Disturbing Reasons Animals Go Insane

From primate nests in the African canopy to 5,000-year-old stone villages still standing in Scotland, this video traces fifteen discoveries that reveal when our ancestors stopped wandering and started building. Mammoth bone domes that stood for 429 years. Neanderthal stalagmite rings constructed in total darkness 176,000 years ago. A city of 8,000 people with no streets and no doors. Each entry examines the archaeological evidence, the researchers who found it, and the theories that still divide scientists today. The question sounds simple. The answer spans millions of years.