This is one those chatty, pop-science books designed for the general reader and probably destined for TV. Subject: de-extinction, bringing back T-Rex and whatever else isn't about. And we do learn a lot because Helen Pilcher knows her stuff and has an accessible style. The rungs of the human DNA spiral are made from chemical pairs called "nucleotides", a bit like alphabet spaghetti, she says, adding that you'd need 14 million tins of the stuff (London to Sydney and back) to match human DNA. Of course, DNA is crucial in the brave new world of de-extinction. In 2002 scientists "reproduced" an extinct goat for seven minutes. Jurassic Park may be getting closer, the northern white rhino may be saved, the king brought back. She is in favour of reversing extinction, but also mindful of the ethics involved and scientists seen to be playing god.