We were never fully biological entities. We are, and always have been, the cybernetic ape.
Darwin is one of my heroes, but I believe he was wrong in seeing human evolution as a result of the same processes that account for other evolution in the biological world - especially when it comes to the size of our cranium.
Darwin had to put large cranial size down to sexual selection, arguing that women found brainy men sexy. But biomechanical factors make this untenable. I call this the smart biped paradox: once you are an upright ape, all natural selection pressures should be in favour of retaining a small cranium. That's because walking upright means having a narrower pelvis, capping babies' head size, and a shorter digestive tract, making it harder to support big, energy-hungry brains. Clearly our big brains did evolve, but I think Darwin had the wrong mechanism. I believe it was technology. We were never fully biological entities. We are and always have been artificial apes.
They shaped their tools and thereafter their tools shaped us, quite literally says Tim Taylor. Some ancestor like australopithecines started the stone toolmaking so as to fashion power extensions of themselves from sinew, leather, woven grass and wood; add in a pressing need to relieve mama's aching back, and the rest is a tumbling cascade into history...