

But what is the likelihood of this autonomous stress relieving function arising, how many mutations would be required to implement such a thing? Would it have any significant drawbacks or side effects in other aspects of our biology?
You can’t look only at the propagation side of things.
Another thing, stress isn’t event based per se. It’s more of a floating value that always exists to a certain degree and provides both positive and negative effects at different levels and in different situations. The negative health impacts come in when it remains high for a long period of time. So what we’d really want to look at is something like the frequency of headpats given to your dog or something, and the effects of this compared to other potential stress relieving activities like meditation.
Lastly, I would check your data on pet availability, I think it’d be far, far higher than 10%.
Certainly. But we still cannot say that should mean every beneficial mutation for their lives was likely to be adopted. Like I said earlier, the majority of possibly good things are left on the table, even when drawbacks are not considered.
Including drawbacks muddies it up even further, we can look at how cardiovascular shock occurs and how the particular traits that create it were a bit of a double edged sword.