In 2018, the International Association of Athletics Federations (IAAF) introduced new eligibility regulations for female athletes with differences in sex development (DSDs). These regulations are based on the contention that women with high levels of endogenous testosterone and androgen sensitivity have a performance advantage over their peers. South African middle distance runner, Mokgadi Caster Semenya, who won two Olympic gold medals in 2012 and 2016, and Athletics South Africa, are contesting the legality of these new regulations. The basis of their objection, at the Court of Arbitration for Sport, is that there is a lack of scientific evidence showing that endogenous testosterone concentrations substantially enhance sports performance. Caster, who is DSD herself, has lost her case and Adam turns to expert in sport, exercise and genomics at Manchester Metropolitan University, Dr. Alun Williams to explain the implications. Less than a decade ago, an entirely new branch of the ancient human tree was discovered. These new hominins were named the Denisovans, after the Denisova cave in the Altai Mountains in Siberia where fragments of finger bone and teeth were discovered, and genetic sequencing of a finger bone revealed that they were a new hominin group, an extinct sister group to Neanderthals. This exciting find contained a tantalising puzzle. Traces of Denisovan DNA are found in modern-day population groups like Sherpas, Tibetans and some other neighbouring populations and this includes genetic variants which help them to survive at high altitudes where the oxygen levels are low. The original Denisovan cave is only around 700 metres, so why would such an adaptation be necessary at these altitudes? This week a new paper in Nature slots a big piece into the puzzle. Teams from the Institute of Tibetan Plateau Research and the Max Planck Institute for Evolutionary Biology have found another Denisovan fossil – this time a mandible, a lower jawbone, still containing teeth – from the vast Tibetan plateau in China. At 2.3 Km above sea level, it’s very high and the air is thin, and 160,000 years ago, which is when the fossil has been dated to, it would have been a very challenging place to live indeed. In fact this jawbone is the earliest known hominin fossil found on this enormous plateau. Adam calls in Professor Fred Spoor, from the Centre for Human Evolution Research at the Natural History Museum in London, to examine the facts and to see if we can work out how far and wide these hominins travelled. Producer: Fiona Roberts