If humans never came to be, what animal would have dominated the world? Because one animal has to be at the top of the food chain... And that animal will always overproduce - no escaping it...
Also, would the alternate animal have been more or less environmentally healthy, considering it's appetite, and what it would have eaten. Would the food chain have been altered for the better or worse?
...What about that animals waste? Would the planet be covered in feces? Because they surely wouldn't have waste management.
Our animal ancestors made choices which developed a larger brain. Homosapiens are just one branch among many. Other species are fairly well adapted to their environment so maybe wouldn't have to face the same choices mammals had to. Maybe from mammals a humanoid species is inevitable. So some other humanoid type species not particularly different from us. Or maybe none survived, Homospaiens made some random choices which allowed us to survive.
At any point could have made wrong choices which wiped out the species, still can.
Some maybe reptiles & insects would be around but I suspect the evolution of humanoids pretty unique.
Feces, no problem really. It's fertilizer basically. Humans have problems with it because of our choice of sanitation. Other animal sometimes even eat feces. Their immune system can handle it, ours can't anymore.
I suspect if not humans, some humanoid branch then just a bunch of reptiles and insects with not much more intelligence than what they have today. Intelligent life maybe a fluke.