Neil Shubin bases his argument that the anatomy of Tiktaalik is relevant to that of humans by discussing specific features of the anatomy of Tiktaalik that vary from typical fish anatomy and correspond to features of the human body. For example, he points out that Tiktaalik has a neck that is able to bend independently of the rest of the body, unlike fish, and like all terrestrial vertebrates, including humans. Therefore, the evolutionary history of humans can be traced to an organism similar to Tiktaalik, resulting in the concept of the "inner fish."
This process is called osmosis whereby water exits the cell through its selectively permeable membrane and into the salt solution to dilute and balance the pressure caused by the concentrated salt solution.
