We actually do not, we feed on and use the ecosystem as we see fit.
That's true of every invasive species when you put it in a new habitat. Our natural niche was as omnivores in the Ethiopian savanna, but we spread far beyond our natural environment. Just like rats in the cities, dingos in Australia, feral dogs/cats/hogs anywhere.
But the everything about this planet continues to go on if you remove humans, we're not integral to its function.
The world can go on just fine without any individual species.
My point was not about scientific classification, it was about documented history, in which there is a lot more than 400 years worth.
But there's only 400 years of history where we've been documenting closely enough to even distinguish one species from another. So how can you claim that evolution wasn't happening when you're relying on records that can't even tell, say, one species of crocodile from the next? And crocodiles take millions of years to speciate.
We did not see major genetic evolution, we saw genetic mutations between variants and even some cases of recombination - there is a difference.
But those are literally the building blocks of major genetic evolution, you just need many more of those events over tens of thousands of years to lead to a major change.
Here's an example of a significant adaptation in a much larger animal - a new sea snake species that appeared just in the last 500 years:
Hydrophis semperi - Wikipedia
en.wikipedia.org
Adaptation to fresh water in the sea snake Hydrophis cyanocinctus: tissue electrolytes and peripheral corticosteroids - PubMed
Adaptation to fresh water in the sea snake Hydrophis cyanocinctus: tissue electrolytes and peripheral corticosteroids
pubmed.ncbi.nlm.nih.gov
But that's as much evolution as you're going to be able to see in 500 years. When it takes hundreds of thousands of years to accumulate enough changes to make major breaks, why do you imagine you'd see anything more significant in just a couple thousand years of recorded history?