It is the Chicken that came first.
I do not know 'why' people can not work it out.
I have not read the answer from any scientist to this question.
In fact I didn't know till reading this question....they had come to a conclusion.
That is the honest truth.
But after this answer, I will look it up and see if I have been right,
all this time.
I will be disappointed if I am wrong, because you need to have a 'starting point' with anything in life.It is just common sense.
The Chicken to me, is that point.