* One of my intrepid research assistants, Michelle Pearl, called up some of America’s leading urologists to ask them why bladders evolved. One comparative urologist (as well as Jay Kaplan, whose research is discussed in this chapter) took the findings about territorial rodents having bladders to make scent trails and inverted the argument—maybe we have bladders so that we can avoid continual dribble of urine that would leave a scent trail so some predator could track us. The same urologist noted, however, that a weakness with his idea is that fish also have bladders, and they presumably don’t have to worry about leaving scent trails. A number of urologists suggested that maybe the bladder acts as a buffer between the kidney and the outside world, to reduce the chance of kidney infections. However, it seems odd to develop an organ exclusively for the purpose of protecting another organ from infection. Pearl suggested that it may have evolved for male reproduction—the acidity of urine isn’t very healthy for sperm (in ancient times, women would use half a lemon as a diaphragm), so perhaps it made sense to evolve a storage site for the urine. A remarkable percentage of the urologists questioned said something like, “Well, it would be an extreme social liability to not have a bladder,” before realizing that they had just suggested that vertebrates evolved bladders tens of millions of years ago so that we humans wouldn’t inadvertently pee on our party clothes. Mostly, however, the urologists said things like, “To be honest, I’ve never thought about this before,” “I don’t know and I talked to everyone here and they don’t know anything either,” and “Beats me.”
      The strangest thing about it all is that many animals may not actually take advantage of their bladder’s storage capacity. In my vast experience watching baboons go about their urinary business, it is apparent that they very rarely hold it in when they have to go. Clearly, there’s a lot of work to be done in this area.