First of all, language is biological system. It's virtually unstoppable. Just like our visual or hearing system. Language is a basic expression of the genes. At this level, the environment is just the switch-on button.
All languages are pretty much the same, universal, even though on the surface they look different.
If we look at all languages across the world whether Japanese, Russian or Welsh we can see that they all contain identical elements. We have a lot of evidence for this. So, language proceeds along a predetermined course and linguists are interested in what this course is and in what basic rules all languages share. But language has a second feature. It's a complex system of shared behaviour and social values.