Can Inuit people survive the Arctic cold thanks to deep past liaisons with another species? Adam Rutherford talks to geneticist Rasmus Nielsen who says that's part of the answer. His team's research has identified a particular section of the Inuit people's genome which looks as though it originally came from a long extinct population of humans who lived in Siberia 50,000 years ago. The genes concerned are involved in physiological processes advantageous to adapting to the cold. The conclusion is that at some point, the ancestors of Inuits interbred with members of this other species of human (known as the Denisovans) before people arrived in Greenland.

Also in the programme:

The woodlice which are made either female or male because of a gene that once belonged a bacterium. The gene came from a dead microbe and was incorporated by chance into the woodlouse genome. This is the first known instance of the invention of an animal sex chromosome through bacterial donation. We talk to Richard Cordaux of the University of Poitiers and Nick Lane of University College London about the discovery.

Peace through particle physics. Roland Pease visits SESAME in Jordan - the Middle East's first synchrotron facility is about to start operating. The experiment brings together scientists from all over the Middle East in common cause, with for example Israeli, Palestinian, Iranian, Egyptian and Turkish scientists working side by side.

Marine ecologist Autun Purser tells Adam about his European team's discovery of ghostly octopods living at 4,000 metres on the dark, cold sea bed of the Pacific ocean. Autun's camera has caught extraordinary egg brooding behaviour by this new kind of octopus. It lays its eggs half way up the stalks of dead sponges and then guards them for several years until they hatch. Unfortunately, the sponges only grow on lumps of metal-rich rock called manganese nodules which form slowly on the deep sea floor. Several companies are now exploring the possibility of extracting vast quantities of these nodules in deep sea mining, threatening the existence of the sponges and the octopods depending on them.