Complex sentence: Like human nature, the tribal mind naturally resists overt change--a survival/growth mechanism that tends to filter out random thought migrants that don't serve its native purposes and prejudices, while allowing entry to those that do.
Split into simpler sentences: Like human nature, the tribal mind naturally resists overt change. This resistance acts as a survival/growth mechanism that tends to filter out random thought migrants that don't serve its native purposes and prejudices, while allowing entry to those that do.