With a sixth mass extinction upon us, many species on their way to extinction may vanish without leaving a trace in the fossil record. That's according to a recent study led by three paleontologists from the University of Illinois at Chicago.
By comparing the "Red List" of endangered species with several ecological databases of living species and three paleontological databases of catalogued fossils, researchers found more than 85 percent of the mammal species at a high risk of extinction currently lack a fossil record.
What's worse is researchers believe that the five great die-offs of prehistory may be sorely underestimated, too. These findings came as a surprise to paleontologists, who struggle to compare the magnitude of Earth's ongoing sixth mass-extinction event with those of the past.
"Comparing the current biodiversity crisis, often called the 'sixth extinction,' with those of the geological past requires equivalent data," explained Roy Plotnick, professor of earth and environmental sciences at the University of Illinois at Chicago.
Their study also revealed that those animals at the highest risk of extinction have about half the probability of being incorporated into the fossil record compared to those at lower risk.
Furthermore, animals least likely to leave their mark in history are "the small, cute and fuzzy ones, like rodents and bats," Plotnick added. "Body size is an obvious factor - bigger things tend to leave a fossil record, as do things with larger geographical ranges."
However, land-dwelling vertebrates may have it the worst, as only three percent of today's threatened bird species and 1.6 percent of threatened reptile species have a known fossil record.
"Comparing the scale of the current extinction episode, which is based primarily on terrestrial vertebrates, to earlier extinctions that are mostly calculated from the fossil record of hard-shelled marine invertebrates, is particularly problematic," Plotnick said.
Even still, fossils are the only reliable record of life on Earth for future generations.
"There are species going extinct today that have never been described," Plotnick continued. "Others are going extinct that are known only because someone wrote it down."
It follows then that many of these species could vanish as if they never existed.
"As humanity has evolved, our methods of recording information have become ever more ephemeral," Plotnick concluded. "Clay tablets last longer than books. And who today can read an 8-inch floppy? If we put everything on electronic media, will those records exist in a million years? The fossils will."
Their study was recently published in the journal Ecology Letters.
