Sunday, June 26, 2011

Why Juvenile and Adult Animals Look Different

Ever wonder why juveniles and adults can look so different, especially in fish and birds?  And in humans, what's up with all the hair we grow post puberty?

The Differences:

Blue Headed Wrasse

Blue headed wrasse reproduction is a little different.  The individual on the right is a super male and the one on the left is an immature female or male (but reproductively mature).




Frigate Bird

Baby of right, adult on left


Little Black Dresses
This is kind of a weird thought, but I've wondered before if  we wear black to be sexy  because it subconsciously is connected to the darkness of pubic hair.  Maybe not.  But maybe.

The Possible Reasons Why

  • For Adults
    • Reproduction
      • Handicap Principle - Think about it.  If a display was easy to fake everyone would evolve to have it.  It's got to be hard and costly to be honest.  Testosterone in humans has been linked with shortened life spans--it's costly.
      • To Look Different From Women
        • To be noticed in a crowd
      • Delicate Hormonal Balance
        • Sexual displays will often use really complicated genes, because it says to the female that if large stretches of their genome are unmutated that the rest is probably ok too.
      • Age Display
        • Healthy
          • Being healthy into old age is a great sign of good genes.  Age indicators like a silver back, a beard, baldness could serve as showing age to show good genes.
        • Status
          • Resources
            • Many social species use status to gain resources and then gain mates. That takes time and having age indicators might be used to indicate the possibility of status, knowledge and resources.
        • Desirable genes
          • A female wants a male that will give her sons desirable traits so they in turn reproduce.
  • For Juveniles
    • Camo
    • Stay out of the way of the reproductively mature males
      • If other males see you as a threat you may not make it to the age of maturity.

Pictures from here, here, here, here, here, here.

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