Viruses
Viruses are interesting little things. Some say they aren't even alive, though seems more logical to expand our definition of life. Viruses have been around for a long long time, billions of years. There are bits and pieces of viruses in our cells from way before homo sapiens appeared on the scene, in part, defining who we are. Talk about your identity quandaries!
Viruses are the ultimate parasites. There are viruses that infect animals, plants, and bacteria. They need to enter a host's cell and use that cell's replication functions in order to reproduce – you know, like bankers.
Viruses are extremely small, so small our minds can't really understand. At the same time, there are trillions upon trillions of viruses, numbers so vast our mind can't really conceptualize. And take my word for it, trying to imagine these sizes or numbers will do yourself or anyone else no good, nonetheless they are very real.
As a life form that seeks to replicate, and maybe that's the simplest definition of life, viruses must conform to the processes of natural selection. Most simply, all life seeks to replicate. For some individuals, this replication process isn't exact, causing a change or mutation, a not exact copy. This mutation must then contend with the larger environment in which it finds itself. If the mutation helps the virus thrive and reproduce, the mutation gets carried on. If it doesn't, the mutation is gone.
The most important thing to understand is the mutation is not a reaction to the environment, it is simply a fault in replication. If the mutation then “fits” into the larger environment, it is carried to the next generation. All life can only be understood in the larger environment from which it evolved.
Over the last two years, a virus, either naturally mutated or human reconfigured, infected humans. This has caused the most disruption in human life I've experienced in my long life, a number unfortunately too easy to count. Unintentionally, the virus revealed all sorts of things about its hosts social environment. Two big ones; the great ignorance of the vast majority of people to all biological understanding, even or especially of their own bodies; second, America has no public health system, it has, like almost every other aspect of society at this point, a mega-corporation organized healthcare system, both resulting in plenty of problems dealing with the virus. Yet, if you ask what we've learned in the last two years, little to nothing is pretty much the answer. The conclusion, we have some tremendous systemic problems, and the viruses don't care about any of them.