A critical difference between humans and all other life-forms is language. Neo-Darwinism teaches that language evolved from gestures into grunts, then into primitive and, eventually, highly evolved languages. A comparison of ancient and modern languages reveals that the so-called primitive languages are as complex—or in some ways more complex—in grammar and syntax, the ability to accurately express ideas, and other central aspects of language as most modern languages. One advantage in studying ancient languages compared to other ancient artifacts is that many ancient languages are known today in a fair amount of detail. All languages change, as can be easily determined by a study of a single language such as English, but no evidence exists that language began as animal grunts and evolved into fully developed human language.