Continuance (and probably some conclusion) on densities

[Bring4th_Austin]

good news is

This transitional body is one which will be, shall we say, able to appreciate fourth-density vibratory complexes as the instreaming increases without the accompanying disruption of the third-density body. If a third-density entity were, shall we say, electrically aware of fourth-density in full, the third-density electrical fields would fail due to incompatibility.

Where do the 4D bodies come from? Are they born from 3D parents?

its told in the Ra quote linked.

With this bit of clarity comes some more confusion for me. I now understand the transitional bodies are designed to facilitate 4D vibrations in a 3D reality. But I'm still not completely sure on how we as Humanity, not individuals, go about shedding the 3D bodies. What I can gather at this point is as the 4D vibrations take time to manifest in reality, we continue to incarnate dual-bodies. Once 4D manifestation is complete, we begin to incarnate into 4D bodies, but the humans present on earth at that time are going to be in dual bodies. Is this particular generation of dual body humans going to birth 4D bodies? Since they are dual body, will they be able to perceive this child with only their 4D body, not their 3D body? I just can't see, out of a chemical body pregnancy, a birth of only an electrical body.

I understand reproduction varies throughout densities...is it possible we stop reproducing 3D style and start only reproducing 4D style, however that may be?