Maybe they are not our alien counterparts and do not look like us like two peas. But extraterrestrial life - if it does exist - may look "very similar to the life we see on Earth," says Charles Cockell, professor of astrobiology at the University of Edinburgh in Scotland.
Cockell's new book (Equations of Life: How Physics Shapes Evolution) sets out the theory of "universal biology." Alien species that greatly resemble terrestrial life - from humanoids to hummingbirds - may inhabit billions of worlds. “Life on Earth can be a model for life in the universe,” he says.
Here's a quick background to Cockell's intriguing theory: the laws of physics are the same. (Gravity, for example, is present everywhere, not just in our solar system.)
There are restrictions everywhere. Organic molecules, on Earth or elsewhere, still decay at high temperatures.
Certain elements, wherever they are, are indispensable for life. (Carbon is the optimal element for connecting the dispersed constituents of nascent life; water is the ideal solvent for its diffusion).
And now - Cockell's provocative theory: these limits deny the "huge variety" in the appearance of living things in the universe.
“The laws of physics reduce living things to limited forms,” he says. - They narrow the scope of evolution. Foreign life can have a lot to do with life on Earth."
“Here's an earthly analogy. Go to the ocean, he says. "There you will find creatures with narrow, streamlined bodies, and for obvious reasons - they are needed to move quickly in the water."
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And, of course, it has been that way for hundreds of millions of years; dolphins, sharks, mammalian ichthyosaurs, fish and extinct dinosaurs all have a fairly similar appearance.
“Ultimately, they all look the same, although they are completely different species,” says Cockell.
On land, most animals have appendages, limbs, necessary for movement; among flying creatures, be they pterodactyls or pigeons, the laws governing aerodynamics are respected. Even butterflies, albeit exquisitely detailed in their riot of colors, shades and patterns, follow the pattern.
“If the wings are too small, the butterfly won't be able to take off,” Cockell says. The details, he admits, may be "endless," but "physics limits form."
Of course, there are no exceptions. Snakes that have no limbs glide along the ground. Tumbleweed - rolls over. “These are all experiments of nature,” explains Cockell. But much of life is "determined by rules that can be extremely limited."
Including smart, technologically savvy humanoid aliens - if they exist.
They probably have limbs. “You can't build civilizations without the ability to use tools,” says Cockell. But they may not have arms and legs; but there are tentacles with which you can also take objects. And they all have heads - and maybe eyes, ears and mouth? Most likely it is. “But all of these organs are not necessarily located in one place,” he says. "The mouth should not be below the eyes."
Not doubles, but distant relatives … Maybe classic films, without CGI, but with skillful makeup - hit the mark.