"I ask another question, 'Why?'
I will ask the first question again, 'Was it worth it?'"
(By "was it worth it" I take it you mean, was it worth it for us to domesticate what Nature originally designed to be tameless and wild.)
Re: Why? ... Why ... I don't know. Well I guess the cows thing I get. Readily available meat, right? But dogs? I don't know. Maybe as human civilizations became more ... complicated ... we stopped needing the wolf's hunting assistance so much, but felt that we still wanted the wolf's company ... and the wolf, no longer having an official job to do, found it all too easy to relax into the role of a mere household pet.
Just one of many possible guesses.
By the by: Visit, say, New Zealand sometime, and behold some dogs who still have very real jobs to do for their human "masters," who in fact do rather live outdoors and could probably easily escape if they wanted, technically. But these dogs take their jobs very seriously, and it's incredible to behold how complex their jobs are, and how proudly expert they are at executing these jobs. They are sheep-herding dogs, and different dogs specialize in different parts of the trade. Some of them are responsible for prodding the sheep into moving along in their pens. Some of them are responsible for aiding humans in the literal herding (to and from pasture and pen).
Can't nearly remember what all the jobs are, but there's a bunch. Some involve barking at sheep. Some involve running along the sheep's backs to get to "the bottleneck sheep." Many involve receiving complex commands from the humans by way of a sizeable vocabulary of whistles by the humans. And check this: One of the jobs involves dogs who approach the sheep slowly in a state of utter silence, and stare the sheep down! Those dogs virtually hypnotize the sheep with that stare. The dog creeps back and forth, and the sheep (the whole herd) creep back and forth in concert with the dog, mesmerized and mastered by the dog's relentless stare. I believe that's part of the actual herding process, but anyway -- just, wow!
Re: Was it worth it? ... Why ... I don't know. You know we have handicapped people today who rely on their own personal dog to help them out. Leading dogs for the blind of course. But also, dogs who help folks in wheelchairs. Who help retrieve things for those folks. Turn off the light switch for them when they're in bed and then, sleeping with them (thus sharing valuable companionship as well as amazing services). Even helping such folks socialize with non-handicapped humans, who feel awkward talking with a guy in a wheelchair but feel naturally drawn to the inviting, unjudging charm of the dog. In which case the dog's official job at that moment is breaking the ice for the psychologically distanced humans. Again, dogs with very sophisticated jobs, who take those jobs supremely seriously and carry them out with flawless grace and aplomb. Just try to "not respect" that! Now that's a dog that earns its keep.
I don't know if it was worth it. What about the psychological aid that cats and dogs lend to people with emotional disabilities? I myself suffer from a shitload of emotional limitations, and gods do I remember the day when Rainee was first introduced to our home. She was basically a kitten at the time, a tiny little thing. And on that day, I was so lost and depressed I was just laying on the floor, with the will to do only nothing, feeling unloved though my mind *knew*
I had two poly companions that loved the hell out of me as well as lifelong blood and chosen family and friends. Well for whatever reason, when my "hinge lady" placed Rainee by my side and handed me a feather toy, Rainee immediately inspired me into playing with her, staring at her wild jumping (with backflips!), and shit, straight up making me feel like I was alive again.
From that day on, Rainee has been an utterly loyal and faithful friend to me. Nothing fake or trivial about what Rainee has to offer! Can I say the same about what I offer her? Gods, I just don't know. I try -- I do try. How does one convey adequate appreciation to a cat who's employed her feline magic into saving one's emotional life? OMG ... [sobbing] ... Who's really dependent on who, I wonder ...
I'll never know "if it was worth it." How can anyone ever possibly know? You can't measure or put a price on those types of things. Fuck, it sure seems to have been worth it for us humans. Maybe non-humans have in essence selflessly sacrificed themselves for us just because they just plain cared. Maybe? We've already established that none of us knows what our pets are thinking.
Sure you could argue that you might still get all that with a non-human person who was 100% independent and could come and go as he/she pleased. But we keep our pets safe and sound and in that way, we know they'll always be at home waiting for us. Hell of a deal for us humans. The non-humans? Well, they'll never have to worry about where their next meal is coming from, for what that's worth. Shelter; no cold, rain, driving snows. And the "friendship" (be it trivial or profound, illusion or real) that human "masters" extend to their non-human "slaves." Pets are "house slaves." As deplorable as deporting some poor slob from Africa and turning him into a house slave? These are the kinds of riddles I just don't know how to answer.
Re: forcing spaying and neutering upon a non-human person ... tricky, since there's no way to know whether the non-human does/would want/consent to the operation, and thus, no way of knowing/agreeing on whether that operation constitutes force. We are only guessing at whether the non-human person (if he/she knew what the hell we were doing to him/her) would agree with us that the operation was a good idea and for the best. Yet another unsolvable riddle, in my mind.
Similar to the riddle of infant circumcision, I suppose. I personally like being circumcized, and fancy that I prefer having had it done when I was too young to dread the ordeal. But that's me; plenty of other men feel violated by having been thus mangled. And of course we could argue about foreskin pros and cons all day; ultimately much like clothes and shaving it's a personal/cosmetic choice. And yet that baby boy has no choice ... or has he, if he'll grow up to like the decision that was made for him? Maybe others can solve that riddle, but I can't.
Re: human overpopulation ... well that's an easy one, Utah (especially Utah Valley) being, like, the ultimate example of overpopulation!
"Is this [sexual mutilation] an adequate solution for either non-humans or humans and if it is, is it a permanent solution to always be practiced?"
Don't know and it gets worse. That particular riddle is going to become increasingly complicated as life extension is developed. And I can practically guarantee that life extension will be developed (for all animals, both human and non). Just a matter of time. Guess we'd best start puzzling over its implications ahead of time (but who knows where to begin with that puzzle).
"How do we get back to that: the times when a long time ago humans and certain non-humans were 'truly friends?'"
With a time machine, by setting all the non-human people loose, or (if this last one be possible) by somehow inventing a whole new way of relating to each other (as "masters" and "pets"). Yeah yeah I know, that's a dumb-ass answer on my part, stating nothing more than a combination of the obvious and the absurd. Sorry but I just can't think of any answer that sounds better to me. In other words, I'm (once again) stumped.