Nov. 1 (UPI) -- On TV and in the movies, aliens have been imagined a variety of strange forms -- slimy, green, reptilian, insect-like, big-headed.
But new research suggests alien life forms wouldn't necessarily be exotic or especially strange. Aliens might, in fact, look familiar. Some might even look like us.
Of course, artists and directors have to use their imagination. If there is alien life out there, there is no documentation of it. To figure out what aliens might actually look like, researchers at the University of Oxford abandoned creative license and turned to science for clues -- specifically, to evolutionary theory.
Most serious attempts at imagining what alien life might look like have taken examples of life forms from Earth and remained them under unique combinations of chemistry, geology and physics.
"In our paper, we offer an alternative approach, which is to use evolutionary theory to make predictions that are independent of Earth's details," Sam Levin, a researcher in Oxford's zoology department, said in a news release. "This is a useful approach, because theoretical predictions will apply to aliens that are silicon based, do not have DNA, and breathe nitrogen, for example."
Researchers used what they know about evolution on Earth to predict how the same forces might inspire adaptations on other planets. On Earth, biological complexity has accelerated on only a few occasions -- dubbed "major transitions."
The evolution of single cell organisms to multicellular organisms is an example of a major transition. A combination of evolutionary theory and hard evidence suggests such transitions came about because of extreme conditions.
This understanding of how species become more complex through evolutionary history can help scientists predict how aliens might evolve under different chemical, geological and physical circumstances.
"Like humans, we predict that they are made-up of a hierarchy of entities, which all cooperate to produce an alien," said Levin. "At each level of the organism there will be mechanisms in place to eliminate conflict, maintain cooperation, and keep the organism functioning. We can even offer some examples of what these mechanisms will be."
The findings -- detailed this week in the International Journal of Astrobiology -- suggest highly developed aliens would likely look similar to humans.
"There are potentially hundreds of thousands of habitable planets in our galaxy alone," Levin said. "We can't say whether or not we're alone on Earth, but we have taken a small step forward in answering, if we're not alone, what our neighbours are like."