Complex human conversation began around 50,000 to 100,000 years ago . Professor Shigeru Miyagawa notes single words bear traces of syntax . For example, the word " dog " is a combination of two separate sounds that are both pronounced as one sound. He believes humans combined an 'expressive ' layer of language , as seen in birdsong , with a 'lexical ' layer , as seen in monkeys .
Complex human conversation began around 50,000 to 100,000 years ago . Professor Shigeru Miyagawa notes single words bear traces of syntax . He says this shows the words came from an older , syntax-laden system . He believes humans combined an 'expressive ' layer of language , as seen in birdsong , with a 'lexical ' layer , as seen in monkeys .