Three problems sit under every other problem humanity has. I find them largely invisible at first glance.
The biological problem is that our genes strongly shape our behavior. Twin studies in behavioural genetics put the heritability of most behavioral traits near half. Evolutionary psychology has been showing why for decades, though society is still catching up. Knowing this makes it easier to accept ourselves and others. It also makes it unreasonable to expect people to change their minds easily.
Some brains are wired like a program that returns one result. We also carry a built-in list of cognitive biases. The strongest is confirmation bias, which I treat as the ultimate bias, and the deeper limit I call the reflexivity limitation. Progress is still possible, only slow.
The social problem is the set of imperfect institutions that grow out of those biological limits. Edward O. Wilson put it best in a debate recorded on Wikiquote: “we have paleolithic emotions; medieval institutions; and god-like technology.” Technology, at least, is a good outgrowth of our biology. History shows the social problem gives way. Advanced nations have built fairly stable societies. That is a long way from the “solitary, poor, nasty, brutish, and short” default that Thomas Hobbes described.
The entropy problem is the least acknowledged. Its formal statement, the second law of thermodynamics, sounds abstract. So I prefer the memory aid from Steven Pinker: things fall apart. Bodies, societies, and the planet decay without care and upkeep. Life is a constant struggle to survive and to flourish.
The essential question for our species is this. Is progress limited to the slow change we have seen, or can solutions be sped up?