In our third and final week looking at great unsolved mysteries Peter and Russell visit the Antikythera Mechanism. This complex analogue computer could predict astronomical positions and eclipses decades in advance. Then off to Peru and the mystery of the Nazca Lines. Why would people carve 70 different images into the Earth? Was this a way to communicate? Who would have done it? Join us as we talk about another two great mysteries.

Did you know that the Neanderthals were not the only other human species that lived? At one time we shared this planet with about 5 other "homo" species and we believe our human ancestry was made up of at least 14 other human species. This week Peter and Russell will take a look at our ancestral family tree and find out what other hominins lived before and while we were around. What did we share with them? What did we learn from them? and most important of all What happened to them and why are we the only one's left?

Do you have a favourite fun fact? Something to share when you're at dinner parties or filling an awkward silence? This week, Peter and Russell will try and get through 100 fun facts. Do you think they can do it? Do they side track too much? Let's see if they can get through 100 fun facts or will this turn into a multi-episode challenge.