To simply describe this movie, it is a version of Lord of the Flies. The idea is that isolated from civilisation, people become like animals. This is partially true in this movie but moreso it seems to fall apart when we see one group of people who are developing their own civilisation. Still, this is similar to Lord of the Flies were one group became savage and hostile, while the others tried to become more civilised.
This movie, though, is based on another book: The Penal Colony by Richard Herley and supposedly it is supposed to be a critique on the prison system. In the film, the prisons are supposed to be money making corporations where prisoners assigned there are reduced to slave labour. Basically there is a hierarchy, and the island Absolom is at the top. Prisoners who prove to be too troublesome to turn into slave labourers are banished to the island and are left to fend for themselves. The prison is nice to drop in small amounts of food, but most of the time the inhabitants must scrounge for themselves.
If this is supposed to be a critique on the prison system, there seems to be a huge lack of it. What I saw in this movie was a treatise on the savagery of humanity, and the warden is actively trying to encourage the savagery. If they are civilised then they might turn against him, so if they are busy fighting, then all the better. The weird thing I noticed, is that the warden personally came to the island to deal with the problem. Thus he was sticking his neck out in a way that was purely illogical. It seemed to be an excuse to get him there to kill him.
Review by david-sarkies from the Internet Movie Database.