The boy’s immoral behavior had nothing to do with biological factors. Because when the plane crashed on a deserted island, they were able to find a way to keep the peace between them. So they were really nothing wrong with them biologically.
I believe that the boys immoral behavior and savageness begun when the conch shattered into pieces. Order was disrupted and there was no parental guidance. The environment that the boys were in, played a big role in their behavior. They did not have proper shelter, food and clothing. They only had the clothes that they had on their backs. They were exposed to the elements.