There are lots of modern scavengers which prove the falsity of your assertion. Think hyenas, buzzards, and vultures. Condors are going extinct not because of the National Rifle Association, but because they evolved to eat the carcasses of dead mammoths. When the mammoths all died off, the condors days were numbered. Primitive tribes can easily find dead animals by simply noting gatherings of scavenger birds. A man can easily chase off the birds and keep the remainder of the carcass.
Exactly. Tribes of humans wouldn’t have a chance against the animal competition. In the thousands of hours I’ve spent in wilderness country I rarely ran across carcasses that weren’t stripped or rotted beyond nauseum. And that’s with far fewer scavengers in today’s world than existed 400K years ago.