The earliest populations are on the bottom of the dogpile of population replacement. Using a 90/10 split for each fused population after a successful demic replacement, the original host population genetics remaining would work out this way:
Pop A (prior to first wave)-- 100%
100 * .1
After first wave-- 10%
10 * .1
After second wave-- 1%
1 * .1
After third wave-- .1%
There is likely very little left from homo sapien sapien populations from Paleolthic, maybe nothing from Neanderthals of Western Europe, for this reason.
Most of our Neanderthal was picked up >60 kya in the Levant as part of the founder OOA population. The Neanderthal of <30 kya in Western Europe may have been annihilated without genetic issue at this point. There's barely a trace of Paleolithic hunter gatherers, a little bit more for the more recent mesolthic migrants, and then more from Neolithic and Bronze Age newcomers. Now, there are new major demic movements, birth rate differences among populations, etc. It goes on and on. Right now, Paleolithic Europeans' genetic legacy is on the bottom of the dog pile (Western European Neanderthal already crushed beneath them) and new pops are piling on everyday. Sorry to see them go.