Well, off the top of my head I would say it's a mixture of nature vs nurture I guess. But that's not the question I'm interested in (right now) which is, whether people then had any individual personality at all.
I might not have followed this conversation to the minutest detail, but everything about us has evolved over millions of years.
We've always had "traits", but it wouldn't have been adaptive at an earlier stage in human development to have a strong "personality", as in a set of identifiable characteristics that set you apart from others, that made you more demanding on others, or command more attention, etc, UNLESS (possibly) it made you a good leader. Early in human evolution, in hunter-gatherer societies, the social contract was essential to survival. Keeping with the tribe or group made you much more likely to survive--you'd be able to share resources, have more protection from the elements and from predators, or other warring tribes, etc.
This is how "culture" slowly evolved, as a set of signs that were unique to a tribe, that formed around their specific food preparation rituals, rites-of-passage, warrior initiation rites, celebrations, legends, etc.
What we have now, though, under late capitalism, is this somewhat strange idea that humans need to find fulfillment alone, that we're all lone wolves that should be competing to the death for every last bread crumb. There's no precedent for this way of life in human evolution. Industrialization is ruining the planet quite obviously. But people have convinced themselves that the only way to be "happy" is to be "free" to become who you "really are" by choosing between a bunch of different retail stores in a mall, and then stopping by the supermarket of ideologies on the way home and patching together a belief-system that justifies anything you want to believe. All the while irreversibly damaging our ecosystems in ways we probably can't even begin to understand yet.
