As the field of geology began to solidify and move from an infant to a mature science, its applications were examined.  The works of Hutton, Lyell and William “Strata” Smith had established that the layers of the earth were a succession of historical periods in the life of the planet.  The works of Steno and other naturalists such as Baron Cuvier, the father of paleontology, and John Ray fueled interest in examining the fossil record.  By the middle of the last century, the wealth of data was being used to infer much about what had happened in the biological past. 

As the field of geology began to solidify and move from an infant to a mature science, its applications were examined.  The works of Hutton, Lyell and William “Strata” Smith had established that the layers of the earth were a succession of historical periods in the life of the planet.  The works of Steno and other naturalists such as Baron Cuvier, the father of paleontology, and John Ray fueled interest in examining the fossil record.  By the middle of the last century, the wealth of data was being used to infer much about what had happened in the biological past. 

 Evolution as Predictive Theory
As I wrote in the first post for this forum, one of the strengths of the theory of evolution is its predictive capacity.  If evolution is true, then it should predict what is found in the fossil record.

From Fins to Feet
One of the most stunning transitions in the fossil record is from fish to land animals.  Palaeontologists have determined that by 400 million years ago, during the late Devonian period, a group of fish had partially developed digits in place of fins.  Known as “lobe-finned fish” or crossopterygians, these are found in the fossil record 40 million years before the first tetrapods, and are also characterized by a long fish-like body with an immobile neck-head joint.  It has long been hypothesized that there was an evolutionary transition from the first group to the second between 360 and 400 million years ago and that the fossil record would record such a transition, but it has only been within the last twenty years that this evidence has come to light.  One such find was made in 2006. 

Neil Shubin, a palaeontologist from the University of Chicago who working with these fossils, hypothesized that the transition to the earliest tetrapods should involve a shift to a mobile neck joint and continued transition toward limbs.  Working in sediments in northern Canada that date to 380 million years, he discovered a fossil he named Tiktaalik rosaea—the fossilized form of an animal with a fishlike body, digits for fins and a neck-head connection that showed that the animal could whip its head back and forth, like an early tetrapod.  As Shubin was quoted as saying at the time:

“Here’s a creature that has a fin that can do push-ups,” he said. “This is clearly an animal that is able to support itself on the ground,” probably both in very shallow water and for brief excursions on dry land. On land, it apparently moved like a seal,” he said.

This find was exactly what Darwin had predicted from evolutionary theory—a transitional form that showed a mosaic of traits between two classes of organisms, late surviving fish and early land animals. 

For the next post, I will offer evidence of the transition from dinosaurs to birds and how the modern placement of marsupials also support evolutionary theory.