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Episode 2 of 3

Duration: 1 hour

In this second episode Dr Alice Roberts charts how our ancestors’ hunt for food has driven the way we look and behave today – from the shape of our face, to the way we see and even the way we attract the opposite sex.

Clues to our ancestor’s diet can be found in some surprising places. Alice goes in search of a lion kill to find out how the tape worms in lion’s food reveal our ancestors were eating the same diet of big game 1.7 million years ago. She puts her teeth to the test to reveal that our teeth have evolved to shear through meat. But by comparing her saliva with that of chimpanzees she demonstrates that our body is as much designed to eat starch as it is to eat meat. And visiting a tribe of hunter gatherers in Tanzania, who still gather food in a similar way to our ancestors, Alice discovers that starchy tubers are crucial to survival when meat is scarce.

The latest research suggests that the way the different sexes found food throughout our evolution has shaped the way we relate to each other today. The way the Hadza tribe share food and form long-term couples is thought to be the origin of love and marriage in all of us. And a fun experiment with Britain’s best skateboarders shows they take more risks when women are present – it seems men are designed to show off to attract a mate.

  • Interesting facts

    • You will eat about 50 tonnes of food and drink 50,000 litres of liquid during your lifetime.

    • Your digestive system, from the mouth to the anus, is about 30 feet long. The small intestine is the major part of this, measuring about 20 feet long.

    • The inner surface of your small intestine is the size of a tennis court, to efficiently absorb nutrients.

    • It takes about 32 hours for food to pass through you, from being swallowed to excreted, travelling at about 1 foot per hour. Swallowed food moves into your throat at about 25 feet per second.

    • The digestive acids in your stomach are strong enough to dissolve metal, but you renew you stomach lining every three or four days so it doesn’t dissolve your flesh from the inside.

    • Your salivary glands will produce enough saliva to fill two swimming pools in your lifetime, pouring about 1 litre into your mouth every day.

    • Adults break wind about 14 times a day, producing 48 gallons of gas per year.

    • Methane is odourless, but the smell is caused by trace amounts of sulphur released by bacteria in your large intestine.

  • BBC TV blog

    BBC TV blog

    Find out what Origins Of Us presenter Dr Alice Roberts discovered when she studied wild chimpanzees in the Ugandan forest: “they were all around us in the forest, and would often pass by very close, sometimes a metre or two away - which was both terrifying and exciting”

    Read Alice Roberts' full post on the BBC TV blog


Alice Roberts
Series Producer
Zoe Heron
Executive Producer
Sacha Baveystock
Matthew Dyas
Matthew Dyas


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