The thing to remember is that, in the past, humans. . . were humans. As a species, we haven't really changed a whole lot.
Would you personally be able to do all the work it takes to live entirely on your own? Would you be able to go hunting and fishing and foraging for all your own food? Would you be able to grow every other food you need? Would you be able to raise livestock and collect eggs and shear sheep and milk cows/goats/etc? Would you be able to tan hides and grow and prepare plants and spin wool into yarn and thread to make cloth? Would you be able to make all your own clothes from that cloth, do all the sewing and weaving and knitting?
Would you be able to cut down trees to build your home and cook your food? Would you be able to collect and filter water for drinking? Would you be able to go put and mine for metal? Would you be able to smith your own tools and other metal materials? Would you be able to build all your own furniture?
Would you be able to make your own parchment or paper? Would you be able to make all your own ink and pigments and paints and dyes? Would you be able to make things like shampoo and perfume with only things you've collected yourself? Would you be able to blow glass to make containers? Would you be able to make all your own dishes woth only materials you've gathered yourself?
Would you be able to do all that entirely on your own? For your entire life?
No, obviously not, that's just absurd. Sure, you could do some of those things, but not all of them and certainly not constantly or as well as other people could do them. And that's just the very basics; there's so much more you'd have to do to not only survive but also be happy.
Humans were not more capable in the past, they either had support from each other to thrive. . . or they didn't and often didn't survive at all. This "everyone is on their own" attitude that's become so common in anarchist and anti-capitalist communities is the result of capitalism specifically isolating people to make them more dependent on exploitative systems rather than each other.
Humans have survived as long as we have by living in communities and supporting each other. That's how we lived in the past and that's how we need to live to have a future.