Consider the Pacinian corpuscle. This is very specialized type of sense receptor, called a mechanoreceptor, located deep in your dermis. It is only 1 mm in length, and it is responsible for detecting deep pressure sensations. It is oval-shaped, displaying concentric circles of a type of insulated cell called Schwann cells. In the center of the Pacinian corpuscle, there is an uninsulated, or unmyelinated, nerve that, upon stimulation, will send signals to your brain.
The usefulness of this type of receptor is not difficult to imagine. The skin provides a critical barrier against the constant barrage of microorganisms in our external environment. An invasion of certain types of bacteria or viruses, perhaps by a splinter or some other undetected vector, into our body can cause a nasty infection. If the infection is severe enough, it could potentially kill us.
So, where did these interesting little pressure detector instruments come from?
All humans have them, so presumably, they were the result of a mutation, or many mutations over the course of thousands or millions of years. And since we all have these corpuscles of touch in our deepest layers of skin, we must all be related to the one individual who was born with the precise genetic make-up to code for these wonderous little receptors.
Do other animals have Pacinian corpuscles? Do amphibians have them? How common are these things, and could they themselves indicate a common ancestry amongst the animal kingdom?
I was sitting in my office today, trying to understand this hypothesis when a student worker walked in. She had a beautiful shiny white iPhone in her hand. I stared at it, and asked her about some of the features. She effortlessly checked both of her e-mail accounts, searched a map for the quickest route to a Florida beach, and taught me how to "shady button" someone undesirable who was trying to call her at that moment. Cell phones have evolved, I thought. I looked at my own little flippy-phone in disgust. It had no Internet capabilities. It did not have the effortless, gliding-touch software of the iPhone. Soon, I thought, little cheap flippy-phones like mine will become the market minority. The buyer's market will select for all cell phones to have user-friendly access to the web.
Like the Pacinian corpuscle, a mechanoreceptor with a useful enough function to contribute to the survival rate, and therefore the reproductive success of humans, which ensured the survival of the corpuscle itself, the iPhone and its vast capabilities will be selected for by the hungry market of cash-bearing individuals in constant need for access to information, immediately. Could having an iPhone directly contribute to the survival rate and reproductive success of humans? I don't know about that, but I am going to test my hypothesis. :)