I can only imagine when the first cat came in from the cold to sit in front of the fire, grooming or patently staring at nothing in particular until someone offered it something to eat.  We've been attending to their kind ever since and what have we received in return?  An occasional half eaten carcass, claw marks everywhere, and a thick carpet of discarded fur follicles. If Earth is ever invaded by technically advanced, 6 foot tall, dog-eating, hyper-intelligent felines from another galaxy then they should, rightfully, give some small consideration to the portion of humanity that has attended to their kindred for so long.  If I might ask some small favor from our cat in return for a lifetime of door opening and closing it would these things:  learn to flush the toilet as I do not enjoy the fragrance of kitty litter, consider waking me up at 3am only infrequently and, after my demise, stare pitifully into the starry night at nothing in particular.  Of course that implies that I will no longer be here to open the door but those are the breaks.