I remember it as portraying them using lots of subtle gesturing, sign language and slight head/posture changes to supplement sparse verbal communication, which made it seem like they knew what the other was thinking until you learned to decode it.

Did they actually have telepathic abilities in the book? Did I mentally erase that?

Yes, it's there. Th series is kind of all over the place.

God damn. I read a bunch of them as a teenager and went back as an adult to read one of the later installments and I was pretty weirded out by domestic scenes that I can only describe as Flintstones-esque. It surprised me because I remembered the series having a reputation for being well researched (albeit some of that research was outdated by the time Shelters of Stone came out).

Likewise the sex scenes struck me as very frequent and drawn out. Odd to pivot that series to caveman themed romance novels!

AFAIR the shaman of the tribes have some psy/spiritual abilities, which actually connect with the rape bit, during some shamanic meetup (?) the religious leaders ee into the future... and the neanderthal/sapiens offspring is the only one who has one. I liked that bit.