Lab notes: a week of penis bones, Chewie's footprints and reverse ageing

Why don't humans have penis bones? I bet you've been asking yourself that question for ages, right? Well, now we have at least part of the answer. Be warned: it's not exactly flattering. Still, onto other intriguing evolutionary news: footprints discovered in Tanzania almost certainly belong to a species of human ancestor called Australopithecus afarensis. Even more exciting is that measurements have revealed that these belonged to the largest Australopithecus yet recorded, leading the Star Wars-loving researchers to nickname him Chewie. Leaping forward in time (and possibly back again as well), a new form of gene therapy has been shown to produce rejuvenating effect in mice, leading scientists to claim that the ageing process may be reversible. And more historic progress has been made this week as the UK's fertility regulator gave the green light for clinics to seek licences to create embryos with the DNA of three people, an experimental technique developed to help women with mitochondrial mutations have healthy babies.