http://news.bbc.co.uk/2/hi/health/4067039.stm The parathyroid gland used to be our gills. All we need to do is a little gene therapy, and we could have gills once again. I think that gills would be a valuable asset to have. Better than a tail, but not as good as wings. This article says we will have gill implants in 2043. http://www.enigmata.org/writing/fut-his/2031-2049.html I think it will be much earlier, as the demand for gills will rise sharply as the oceans rise due to global warming.