Or here's an obvious improvement: catnip response. It's good for the owner and good for the cat - fun, energizing, cheap, and safe. But around a third of cats a

Or here's an obvious improvement: catnip response. It's good for the owner and good for the cat - fun, energizing, cheap, and safe. But around a third of cats are catnip-resistant ( https://www.gwern.net/Catnip https://www.gwern.net/Catnip ). It's autosomal dominant at high frequency, so it would be easy to increase all the way to fixation with a little selective breeding (and that also implies, along with the widespreadness of catnip response in the Felidae family, that catnip response isn't harmful). Just, no one has.