Now, for a different angle, let’s take a look at aliens.  Don’t worry; I’m not advocating the myth that little green men from Mars are coming to Earth to eat our brains and rape our women.  Rather, I’m going to explore the modern structure of beliefs about extraterrestrial life.  Here, we’ll take a look at pseudoscientific claims about aliens visiting Earth in UFOs, the underlying assumptions of the SETI program and programs like it, and probe the possibility of some form of extraterrestrial life actually existing.

Perhaps the image most people have in mind when the term “alien” is mentioned is the classical Roswell-type alien.  You know the image.  A balloon-shaped head with huge eyes and a tiny mouth.  This head is attached by a short inconspicuous neck to a body with two legs, two arms, shoulders, a torso, and four to five fingers on each hand.  These things are bipedal, moving in human fashion.  If one were to probe the evolutionary history of these supposedly real aliens using only what we have available for evidence (that being alleged eyewitness accounts), these aliens would likely be classified within a quintessentially terrestrial system.  The reason is simple. The description given for these aliens suggests that the aliens are, in fact, derived tetrapods.  You’re familiar with these creatures.  Beginning with the evolution of early amphibians during the Devonian period, the tetrapod lineage has proven to be immensely successful.  Tetrapods include birds, amphibians, reptiles, horses, dogs, pandas, and humans. It’s safe to assume that most people would accept that these organisms are “earthlings”, native to our own planet.

Yet people who claim that aliens have visited Earth and even abducted humans often overlook this fact.  To assume that these humanoid aliens evolved on another planet far from Earth is to assume that an entire planetary history, almost exactly similar to that of Earth’s, has played out.  One must assume that the same selection pressures were present in both locations, thus fueling the development of a backbone or similar structure (these aliens appear to be vertebrates), a terrestrial lifestyle, exactly four limbs (rather than five, or eight, or two, for example), a head with two eyes, two nostrils, and one mouth, a bipedal stance, and also human-like intelligence with an emphasis on engineering, math, and science.  While convergence is a common trend within evolution (we see it in bats, birds, and pterosaurs, for example), convergence to this extent is pretty difficult to swallow.  To have the development of an almost exact replica of a human evolve thousands of light years away, while possible, is not exactly probable. And while some people claim that these aliens are visiting Earth, we should ask “why Earth?”, and also “why no physical evidence?”  If these aliens are visiting Earth, we should have some definitive physical evidence, not just some eyewitness accounts.   If, as some would claim, these aliens were instrumental in building the pyramids or the Nazca lines, then why don’t we have any physical evidence of their presence?

If you’re familiar with the work of Carl Sagan, you’re probably thinking “well yes, the aliens supposedly visiting Earth probably don’t exist, but the Drake equation suggests…”.  If you’re totally lost right now, things will make more sense if I briefly explain the Drake equation.  The Drake equation, a relatively speculative enterprise (mainly with regards to results, as they are extremely subjective) first explored by Francis Drake of Cornell University, seeks a number (N, which roughly illustrates the likelihood of extraterrestrial entities from within the Milky Way contacting Earth) by multiplying:
the number of stars in the Milky Way Galaxy by the fraction of stars that have planetary systems;
the number of planets in a given system that are ecologically suitable for life;
 the fraction of otherwise suitable planets on which life actually arises;
 the fraction of inhabited planets on which an intelligent form of life evolves;
 the fraction of planets inhabited by intelligent beings on which a communicative technical civilization develops;
and the fraction of a planetary lifetime graced by a technical civilization
” (Sagan 248)

As you can see, this is an extremely speculative venture.  First, we don’t have a solid number of planetary systems within the Milky Way Galaxy, or a good number of planets with life.  Thus, the outcome of this equation will vary by user.  While some people would rank the probability of the evolution of “intelligence” (by human standards; here meaning something along the lines of proficiency in math, science, engineering, etc.) on other planets as probable, this represents a specific progressive reading of evolution.  This interpretation of the way evolutionary theory works implies that natural selection naturally favors “intelligence” over other factors. However, this interpretation is flawed.  While “intelligence” certainly offers a selective advantage in some circumstances, a lack of “intelligence” does not always spell extinction.  Hadrosaurs prospered during the Cretaceous Period without being overly bright (judging from their brain cases at least).  The case for “intelligence” as the key beneficial trait for dominance is thus flawed.  “Intelligence” does provide a selective advantage in many cases.  However, other traits can also drive evolution. In terrestrial evolution, “intelligence” to the point of intellectual pursuit has only evolved once (out of 4.6 billion years of Earth history).  If you read evolution as inherently progressive, then it is natural that the human brain is a late appearance on Earth.  You also probably read the hundreds of millions of years before the arrival of humans (at least subconsciously) as leading towards the evolution of “intelligence”.

