[aaaxyz]

>I wonder can it instead of "transmission" be that the fire-capable just out-competed the rest and dominantly spread all over the place as a result

One argument against that is that transmission is much more frequent than replacement in human history. We have countless examples of technologies (agriculture and writing notably) being transmitted to different cultures, whereas the examples of cultures out-competing and replacing others through technology are rare.

[trhway]

>the examples of cultures out-competing and replacing others through technology are rare

Alexander the Great - phalanx with resulting spread of Greek culture over all the Middle East, Roman Empire - countless advantages over the cultures they dominated, Vikings - sea faring ships and navigation, Columbus+/Americas and the whole colonial period across the world, ...

[aaaxyz]

I used the word culture but I really meant population in the sense that the original commenter used it (i.e. a group of people replacing or displacing another, rather than imposing their customs on another).

[sudosysgen]

Except for the last one, you're describing transmission not replacement.

[mytailorisrich]

That's exactly what happened in Europe, though:

Farmers moved in from the near East and replaced previous populations of hunters gatherers.

[inglor_cz]

There is a continuum between transmission and replacement.

The Japanese adopting democracy after WWII was almost pure transmission; the population stayed basically the same.

The Holocaust was almost pure replacement; only a few people from mixed families survived in some areas.

But "something in between" is much more typical. Contemporary Iran is as much a heir to ancient Persia as it is to the Arab conquest and Islamization. Roman conquest of Britain led to a significant population admixture from the rest of the Empire and Romanization of local Celts at the same time. Expansion of Germans through Central and Eastern Europe in 12th-18th century was a thorough mix of replacement and transmission.