Scientists have been injecting human brain cells into monkey fetuses (NEWS.com.au, LiveScience.com, Google News). The resulting animals, if left to grow, could develop self-awareness--or, if as some argue, many animals are already self-aware, they could develop consciouis characteristics more indiscernible from humans.
Last November, I noted that animals were begin engineered to produce more human-like organs. Fukuyama's Our Posthuman Future [Amazon] addresses many of these issues and suggests that limits be defined soon so that the "natural" definition of human is not altered.