Life on earth is so diverse that it’s easy to think that anything is possible, as long as it doesn’t break the laws of physics. So can biologists predict what alien life might be like? Nick Lane will argue that the answer is yes. All complex life, from plants and animals to mushrooms, is shockingly similar at the level of its cellular building blocks. And all complex life is sexual. Beneath its many-splendored appearance, there are deep constraints on how life has to be. If we can predict the sex of aliens, what does that say about ourselves?