You’ve seen the trailers. An impossibly young, brash James Kirk racing down the road on a motorcycle. Images of the starship Enterprise in battle with Romulan Warbirds while an equally young Spock – with his humanoid body and emblematic pointy Vulcan ears – proclaims, “You will experience fear; fear in the face of certain death.”
Star Trek (2009), the latest offering of the Star Trek mega franchise, includes some of the more familiar Star Trek races – Vulcans and Romulans. If you’re a hard-core Trekkie, you know there are over 400 such races. Ever wonder why most of the Star Trek races are so human-like? How come no acid-blooded extraterrestrial endoparasitoids like the famous xenomorphs from the Alien film series?
It turns out that Star Trek originator Gene Roddenbery may have had it right when he created human-like races such as Vulcans, Romulans, and the familiar darkly colored humanoid race that inhabits Qo’noS, the Klingon home world. A new study published by Paul Higgs and Ralph Pudritz at McMaster University in Hamilton, Canada suggests that ten of life’s twenty carbon-based amino acids may be shared wherever life exists. yIn ‘oH, the Klingons would say: life is everywhere.
Amino acids are critical to life as we know it here on Earth. They serve as the building blocks of proteins, which are linear chains of amino acids. Amino acids are also important in many other biological molecules, such as forming parts of coenzymes or as precursors for the biosynthesis of molecules such as heme – the foundation of the hemoglobin that delivers oxygen to our tissues.
Twenty amino acids are encoded by the standard genetic code and are called “proteinogenic” or standard amino acids. Higgs and Pudritz ranked ten of these amino acids according to the thermodynamic likelihood of them forming. This turns out to match the observed abundances in meteorites and in early Earth simulations almost exactly. They argue that the first genetic codes must have evolved using these ten amino acids, whether they come from space or from right here on Earth.
The implications of this are profound. If these ten amino acids are the basis of life on Earth, then there’s a very good chance that life on other planets – if it exists – may have originally used these same ten “prebiotic” amino acids, the precursors to life as we know it. The fundamental building blocks of biochemistry may span the universe.
Higgs and Pudritz’s study analyzes the twenty amino acids used in proteins, of which ten were formed in Stanley Miller’s well-known experiments first done in 1952. Miller used water along with methane, ammonia and hydrogen – the kinds of gases then thought to have dominated the Earth’s oxygen-free atmosphere more than two billion years ago – to create a primordial stew.
The lightening-like electric sparks used in Miller’s atmospheric discharge experiments turned the mixture red, then yellow-brown, and made a number of amino acids, including glycine and alanine, commonly found in proteins.
When Stanley Miller died recently, his former student Jeffrey Bada inherited several boxes containing vials of dried samples from those 1950s experiments and accompanying notebooks. "We started going through some of the stuff that was piled up in the corner, and here were several little cardboard boxes, taped shut and all dusty, carefully labeled with all of these little vials with dried material from his experiments," says Professor Bada of the University of California, San Diego, during a recent interview with the BBC. “We found not only did these make more of certain amino acids than in the classic experiment, but they made a greater diversity of amino acids."
While Miller initially found five amino acids, Bada and his team tracked down twenty two. The overall chemical yields were often higher than in the first set of experiments — the mixture appeared to be more potent.
Bada points out that today, almost all volcanic eruptions are accompanied by violent electric storms. The same could have been true on the young Earth. "What we suggest is that volcanoes belched out gases just like the ones Stanley had used, and were immediately subjected to intense volcanic lightning.”
Higgs and Pudritz propose two other sources of prebiotic amino acid synthesis in addition to lightning: formation in hydrothermal vents and meteorites. By combining observational and experimental data of amino acid frequencies from lightening, vents, and meteorites, they show that the ten early amino acids identified by Miller “can be ranked in order of decreasing abundance in prebiotic contexts.” This order, they say, can be predicted by thermodynamics.
Higgs and Pudritz’s astounding conclusion: “the combined actions of thermodynamics and subsequent natural selection suggest that the genetic code we observe on the Earth today may have significant features in common with life throughout the cosmos.”
Physicist Stephen Wolfram, recently interviewed by h+ contributor Rudy Rucker, describes how Cellular Automata (CA) can be viewed as discrete approximations to molecular dynamics such as amino acid synthesis. It’s possible to study thermodynamics using simple models represented by a few bits that follow simple logical rules. The laws of thermodynamics – conservation of energy, entropy (randomness) increasing over time, and the physical impossibility of absolute zero – are as valid on Earth as they are in interstellar gas clouds, “where evidence of amino acids has already been seen.” Based on the new evidence discovered by Higgs and Pudritz, it would be interesting to see whether CA computer simulations provide additional support for a universal genetic code.
In the Star Trek series, the starship Enterprise’s crew contact and discover many humanoid races and species with whom they interact – this was a plot device for Roddenberry and his writers to explore the "human" condition. If we share a common genetic code with extraterrestrials, perhaps it’s not too much to expect to encounter human-like Andorians, Klingons, Vulcans, or Romulans rather than alien endoparasitoid chest-bursting xenomorphs. Let’s hope!