What a bizarre statement. Of course you are not designed for anything. You have adapted, genetically and socially. And you keep doing that. Modern society would collapse if change to a state of the world that you describe would quickly come. If it comes slowly, no matter what change, humans will adapt. Not all of that will be pleasant, but it eventually works out.
That means the modern society is not sustainable and cannot adapt to long-term changes. It's like those cities, where all traffic and power supply would be affected for every rain. That's not adaptation. That's just living precariously on greed and assumptions.
The drastic changes, if any, themselves would be purely man-made, not like asteroids that killed dinosaurs. A proper evolution or adaptation would not have drastic changes. Changes would be gradual in synch with the pace of biological evolution.
Adption is not just genetical. A person can move from northern Europe to southern italy without problem. Its genetics don't need to change for that.
> That means the modern society is not sustainable and cannot adapt to long-term changes.
I don't see that connection. As long as change comes sufficiently slowly, adaptation is no problem. It's mainly that the quicker change comes, the more painful adaptation is. This it unrelated to how sustainable society is.
We seem to be talking past each other?
Why? I, as the poster you replied to, do not see it this way at all. Any society, modern or not, can adapt to slow changes. And rapid changes would be at least as damaging several centuries ago, when for example 2-3 consecutive years of bad harvests meant a major upheaval.
Things can look a lot smoother after a few centuries. My 2c.
Back then 2-3 consecutive years of bad harvests meant a major upheaval for a few affected areas. Now that those areas supply food to the whole world the problem has grown in scale and fragility.