Heredity and social fitness a study of differential mating in a Pennsylvania family. This book, "Heredity and social fitness a study of differential mating in a Pennsylvania family. Volume 1", by Wilhelmine Marie Euteman Key, is a replication of a book originally published before 1920. It has been restored by human beings, page by page, so that you may enjoy it in a form as close to the original as possible. This book was created using print-on-demand technology. Thank you for supporting classic literature.