All the Bayaka tribes people roles are performed by members of the tribe. According to production notes online they were initially perplexed as to what was expected of them. They had become so used to people making documentary film about them the idea of acting out something instead of just doing it was at first confusing. Judging by the results it's obvious they caught on quickly enough, as the performance by all are natural and completely believable.
Oka is a wonderful movie on a couple of fronts. Not only does it do a wonderful job of telling Whitman's story, including his obsession with recording all the sounds and music associated with the Bayaka people, it is as honest as portrayal as you'll ever see of the effects of displacement upon the displaced. Here are a people who if left alone would simply carry on as they've done for generations. Ideally suited to their home environment, they don't need to be rescued, they need to be left alone. Unfortunately we don't have the greatest record when it comes to leaving things alone. Maybe films like this one will help us understand how somethings are fine just the way they are and in some cases change isn't necessarily for the better.
Oka was first released in theatres in October 2011 and is being shown in selected theatres on specific dates around the world. Check the web site for dates of a screening near you.