Or: Reason number 1,347 why I like Steve, who sent this to me at 3 am:  

‘We have animals living with us. As us. Over thousands of years they
have been bred and evolved to live in harmony with us. Have we evolved
in unison with our domesticated animals? I propose that living with
animals increases overall health and happiness of people. Thus our
pets allow us to live a longer life, have more babies, and spread our
evolutionary seed. So, perhaps we have evolved to love animals as a
survival instinct. Petting a cat is soothing and relieves stress that
would keep me occupied when that bear turned the corner and tried to
eat me.’