To be honest it's both interesting and embarrassing to discover that no brain researcher had ever investigated brain cells' development from the very beginning to know the lineages of various cells.

This just goes to show how huge holes we have in even the most basic knowledge about biology.

We can cut'n'splice DNA in various ways, but up until now we didn't even know where do all of our neurons come from.

There are still more unknowns in those basic areas of biology e.g. how bio-currents shape development of organs in both an embryo and a fully developed organism.

It's rather obvious that there are key differences there but we don't have any solid knowledge about this mechanics itself, let alone on how it differs as the organism matures.