Why does it need a response? It's like asking you whether you have stopped having sex with your daughter.
Your so-called problem bears no resemblence to anything asserted by biologists.
Because it is simplified in favor of evolution to show the difficulty of the number of differences between the "proto human" gene and a human gene and 10 million years to get from the one to the other.
It sounds like an Economic model. Like the economist on the desert island with canned goods and nothing else from the ship: "assume we have a can opener."