Science fiction writers have long had bizarre, vivid images of extraterrestrial life from Plutonians resembling intelligent ice cubes to H. G. Wells’ vision of silicon-aluminum men in “Another Basis for Life” dwelling in an atmosphere of gaseous sulfur on the shores of a liquid iron sea. Astrobiologists have hotly debated how closely extraterrestrial life would evolve to resemble that on Earth, with some arguing that with a slightly different roll of the “Darwinian dice”, Earth would have been inhabited by creatures unimaginable. Others argue that if there is biology elsewhere in the universe we would find it strikingly familiar down to the carbon-based machinery in its cells.
Not so, argues Harvard’s evolutionary biologist, Stephen Jay Gould, in his book Wonderful Life, we are here because “one odd group of fishes had a peculiar fin anatomy that could transform into legs for terrestrial creatures; because the earth never froze entirely during an ice age; because a small and tenuous species, arising in Africa a quarter of a million years ago, has managed, so far, to survive by hook and by crook. We may yearn for a ‘higher answer’– but none exists.”
Equations of Life
Enter Charles S. Cockell, an astrobiologist at the University of Edinburgh and Director of the UK Center for Astrobiology, who, 180-degrees contrary to Gould, argues in The Equations of Life that the cosmos if populated, would harbor creatures more like like those lined up at Mos Eisley’s dimly-lit cantina on the Star Wars planet Tatooine. No matter how different the conditions on distant worlds, suggests Cockell, “all life being living matter –material capable of reproducing and evolving–is presumably subject to the same laws of physics — from quantum mechanics to thermodynamics and the laws of gravity.”
Cockel, reports George Johnson at the New York Times, “argues that even at this deep level, the possibilities of life were tightly circumscribed. Rerun the tape of evolution, and DNA, RNA, ATP, the Krebs cycle — the rigmarole of Biology 101 — would probably arise again, here or in distant worlds. Single cells would then join together, seeking the advantages of metazoan life, until before you know it something like the earthly menagerie would come to be.”
“The Right Stuff”
An analysis by Ralph Pudritz, a theoretical astrophysicist and director of the Origins Institute at McMaster University shows that the first ten amino acids are likely to form at relatively low temperatures and pressures, and the calculated odds of formation match the concentrations of these life-chemicals found in meteorite samples. The study indicates that you don’t need a miracle to arrive at the chemical cocktail for early life, just a decently large asteroid with the right components. That’s all. The entire universe could be stuffed with life, from the earliest prebiotic protein-a-likes to fully DNAed descendants. The path from one to the other is long, but we’ve had thirteen and a half billion years so far and it’s happened at least once.”
Early Earth was covered with carbonaceous material from meteorites and comets that provided the raw materials from which first life emerged. In his book, The Eerie Silence, astrophysicist Paul Davies echoes Harvard’s Gould suggesting that the original cells would have been able to pick and choose from the early Earth’s organic cocktail. To the best of our knowledge, he writes, “the twenty-one chosen by known life do not constitute a unique set; other choices could have been made, and maybe were made if life started elsewhere many times.”
Image credit: Scene from the movie, “Arrival”.