I think you are underestimating the intellectual capacity needed by prehistoric humans to perform all their activities; in short, to survive. It is true, prehistoric humans did the same things animals did. But they did it in a fundamentally different fashion.
Animals are largely driven by instinct. By contrast, we humans have very few instincts — perhaps none! — we cannot overcome. We can choose not to follow even the most basic survival instincts: We can voluntarily hunger to death, refuse to procreate, go out in the cold and freeze to death, with a warm home in sight. We can even actively end our lives.
But this freedom from pre-cast behavior has enormous benefits: It enables us to adapt to environments to which we are physically not well suited. Too light-colored people inhabit the Sahara; fur-less humans dwell in the arctic. We grow food in arid places, by means of irrigation. What makes this possible is a system of knowledge and customs commonly referred to as culture. This puts humans in a unique position among animals. Our survival depends on our mental capacity, not any longer on our instincts or our physical shape.2 This shift is what characterizes us. This shift was made possible by a change in our brains.
Some time in the evolution of homo sapiens something astonishing happened. It is the ability for symbolic reasoning and reflection. We see things not only as what they are; we imbue meaning in them which isn't obvious at face value. We tell stories about ourselves, about our ancestors, and about everything else we see. We keep memories of the past, and tell them to our children. We have rites which reinforce these memories and our sense of belonging, belonging to the place and to each other. The stories we told (like heavens full of scheming gods) were often much more complicated than the reality they tried to explain (like rotating balls on elliptic trajectories). We could create an adaptive symbolic working model of ourselves and our environment; one which was elaborate and complicated, and often poetic and beautiful.3
This ability proved an evolutionary advantage in times of rapid environmental changes and allowed us to survive where other species went extinct. We developed a brain that's "almost entirely plastic" (Feynman)1.
This unique ability to create internal models of the ever-changing world around us allowed us to make Gedanken-Experimente, predict the consequences of our actions. We could be strategic. Ockham hadn't been around yet, and the Ptolemaic way of making sense of it all was blossoming.
This ability to create and manipulate mental models with a high degree of freedom (not hard-wired to specific inputs or instincts) is key to our humanity. The result of our evolution was a brain which is almost completely unshackled. It is aggressively designed to invent stories and see patterns. We are the zoon politikon as much as we are a zoon poetikon, a story teller and singer.
Our mind is not modeled for a specific environment. We can live everywhere we can physically go — and beyond! This enables us to do things that seem very removed from what we did when we evolved. We are physical explorers as much as we are mental explorers. The very advantage of this particular line of evolution, its very essence is that it is not only ready for the unknown, but actively seeking it.
The lady whose leg he pulled responded: "No, really!?"
2 In fact, our instincts, for example our aggression, appear to become a danger to our survival rather than a requirement.
3 As an example for sophistication and information content consider Australian Aboriginal mythology with stories possibly describing events thousands of years ago.