Tiktaalik: Evidence of Evolutionary Change
Thinking about time on the scale of tens of millions of years is a concept that paleontologists deal with on a regular basis. In this intriguing film, Dr. Neil Shubin discusses the discovery of a fossil that seems to bring together life in water and life on land. He dives into the fascinating concept of homology and structural evolution through observation of the humerus bone and how it presents in fish, amphibians, reptiles, mammals, and humans.
Neil Shubin, Professor of Organismal Biology and Anatomy, University of Chicago
Dr. Neil Shubin: We live our daily lives working on a timescale of hours and minutes and days and years, but the time scale that I dwell in as a paleontologist is on the order of millions of years, tens of millions of years, hundreds of millions of years. When we take a great transition, say the one where fish evolve to walk on land, what we’re really dealing with is something that happened over tens of millions of years. It’s so hard to wrap your head around that stuff. What’s a million years, let alone tens of millions of years? Yet as scientists, we have to grapple with those almost unimaginable quantities every day.
We began the hunt for Tiktaalik in 1998, and the idea was we wanted to find a creature that really bridged the gap between life in water and life on land. One day in 2004, in the sixth year of our hunt, a colleague, working a layer with bones in it, saw this V sticking out of the rock. When I saw this V, I knew we had found what we had spent six years looking for. The reason was is it was very clear it was a V of an upside down jaw and that jaw was connected to a flatheaded snout. One of the big transitions from fish to early land living animal is going from an animal with a conical head to one with a flat head. Here I had a flat headed fish sticking out at me. It was really exciting for us. Here was a fish right at the cusp of the transition from life in water to life on land.
Where Tiktaalik really gets fun is when you look inside its fin. Here is a fin of one of the big specimens of Tiktaalik. What you see here is the shoulder, so you’re looking at it from the lateral external side, but inside these are the fin bones. If you remove the scales, if you remove the fin webbing, this is what you see inside. What does it have? It has one bone, two bones, and small bones and a joint out here. What do we have in our limbs? We have one bone, two bones, and a joint out here. Here is a fish with a shoulder, an elbow, and even parts of a wrist. This was really fabulous to see because here is a fish with parts of our own limb bones inside. What’s remarkable about this is I can trace this upper bone here called the Humerus from fish, to amphibians, to reptiles, to mammals, to me. I am deeply connected to this fish, and I am connected to this fish by a shared history. That history is knowable. That we can discover creatures that show us that history; that’s the power of science, that’s the power of paleontology. That’s why I’ve been spending the last 35 years doing this stuff this stuff because it’s inherently exciting to me.
- Course Categories: Biblical Studies, General Theology
- Science Topics: Earth Science & Environment, History & Philosophy of Science, Life Sciences
science and religion, biology, evolutionary biology, tiktaalik, fossils, homology, paleontology, Dr. Neil Shubin