Our ancestors' brains went from chimpanzee-sized to modern-sized (actually slightly bigger than today) between two million and one million years ago, and more importantly the language-governing areas increased in size during that stretch. So human beings a million years ago were very much like us today, just without the advanced technology.
Millions of years, likely. The whole reason we’re successful is because our pre-human ancestors were empathetic and cooperative enough to build societies.
We see those same traits in many other primates, and they’re not something it makes sense to evolve, lose, and evolve again. Those traits predate us.
Language almost certainly predates us, since we see it not only in other primates, but in non-primate species, too. And based on the humour we see in many animals, you can bet we were making dick jokes nearly out of the gate.
Societies weren't built on empathy, they were built on security. Not just physical security but food as well. No society in history was built on empathy, ever.
What about caring for the elderly and disabled? We see anthropological evidence of many behaviours that can only be explained by compassion and empathy, some of which would have actually detracted from security.
The notion that the early formation of societies was based on security rather than empathy is outdated. Compassion has many evolutionary advantages, especially in primate species where offspring are born vulnerable. It’s clearly evident in other primates who live in groups (or ‘societies’), as a driving force of cooperation and group cohesion.
Those papers are both fascinating reads, and I highly recommend them both for a deeper understanding of why and how empathy is crucial to our success as a species.
Always has been. This is where the whole "Dark Ages" idea comes from, IIRC: people further on in time wanting to separate themselves as special and more advanced.