Extraterrestrial life may have different chemistry, but evolutionary forces will be Earth-like

More than 2,500 years ago, the philosopher Anaxagorus suggested that life existed on multiple worlds, due to “seeds” propagating through the cosmos. Nealy a century later, another philosopher, Epicurus, noted explicitly that Earth could be just one of many inhabited worlds, and five centuries after him, still another Greek thinker, Plutarch, noted that probably the Moon was inhabited by creatures.

For centuries, people speculated about how those extraterrestrial creatures might look and behave. Meanwhile, about a century prior to Anaxagorus, the philosopher Anaximander proposed that humans came into existence through an evolutionary process beginning with fish. It was a forerunner idea of evolution by natural selection that Charles Darwin would propose and then turn into a theory through years of observation and study.

Charles Darwin 12 20 17 w
Charles Darwin

Natural selection achieved the status of being a scientific theory, because it makes predictions that could be tested and today it continues to pass the tests. Consequently, in biology we consider natural selection as the prime evolutionary force. We see it as the basis for the presence of life on Earth, and the numerous directions that life on this planet has taken over 4 billion years. And new research suggests there’s no reason to think the forces of natural selection are limited to our own planet.

In astrobiology, we assume that natural selection must be the prime mover of evolution of life everywhere else. This makes perfect sense, given that Darwin had no idea about the mechanisms of genetics. He knew traits were passed down through generations, but he didn’t know what carried those traits any more than Anaximander knew. And despite not knowing the mechanism, his natural selection works just as well to explain today’s molecular data as it worked in the 19th century to explain observations of animal forms.

Natural selection is worked into our investigations of possible prebiotic chemical systems that could have led to biology here on Earth, and elsewhere. On Saturn’s moon, Titan, for instance, hydrocarbon compounds comprise lakes, rivers, and rain that could act as a model for chemistry on Earth prior to life. Moreover, when scientists experiment with prebiotic chemical systems, the idea that prebiotic chemicals should evolve through natural selection is axiomatic, because such selection can enable complex molecules to improve their capability to make copies of themselves. Thus, a research team at Cambridge University in the UK published a study in the International Journal of Astrobiology. Using the a natural selection framework, they make specific predictions about the direction that evolution should take on other worlds, namely that complexity should increase over time, just as it did here on Earth.

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cosmos 12 20 17 2This is a perfectly rational approach. Moreover, failing to acknowledge that natural selection should be as central to biology throughout the Cosmos as it is here would imply that life here is special, and thus it would constitute a regression to a mindset that for centuries placed humanity at the center of the universe.

Appreciating that natural selection must drive biology everywhere does not fall in the same category as assuming that life everywhere must utilize the same 20 amino acids that Earth life uses to make proteins, or that extraterrestrial life must use DNA to store genetic information. The very fact that natural selection was discoverable so many decades prior to the discovery of DNA illustrates that it is really a kind of universal principle of life. Natural selection enjoys a status in biology similar to what gravitation, electromagnetism, and other forces enjoy within physics.

Now, appreciating how natural selection should be a universal phenomenon is not a reason to forget that evolution of life also depends on other forces. Mutation is one of those forces. In order to become more complex, living forms must accumulate reproductive errors, in order to provide natural selection with some working material. There also are numerous mathematical phenomenon that drive evolution one way or another. These include genetic drift, founder and bottleneck effects, and gene flow — forces that shape species almost as much as natural selection does. But like natural selection, these mathematical forces must also generalize to off-Earth environments.

This means that when we finally do identify living systems on another world and seek to classify and understand the various organisms that comprise it, we won’t be starting entirely from scratch. We’ll have a lot to learn in terms of the chemistry, what the particular extraterrestrial system uses to carry hereditary information, which chemical compounds it uses for energy metabolism and the like. But the forces driving evolution will be same as they are here. This means not just natural selection, but mutation and all the other forces too.

David Warmflash is an astrobiologist, physician and science writer. BIO. Follow him on Twitter @CosmicEvolution.

24 thoughts on “Extraterrestrial life may have different chemistry, but evolutionary forces will be Earth-like”

  1. Sort of. According to the Drake equation there are trillions of advanced technological intelligences in the Universe. Billions of these ‘others’ a few billion of years in advance of us. It may be that only a fraction of what we call ‘life’ is based on some type of organic chemistry. Existence for most non organic life forms may be at some purposely designed non natural selection. There is no reason to think that billions of artificial intelligences will all be subject to natural selection…especially when they may long ago have figured out what existence is all about.

    • Drake equation is stupid. You can’t assign probabilities to something you know nothing about.

      There is no evidence whatsoever for “arising” as in:

      “The universe arose in the Big Bang”
      “Galaxies and planetary systems arose from cosmic dust”
      “Life arises from non life”
      “Species arise from other species”
      “Human intelligence arises from animals”
      “Consciousness arises”
      “AI machines will arise”

  2. Richard Dawkins – I don’t remember in which book – convincingly speculated about the logical/epistemological likelihood of the mutation+selection evolutionary mechanism in other worlds where life may emerge.

  3. Gene flow is not natural selection. It occurs when organisms, humans or elephants, travel to Stanford University, or some other place, in search of PHD partners, or seek other such criteria. It is deliberate and smart design – by the species. It also occurs when the species uses Crispr to enhance a genome, perhaps its own.

