Wikipedia:Reference desk/Archives/Science/2015 May 30

= May 30 =

animals and humans
I just watched this https://www.youtube.com/watch?v=-NDAd-wn_9M and was shocked at how picky female animals can be on looks. Why is it that for humans male cares mostly about looks but for animals its opposite? I mean when there are gender differences male animals are always better looking, for human it's opposite (best females look better than best males). — Preceding unsigned comment added by Money is tight (talk • contribs) 10:15, 30 May 2015 (UTC)


 * One difference is that for most species the male is merely a "sperm donor", so all the female cares about is that he is healthy, which can be judged by looks. In humans, on the other hand, males were historically important to the survival of the children, due to the resources they bring (wealth) and their position in the social hierarchy (power).  So, wealth and power may be more important than looks alone, to human females.  Of course, having a wealthy and powerful husband (which probably means old) and getting impregnated by young, handsome, and therefore presumably healthy, males is the best of both worlds, provided they don't get caught. StuRat (talk) 11:12, 30 May 2015 (UTC)


 * Best of both worlds?  For immediate gratification, maybe, but not biologically.  If the sexy poolboy is a dunce whose poverty ridden alcoholic family all die at 50 due to a genetic condition, getting impregnated by him would not at all be ideal.  It's also entirely possible that the powerful old rich man was a looker when young, has fathered some quite successful children, and will live to 100. μηδείς (talk) 19:03, 30 May 2015 (UTC)


 * Young sperm carry fewer mutations, and so are more desirable in that sense. And every pool boy comes from a line that has won out in countless generations of natural selection to reach the present day.  While it is possible to assess whether there is something seriously wrong with an organism, the examination only goes so far - and the instinctive examination of basic physical vigor is more likely to target the genes of most interest biologically; natural selection doesn't care if your kid is a drunk or an astronaut, only how many kids he has.  (Cue Idiocracy - and ponder why that premise hasn't come true in any previous generation) Wnt (talk) 19:23, 30 May 2015 (UTC)


 * Yes, that's true, but most congenital mutations are linked to the age of the mother's eggs. Sperm with serious mutations will often lead to spontaneous abortion or failure to conceive, and male fertility does decline over time.  But sperm are produced anew, while eggs have been eggs since before the mother's birth, so they have had a lot more time to acquire lethal mutations.  Should the woman find she can't conceive the couple could always discuss using a close male relative of his as a sperm donor.  If the object is just to have a baby, not a rich and powerful 60 year-old's baby, then of course the woman could resort to the pool boy.  There's no accounting for logic. μηδείς (talk) 21:40, 30 May 2015 (UTC)


 * I went to look this up, and actually see there's been some development of the idea - apparently sperm that undergo mutations can actually have a positive selection driving their abundance in the testis.  Achondroplasia, for example.  Which means I'm no longer so sure about the rate of overall spontaneous mutation in sperm with age, when such positively selected traits are excluded.  In any case, older women characteristically have overall issues with large chunks of chromosome in older eggs (nondisjunction) rather than point mutation per se.  (not accounting for trinucleotide repeats...) Wnt (talk) 01:49, 31 May 2015 (UTC)
 * Thanks,, that's interesting, it would explain the relatively high spontaneous rate of achondroplasia compared to other expressed genetic mutations. I posted a chart showing a huge jump in the rates for Trisomy 21 with mothers older than 35.  I am unaware of any similar issue for males at that age, but obviously sperm quality is not going to increase with age. μηδείς (talk) 02:44, 31 May 2015 (UTC)
 * Sexual dimorphism may not answer all of your questions, but it would be a good start. I don't think "better looking" is a very useful phrase here; in this photo of Mandarin ducks the male is flamboyant but the female is quite pretty in my opinion. Who's better looking is a matter of personal taste, something like art appreciation. &#8213; Mandruss  &#9742;  11:21, 30 May 2015 (UTC)


 * Another article the OP should read (rather than StuRat's "I don't have to provide references because everything I say is stuff I already know" kind of answer) is sexual selection. It's a fairly comprehensive article, and also covers humans, there are further links in that article you can follow to articles about how the concept plays out in humans in even more detail.  -- Jayron 32 19:06, 30 May 2015 (UTC)
 * Bear in mind that whether or not "in humans, appearence and decoration is more important for females than males" is very much culturally dependent, and differs in different times and places. Regarding other animals, I have a hypothesis that this may depend on whether or not they are a prey species, and whether or not survival of the young depends on care by one parent, two parents, or none, but I don't know if there is any research to support this. 62.172.108.24 (talk) 12:10, 1 June 2015 (UTC)

Do milk-cows need to give birth to calves to produce milk?
Do milk-cows need to give birth to calves to produce milk? Or, is it possible to trick the cow's organism through hormones into believing that a calf was born, and milk has to be produced?--Llaanngg (talk) 13:17, 30 May 2015 (UTC)


 * says they do need to have had a calf to produce milk. BbBrock (talk) 13:38, 30 May 2015 (UTC)


 * Yes, under normal conditions the cows would need to have had a calf. The question whether it's still theoretically possible to make them produce milk with a hormone treatment does not get addressed by this claim. --Llaanngg (talk) 16:16, 30 May 2015 (UTC)


 * See induced lactation. μηδείς (talk) 18:55, 30 May 2015 (UTC)

Physiological reasons for vegetarianism and veganism
Is there a good source suggesting non-ethical, possibly genetic reasons for vegetarianism and veganism (excluding meat allergies)? I only found that androstenone in pork may cause aversion, but nothing more than that. My sister had been an avid meat eater during childhood and early teens, but turned largely vegan for non-religious reasons citing unpleasant smell. I'm, however, omnivorous and start to feel myself uncomfortable after abstaining from meat for 2-3 days. I suspect metabolic differences between two sexes and higher energy requirements for males, but not entirely sure. Brandmeistertalk  21:32, 30 May 2015 (UTC)


 * I was thinking perhaps a problem with digesting creatine might be relevant, but due to creatine's central metabolic role, such a disorder might simply be lethal during early development. In any case, I was unable to fid anything on line about where one should avoid creatine. μηδείς (talk) 01:13, 31 May 2015 (UTC)


 * Meat is usually harder to digest than vegetable matter, with the usual exception for unusual allergies, and for a lot of people fish and to a much lesser extent poultry is an exception. Most of the added stress is on the immune system and artery plaques. If you absolutely must have dairy, insisting on grass fed is a good idea, but whether it's cost effective is anyone's guess. I hope the plan to seed the North Atlantic with iron continues to strengthen Pacific salmon stocks. 75.148.42.9 (talk) 01:17, 31 May 2015 (UTC)


 * As for you only being able to go off meat for 2-3 days, that probably means you haven't completely compensated for the missing nutrients. You'll need a new source of protein, like beans and nuts (or dairy, eggs, and fish if you are less strict).  You'll also need to ensure you get enough iron, vitamin B12, etc. StuRat (talk) 01:53, 31 May 2015 (UTC)


 * B6 and cal-mag-D-sunlight are next on (and comprise the remainder of the?) vegan checklists. 63.225.115.25 (talk) 02:25, 31 May 2015 (UTC)


 * In some cases of Parosmia it's reported that animal derived foods smell like carrion. --Digrpat (talk) 16:34, 31 May 2015 (UTC)


 * See meat allergy from the lone star tick (note this refers to the appearance, not its native distribution. Nasty creature indeed, but I see from the former article that others are also blamed for the problem. Wnt (talk) 11:27, 2 June 2015 (UTC)