Modern humans tend to consider their own destructiveness as being minimal up until around the time of the industrial revolution. And indeed, there is no doubt that our impact on the Earth increased. But that was far from the start of our planet-changing activities.
Archaic humans (Homo sapiens idaltu) were migrating from Africa around 70,000 years ago. (From here, I will use the abbreviation ‘kya’ for ‘thousand years ago’, so that would be 70 kya.) 100 kya, the world was dominated by at least three distinct great ape species, including our direct ancestors. By 30 kya, our ancestors were more or less alone; we’d overrun our cousins.
Migration from Africa seems to have been driven largely by population pressures and the need for food. We followed the big game west, out across Europe and Asia, over land and water and ice.
Around 65 kya we arrived in Australia. By 50 kya, many large mammal species here were extinct, hunted and eaten by our forebears. The same pattern can be seen in the Americas; extinctions followed the arrival of humans.
It wasn’t just animals we did as we wished with. It’s estimated that about 10% of the Amazon is in its current form due to the intervention of early humans. We encouraged the plants that were more beneficial to us: the plants we could eat from, or those which would suit the animals we wanted to eat. We discouraged or killed off plants that didn’t suit us. Burning the undergrowth left more space for large game herds.
For about 10,000 years we’ve been domesticating food plants, cultivating what we want to eat and clearing out the plants we can’t use. This in turn lead to an expansion of population, as our deliberately chosen and cultivated crops could support more people than foraging for naturally occurring plants.
So basically what I’m trying to say is that humans and our ancestors have been transforming Earth for our own benefit for a very very very long time, and that’s on top of natural events and constant climate fluctuations. There’s some food for thought when you consider trying to reverse it all. Good luck trying to figure out what’s ‘normal’, ‘natural’, or ‘pristine’; is it a hundred years ago, or a hundred thousand? I’m not saying don’t try. Just be aware of what you’re trying to save the planet from.