Finding A Fish Out of Water: Keys to Understanding Vertebrate Evolution

When it comes to understanding how evolution has greatly influenced the development of numerous organism populations, over Earth’s vast geological time scale; paleontology does an excellent job at chronicling, even predicting, the progression of said populations of life on our planet over the course of millions of years. Paleontologists in their most simple essence are like detectives, trying to put together clues and other viable evidence under the grand culmination of time. They apply their highly insightful knowledge to the development of life itself through these materials and methods; moreover, to specifically pinpoint the biotic turning points in Earth’s history and solve overarching mysteries guarding the origins of life itself.?

These themes within paleontological research are what Dr. Neil Shubin explored personally for the first time in an anatomy class he took prior to receiving his doctorate. From that point on during his rise to becoming a paleontologist, he had in his mind a burning question to ponder, explore, and put massive amounts of research into after being inspired by his lecture sessions. Dr. Shubin from just a few lessons in anatomy, saw an incredibly important question which needed answering amongst paleontologists and other scientists to settle what happened during a vital time in Earth’s deep, geological past: How did the transition from water to land take place amongst the first tetrapods?

To spark an answer to this daunting question, Dr. Shubin needed to set some things straight in preliminary work, as well as set some goals (in said organization of preliminary work) to accomplish for resulting with good and refreshing answers concerning such a challenging question. Moreover, the word “tetrapod” translates from Greek (“tetra”- “pod”) into “four feet”, and this word comprises many animals extinct and extant, whether it be amphibians that Dr. Shubin is searching for specifically in the fossil record, or mammals, reptiles, birds, so on and so forth. The reason why it’s important for Dr. Shubin to discover and describe scientifically the first confidently identifiable tetrapods is because the fossil record for the longest time has never produced a clear explanation to paleontologists concerning how and why the transition from water to land took place in the time it did. Only brief glimpses into solving these questions are based upon a handful of transitional fossils (commonly called by laymen as “missing links”) and other possible bodies of evidence (e.g. named genera such as Icthyostega or Acanthostega), which regardless of importance do not come that close to answering the long-debated question Dr. Shubin is trying to tackle.

Moreover, after getting an idea of what type of organism he had to pursue in the fossil record, Dr. Shubin had to decide what time in the Earth’s history he should be focused on for such a task, dominated by specific biota changes to aid him in the decision. Ultimately based on prior studies and past experiences, Dr. Shubin decided to zoom in further within his search of transitional fossils in Late/Upper Devonian period-aged rocks. This places Dr. Shubin’s search for transitional fossils, temporally speaking, in the approximate range of 383-359 Million Years Ago during the Paleozoic Era. Furthermore, this would then guide the next decision: where exactly Dr. Shubin would dig.?

This would be a location which ideally should bear rock exposures of the age mentioned prior and this regards sedimentary rocks (since igneous or metamorphic rocks do not preserve fossils). Dr. Shubin joined by a colleague of his, then coupled together with a comprehensive-enough bearing started searching for such a place in prior studies and scientific literature, preferably a place unexplored, untouched by other paleontologists. Heated by the decision-making on where to go for this ideal location, an intense conversation boiled over between Dr. Shubin and his colleague, leading to a lucky geology textbook, which revealed to them both in that moment: a diagram pointing them in the direction of where they needed to go; far away from where they were located geographically.?

This lucky textbook diagram took them to one of the northernmost regions of the Arctic Islands far away from the country of Canada, where they ran into the rocks of the right age, type, and appearance which told them they were wandering amongst an ancient river delta, a place exactly in mind for what organism types they were hunting; calculated and from a laundry list of clues as elucidated prior. This predictive methodology coupled with perfect timing in the freezing Canadian arctic ultimately resulted with the discovery of the famous transitional/stem-tetrapod Tiktaalik roseae, named via the language of the indigenous peoples living in the frigid areas bearing the ancient deltaic rocks which preserved Tiktaalik. Dr. Shubin and his colleagues to this day research the fossil specimen Tiktaalik and other similar organisms (i.e. Qikiqtania wakei), continuing the endless search across the fossil record in the pursuit of more fish out of water; to accomplish the goals of understanding the path which vertebrate evolution took millions of years ago, before the ancestors of humanity could even exist.