Why did language develop?

Language developed for communication, to facilitate learning the use of tools and weapons, to plan hunting and defence, to develop a "theory of mind" and the tools of thought, and to attract and keep a mate. The adaptations required took place over many millions of years. The first important one was left-sided specialisation of the neural apparatus controlling involuntary emotional vocalisations that began more than 200 million years ago. The next was the development in primates of "mirror neurones" in the pre-motor cortex some 45 million years ago. These enabled the imitation and voluntary control of previously involuntary manual gestures and vocalisations. The third important adaptation was the descent of the larynx, 100,000 years ago, which greatly increased the phonological range of vocalisations that could be made. Thus, language did not develop all at once as suggested by Chomsky, but evolved gradually building upon adaptations originally meeting quite different needs.