Because there are no written records of origin of human language, since it was spoken and not written down, it is difficult to really know how or when it began. However, most scientists speculate that language started sometime between 30,000 to 200,000 years ago. Around 3.5 million years ago hominid ancestors started walking on two legs and some scientists believe that this caused a significant change in the throat structure that is needed for making sounds similar to what modern-day humans can make. However, although they were able to make these sounds, they may not have had the mental ability to use this until much later. The evidence for this is based off of the size of the areas of the brain necessary for language in these human ancestors -- these areas of the brain became larger as our human ancestors evolved, allowing scientists to speculate at what point in human history could our ancestors really verbally communicate with one another. What are considered to be the first modern-day humans, due to their similarity to our anatomy and tools, appeared around 195,000 years ago. However, not until about 50,000 is it thought that fully modern behavior, as we know it today, was present in our ancestors. It's thought that by this time rather complex language was developed in order to teach offspring how to make tools, etc. It is also thought that our human ancestors who could communicate better verbally would have an evolutionary advantage over those who could not communicate as well -- they would be able to warn others of danger or indicate where food is more easily. This means that those who developed and used language, even in its primitive states, would be more likely to survive and reproduce, creating offspring who would also be good as using language.

Some scientists believe that there was originally one proto-language shared by all human ancestors, while other theories suggest that languages were developed in multiple regions and do not have a common origin. As for the creation of the many languages present in the human race today, this is a good example of evolution -- all languages change over time (for example, what we consider to be English today is very different from what English was several hundred years ago) due to the people who use it, such as by incorporating slang or references of the current cultural trends into an every-day dialect. When different groups of people become geographically isolated from others, and are consequently not influenced strongly by others, their language can become very different from another language that may have shared the same origin, originally -- this is seen with what are called the "Romance languages," including Latin, French, Italian, and Spanish.

Hope that helps explain the origin and development of human languages!

That "experiment" has been run, actually (although not intended as an experiment): a colony of deaf orphans somewhere in South America was created as a place to put them with no parents. They were not taught any kind of language, including sign language. What they did was they invented a language of their own - which is like sign language in that it uses hand signals, but is completely unrelated and independent of the sign language we have for deaf people in our society. When linguists discovered this, the conclusion they drew from it is that human beings are instinctually tied to finding a way to communicate using language, and if no language is available, we make one up. This is one major behavioral trait that separates us from other animals - it may in fact be the only such trait, since some other animals can match us in problem-solving intelligence.