Where did we come from and how did we become the beings who we are. These are among the essential questions which humans have struggled with since the beginning of their consciousness. Neil Shubin made a huge step in answering those questions when his team discovered some 375 million year old fossils on Ellesmere Island in northern Canada. These particular fossils were of the right geological age when fish first temporarily moved out of the shallow water, probably to avoid predation and were adapting to make it their permanent home. All of the reptiles, dinosaurs, birds and mammals are the adapted descendants of these particular creatures. We known this for certain because many rather peculiar adaptations which we possess can be traced through innumerable ancestral fossil creatures which lived between these first land dwellers and us.
Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body by Neil Shubin is a rambunctious romp through the history of evolution. It pauses briefly at various critical points in the past where some new adaptation had occurred which better adapted its owner to its environment. He then shows how this adaptation was carried forward into humans by creatures, every one of which was well enough adapted to its environment to survive and reproduce. Because of the convoluted history of these intervening creatures life styles and their convoluted adaptations we currently living creatures end up with legacy structures of their convoluted structures. No structural designer would make the confused mess of things which anatomy students must try and figure out in their lab courses but adaptations that worked for our ancestors when they lived were reproduced and so we have them.
Shubin’s story begins in Pennsylvania roadside highway cuts where he and his companions are discovering fossils of creatures which are ancient but clearly living on the land. He is able to date these rocks fairly precisely to about 365 million years old. He then describes some sites which are 385 million years old which are clearly related in their bony structure to these younger ones but which are clearly wholly aquatic. Therefore it takes no Sherlock Holmes to go out and search for some rock layers in between which are about 375 million years old. Fortunately he found a map which showed some islands in the very far north which had exposed rocks of just the right age. Getting there on land was a difficult task even if non-stop flights from San Francisco to Moscow fly right over it.
After several expeditions they hit the right spot on Ellesmere Island near (GoogleEarth 77,-87) in 2004 and came home with several Tiktaalik specimens encased in rock. These creatures, when released from their rocky encasement, look at first glance like small alligators but at second glance they look like large bottom dwelling fish who could scoot along the bottom on little leg like fins. That is just about what they were neither fish nor amphibian but something in between. Shubin had found what he was searching for, the ancestor of all the larger terrestrial animals.
The first few chapters are about the field work but then the book is devoted to the development of living forms. What we can observe and how those observations fit together to make a functioning and logically consistent history of our physical existence. There is no need to seek for spooky explanations when the chain of living development is lain before us with such clarity.
The style of this book was aimed at intelligent average person who wants to have an overview of how a scientist peruses the truths which natures offers us. They can witness one of the most fundamental discoveries of all time and see the simple, understandable and reasonable steps which were taken to make these discoveries. This is a book which can be recommended to every person who sincerely wants to know how they came to be what they are—a thinking animal.
This post is about the book but I have three previous blogs about Neil Shubin: