300 million years was the date given for the beginning of the Y chromosome. Doed not mention what came before.

We could use that piece of information alone to suppose that God created the universe at the beginning of the Y chromosome.

Since human forms existed then, we should assume that this particular Y chromsome is peculiar to the human race. For 300 million years ago there was a genetic pool of Y chromosomes. One particuliar Y chromosome conquered the world, perhaps a very superior tribe, and the genetic pool was lost.

Some eastern religions would claim that this is indicative of Shiva taking over from Vishnu, science taking over from poetry.

I imagine all lifemforms have genetic pools of genes that can distinguish male from female. I am not aware of any that have lost its genetic pool. That is the price of conquering the world. Your male chromosomes are doomed to die.

Much regards,

Richard