5 abr 2013
It’s not the “bringing dinosaurs back to life” bit that makes paleontologists snort.
Jurassic Park is the greatest dinosaur movie ever made. I’m ecstatic that the classic film is briefly back in theaters to celebrate its 20th
anniversary. That doesn’t mean the big screen adaptation of Michael
Crichton’s “Don’t Mess with Nature” fable is free from scientific
howlers, though. The twin-crested Dilophosaurus didn’t really have a garish neck umbrella or spit poison, and Alan Grant’s unsupported belief that Tyrannosaurus
had vision “based on movement” should have increased the movie’s body
count much earlier in the story. (Even if we concede that old T. rex
was virtually blind, that doesn’t explain why our favorite Mesozoic
monster could not smell its victims when it nearly snorts Grant and
young park visitor Lex up its nostrils.) And don’t even get me started
on the lack of fuzz and feathers on the dinosaurs.
But whenever I watch the movie with paleontologists—which is really the
best way to do it—most of their bemused laughter comes early in the
film. In the most outrageous scene in the story, a field crew quickly
brushes sand off a Deinonychus skeleton as if the dinosaur were a dusty curio.
I wish that digging dinosaurs were as easy as Jurassic Park made it look. I really do. The “raptor” fossil—called Velociraptor in the film, but really a Deinonychus
to paleo pedants such as myself—that Grant and Sattler’s team exposes
is buried under the thinnest coating of sand. And the complete,
articulated skeleton is so sturdy that one of the field assistants can
stick his grubby hands right into the dinosaur’s nasal cavity and flick
out the sand. Watch the scene carefully. It’s the only time I know of
that someone picking a dinosaur’s nose has ever been shown in a feature
film.
In a real field camp, whoever had the bright idea to jam his paws
into a dinosaur skull and start rooting around would be stopped with a
scream of four-letter invective. How paleontologists and field
volunteers actually find dinosaurs, from spotting the first scrap of
bone to making a dinosaur skeleton nice and pretty, is an intensely
difficult and wonderfully rewarding process that deserves its own
cinematic treatment, complete with a dramatic orchestral score. And
since paleo fieldwork is relatively cheap, “Spared no expense!” would
simply mean making sure there was plenty of plaster and sunscreen for
the day shoots and a full array of beer and whiskey back at camp.
Let’s say you want to find a Tyrannosaurus, Stegosaurus,
or even some yet-unknown dinosaur. Paleontologists can’t just crank up a
machine and get a map of where the best skeletons rest, despite the
sonic technology seen in Jurassic Park. Paleontologists have
actually used sonic setups in the past—pinging sound waves that get
picked up by microphones to detect changes in rock density. But it’s
inefficient and is useful really only when you know you’ve already got a
skeleton in the ground, and even then it doesn’t send back the kind of
immaculate X-ray imagery seen in the film. Finding dinosaurs requires
squads of field workers to scour as much ground as possible, then pick
and shovel their way through stone. Really, the way paleontologists find
dinosaurs today is the same way bone sharps did during the 19th century.
Finding dinosaur bone takes some planning, a bit of experience, and a
lot of luck. After using geologic maps to identify the right kind of
rock for dinosaur fossils—usually sedimentary rocks laid down by lakes,
rivers, or deserts from 245 million to 66 million years ago—finding bone
is mostly a matter of keeping your eyes on the ground. I’ve spent days
nursing a nice sunburn on the backs of my ears while I’ve kept my head
down looking for any glint of enamel or trace of bone in places like
Dinosaur National Monument, Utah, and Ekalaka, Montana. The key is
learning what “search image” to look out for—a combination of color and
texture that gives away bone that might be hiding in plain sight, easily
stepped on or over if you’re not careful. Licking a bone or two helps.
Their porous construction means that the bone will stick to your tongue,
whereas a chunk of rock typically won’t. (Suggesting to new field
recruits that they should lick bones obviously leads to a lot of “That’s
what she said” jokes.)
During all the hiking and occasional fossil tasting, dinosaur hunters
are looking for trails of bone shards leading into a layer of rock.
Bones rarely appear intact on the surface. If they do, they’re probably
just days or weeks away from crumbling into pieces. I’ve seen plenty of
these exploded bones in Utah’s Grand Staircase-Escalante National
Monument—piles of tan and chocolate-shaded fragments that constituted a
bone for 75 million years until being eroded away from the rock and
totally falling apart within the last few months. They’re so far gone
that it’s almost impossible to tell what they originally were. Far
better is to find a few such shards at the bottom of an exposure and to
follow them up to where they emerged. With luck, those petrified crumbs
lead the way to bones that are just starting to peek out of the rock but
are still mostly safe within.
Whether or not to remove the skeleton is a matter of triage. Field
crews have a limited number of hands, constrained budgets, and only so
many days of good weather to work in. Determining whether a dinosaur is
worth digging out this season or next, or at all, depends on factors
such as what the dinosaur might be, how complete it is, and how
difficult an excavation is likely to be. Researchers might be willing to
break their backs to saw out the rock containing what looks like a new
species of armored dinosaur from a tricky overhang, whereas a scattered
collection of damaged leg bones from an already-known shovel-beaked hadrosaur might not be worth even picking up.
Fieldwork is done with shovels, picks, saws, chisels, and brushes,
usually without exposing much of the bone. The goal is to trace the
outline of a skeleton in its encasing rock and trim those blocks down as
small as possible so that the crew can get them out. Most dinosaur
bones are incredibly friable and fragile. Trying to chip one out with
hammer and chisel would likely destroy the fossil and lead to you being
banned from the field. (I know of one field volunteer nicknamed
“Destructor” for this very reason.) The rock also protects the dinosaur
during transport. You really don’t want a jumble of cleaned, fragile
fossils bouncing around a truck bed while bumping over the road out of
the badlands. The Jurassic Park crew made a boneheaded mistake
by exposing so much of their fossil. They would have had to pile some
sediment back on to create a barrier between the precious bones and the
thick plaster jackets needed to get the fossils out.
The delicate prep work—the effort that truly brings a dinosaur out of
the rock—is done with dental tools and air-powered scribes back in the
lab, where preparators can reveal bone bit by bit, keeping the fossils
intact with consolidants and glues as they go along. Paleontologists
usually aren’t even entirely sure of what species they’ve got or how
much of the skeleton there is until the bones start coming out in the
lab. Between collecting, preparing, and studying, it can take years for a
dinosaur to materialize.
Most dinosaur recovery work is obscured in scientific papers and
museum displays. We emphasize the stories a dinosaur has to tell us
about life, death, evolution, and extinction, but there are also tales
of hard-won discovery, often driven by amateurs who were passionate
enough to spend their vacation hiking through badlands or their weekends
picking at rock in a lab. Skeletons carry lessons from the deep past,
but they are also intertwined with private tales of long days spent
shuffling over outcrop, fighting off gnats, shoveling a seemingly
never-ending amount of rock, drinking around the campfire, gently
freeing bone from rock, and trying to instill vitality to an animal that
has been dead for millions upon millions of years. I think that’s why
the paleontologists I know always chuckle hardest and a bit derisively
during Jurassic Park’s camp scene. People who know dinosaurs,
who have spent time among them and their geologic haunts, know just how
elusive those vestiges of prehistoric life truly are.
