I think Nicholas has already done a good job of pointing out an underlying flaw in the OP perspective concerning the theory of evolution, natural selection, etc., so I won't address it myself. I also think the first question is steeped in that understanding, so I'll avoid addressing it for now. I do, however, have a few things to add concerning the second question:
And where does one draw the line between a human and an animal?
"Then God said, “Let Us make man in Our image, according to Our likeness; let them have dominion over the fish of the sea, over the birds of the air, and over the cattle, over all the earth and over every creeping thing that creeps on the earth.” (Genesis 1:26)
"And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living being." (Genesis 2:7)
These are the unique properties of humanity from the Genesis narrative. We are crafted especially by God, molded into his image and vivified with his Spirit. No other creature claims these attributes, no matter how sentient or humanoid they are.
Why would God create these other species with the sole purpose of allowing them to go extinct for us? And are they really just as important as humans? Do they have souls? What is their fate? I have trouble accepting that modern humans were really any different than these species so why are we the special chosen ones?
Why was Abraham selected, when he was simply a pagan man in Chaldea? Why does Israel become the Chosen People? Yes, Abraham was faithful, but he had done nothing but be a good pagan up until the time God calls him. There are plenty of other "good pagans" in the Scripture, but God wipes them out. Why?
I think it's a similar question.