Big question.. As a purely biological being we would have been extinct some centuries ago..the wild card in the equation however is our inate intelligence & how it has preserved the species.As we know, humans live & thrive in environments which are fully hostile to other mammals...we can survive on top of Mt. Everest, miles under the sea, in outer space...this is the intelligence factor. Removing the support structure a little or a lot would narrow down these choices...It would depend on the degree of "breakdown" of the "order" of the society. Assuming we would be reduced to wearing fur skins & weilding wooden clubs we would then be on par with most other mammels...I don't see that happening any time in the forseable future.