Why do only females select males?

Discussion in 'Biology & Genetics' started by aaqucnaona, Dec 18, 2011.

  1. Hellenologophobia Registered Senior Member

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    System failure? Try megalomaniac failure. :crazy:
     
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  3. Gustav Banned Banned

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    well all right
    i am convinced so....the more, the merrier...... why not an eye in the back of our heads?
    *One question not addressed by the paper is why only females lactate—you'd think the young would have benefited if Papa Proto-mammal was also slathering them with immunoprotective slime. I'd guess that this supports the idea that those ancient males weren't particularly involved in caring for their progeny, so it made little difference in infant survival if the father turned these secretions down to a level sufficient to selfishly protect just himself.

    *Evolutionarily speaking, there are two reasons that might explain why males haven’t evolved to lactate. One: since babies grow inside the female, males can never be certain that it’s their child they’re caring for. Why expend all that milk for a child that isn’t your DNA? And two, since females are carrying the baby it might be advantageous (for the species) if the male ran off and impregnated another women instead of waiting around for the baby to get thirsty.

    *Many male mammals have been observed to lactate under unusual or pathogenic conditions such as extreme stress, feeding castrated animals with phytoestrogens or animals with pituitary tumors. Hence it was hypothesized that while most mammals could easily develop the ability to lactate this does not provide the males, or the species with any evolutionary advantage. While the males could in theory improve the chance to pass on their genes by improving the feeding their offspring by male lactation, most of them have developed other strategies such as mating with additional partners. Presently only very few species are known where male lactation occurs and it is not well understood what evolutionary factors control the development of this trait​



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    Last edited: Dec 24, 2011
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  5. aaqucnaona This sentence is a lie Valued Senior Member

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    First of all, thanks for that piece on evoution of lactation.

    Why not an eye in the back of head?
    Because its not worth the extra nutrition being put into an embryo that could have been used for better bones or body systems, etc. In the long run, turning your head is more advantageous than having an eye there. But it can happen [as in spiders:]

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    How did you do that torn snapshot thing?
     
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  7. scheherazade Northern Horse Whisperer Valued Senior Member

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    Slightly off-topic and merely an observation: Spiders are notoriously hard to catch-and-release unless they have managed to entrap themselves on a surface that provides poor traction. They are quick, lol... and very hard to sneak up on.

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  8. aaqucnaona This sentence is a lie Valued Senior Member

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    True indeed. Looks like someone has spent some time messing around poor lower lifeforms. I used to [age 7-11] catch lizards, watch them swim in buckets and was entralled by their scales trapping a shiny layer of air. Being cold blooded, and due my lack of knowledge, some of them died of hypothermia. Many were cold enough that even if they survived after a swim, they would be slow enoughs for crows to pick them off. I feel bad for them.

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    But, yes, the spiders. They are hard to catch because they have good reflexes, powerful limbs and an amazing visual system:

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    Not included are the two eyes on top of the head which look upwards.
     
  9. scheherazade Northern Horse Whisperer Valued Senior Member

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    Messing around poor lower lifeforms?

    I fear you misunderstand me. My goal is to live capture these insects when they find their way into my den and then release them, unharmed, to pursue their role in the natural order of things.

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    This little detour into the visual range of the spider explains a lot. They appear to be very difficult to 'blindside' unless they are busy rappelling down a thread. Thank you for posting the pics and the information and a thank you to Gustav also for the interesting post on lactation and reproductive strategies.
     
  10. Gustav Banned Banned

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    why? it does not seem as if you find it particularly useful since you....

    are still residing in geoff's house of woo with useless speculation like that.
     
    Last edited: Dec 24, 2011
  11. scheherazade Northern Horse Whisperer Valued Senior Member

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    LOL....'useless speculation'.

    Endless speculation at least keeps us occupied and occasionally entertained.

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    Worked all night and now switching my 'clock'.

    My mind is mush so I am being a nuisance poster. I actually have some chores to attend so I shall relieve you of my frivolous presence for an interval at least.

    Later.

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  12. KilljoyKlown Whatever Valued Senior Member

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    Reminds me of a time when I was a kid on vacation up in the mountains. I caught a whole bucket full of blue belly lizards and it got below freezing at night. In the morning they were all frozen solid. I could pick them up by their stiff tails and if not careful they would break like a twig. So I dumped them out into a pile thinking they were dead. Imagine my surprise when they thawed out and crawled away.

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  13. aaqucnaona This sentence is a lie Valued Senior Member

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    Mountain lizards would have evolved some anti freeze [like arctic fish], IMO. But the ones I 'worked with' were tropical. 20 minutes of immersion in water would be enough to kill them.

    Oh, btw, Sch, good thing you'r not doing stuff to your creepy crawlies - I read that in pretty much all countries its legal to do whatever you like with invertebrates - so you can pull a crab apart alive, but not beat up a cat.
     
  14. KilljoyKlown Whatever Valued Senior Member

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    I found the following Info on Blue Belly Lizards and that note about Lyme disease was news to me. Didn't say anything about anti freeze blood though.

     
  15. aaqucnaona This sentence is a lie Valued Senior Member

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    ...are a guy? Yes, but can't I satiate my intellectual curiosity?

