Sibling relationships can include everything from love and support–to tension, competition, and conflict. They might also play a fundamental role in the evolution of our species. In the final installment of our three-part series on family relationships, researchers Karen Kramer, Cat Hobaiter, and Rachna Reddy explore surprising new science about the role of siblings in primate and human evolution. Links to learn more: Why are there so many humans? Children and social learning Karen Kramer Cat Hobaiter Rachna Reddy Support Origin Stories and help us explore human evolution one story at a time. Your tax-deductible gift makes our show possible. Click here to donate! Credits: This episode was produced by Leo Hornak. Sound design and production by Ray Pang. Host and executive producer, Meredith Johnson. Our editor is Audrey Quinn. Theme music by Henry Nagle, additional music by Lee Roservere and Blue Dot Sessions. Sponsors: Dana LaJoie and Bill Richards, Jeanne Newman, the Ann and Gordon Getty Foundation, and the Joan and Arnold Travis Education Fund.