My definition of human nature includes all qualities that human beings have. For example, breathing, consuming food, urinating and a host of other physical functions and in addition to that; basic intellectual cognition and emoting. Its very much possible to construct a definition of a human which will include all mutations and other cases of idiosyncrasy. Human nature is a set of traits that all human beings will inevitably share.
Really, there could be a village where no human being does anything that is in its natural tendency to do? This human being won't breathe or eat? Its possible that some natural tendencies of a human being may be abrogated as a result of our experiment, yet not all as I have shown. However, once at least one of them undergoes an alteration, a new specie will have evolved as the creature's nature and indeed 'human' nature has changed. As a result the speciation in the strictest sense of the term will occur, or a change of the biological status of a creature from human to something else. Notably, some properties of human nature are part of 'creature nature' or living thing-nature and therefore its inevitable that any creature that exists has at least some of the qualities a human has; such as breathing for example.