The “Jurassic Park” films don’t entirely track the latest science. (UNIVERSAL STUDIOS)

With a 3-D version in the theaters and a sequel due out next year, “Jurassic Park” roared into its 20th anniversary on June 11.

Two decades might seem like the blink of a lizard’s eye on top of 65 million years, but the science and speculations of “Jurassic Park” have evolved significantly since Steven Spielberg’s beasts first shook movie theaters.

If filmed today, the science suggests many of “Jurassic Park’s” dinos would look a bit more Tweety Bird than Terrible Lizard. The first film hewed to the long-standing image of dinosaurs as big, scaly reptiles. Subsequent research, however, has provided more and more evidence that many meat-eating dinosaurs sported plumage. A year ago, scientists in China unearthed a feathered tyrannosaurYutyrannus huali — a slightly smaller relative of Tyrannosaurus rex. Velociraptors also clearly had feathers, confirmed by the 2007 discovery of quill knobs, a type of feather anchor, on raptor arm bones.

This was suspected even at the time of the 1997 sequel, “The Lost World.” Spielberg made a gesture toward the science by putting a few feathers on his speedy killers in that film, though not as many as the paleontologists requested. If he had, the raptors would have looked too different from the first film, said Jack Horner, a renowned paleontologist at Montana State University and a technical adviser on all of the “Jurassic Park” films. Nevertheless, reports suggest that the fourth “Jurassic Park” film, due out next year, will keep the dinos scaly — despite what experts say.

Mammoth boost to cloning?

Back when “Jurassic Park” debuted, science was still three years away from the arrival of the sheep named Dolly, the first cloned adult animal. In 2001, scientists replicated the first endangered species — Noah the guar, a type of threatened ox. Since then, cloning and genetic technologies have continued to advance, with some researchers turning their attention to extinct species.

Now, new genetic tools and well-preserved specimens could make one Jurassic Park-type feat a reality: cloning a mammoth. Last year, a South Korean and Russian team announced its goal of doing just that. [6 Extinct Animals That Could Be Resurrected]

In the film, a fictional educational cartoon credits “thinking machine supercomputers and gene sequencers” with reading dinosaur DNA. No technology in 1993 could have done that. In 2005, however, the 454 Life Science Genome Sequencer made such massive genetic analysis possible. “The change in technology really sparked our ability to deep-sequence these extinct species,” said Hendrik Poinar, an evolutionary biologist at McMaster University in Ontario who is studying mammoth DNA.

The film correctly predicted the need to repair ancient DNA, which degrades over time, and to use modern relatives to bring extinct animals back to life. In Jurassic Park, scientists plugged holes in degraded dino DNA with substitutes from frogs, incubating the extinct animals’ embryos in emu and ostrich eggs. Similarly, current or near-current science could repair the fragmented genetic material of mammoths using elephant templates and then implant an embryo in an elephant womb. Ensuring that the elephant could bring a mammoth embryo to term poses the next challenge, but much of the science is in place — such as synthesizing long sequences of DNA and modifying cells to be pluripotent stem cells, which can turn into any cell in the body, Poinar said.

He predicts a cloned mammoth within 10 to 50 years. “We’re closer and closer than we ever expected to be,” he said. “People with enough money will absolutely do it.”

Orange dino? Blue dino?

In April, scientists made the remarkable discovery of intact dinosaur skin, which may reveal the hues dinosaurs came in — perhaps far beyond the green and brown traditionally portrayed. Scientists are using particle accelerators to probe the samples for pigments, said Mauricio Barbi, a physicist at Saskatchewan’s University of Regina, who discovered and is investigating the sample.

Even at the time of the first “Jurassic Park,” scientists suspected dinosaurs had been more colorful than historically assumed, and Horner argued for brighter beasts. But Spielberg wanted more frightening, dragonlike shades. “Steven wanted them scary,” Horner said.

The bird connection? Yawn.

The fictional scientists of Jurassic Park argued energetically that dinosaurs evolved into birds. Today, the family ties between birds and dinosaurs are pretty much conventional wisdom.

In 1993, evidence of the link was sketchier, based on skeletal resemblances, mostly compiled in the 1980s. “Back then, it was based solely on bone structure,” said Luis Chiappe, a paleontologist at the Natural History Museum in Los Angeles who specializes in dinosaur evolution. Today, “we’ve had so many lines of evidence telling us the same thing.” Feathered dinosaurs, commonalities among dinosaur peepers and bird eyes, and similarly structured eggs all point to dinosaur-to-bird descent, Chiappe added.

Warm and cuddly creatures

Scientists’ early perception of dinosaurs as big crocodiles portrayed them as cold-blooded, slow-moving brutes. In the movie, the reborn dinosaurs appear warm-blooded, notably demonstrated when the velociraptor’s breath steams up a window. New discoveries say the movie had it right.

“For the last 20 years, we’ve known dinosaurs were warm-blooded,” Horner said. “We’ve just been getting more and more facts.”

The vasculature and growth rates of baby dinosaurs required warm innards, Horner said. “There’s nothing alive today that has the vasculature of a dinosaur that is cold-blooded.” [Baby Beasts: Images Reveal Dinosaur Embryos]

T. rex the scavenger?

A 12-year study detailed in the journal PLOS One in 2011 helped downgrade T. rex from terrifying hunter, capable of chasing down Jeeps filled with mathematicians and children, to a big lug rummaging through the garbage. The research compared relative numbers of T. rex individuals and their purported prey (duck-billed dinosaurs), finding far too many T. rexes for the enormous beasts to be top-level predators. An environment can support about the same number of scavengers, such as hyenas, as prey, but far fewer high-level predators, such as lions. The conclusion: T. rex doesn’t want to hunt; he wants to be fed.

Horner first probed the theory of T. rex as scavenger around the time “Jurassic Park” premiered. “I was struck by the idea that the [T. rex] morphology was almost completely the opposite of velociraptor,” Horner said. T. rex had a big head; “big, bone-crushing teeth”; and those famously tiny forearms, Horner said. All of this suggested “the Tyrant Lizard King” rummaged for its meat, crunching up carcasses instead of running after prey. “If it hunted at all, it probably just targeted weak, sick or dead animals,” Horner said.

Bad news: DNA decay

If the demotion of T. rex from king to peasantry weren’t enough, perhaps the cruelest blow to dino lovers came last year, when researchers determined that Jurassic Park would be impossible.

The reason? Too much time has passed to recover the terrible lizards’ DNA; the molecules would have decayed long ago. Researchers in Australia last year made the first-ever calculation of DNA’s half-life, or the time for half of a DNA molecule’s bonds to break. By the researchers’ calculations, all DNA would disappear, “even under the best scenarios, in 6-7 million years,” researcher Mike Bunce, from Murdoch University’s Ancient DNA lab in Perth, Australia, wrote in an e-mail. That means cloners could still use DNA from the relatively recent woolly mammoth, which survived until a few thousand years ago. But the last T. rex roared 65 million years in the past, and most dinosaurs disappeared much earlier.

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