Not All Twins Are Identical (Even ‘Identical’ Ones)
Fraternal, identical and even semi-identical: the biology of twins is fascinating and complex
In my family, I have relatives that are ‘identical twins’. It has always fascinated me.
For a start, my twin relatives are not identical: they have different physical characteristics, different skin and hair colour, different mannerisms and different personalities. Environmental factors, like room in the womb, different diets and living in different locations have all governed these distinctions. Take a look at identical twins Mark and Scott Kelly — both former NASA astronauts. They share many similar physical characteristics, but there are observable differences too.
Of course, not all twins are classed as ‘identical’, and some ‘identical’ twins are born with variable traits, such as being ‘mirror images’ of one another.
How does this happen?
