moving surface objects. They likely lack the cognitive ability to understand the ramifications of such objects, in the same way that many land mammals fail to cope with the characteristics of motor vehicles and end up as roadkill. Some of the latter may to some extent be evolving instincts helping to avoid traffic, but are evolutionarily aided by greater numbers and shorter generation lengths. {The poster formerly known as 87.81.230.195} 90.200.129.108 (talk) 20:17, 28 May 2017 (UTC)

The research papers are helpful. Thanks for that. I agree, the whales that avoid ships will be selected in, and the ones that don't will get selected out. There are deer whistles sold that one puts on the front of one's truck, and its supposed to warn deer to get out of the way. Maybe just another gimmick, eh? I have an idea! How about a giant airbag that inflates at the front of the ship to cushion the blow? Or maybe some powerful jets of water to give a warning? Just thinking out loud here... --InverseSubstance (talk) 20:34, 28 May 2017 (UTC)
 * Whalebags? Sagittarian Milky Way (talk) 20:42, 28 May 2017 (UTC)
 * Its very, very unlikely whales collide with ships because the oceans are really huge areas and shipping lines only use a tiny tiny fraction of the space. Also whales, especially as in this case a blue whale, usually avoid humans. Strangely in this case there are no reports about evidence like huge wounds or broken bones, far as i have read. So i wonder how this "ship collission"-Story made it to the news. Would not shock anyone if it turned out that someone boldly made it up just to fill some space and everyone else started copying it, would it? --Kharon (talk) 20:45, 28 May 2017 (UTC)
 * See here: "The entire left side of the whale was damaged from a boat strike, and the whale had 10 broken ribs and 10 fractured vertebrae from close to its tail to mid-body, according to Halaska. The whale was identified through photographs of its tail in a database of the Cascadia Research Collective. It was spotted 11 different years beginning in 1999, most often off Santa Barbara. The carcass will be left on the beach to decompose and be eaten by birds. A reef along Agate Beach would make towing the carcass back out to sea difficult." Count Iblis (talk) 00:30, 29 May 2017 (UTC)
 * mentions "“It’s an unhappy coincidence,” Irvine says. Over a 2-week period in 2007, for example, at least three blue whales were killed by ships striking them near California’s Channel Islands. (Two other blue whale carcasses were spotted during the same 2 weeks, but the scientists weren’t able to study them.)" So actually it seems in the more reliable sources at least, when they say struck by a ship they mean we studied the carcass and decided it was most likely struck by a ship. This blog by someone who seems to be a nature photographer is similar circumspect, it does have the photos if you want to check them yourself. Although interesting, the author does specifically note it was in an area with high shipping traffic. That was in Sri Lanka and  notes it's particularly an issue there (the claim is it's a leading cause of death). The first source suggests it is possible but less certain, it's also problem along the Californian coast. (Although the certainty may relate more to who's talking since one was a scientist studying whales whereas the other is an advocacy group.) I suspect some of the sources linked above by others before you posted also discuss the evidence blue whales are being struck by ships. Nil Einne (talk) 07:11, 29 May 2017 (UTC)
 * I think that a ship coming into port with a dead whale draped over its Bulbous bow is pretty good evidence that ships hit whales. -Guy Macon (talk) 14:47, 29 May 2017 (UTC)
 * There's several obvious flaws in your hypothesis. First, you can't say random chance is unlikely simply by saying the ocean is big, you need to determine what percentage of the ocean is covered by blue whales (in general) over a defined time period, e.g. ten years. If it's something like 0.00000001% then yes, random chance seems unlikely. But even at 0.1% it's starting to seem possible. Maybe you have some idea what this is based on evidence but that hasn't been presented here. And while I admit it seems likely it'll be small to me, you need to actually have some evidence (even OR) before you can just assume random chance isn't enough. The bigger flaw though seems to be in assuming random chance. It's possible shipping lanes and the areas blue whales tend to swim in overlap for some reason e.g. favourable ocean currents or location near but not too near certain coasts. Maybe also favourable feeding/fishing grounds (yes I know blue whales are filter feeders but krill etc are eaten either directly or indirectly by some of the fish we eat); although shipping lanes was mentioned above I'm not sure if it's certain this was a cargo vessel (and of course if there is, it would be because the wounds etc have been carefully studies, as it seems they have been per Count Iblis). Maybe size would make it unlikely to be one but some Factory ship aren't exactly small. And these are a lot of assumptions, how well have you considered each one. To give a related example, if I see my neighbour on the bus in the morning on my way to work/uni/whatever regular activity and then see them on the way back as well, and then see them again tomorrow; thinking stalker is generally (but not always) silly regardless of there being many buses in Auckland. An even closer example, it's no surprise that whale watching ships can encounter whales somewhat regularly.  Also  for the claim that "especially" blue whales avoid humans, I briefly looked but couldn't find any source discussing this. And what is meant by humans? Swimming humans? Large ships? There's a fair chance the whales aren't going to see these as the same thing, as others have indicated. (Actually the view including from people who actually study blue whales seems to be the opposite, blue whales don't avoid ships.)  Nil Einne (talk) 06:55, 29 May 2017 (UTC)
 * P.S. Especially in light of my other comment above, I should also point out if shipping lanes and the grounds some blue whales tend to inhabit overlap in at least one instance, it's interesting but ultimately irrelevant when it comes to considering the likelihood of collisions; why there's this overlap. Nil Einne (talk) 07:16, 29 May 2017 (UTC)

So you mean, That's a Whale of a Story! --InverseSubstance (talk) 20:49, 28 May 2017 (UTC)


 * I agree with Guy Macon: the ships are already really noisy. Underwater noise pollution is widely thought to contribute to deaths from cetacean stranding and so forth.  The ship could start beeping when it detected a whale, but how would a whale understand that is in reference to it?  Still, the wildcard here is whale language.  If someone can figure out something to play that means "MOVE IT!", and broadcasts that when a whale is detected, maybe you have a winner.  But without the experiment, that's just pure hot air on my part. Wnt (talk) 00:17, 29 May 2017 (UTC)
 * Sagittarian Milky Way (talk) 19:21, 29 May 2017 (UTC)

The interested reader may find the following to be helpful; Amazon has a bunch of reviews of the book How to Avoid Huge Ships by those who have successfully avoided huge ships (and a few cautionary tales by those who failed to do so). The reviews are here: --Guy Macon (talk) 15:00, 29 May 2017 (UTC)
 * There are about 9,000 blue whales in the world. About 2,900 of them hang out off the California coast. Containerships from China usually visit Los Angeles and then Oakland before heading back to China, so there are a large number of very large ships in these coastal waters. On my only containership trip in these waters (in 2009), we saw two Blue whales fairly close up, and the officers said that this was routine: they see them more often than not. For some reason 2017 appears to be a record year for whale sightings. Containerships travel at 20 knots or more. Their enormous propellers are directly coupled to the engines and rotate very slowly at 100 RPM or so. -Arch dude (talk) 21:30, 29 May 2017 (UTC)