Perhaps the old egyptain was never a coherent language. The pharaohs of the first dynasties are known to have united egypt, perhaps only then having created the opportunity for a united language to begin with, because it's reasonable to assume fragmented language beforehand. This means slow diffusion and many substrata of dialects and mutually almost incomprehensible variants as we still have (I don't know how bad it is in America but some German Dialects are incomprehensible). And Egypt isn't just the Nile that makes travel and exchange easy. E.g. nomads held key positions in trade and could hide a long time ignoring local struggles because they had domain knowledge in the desert, but also alienating themselves and their language. This increases the chance for a fragmented language continuum (a continuum of continua if you will, kinda fractal).

You think the pyramids are old? To the contrary, the north African Sahara is speculated to be as young as 5,400 years (although I remember reading something north of 100'000; indeed, it is not certain, probably fluctuating on and off for periods of time, too). I think that the pre-desert is the archetype of the reed fields, the paradise of the Egyptian mythology, https://en.wikipedia.org/wiki/Aaru -- to top that off, could the tree of knowledge be symbolic for the rain forest that was in the Mediterranean basin before it flooded a handful of million years ago or afterwards as it swelled on and off further along?

The article is too conservative? The article makes a few points about the wider Danube valley being central to early PIE civilization and industry. Which resonates very well with me. There is no certain PIE homeland hypothesis but this fits with the Krugan hypothesis.

Egypt went though several desertification periods some of which caused the collapse of the old kingdom this isn’t exactly a new discovery.

When the pyramids were built the Sahara has already existed but it didn’t creep that far up north as it did today.