If I gave you 15 seconds you could come up with a pat evolutionary just-so story to account for this, speculating on what reproductive advantage it serves.
Sean talks about changes over past decade: Everyone has a smartphone and can, quicker than ever, find someone taking the other side of an argument.
Thomas Hills argues that we will accord human-style rights to robots because we will come to empathize with them.
We are often awed at the medical miracles that save so many of our lives and alleviate unquantifiable levels of human suffering.
These biological facts are often misused to try to push us beyond our welfare duties and into according animals human-type rights.