different from other animals. This relates to more than just brain size; it is important what other things our brains can do and when and why they evolved that way. And for this there are very few physical clues; artefacts left by our ancestors don't tell us what speech they were capable of making. One thing we can see in the remains of early humans, however, is the development of the mouth, throat and tongue. By about 100,000 years ago, humans had evolved the ability to create complex sounds. Before that, evolutionary biologists can only guess whether or not early humans communicated using more basic sounds. D Another question is, what is it about human brains that allowed language to evolve in a way that it did not in other primates? At some point, our brains became able to make our mouths produce vowel and consonant sounds, and we developed the capacity to invent words to name things around us. These were the basic ingredients for complex language. The next change would have been to put those words into sentences, similar to the 'protolanguage' children use when they first learn to speak. No one knows if the next step – adding grammar to signal past, present and future, for example, or plurals and relative clauses – required a further development in the human brain or was simply a response to our increasingly civilised way of living together. Between 100,000 and 50,000