Interested to see what you think, if you do reread them! Gentle Giants sounds familiar by title, but for content I draw a blank. I can still visualize the cover of Inherit the Stars, possibly because of that temporally inconsistent man. There's a very vague sense that the Hogan has stuck better than it might've because I read Benford's Timescape around the same time.

ETA huh! The Wikipedia page for Timescape links to a different Hogan novel, one I hadn't heard of.