Question

why external fertilization cannot occur in humans

Answer 1

In humans external fertilisation cannot take place naturally because the egg and sperms are not adapted to survive outside the human body.

However, providing the same environment as that in the mother's womb artificially can result in the fertilisation of egg and sperm outside the body of female. This technique of fertilisation outside the body of female in humans is known as test tube baby. After fertilisation outside, the embryo is transplanted back into the womb of mother for further development.