We will nvestigate the first skeleton that really looks like us –Turkana Boy– an astonishingly complete specimen of Homo erectus found by the famous Leakey team in Kenya. These early humans are thought to have developed key innovations that helped them thrive, including hunting large prey, the use of fire, and extensive social bonds. The program examines an intriguing theory that long-distance running –our ability to jog– was crucial for the survival of these early hominids. Not only did running help them escape from vicious predators roaming the grasslands, but it also gave them a unique hunting strategy: chasing down prey animals such as deer and antelope to the point of exhaustion. Birth of Humanity also probes how, why, and when humans' uniquely long period of childhood and parenting began.

xamines the fate of the Neanderthals, our European cousins who died out as modern humans spread from Africa into Europe during the Ice Age. Did modern humans interbreed with Neanderthals or exterminate them? The program explores crucial evidence from the recent decoding of the Neanderthal genome. How did modern humans take over the world? New evidence suggests that they left Africa and colonized the rest of the globe far earlier, and for different reasons, than previously thought. As for Homo sapiens, we have planet Earth to ourselves today, but that's a very recent and unusual situation. For millions of years, many kinds of hominids co-existed. At one time Homo sapiens shared the planet with Neanderthals, Homo erectus, and the mysterious "Hobbits"–three-foot-high humans who thrived on the Indonesian island of Flores until as recently as 12,000 years ago. "Last Human Standing" examines why "we" survived while those other ancestral cousins died out. And it explores the provocative question: In what ways are we still evolving today?

The episode, devoted to the planet Mars, begins with scientific and fictional speculation about the Red Planet during the late nineteenth and early twentieth centuries (H. G. Wells' The War of the Worlds, Edgar Rice Burroughs' science fiction books, and Percival Lowell's false vision of canals on Mars). It then moves to Robert Goddard's early experiments in rocket-building, inspired by reading science fiction, and the work by Mars probes, including the Viking, searching for life on Mars. The episode ends with the possibility of the terraforming and colonization of Mars and a Cosmos Update on the relevance of Mars' environment to Earth's and the possibility of a manned mission to Mars.

Carl Sagan teaches students in a classroom in his childhood home in Brooklyn, New York, which leads into a history of the different mythologies about stars and the gradual revelation of their true nature. In ancient Greece, some philosophers (Aristarchus of Samos, Thales of Miletus, Anaximander, Theodorus of Samos, Empedocles, Democritus) freely pursue scientific knowledge, while others (Plato, Aristotle, and the Pythagoreans) advocate slavery and epistemic secrecy.

The simple act of making an apple pie is extrapolated into the atoms and subatomic particles (electrons, protons, and neutrons) necessary. Many of the ingredients necessary are formed of chemical elements formed in the life and deaths of stars (such as our own Sun), resulting in massive red giants and supernovae or collapsing into white dwarfs, neutron stars, pulsars, and even black holes. These produce all sorts of phenomena, such as radioactivity, cosmic rays, and even the curving of spacetime by gravity. Cosmos Update mentions the supernova SN 1987A and neutrino astronomy.

The idea of intelligence is explored in the concepts of computers (using bits as their basic units of information), whales (in their songs and their disruptions by human activities), DNA, the human brain (the evolution of the brain stem, frontal lobes, neurons, cerebral hemispheres, and corpus callosum under the Triune Brain Model), and man-made structures for collective intelligence (cities, libraries, books, computers, and satellites). The episode ends with speculation on alien intelligence and the information conveyed on the Voyager Golden Record.