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Do cross-breeding occur?

  1. Nov 9, 2007 #1
    Naturally in jungle, or intentionally by men, does it happen? How about something close to men? Like monkeyxmen?
     
  2. jcsd
  3. Nov 9, 2007 #2

    mgb_phys

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    It occurs naturally, occasionally, lion/tigers or zebra/horses.
    It is quite common man-made, mules are donkey*horses.
    If it is possible depends on how close the two species are.

    If they are too different nothing happens (except perhaps a court appearance)

    If they are closer there is an offspring. Often it is sterile (eg mules) sometimes it's fertility depends on which way round the parent species are, sometimes it depends on the sex of the offspring. Then it gets more complicated in the next generation, if a lion/tiger mates with a tiger ..... This is one of the mechanisms for new species to form.
     
  4. Nov 10, 2007 #3

    jim mcnamara

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    Most of what occurs in speciation is isolation of one gene pool from another. In other words, some mechanism evolves to prevent cross-breeding.

    Ass x Horse -> sterile mule. This is an example of a breeding barrier - the mule can't have offspring.

    So the real question is: how do species stop cross breeding, not if it occurs.

    BTW a lot of our modern crop plants are the result of intentional cross breeding - wheat derives from plants like emmer which was then cross bred over time - result modern wheat.
     
  5. Nov 10, 2007 #4

    mgb_phys

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    It seems to be mostly a case of 'not my type'.
    There is a cricket which occurs in genetically identical groups with different tunes. They will only choose to breed witht he same song type. If you play the correct species' tune they will breed normally.

    Not sure if that's really cross breeding or just picking offspring with desired characteristics.
    Of course the definition of species (like life) gets a bit trickier when you look more closely.
     
  6. Nov 10, 2007 #5
    hmm...how come mules cant have offspring?

    And has there been a cross breeding where humans were involved?
     
  7. Nov 10, 2007 #6

    mgb_phys

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    Simple answer - because.
    Complex answer - to do with biochemistry, chromosones, surface proteins and rejection mechanisms.

    It seems to be just ones of those things. Horses+donkeys breed to produce sterile mules.
    Often the female crossbreed is fertile but the male not eg.If male lion + female tiger -> liger, male ligers are sterile, female ligers are fertile.
    This is probably because a female carries two copies of anything on the X chromosone so has a compatable copy of her own.

    The nearest anaimal to man is a chimp which is too different to produce offspring.
    Sheep also don't work despite the efforts of the more rural parts of the UK + Australia.

    Interestingly there doesn't seem to be genetic evidence that man cross-breed with Neanderthal even though they were genetically much closer. It may be that this occurred but any offspring were sterile and so haven't left any trace in our DNA.
     
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