It seems that the human species is, if such a thing is possible, too successful. We are crowding out other species at a rapid rate and, crucially, on a worldwide scale. There is no spare habitat left, where either our excess population or the displaced species can go and make a new start.

One might imagine something similar happening to the top predator on an isolated island. Can evolution deal with this somehow? It seems like the opposite of "survival of the fittest" -- we have become overly fit.

Not sure I completely agree with you. Yes the human species is increasing but we are nowhere near saturation density worldwide and when/if that happens then same as for any other species numbers will be balanced by availability of food and water.

What we are doing as the dominant species is greatly damaging the planet and threatening many other species. As a rule homeostasis will I suspect reach a new equilibrium but what that will look like in thousands of years is anyone's guess! Even if we were to nuke most of the planet some species would still survive though mutated and different from now.

In summary I am not sure that the current problems are that much to do with evolution which takes place over a longer scale. That is not of course to minimise the issues and gravity of species extinction and global warming.

My 2 cents - let's see what others think.

Yes, I agree we have not yet hit carrying capacity (if only becuase we are still spreading etc., where most other species simly could not inhabit everything from the desert to ice caps). If we do though, then certainly things will kick in thought he complexity of humanity means this might well be more social evolution (pressure to have fewer kids) or technological (increasing plant yields) et.c rather than what we might consider more classical evolutionary pressures.

In the case of your large predaotr example, these patterns are quite consistent and we might indeed expect humanity to follow them - we could have fewer children (less resources used per generation), get smaller (less resources used), diversify (split into multiple species / lineages each focusing on different resources to reduce competition, pretty unlikely for us) or become more competitive (die back from lack of resources).

We already see non-evolutionary responses to higher fitness in humans.  In several countries birth rates/population have been getting lower for many years.  These are countries where individual people have decided that they do not have the resources (time and money) for multiple children.

Another huge factor affecting this is that women are waiting until they are older to have their first child.  This has a giant impact on the number of children they can possibly have and lowers the birth rate overall.

Even though we have used our big brains to build technology to increase our potential fitness (greater access to food and healthcare -> lower mortality rates, higher fertility), we are also using technology to decrease our reproductive fitness (birth control).