Research into the evolution of Homo sapiens forms a significant part of this novel. I consulted many works, notably Sapiens: A Brief History of Humankind, by Yuval Noah Harari; The Gene: An Intimate History, by Siddhartha Mukherjee; Neanderthal Man: In Search of Lost Genomes, by Svante Pääbo; many articles by New York Times science writer Carl Zimmer; and the incredible exhibit at the Musée de l’Homme about Neanderthal man. Dr. Hannah Brooks of Hudson Valley Cancer Genetics gave me invaluable guidance in all things relating to family genetic inheritance.