Not all twins are identical and that's been an evolutionary puzzle, until now
- Written by Joseph L Tomkins, Associate Professor in Evolutionary Biology, University of Western Australia
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When a mother gives birth to twins, the offspring are not always identical or even the same gender. Known as fraternal twins, they represent a longstanding evolutionary puzzle.
Identical twins arise from a single fertilised egg that accidentally splits in two, but fraternal twins arise when two eggs are released...
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