One of the most powerful forms of evidence that there is an innate “language gene” is the development of creole languages out of pidgins. Wikipedia explains it this way:

Pidgins are rudimentary languages improvised by non-native speakers; when pidgins creolize, however, they develop fully-formed and stable grammar structures, usually as a result of the pidgin being natively learned by children.

Unfortunately, while there are many creole languages, and they share many similar features, it is very rare to be able to watch this process in action. That is why work on a community of deaf children in Nicaragua is so important:

Following the 1979 Sandinista revolution, the newly installed Nicaraguan Government had hundreds of deaf students enrolled in two Managua schools. Initially, the education officials adopted “finger spelling,” using simple signs to limn the alphabets of spoken languages. The result was a complete failure, because most students did not even grasp the concept of words, never having been exposed either to spoken or to written language. The children remained linguistically disconnected from their teachers.

Initially, the students could only use crude gestural signs developed within their own families, but once the students were placed together, they began to build on one another’s signs. While the inexperienced teachers found it hard to understand their students, the children had no problem communicating with each other. A new language had begun to bloom. Within just a few generations, a mature language with rules and grammar was born.

The Sandinista officials asked for help from outside scholars. After the linguists finally decoded the children’s creation, Nicaraguan Sign Language became a classical case of modern linguistics.

I mention this because I just saw an announcement for a new article in Science by Ann Senghas, one of the linguists doing research on this group of children. Unfortunately there is a three month embargo on online access to Science at my university, so it will be some time before I read the article itself – still it seems to support the concept of a natural process of creolization:

Senghas studied a property common to most spoken and sign languages around the world: that expressions are constructed from pieces with smaller meaning. For example, if we say a wheel is rolling down the hill, we use different words for ‘rolling’ and ‘down’, even though both are part of the same action. This provides us with a flexible vocabulary that can be mixed and matched to describe other events.

Senghas asked signers of different ages to tell a story and found that, by the second ‘generation’ of children, those speaking the newborn Nicaraguan language had a similar system. Rather than have one sign for ‘rollingdown’, which would be the most economical option, they had two separate gestures.

This suggests that children are born with a natural ability to break down language in this way. Hard wired rules like this help explain how language is acquired so easily.

UPDATE: More links over at Languagehat, including this NY Times Magazine story from five years ago.