As a lover of fossils, I understand the appeal of the big and the bad—dinosaurs, sharks and lizards so large they can eat a man in one bite. T-rex fossils! Megalodon fossils! Mosasaur fossils! Oh my! But it isn’t the biggest and the baddest that make me giddy. There are a number of seemingly unremarkable fossils waiting for their “awesome-ness” to be discovered.
What fossils hold me captive? What fossils cause me to stand and gaze in wonder at the remains of their life, now frozen in stone and held in my hand?
Well, let me first start with the concept of a fossil. What is a fossil? According to my dictionary, a fossil is “The remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.” This is a straightforward definition, easy to understand and easy to express.
But for me a fossil goes beyond this definition and represents an unfathomable span of years. A fossil is prehistoric: pre-writing, pre-history and “pre-us.” When I look at or hold a fossil, I am looking into a past which can, at times, pre-date humans as a species, pre-date mammals as a class of animals or pre-date multi-celled organisms entirely.
Here are a few of my favorite lesser known, but no less awe-inspiring, fossils:
Stromatolites are currently the oldest known fossil. In fact, as an ancient record of life, the remains of fossilized stromatolites can be more than 3.4-billion-years-old. These layered structures of blue-green algae were the predominant life form on Earth for more than 2 billion years, and today exist only in small pockets throughout the world. Stromatolites are thought to be responsible for the creation of the Earth’s atmosphere, consuming CO2 and releasing O2 through photosynthesis, providing life-sustaining atmosphere for the entire planet. Without stromatolites, T-rex’s reign of terror would have been cut terribly short.
Another humble fossil I find fascinating? Sponges. Sponges are among the first of multi-celled animals and sit on the lowest branch of the tree of life. All sponges are descended from a unique sponge ancestor and are alien from all other life on Earth. These living fossils date from between 650 and 550 million years ago. They are extremely simple and have no internal organs, no digestive system, no circulatory system and no nervous system. Early sponges were only 1/4 of an inch in size. However, today’s giant barrel sponges can grow large enough that the average man can fit within their barrel-shaped body.
The last fossil I want to discuss might not be a fossil at all; it is smaller than a speck of dust and comes from Mars. In 1996, NASA published an article about a possible fossil found on a 4-billion-year-old Martian meteorite. Scientists discovered magnetite crystals with rod and oval-shaped forms which appear to be the fossilized remains of bacteria. These remains closely resemble modern magnetotactic bacteria (bacteria containing magnetite crystals that align themselves to magnetic fields). It has been proposed that the presence of these crystals with the rod and oval-shaped forms are the remains of living Martian organisms. While the scientific community continues to debate these findings, the exciting prospect of Martian fossils will keep me looking into the stars at night.
I am captivated when holding a T-rex claw or dreaming of microscopic fossilized Martian bacteria, because fossils give us a connection to times and worlds that we will never experience. Our world is 4.54-billion-years-old, and for much of that time life has been developing, dying and evolving. Our history is written in stone. Every fossil found is a story waiting for us to unfold.