This question is outside recorded history, and probably best addressed to /r/AskAnthropology .

But before asking this question I would recommend thinking long and hard about why you believe that 'fun and personality traits' and 'strongest' and 'best chance at survival' can't co-exist with each other. Moreover, why do you believe selecting a 'potential partner was the strongest and gave offspring the best chance of survival' was actually a thing, ever, to any given group of pre-historic people?

Social abilities are paramount to successes and survival in our species. There was never an extended period of time when humans could survive outside of a society, let alone thrive. You're greatly underestimating the utility of being fun and having a good personality -- our current attraction to those things is likely just as inherited as our preferences for various body types. There is no greater sign of reproductive fitness in an animal as social as we are than a capacity to work with and manipulate others.