The really old DNA from Neandertal has shown that most (iow, non-African) moderns have Neandertal DNA. To have 2% show up after that length of time shows that much (or even most) of our ancestors were Neandertal; our great-great-great-great-grands number 64, which is less than 2% each in our own cells.
And that 2% is NOT necessarily the same 2% across all of us. So your 2% and mine might be off by 1/2%, so between us, we have 2.5% of the Neanderthal genome.
Scientists now say that up to 70% of the Neanderthal genome is found within the current living population of homo sapiens!
From a two hour PBS special on the latest research on Neanderthals, from this past October:
Watch it here: https://www.pbs.org/program/neanderthal/
You might have to put in your local PBS Station web site to watch.