It sounds like the ultimate science fiction storyline: What if the dinosaurs weren't wiped out by an asteroid impact 65 million years ago?
Perhaps they'd still be alive today, in an advanced evolutionary state, developing their space program and their own asteroid impact mitigation strategies. Sadly for us, this would have probably meant that mammals wouldn't have gotten a foothold and the fledgling human race would have become glorified dino-chum.
In new research published in the Journal of the American Chemical Society, the rather outlandish prospect of alien -- not terrestrial -- dinosaur life is explored by Ronald Breslow. And these dino-aliens ("Dinolians"?) didn't have the misfortune of being smacked by an asteroid and/or get snuffed out by a volcanic eruption.
But before we get too carried away with thoughts of pirate Velociraptors flying space shuttles, attacking interplanetary supply ships (too late!), there is actually some scientific reasoning behind this work -- even though the "alien dinosaur" conclusion is a bit "iffy."
All sugars, amino acids, DNA and RNA exist in one of two possible orientations, left-handed or right-handed. This handedness is known as "chirality." The theory is that for life to be possible, proteins must contain only one chiral form of amino acids, left or right, for example. Apart from a few bacteria, the chirality of amino acids of all life on Earth is left-handed.
One theory of how life was spawned on Earth is through a mechanism known as "panspermia" -- basically, life has the ability to "hop" from one planet to the next encased in the protective shell of meteoroids. If life on Earth was indeed started via a cosmic "seed," then perhaps life evolved elsewhere in a similar manner as it did on our planet. Perhaps life even evolved with a different chirality than Earth.
"Such life forms could well be advanced versions of dinosaurs, if mammals did not have the good fortune to have the dinosaurs wiped out by an asteroidal collision, as on Earth," Breslow speculates. "We would be better off not meeting them."
But this conjecture makes Dinosaur Tracking's Brian Switek's "brain ache" -- why Breslow is speculating about advanced alien dinosaurs doesn't make a whole lot of sense.
"Our planet's fossil record has intricately detailed the fact that evolution is not a linear march of progress from one predestined waypoint to another," says Switek. "Dinosaurs were never destined to be. The history of life on earth has been greatly influenced by chance and contingency, and dinosaurs are a perfect example of this fact."
In other words, there's no reason to think dinosaurs are an inevitable consequence of the evolution of life. It just so happened that life on Earth produced dinosaurs, but they aren't the only examples of life and life doesn't have to go through a "dinosaur phase" before it can move onto the next evolutionary step.
So, although there may well be alien equivalents of T. rex's elsewhere in the galaxy struggling to steer spaceships with their tiny arms (an evolutionary attribute that may have snuffed-out that particular dinosaur species anyway), this is just as fanciful as any other science fiction alien.