Despite all of the scientific advances in genomic sequencing, genetic testing, and gene editing, science writer Carl Zimmer suggests we lack a rich understanding of what heredity means and how traits travel from one generation to the next. Cultural and environmental conditions have complex and nuanced influences on human biology, personal and family characteristics are not embedded exclusively in our ancestral DNA, cells within our own body birth new cells, and an infant’s DNA endures for years in a mother’s bloodstream. All of that, and much more, play significant roles in the legacies we inherit and pass on.