However, from a paleontological perspective, looking at Earth’s history, one sees a series of accidents punctuating evolution.  Early chordates survive the early Cambrian even as many other genera go extinct.  Early plants find a selective edge on land, leading animals to follow.  Mammal-like reptiles rise to prominence in the Permian, only to be all but extinguished by an extinction event at the end of the period (after which the dinosaurs take over for a huge chunk of time).  At the K-T boundary, the dinosaurs get wiped out, largely as a result of non-biological processes (likely a meteorite impact).  Earth’s biological history is filled with accidents, non-biological events that have had a biological impact nonetheless.  Chance occurrences can play a key role in extinctions, which can pave the way for an inconspicuous group to conquer the planet (I mean, seriously, who would have thought that a few tiny shrews would eventually produce one of the most dominant species that the Earth has ever seen?!).  It is likely that these chance occurrences are key on any planet.  Mars, Mercury, and the Moon have all been repeatedly pelted by meteorites, for example.  Mars has had some highly active volcanoes as well.  Geologic and cosmic events can have as much an effect on evolution as biologic ones. 

With this in mind, it becomes extremely difficult to argue that evolution is “progressive.”  There are illusions of progress, to be sure.  We have more “advanced” organisms appearing after less “advanced” ones.  However, these trends are necessary; one would not expect a dog to appear before mammals evolved, after all!  However, it is wrong to assume that natural selection is goal-driven (I am assuming that natural selection works on other planets because it is the only viable explanation we have for the diversity of life on Earth.  However, the concept should work on other planets as well, as long as there is some sort of competition among individuals).  Natural selection merely weeds out poorly-adapted individuals.  If a mutation were to occur that led to the birth of a litter of bright pink leopards, one would not expect them to survive for long, depending, as the species does, on camouflage for hunting.  Natural selection predicts that these individuals will likely be weeded out.  However, natural selection does not strive for the development of intelligence 4 billion years down the road, any more than I strive to ensure that my great-great-great-great-great-great-great grandchildren have food on their table by going to work today. 

Therefore, it is bad practice to merely assume that intelligent life exists elsewhere in the universe.  The universe is extremely large.  We don’t know everything about it.  Intelligent life may exist elsewhere.  However, from what we know about Earth’s history and evolution in general, it is likely improbable.  While it is likely that “simple” lifeforms (think bacteria) exist elsewhere, judging from the abundance of amino acids and other materials present in the parts of the universe our species has explored, this does not mean that these lifeforms are striving to become “intelligent” in the future.  They are merely attempting to survive.  “Intelligence” may have evolved elsewhere in the universe, but it is not because of some goal-driven process of evolution.  Unless selection pressures strongly favoring “intelligence” over other factors are present, it is very possible that “intelligence” has not or will not evolve elsewhere in the universe. 

Works Cited:
Sagan, C.  Cosmos. Random House, New York, 1980

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7 Comments on “aliens”

  1. johnG Says:

    You’ve been busy. I liked this post.

    A quick, unscientific comment: years ago I read some speculation about how a baby perceives the world, that they key in on eyes most and the faces second. I don’t know if the article I read planted this idea, or if I made it up, but a spatial rendering of eyes most and faces second, could create a creature that looks like the standard, agree-upon alien: big eyes, then face, perhaps hands 3rd.

    While changing my first child’s diapers, I realized that an alien abduction may have a lot more to do with a bad diaper change from the baby’s perspective: these superior creatures capture you and carry you against your will to this room, place you under a bright light, and then perform invasive procedures.

    I have no reason be believe anyone remembers a diaper change, but perhaps they mis-remember it. Makes more sense than aliens.


    • darwinaia Says:

      I’ve been interested in this type of stuff since my first semester in college (I spent 3 semesters as a paleontology major before switching to history); I’m curious about the probable ways evolution would play out on other planets, as explored here. It’s obviously a speculative enterprise at this point, but still pretty interesting to me.

      You raise a good point; the mind can do wierd things when it comes to memories, especially early ones. The similarities between the two experiences are quite striking.

      Michael Shermer (the guy from Skeptic magazine) tells an entertaining story about a personal abduction experience. He used to do marathon bike races, which leave you extremely sleep-deprived. In his words:

      “I was falling asleep on the bike so my support crew…put me down for a 45 minute nap. When I awoke I got back on my bike, but I was still so sleepy that my crew tried to get me back into the motorhome. It was then that I slipped into some sort of altered state of consciousness and became convinced that my entire support crew were aliens from another planet and that they were going to kill me…The motorhome with its bright lights became their spacecraft. After the crew managed to bed me down for another 45 minutes, IU awoke clear-headed and the problem was solved. To this day, however, I recall the hallucination as vividly and clearly as any strong memory.” (p. 89, Why People Believe Weird Things, Michael Shermer, Owl Books 2002 edition)

      I like this statement from Shermer because the guy has spent some time studying this type of phenomenon from a critical perspective. It shows how an everyday event can be mistaken for an alien abduction. Shermer’s aliens looked exactly like his crew (because they were); he takes alien abductions as the result of an altered state of consciousness playing on popular themes rather than actual events. Memory plays a key role in this process; you’re likely not going to pick up on something you’ve never seen. Your point fits in nicely here; the memories are there, with regards to the alien body plan; people obviously have a memory of such a figure. Could have been picked up from popular culture or some other type of memory, such as the diaper changing experience. The similarities are definitely there, and an altered state of consciousness might be able to bring the memory structure out (I don’t have much of a background in psychology though, so I’m relatively weak on that end of things).

