Sagan discusses the story of the Heike crab and artificial selection of crabs resembling samurai warriors, as an opening into a larger discussion of evolution through natural selection (and the pitfalls of intelligent design). Among the topics are the development of life on the Cosmic Calendar and the Cambrian explosion; the function of DNA in growth; genetic replication, repairs, and mutation; the common biochemistry of terrestrial organisms; the creation of the molecules of life in the Miller-Urey experiment; and speculation on alien life (such as life in Jupiter's clouds). In the Cosmos Update ten years later, Sagan remarks on RNA also controlling chemical reactions and reproducing itself and the different roles of comets (potentially carrying organic molecules or causing the Cretaceous–Paleogene extinction event).

Richard Dawkins examines the growing suspicion the public has for science-based medicine, despite its track record of successes like the germ theory of disease, vaccines, antibiotics and increased lifespan. He notes a fifth of British children are currently not immunised against measles, mumps and rubella, attributing it to fears arising from a highly controversial report linking the vaccine with autism. Dawkins criticizes the growing field of alternative medicine which does not pass the same objective and statistical rigour as scientifically derived treatments using controlled double-blind studies. Without verifiable evidence, alternative therapies must rely on biased anecdotes and word of mouth to perpetuate. Dawkins observes these treatments have fanciful rationales and rituals behind them, with many alternative treatments employing pseudoscientific jargon such as "energy", "vibration" or "quantum theory" to give themselves greater credence to patients.

Has the age of antibiotics come to an end? From a young girl thrust onto life support in Arizona to an uncontrollable outbreak at one of the nation’s most prestigious hospitals, The film investigates the alarming rise of a deadly type of bacteria that our modern antibiotics can’t stop.

The film examines the profound claim that most, if not all, of the degenerative diseases that afflict us can be controlled, or even reversed, by rejecting our present menu of animal-based and processed foods.
Despite the most advanced medical technology in the world, we are sicker than ever by nearly every measure. Cases of diabetes are exploding, especially amongst our younger population. About half of us are taking at least one prescription drug and major medical operations have become routine. Heart disease, cancer and stroke are the country's three leading causes of death, even though billions are spent each year to 'battle' these very conditions. Millions suffer from a host of other degenerative diseases. Could it be there's a single solution to all of these problems?