Your Inner Fish is a fairly recent science-for-the-layman book by a paleontologist, Neil Shubin, who in 2004 discovered a revolutionary fossil fish that had developed many characteristics of land animals, characteristics we ourselves still have. It had both gill slits and lungs and could waddle up out of the water onto the beach. He named it a “Tiktaalik,”from the Intuit language, a name I find impossible to remember.
The fish-animal resembles a large shoe tree with a heavy, flat head. The discovery gained a lot of publicity at the time that I had forgotten until I saw the picture again. You can see an excellent animation of it made for the TV channel AnimalPlanet at http://www.youtube.com/watch?v=2-WV9vDcyvc&feature=fvwrel. Unfortunately, you will have to watch a 30-second introductory advertisement, but it is worth it. If so inclined, you can also watch an hour-long lecture by Shubin that describes most of the story at http://www.youtube.com/watch?v=2qTarQaUlqM
Shubin began his career at the nearby University of Penn and did his early fossil hunting in central Pennsylvania, but he is much more than a fossil-hunter. He also teaches anatomy to medical students and is a leader in describing the evolution of the human body from the earliest forms of life.
Up to the time of Tiktaalik, the highest form of earthly life was fish. Tiktaalik was the first known creature with the characteristic bone structure of all limbs on all animals today: big bone/two bones/group of small bones. For example, our arm bones are, starting from the shoulder, the humerus (big bone), the ulna and radius (two bones), and the wrist and finger bones (group bones). All animal limbs, including our legs, have this same pattern. Tiktaalik is also the first known creature to abandon the fixed, vertically oblong fish head for a flat head with eyes on top and a neck that can move the head independently of the body.
But Shubin’s discussions range much wider. If you compress the history of the earth into one year beginning January 1, single-celled organisms, like the amoebae and paramecium we saw under the microscope in Mr. Eply’s biology class, did not begin to clump together into multicelled creatures until October. (Humans did not appear until the last day, December 31.) This was a big jump. For cells to clump together, they had to evolve methods of holding themselves together and methods of communicating (“We are getting too thick. You outer cells need to die and slough off.”) But once they learned it, evolution was off to the races.
Shubin is also comfortable discussing discoveries in DNA that tie together the fossil records and anatomy anomalies of a variety of living creatures. Whenever the science gets deep, he frequently gives we readers a breather by switching to descriptions of fossil hunting.
The slim and very readable book lays out the case for evolution based on the pieces of our own bodies that were adapted from earlier life forms. It took him two years to write it, and the effort is evident in the smooth flow of information. You learn a lot without even realizing it.
[I have a nice collection of 75 million-year-old sea fossils I collected years ago from the banks of the nearby Chesapeake and Delaware Canal. The banks are heavy clay that are constantly eroding and exposing new fossils. Pick the right spot and the fossils are everywhere underfoot, free for the taking. They are mostly belemites, ammonites, and an ancient form of oyster.]