Various cultures considered less evolved by the technology-obsessed Europeans had a sense of generational responsibility and a reverence for the land that gave them life. Whether their practices actually worked we cannot say, since the Europeans sprawled across so much of the globe and smashed the balance those cultures had maintained. That's a part of history and a reality from which the life of our species must go forward. Technologically advanced science may manage to put measurable numbers on the things that older cultures handled intuitively, so it could net out as a gain overall.
Our ancestors did hunt species to extinction. You have to eat, after all, and they were only human. On the rise to become human, plenty of them probably became meals for other predators. This engrained a sense that humans can do anything they feel they need to do, in order to survive and proliferate.
In reality, in any era, a person will do whatever looks like a good idea at the time, to get ahead. This may mean just staying one jump ahead of starvation or it could mean acquiring another million dollars to bolster an already immense fortune. Most people are wired to seek a sense of security. If a little is good, more is better. While many things may be normal, their effects can still be pathological. In other words, everybody feels a certain way, so it is widely accepted, but its long-term effect is detrimental. Think of fossil fuel consumption, or the presumption that wealth is good.
The idea that one individual's actions can do no harm grows directly from the sense that a person can and should do whatever is necessary to survive and proliferate. When survival itself is no longer in doubt, the perception extends to mere wants that loom in stature to seem like needs.
Humans have eaten carrion and each other in the course of our often unappetizing history. Someone, somewhere, has tried to eat just about everything. And when we learned to exploit more difficult resources, we developed more and more efficient implements to extract and refine everything from trees to minerals to sea creatures.
We are really just opportunistic scavengers. While some of us have figured out that we need to set limits on this tendency, the vast majority of people live by the old rules: if you need something, take it. If you no longer need something, drop it by the wayside, or throw it somewhere far from your house, if you don't want it stinking up the neighborhood. That may be in someone else's back yard, but we can deal with that later if they complain.
Sure, we have Earth Day and a lot of public awareness. But then a guy I know who seems quite environmentally aware shows up with the lunch his wife packed, with every single item in an individual plastic bag, and he tosses all the bags into the trash after he extracts the food. These bags get used for a total of three or four hours to contain this guy's food before they go into the waste stream. And we're talking sturdy zippered sandwich bags. Opportunistic scavenging supersedes education even in someone who appears to care. Lunch comes to him in these bags, and he consumes it without a critical thought.
As we revert to divisiveness and distrust, as we embrace insular religions and draw up teams for a future of conflict, our children's children could end up eating carrion and each other once again. Will we be honest enough to admit that we don't really care how they live? Evolution moves forward on a broad front, never stopping. Whatever is alive at any given time figures out how to manage conditions as they find them. There is no real need for long life, or happiness. Planetarily speaking, there is no need for life at all. We who are alive at this moment will do whatever makes us feel happy. If you want to cloak it with some glorious embroidery about the future, go ahead. We're all just taking our best guess, and hoping we remain comfortable up to the point of our individual deaths.
Our species will only have the future that enough of us collectively turn out to want.