female intimate characteristics are substituted for male ones, or vice versa.
What's the substitution process all about?
Its as a result of sequential hermaphroditism observed in some species.
What's hermaphroditism?
It can change from a male to female (protandry), or from female to male (protogyny) or from female to hermaphrodite 
Any genetically related?
used for the medical procedures applied to intersex people.
You mean a specie can have both a male and females organs of reproduction?
Yes! An example is found in fish , reproductive organs include testes and ovaries. 
OK now I understand! When was the earliest research conducted,?