I read this book in 6th grade (2000-2001). It was about an archaeological dig – they were looking for the missing link. There were chapters about the daughter of the archaeologist, and also about a girl of the species they were studying. The missing link girl used nets to catch fish.
Lost Classics of Teen Lit: Name That Book! 
This sent me on a long search — I think it’s this book I also read as a teen at about the same time as you. Is the book you’re looking for A Bone from a Dry Sea by Peter Dickinson? https://www.goodreads.com/book/show/229459.A_Bone_from_a_Dry_Sea
LikeLike