In the back of my mind, is the memory of an article--popular science stuff--that explains modernity as the result of infantilization, with the moderns retaining the relatively large skull of the infant. That would make the Neanderthal types our ancestors and collateral cousins.
I think the infantilization was to permit a large brain through a small birth canal. The trick is to have a long infancy during which most of the brain growth occurs.
It will take more than this to show that Neanderthals were our ancestors.