Dogs and some birds communicate more complexly than he thought.
A few errrors exist; the ones I can find are largely cases in which facts that emerged since the book was published have disproved his contentions. Dogs and some birds communicate more complexly than he thought. Neanderthals did interbreed with modern humans—quite a lot. (As of publication of this book, that fact was unknown.) A few other points are too minor to note. One annoyance is the number of misspellings and typos, quite high for a Cambridge University Press book.