And why did he invent this concept? HE didn't. Goldsmith came up with it about twenty year prior. Some called it the hopefull monster mechinism. The idea was a turtle laid an egg and a bird was hatched.
But why was this theory necessary? Because both scientists realized there are no transitional forms in the fossil record.
So what we have is evolution happend too fast in the past to leave a record and it happens to slowly in the present to observe. Very convinent.
Could you do us all a favor and actually read a scholarly text on evolution not written by a denier? A good one is Evolution, What the Fossil Record Says, and Why it Matters, by Prothero.
