Perhaps the greatest question driving science—and human thought in general—is the mystery of origins. This question has manifested itself in myriad shapes and sizes: our fascination with the Big Bang, the birth of our Earth, the evolution of our own species, and even our own individual genealogies. Especially as many have turned away from religion—the “why” of our existence—we are drawn to the equally enigmatic “how.”
Recently-uncovered ancient fish fossils bring us a little bit closer to one “how”: our species’ evolution from sea creatures. In Southwest China fossil beds, scientists discovered preserved fish fossils from the Silurian Period—a climatically chaotic time in Earth’s history from which few whole fossils remain—helping to piece together the origins of the jawed vertebrate.
“Nearly all the backboned animals or vertebrates you know—for example, those you see in zoos and aquariums, and even including ourselves—are jawed vertebrates,” said Min Zhu, one of the researchers involved. “We can trace almost all our organs in the human body to the first jawed fishes. That’s why it is important to look back, tracing the origins.”
While scientists had speculated that jawed vertebrates evolved some 450 million years ago, the earliest fossils we had were from the late Silurian (425 million years ago). These newly discovered fish species date back to the early Silurian (about 436-439 million years ago), working to fill in the gaps.
One of these new species is based solely on twenty-three tooth whorls, the oldest vertebrate teeth ever discovered. This new species was dubbed the Qianodus duplicis—Qian is the ancient Chinese name for the province in which it was found, while dus comes from the Greek word for tooth. The Q. duplicis fossil provides the earliest evidence of a jawed fish, given their notable similarities to the teeth arrangements of modern jawed vertebrates.
Another remarkable finding on the evolution of jawed vertebrates came from a jawless fish. The group to which the species—Tujiaaspis vividus—once belonged is now extinct, but is nonetheless a close ancestor of jawed vertebrates living and dead. Thus, studying this group may provide “key insights into the evolutionary assembly of the gnathostome [jawed vertebrate] body plan.” Until now, these insights were limited to scraps of fossils, mostly comprised of fish heads, but the T. vividus fossil was nearly complete. T. vividus’s long, sloping fins back up the “fin-fold” theory that describes how fins were first developed, eventually morphing into the paired limbs we know and love.
Part of what is so special about science is its ability to bypass the forward momentum of time. Whether studying the fossil record or peering into space, we can revisit the far reaches of the past, gradually retracing our steps to how it all began.