  4. What a truly silly article.

    “Natural selection” as the definition of any process that changes something in a way that gives it an advantage for replicating is of course true- in fact, it is axiomatic in that it just describes reality!

    “Natural selection” as an entirely random process that results in occasional mutations that give a living organism a reproductive advantage is another story altogether as is obvious.

    Of course the first definition is applicable through out the Universe- it is almost a tautology, and the author’s attempt to make it sound like anything more profound or insightful than that is either silly or disingenuous.

  5. Evolutionists confuse adaptation with evolution. It is one thing for an organism to adapt to its environment and quite another for an organism to evolve into another completely different organism. We know that organisms can adapt to their environment such as the Galapago finches. The finches’ beaks ADAPTED to a drought stricken environment in the Galapagos. They did not evolve into another form of life. Adaptation is programmed into an organism’s DNA. Evolutionary theory violates the DNA genetic code.

    • I love how creationists presume to tell evolutionary scientists what they misunderstand about their own fields of study. Your comments only serve to show your fundamental misunderstandings about evolutionary theory and ignorance of genetics and biology in general.
      Define “form of life” and then explain how evolutionary theory “violates the DNA genetic code”, whatever that means.

      • So you are saying evolution is a science? If it was a true science it would be happening today in every corner of the earth. The great french biologist Pierre de Grasse called it what it really is: a fairy tale for adults.

        • Yes, evolutionary theory is by definition a science, despite what the religious nutters continue to proclaim. It’s no different from physics, chemistry, or any other science.

          Not sure why you would assume that evolution is not happening today. Organisms are still reproducing and creating new generations every day. You obviously have a fundamental misunderstanding or ignorance about what evolution is and how it occurs. I recommend you pick up an actual science book and read it sometime rather than just believe what your religious apologetics websites say. Plainly, they are wrong.

          • Of course “organisms are still reproducing and creating new generations every day.” But that’s not evolution. It’s simply organisms reproducing “according to their kinds” which is what Genesis chapter one clearly states which agrees with the basic laws of genetics. No evolution here!

          • Standard expected answer from someone who doesn’t understand evolution or genetics. Fortunately, entire fields of science continue on progressing and learning despite the ignorance of people like you.

            Define “kind” specifically with a general definition that allows one to definitively separate one “kind” from another.

          • “Evolutionary theory” as you call it, is a theory born dead due to the fact that the cell with its DNA genetic code is so staggeringly and overwhelmingly complex that it is absolutely impossible for it to have come into existence by random chance. Only a Divine Being with infinite Wisdom could have designed and created it. Spontaneous generation by random chance is puro hallucination.

          • It is a science. There’s proof. Fossils are different when you look at different rock layers, and they seem to change gradually. The basic encoding in DNA for feathers, fur and scales is extremely similar, as is suggested by the fossil record. The thing about evolution is that it happens SLOWLY. A reptile doesn’t sprout feathers and fly off into the distance. However, we have observed fossilized dinosaurs covered with fur-like feathers. There skeletons are very similar to modern birds. In later specimens, the feathers of the wing and tail are like modern feathers, presumably for balance while running, and in some cases, possibly gliding. Then in even later specimens, the muscles and frame are correct for gliding and flapping. This is one example of proof for evolution. While evolution can’t explain some things like consciousness (for all we know, those could be attributed to God), we know that it has shaped the creatures of Earth for billions of years. And frankly, I don’t see why evolution can’t be part of a creator’s plans for the universe.

          • And I’d say a bird is fairly different from a velociraptor. There are plenty of other good examples- if you want evolution we can actually observe, try bacterial immunity to antibiotics (especially when the antibiotics aren’t used long enough to kill all the bacteria), or one of the studies done with fruit flies isolated in different environments. However, major changes require lots of time. It took billions of years for the complexity of life on Earth we have today.
            Also, studies of Galapagos Hawks and Marine Iguanas vs their cousins on the mainland are quite interesting

          • And the first life form, whether created by God or by chance, was presumably much simpler than what we have today. It’s likely that it didn’t even have DNA, only RNA. It would have been much simpler. It would only need to be able to reproduce and mutate

  6. Ah Americans and science lol ! Rather than write this article the author, if he was seeking agreement should just have written.”Look what Jesus did ! Look what Jesus did!” LOL

  7. Good day,

    I see that you are posting over on The Skeptical Zone. In the thread about bird kinds John Harshman mentions nested hierarchies. He is ignorant of the concept as Common Descent does not expect to produce a nested hierarchy. There is a peer-reviewed paper that easily refutes those guys:

    Knox paper- “The use of hierarchies as organizational models in systematics”, Biological Journal of the Linnaean Society, 63: 1–49, 1998

    Also the TSZ ilk use Theobald’s talk origins article to support their claims yet Theobald is easily refuted- Linnaean taxonomy is the observed objective nested hierarchy and it doesn’t have anything to do with branching evolutionary processes.

    If you want more info just email me. [email protected]


  8. There is no way ET life will have a different chemistry as there aren’t any atoms besides carbon that can be part of the macro-molecules required. If we find silicon beings they will be manufactured by carbon-based beings.

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