This is a problem of scale. You can't think that everything in society derives entirely from the raw intellect and talents of the individual people that live in it. When dealing with population-scale phenomena, you have to think more in terms of probabilities than in terms of individual talent.
For any given innovation, we can go ahead and assume that every population on Earth has the same proportion of "geniuses" with sufficient raw intellect to produce that innovation. But, raw intellect can only work within the limitations imposed by its environment. So, naturally, large populations with access to large landmasses will likely have more "geniuses" and more resources, and will therefore be more likely to produce more innovations. And, this becomes a self-feeding process: once someone gets ahead in the innovation game, they increase their capacity to continue innovating, so they become increasingly farther ahead.
Of course, it's not entirely a game of probabilities, but the probabilities do have a major impact.