People alive today and their immediate ancestors—modern humans—had multiple ancestors in the Middle Pleistocene. They did not originate as a new clade—the unique descendants of a recent, small African population. Therefore, the anatomical, behavioral, and genetic aspects of their modernity are not tied together in their origin. Instead, these key components of modernity have different origins and evolutionary pathways that can be understood as distinct, although interrelated, processes. Each process characterizes all living and recent human populations, and their interrelationship derives from a shared unifying factor: changes in human demographic history originating as the consequence of increased adult survivorship. Longer lifespans helped make humans modern.
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