Half of an aurochs is a bit like half a brownie. If you cut a brownie in half, you don't have two half-brownies. You have two brownies, each half the size of the original. The indivisible nature of brownieness extends right down to the near-molecular level. It is a Platonic ideal.

A brownie stands in counterpoint to half a sandwich. You can't make half a sandwich. You must make a whole sandwich and cut it in half. A sandwich made from one slice of bread, folded over, is not half a sandwich. It is a half-sized sandwich.

Now, my I please have a barbecued aurochs sandwich and a large brownie?