March 19, 2010 | 17
Dinosaurs are frequently cited as the ultimate exemplars of failure. “Dead as a dinosaur” is now deeply embedded in our vernacular. Yet death for a species, and even for groups of species, is as inevitable as your death. Somewhere around 99 percent of all species that have ever existed are now extinct. The 10 million to 50 million species that comprise the modern day biosphere (the uncertainty due mostly to our lack of understanding of microbial diversity) are but the latest players in a four-billion-year drama—“The Greatest Show on Earth,” to borrow the title of Richard Dawkins most recent book.
Similarly, the event that decimated the dinosaurs about 65.5 million years ago killed off only those dinosaurs like Tyrannosaurus rex and Triceratops horridus alive at the end of the Cretaceous Period (with the exception of some birds, which managed to survive this biologic bottleneck). Dinosaurs existed for 160 million years prior to that doomsday event, birthing a bewildering array of forms that succumbed to the scythe of extinction long before a giant asteroid slammed into the Gulf of Mexico. By comparison, we humans have been around a mere 200,000 years or so, and our small clan of bipedal primate cousins originated about six million years ago. In other words, dinosaurs are a great success story rather than a bunch of prehistoric washouts.
The notion of dinosaurs as failures underscores a pair of conditions that threaten the persistence of humanity: myopia and hubris. Lacking a meaningful sense of deep time, we tend to lump all pre-human life-forms into a single box labeled “extinct.” Virtually blinded by our severe temporal myopia, we ignore the multi-billion-year skein of life-forms, the dramatic comings and goings of organisms through the geologic ages. Meanwhile, our hubris derives from a worldview that transforms other life forms to objects, and places humans not only outside but superior to (nonhuman) nature. While I admit to personal bias on the matter, it’s simply ridiculous to thumb our noses at dinosaurs and laugh derisively at their present-day absence. We might as well speak contemptuously of our great grandparents; after all, they’re no longer with us.
Ecology and evolution are deeply intertwined. Just as the death and decay of organisms provide raw materials for subsequent generations, so too the deaths of species spawn new possibilities for future generations of species. Without extinction, there would be insufficient ecological space for evolution to explore alternative solutions and diversify into new life forms. When initially faced with some change to their native environments, species don’t grimly stay put and evolve into new forms better suited to the transformed conditions. They move, tracking the old habitat. In general, it’s only when the old habitat disappears that species are forced to adapt or die. Mass extinctions—the dying off of multiple, distantly-related lineages over vast areas in a short span of time—occur when one or more external forces wipe out a range of habitats, cutting off opportunities for tracking habitats.
Over the past half-billion years, there have been five major mass extinctions, with the dinosaurs wiped out in the most recent of these. We now face the sixth mass extinction, which threatens to tear apart the fabric of the biosphere, with drastic consequences for most life on this planet, including us. In better times, species losses tick along at a barely discernable rate—perhaps one every five years. At present, somewhere between 50 and 150 species disappear every day, never to be seen again. (Once again, uncertainty in the actual value comes mostly from a lack of basic knowledge about how many species exist.)
This time around, a single species—Homo sapiens—has become the external force driving the decimation of millions of other species. Yes, we are the asteroid now colliding with the planet. The list of anthropogenic factors is all too familiar, among them habitat destruction, overhunting, toxic pollution, and climate change. In particular, the duo of global warming and environmental destruction has eradicated habitats at a pace far exceeding the abilities of many species to track or evolve. At the current rate of extinction, about half of all species alive today may be extinguished by the close of the 21st century, an eco-evolutionary experiment not run since the end of the Cretaceous. Paleontology teaches us that the biosphere takes up to 10 million years to recover from a major mass extinction. So the decisions we make today will have cascading consequences well into the unimaginable future.
Are we (currently) capable of eliminating life on Earth? No. Although this claim is commonly made, life has persisted without hiatus for almost four billion years, and it will be here long after the last human. Life-forms at the small to microscopic end of the size spectrum are the most resilient, some of them hunkered down miles below the Earth’s surface. On the contrary, humanity is far from immune from the profound changes now taking place. Like it or not, we are inextricably embedded into nonhuman nature and dependent on its flows of energy, food, and water for our very survival, as well as for our physical, mental, and emotional health. So we have every reason to raise our awareness of these issues and act accordingly.
Yet, notwithstanding many years of dire warnings from biologists, the sixth extinction has barely touched the collective consciousness of Western cultures. Global warming currently garners the media spotlight, yet recent polls show a significant drop in the numbers of people concerned about even this issue. Despite the bounty of rhetoric, we’re not behaving as if we live on a planet in peril. Consider the recent climate change summit in Copenhagen, where world leaders had a unique opportunity to make history, but failed to reach a meaningful agreement. At this pivotal moment in history, we lack the strength of public opinion necessary to spearhead a World War II-style mobilization to achieve sustainability. Why?
In large part because we’re crippled by an outdated worldview. As a species, we need new glasses capable of curing our temporal myopia and inserting us back into the evolutionary epic—sometimes called the Great Story. We need a mindset that moves beyond our human-centered hubris and inserts us back into the natural world, where we belong. Learning the scientific truth of the matter is part of the solution, but connecting with the nonhuman world through direct experience is equally important. Those of us raised in urban settings may find it tough to establish meaningful connections of this sort, but we can make key steps in the right direction. We can also encourage our children move beyond our limited perspective—to see the world in new, healthier ways that are truer to our nature and critical for a sustainable future.
“But hold on a minute,” I can hear you saying. “If all species go extinct anyway, why should I lose sleep over the current hemorrhaging of life forms?” Ultimately, the answer to this question comes down to ethics, morals, and values. Do we have the right to kill off other species? Do we have the right to rob future human generations of the opportunity to see a whale, a bear, or an elephant in the wild? More to the point for most of us, is it reasonable that we knowingly bring about the downfall of civilization while alternative paths lie before us, untaken? Your call.
ABOUT THE AUTHOR
Scott D. Sampson is a dinosaur paleontologist and science communicator. He served as science advisor and on-air host of the Discovery Channel series "Dinosaur Planet" and is currently serving the same pair of roles in the new hit PBS KIDS series "Dinosaur Train," produced by the Jim Henson Company. He recently completed a book—Dinosaur Odyssey: Fossil Threads in the Web of Life—that is the first general audience review of dinosaur paleontology in a generation. His blog is The Whirlpool of Life. For more information, go to: www.scottsampson.net.
Image of dinosaur skull and Scott Sampson courtesy of Jedrzej Borowczyk.
The views expressed are those of the author and are not necessarily those of Scientific American.