It is estimated that 99 per cent of species have become extinct and there have been times when life's hold on Earth has been so precarious it seems it hangs on by a thread.nnThis series focuses on the survivors - the old-timers - whose biographies stretch back millions of years and who show how it is possible to survive a mass extinction event which wipes out nearly all of its neighbours. The Natural History Museum's professor Richard Fortey discovers what allows the very few to carry on going - perhaps not for ever, but certainly far beyond the life expectancy of normal species. What makes a survivor when all around drop like flies? Professor Fortey travels across the globe to find the survivors of the most dramatic of these obstacles - the mass extinction events.