Warning: This is fully 100% conjecture and opinions that I don't have any significant amount of backing for (as usual). Feel free to verbally destroy me with intimate knowledge, scientific studies and scary numbers. But if you choose to do so, please be nice...I'm rather sensitive :(
We often talk about the idea of nature vs nurture - whether our genes or our environment are the determinants of our psychology. For all the debate out there, I feel that it is (or should be) reasonably obvious that both play a significant role in shaping our world view and personality (i.e they're not mutually exclusive). Moreover, the two interact with each other - it is in our nature to adapt and learn from the environment in which we live. That innate ability to adapt is what has made us such a versatile and successful species.
Personally, I often find myself falling on the side of nature when thinking about these things. Part of the reason why is because I really do view humans as one views animals - driven by primal desires to survive and propagate genes. This is consistent with my evolutionary worldview (that consistency being a worthy exchange for the large quantities of cynicism this type of thinking brings). The nice thing is that even if humans are ultimately animals, I'm one of them and understand their language and individuality. I also think that we have a lot more complexity and layers, so much so that connecting our actions to those primal instincts can often be difficult or impossible.
There's one more caveat to my view. I sometimes feel that we're outgrowing some of those instincts, and slowly (or rapidly in geological age), we're finding enough distractions to give life a new meaning. And our emotions are what drive us to that meaning. But I'm not sure, and maybe those emotions just ultimately tie back to a primal instinct.
As a more specific example, a lot of us have made it our life's purpose to be joyful. This makes sense to me. Joy feels good. But maybe joy exists so we re-do what we just did to bring us that joy? Maybe this is important because whatever we did pertains to survival or gene propagation. It's easy to imagine in social settings. I imagine that the nice homo sapiens sitting around their fire 100'000 years ago felt joy in each other's company just as we do sitting around a pub table sharing drinks and food with friends. That feeling of joy would encourage them to seek that experience again, and thus strengthen those bonds with their fellow tribesmen. Social bonds directly led to survival (like when your buddy saves you from a lion), as well as gene propagation/protection of offspring.
Maybe the link to modern day is direct. Like when your buddy saves you on the math exam, thus letting you pass engineering, thus reaching the promised land of attractive ladies and a successful life (note: it's a lie). But likely it's not that simple. What is clear to me though, is that our survival has always been incumbent on social interactions, and that's why our emotions are so sensitive in social settings.