    Its not speculation, its well establised fact of evolutionary trade offs:

    http://www.google.co.in/url?sa=t&rc...gaofeS3JljqCQvbdw&sig2=R2ecKEIxHceGrOYw3fNebQ

    http://oikosjournal.wordpress.com/2011/04/27/why-expect-trade-offs-in-ecology-and-evolution/

    http://en.wikipedia.org/wiki/Life_history_theory
     
  16. aaqucnaona This sentence is a lie Valued Senior Member

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    Hey guys, this is my biology documentaries collection [torrents of course!]:

    {D- done, P- in progress, W - waiting}
    [No. Title. Year. Status]

    01. Life on Earth. 1979. D

    02. The Living Planet. 1984. D

    03. The First Eden. 1987. W

    04. Lost Worlds Vanished Lives. 1989. W

    05. The Trails of Life. 1990. W

    06. Life in the Freezer. 1993. W

    07. The Private Life of Plants. 1995. W

    08. The Life of Birds. 1998. D

    09. The Blue Planet. 2001. D

    10. The Life of Mammals. 2002. D

    11. Life in the Undergrowth. 2005. D

    12. Planet Earth. 2006. P

    13. Life in Cold Blood. 2008. D

    14. Nature's Great Events. 2009. W

    15. Life. 2009. D

    16. The Tree of Life. 2009. W

    17. First Life. 2010. W

    18. Human Planet. 2011. D

    19. Madagascar. 2011. W

    20. The Frozen Planet. 2012. W

    What do you think?
     
  17. keith1 Guest

    I never liked you either, IQ-in-the-hundred-level-bonehead. But I don't hate you. You offered yourself up as a teaching example.
    Megalomania is an incompetent lower intellect posing as an intellect level they cannot sustain. The majority of lower intellects are fine, and productive individuals, with great levels of understanding. Some, as the quoted above, have an inane hatred of those of a higher intellect.

    To finish:
    After it is initiated, system failure can still be avoided.

    --After the delay of a period of personal reorganization, the higher intellects gravitate to a lower management position, where they quickly rise to upper management.

    --The system stabilizes after a quiet intellectual coup, and an almost seamless paradigm shift is implemented.
     
    Last edited by a moderator: Dec 25, 2011
  18. Gustav Banned Banned

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    lets eyeball the link....
    Evolutionary biologists and ecologists believe that evolving organisms are subject to trade-offs. You can’t have a ‘supergenotype’ or ‘superspecies’ that’s optimized to do everything, whose fitness (both in absolute terms, and relative to competing genotypes or species) is high in all possible circumstances. A corollary is that we believe ‘a jack of all trades is a master of none’–organisms that are specialized to be good at one thing (e.g., to survive in a particular environment) should be better at it than generalist organisms. The assumption of trade-offs underpins standard thinking on a whole range of issues, from speciation and adaptive radiation to competitive coexistence.​

    please reconcile with "in for a penny, in for a pound"

    perhaps we can apply it to this...
    Hence it was hypothesized that while most mammals could easily develop the ability to lactate this does not provide the males, or the species with any evolutionary advantage. While the males could in theory improve the chance to pass on their genes by improving the feeding their offspring by male lactation,.....​

    why not go for the "pound" and have males give birth as well? i mean they already have the framework (penny)...

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  19. scheherazade Northern Horse Whisperer Valued Senior Member

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    From a documentary that I was watching recently, it is hypothesized that part of the selection criteria is to select for a complimentary immune system. The female, when ovulating, finds some scents of the male's secretion far more attractive than when she is not ovulating.

    From working with horses, it is known that the mare's colostrum (first milk) transfers immunity to the foal and that this must be absorbed within the first 8 hours or so of birthing as the receptors in the digestive system of the foal cease to be able to uptake the benefits soon thereafter.

    So vital to health is this colostrum that horse breeders have a colostrum bank that can be drawn upon by those close enough to access it. http://www.thehorse.com/TopicSearch/Default.aspx?n=colostrum&nID=5&ID=58

    Perhaps in humans, there is also a similar transfer of protection through that initial breast feeding? The recombined genetics of the offspring takes place in the body of the female so even if the male were to develop lactation ability, the milk may not be of proper chemistry for the offspring's genetics. it would undoubtedly have nutritional value but would it have the same benefits for the immune system through antibody transfer?

    I wonder if a woman's breast milk varies from child to child? I'm suggesting that it would be variable as each person has their own unique genetic code and I'm guessing that the mother's milk would mirror that difference.
     
  20. visceral_instinct Monkey see, monkey denigrate Valued Senior Member

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    Yes.

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    Still not giving birth for anything.
     
  21. Gustav Banned Banned

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    on the face of it, from my layman's perspective, that sounds like a great argument and certainly more scientifically nuanced than those emanating from the house of woo
     
  22. Trooper Secular Sanity Valued Senior Member

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    I thought that would be something that you'd enjoy. Your input always reminds me of other interesting concepts that I’ve previously read about. You might also find microchimerism fascinating, I know I did. I also thought that all the strange frog reproduction strategies were fun.

    http://en.wikipedia.org/wiki/Microchimerism

    Surinam toad-Pipa pipa

    http://en.wikipedia.org/wiki/Rhinodermatidae

    http://en.wikipedia.org/wiki/Midwife_toad

    http://en.wikipedia.org/wiki/Gastric-brooding_Frog#Reproduction

    Cheers!
     
  23. billvon Valued Senior Member

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    That's definitely true. From Wikipedia:

    "The most pertinent bioactive components in colostrum are growth factors and antimicrobial factors. The antibodies in colostrum provide passive immunity, while growth factors stimulate the development of the gut. They are passed to the neonate and provide the first protection against pathogens."

    Why wouldn't it? Indeed it might be more beneficial since infants pick up some antigens from just being born and passing through the (not all that sterile) birth canal. If that were the case they would get a little more diversity from having two sources of antigens.

    Genetically speaking infants are (roughly speaking) equal part mother and father, with the only exception being mitochondrial DNA. I don't think that plays a significant role in immune system development though.

    I think a far more basic benefit is that the woman who conceived the child will be right there (physically) when the child is born. Often the man who conceived the child is not. Thus a missing father would result in the death of the child, which is a bad thing evolutionarily (assuming that males instead of females were the lactators.)
     

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