Host Neil deGrasse Tyson is on a voyage to explore the relatedness of all living things and the possible evolution of life in the cosmos. Go on a journey to discover how artificial selection turned the wolf into canine breeds and how natural selection sculpted the complex human eye. Later, Tyson visits the grand Hall of Extinction, a monument to all the broken branches on the tree of life. Retrace the story of life on Earth and the unbroken thread that stretches from the first one-celled organisms to human life.