Post by Ruthanna Gordon
Evolution is one of the most well-supported theories in science. It draws on many types of evidence, most notably the millions of datable fossils gathered by researchers from all over the world. At times, fossils can seem almost mundane: small ones dot any marble floor, and slightly larger ones go for a few bucks in museum gift shops. It can be a shock to realize how spotty the fossil record really is.
Most living organisms never become fossils. They live and die in open air or water, and their bodies eventually decompose without a trace. A species is lucky to leave any remnant at all. The infamous Tyrannosaurus rex, for example, probably once roamed in the tens of thousands. We have about 30 skeletons in various stages of incompleteness, and one footprint. For comparison, scientists estimate that the current population of North American Homo sapiens may leave between 0 and 2 fossils.
We have fossils from about 300,000 species, far less than 1% of the total that have ever walked, squirmed, or swum the earth. Of these, most preserve only hard materials such as bone and shell. On rare and fortunate occasion, we are able to find fossils of soft tissue. These treasures provide a cornucopia of information about their original owners.
One example: About 500 million years ago, multi-cellular organisms went from tentative experiment to wildly successful profusion. The Cambrian Explosion (which predated the Cambrian era and took several million years) is best documented at the Burgess Shale in British Columbia. Here, regular mudslides covered the sea floor, burying marine animals and preserving their every detail—for a few wormlike creatures, we can still see the contents of their stomachs. The Shale includes some of the earliest recorded ancestors of modern life, families that thrived for several million years before dying out, and a few strange lineages that vanished almost as soon as they appeared.
Pikaia gracilens doesn’t look much like you, although it’s certainly related. Trilobites lasted until the mass extinction at the end of the Permian. But you won’t find anything close to a Hallucigenia wandering around today—a pity, in my opinion.
Another example: Last year, scientists managed something previously considered impossible. They discovered the color of a dinosaur. Exceptionally well-fossilized feathers, including pigment structures, were compared to the pigments in modern birds. What they found was something like a chicken-sized, flightless woodpecker. White stripes on the arms and legs stand out against a black coat. An orange crest tops the whole ensemble. The remake of Jurassic Park may feature impressive levels of accuracy—or you can check out the models at your nearest science museum.