  2. Carissa Madsen Says:

    Think about insects. They dominate the earth but their intelligence comes from the instinct to survive and reproduce. They are quite successful, too, despite our attempts in many places to eradicate them. It is not like the termites plan on how they are going to take down a house or the mosquitoes plan a plague to eliminate humans.
    As for the aliens when things don’t make sense or when weird things happen the mind, consciously or unconsciously, finds a reasoning or rationalization. Also I have heard and do agree with the idea that people sort stuff (problems, occurrences etc) out in their dreams, which can be trippy.

    • darwinaia Says:

      I’ve actually heard some speculation with regards to insects and aliens. Some of the speculative stuff I’ve seen is that if relatively complex life were to arise on another planet, it would likely be something like an insect… highly successful and well-adapted, but with no propensity for complex conscious thought. I put much more stock in that line of argument than in the argument for extraterrestrial self-aware space travelling cultures. Convergence could lead to the emergence of human-like intelligence elsewhere in the universe, but I’m a pessimist when it comes to the assumption that a progressive sort of evolution would lead to the emergence of culture quite regularly throughout the universe. This type of topic is pretty fun to look at, because you have to come at it from an inherently speculative perspective. You can apply scientific principles, but your final argument will always be speculative in nature to some degree, unless we actually manage to begin documenting the existence of actual extraterrestrial lifeforms.

      Also, you’ve got to love the mind for doing trippy things with dreams. At least it keeps things interesting!

  3. Josh Fong Says:


    Thank you for the interesting article. If you haven’t read, “Extraterrestrials, where are they?” look for it. It is a compilation of essays by astronomers, biologists, physicists, etc. on the topic edited by Ben Zuckerman and Michael Hart.

    Some points of contention for you to consider:

    1) I agree that the appearance of the classic ‘greys’ are at face value oddly similar to Earth humanoids. However it might not be so improbable as it sounds.

    Extraterrestrials might well be four limbed tetrapods because at certain scales it may simply be the most efficient design. Why not five legs or eight? Because there is little that a five or eight legged creature could do to survive that a four legged creature couldn’t do with greater economy of energy in terms of limb generation and nourishment requirements.

    If the tetrapod form proved to be one of the most economical designs on Earth, that would only argue in its favor on a similar world, at the very least, it certainly wouldn’t argue against it.

    Furthermore, if the tetrapod proves to be a universal biological form in nature, then an intelligent biped logically follows as two of the limbs would be used for tool making, a requirement for a civilized species I would say.

    As for heads, eyes, and noses, form follows function. But I would tend to think that many extraterrestrials look quite different. Also, though you don’t discuss it there are certainly reports of very nonanthropomorphic aliens as well.

    2) Why would they visit Earth? If and when humans explore the galaxy, should we come across a world with life let alone civilized life, do you think we would ignore it? Then why would they?

    3)No physical evidence. Always a good question. I can offer no satisfying scientific argument here as there is none. The only answer is the socialogical one, the zoo hypothesis, which while unsatisfying, is not at all illogical. The bottom line is if there are extraterrestrials aware of us, they would be cognizant of the cultural disruption that would result from their blatant and permanent intrusion into our culture.

    The advent of European and American civilizations making permanent contact in the fifteenth century was an unmitigated disaster for the less technologically savvy native Americans.

    An extraterrestrial civilization would likely have thousands if not millions or potentially billions of years on us from a cultural evolutionary standpoint.

    (The odds of another species evolving technologically within mere centuries of us is improbable in a 13.7 billion year old universe, unless you assume that civilizations are plentiful)

    They would likely have the patience and moral clarity that would seek to mitigate a disasterous cultural contact (as Carl Sagan has pointed out, they would have had to make it through their own nuclear age).

    4) The accidental nature of evolution. Here I would argue that you are looking at the phenomena of mass extinction and survival in a backwards fashion. While the survival of individuals may well be due to chance all to frequently, the survival of species particularly in regard to mass extinction calamities or any other pressures would be more likely attributable to ‘fit’ design as Darwin would say.

    If chordates have survived many an extinction on Earth, I think it is indeed more fair to say than not that is is because they are stronger, faster, and smarter than their contemporaries not because they are ‘luckier.’

    And if chordates as a biological form naturally evolve on universal biological principles, there is no saying they wouldn’t be equally successful on a like habitat on a like foreign world.

    As you have pointed out we have zero knowledge of exobiology so I am in no position to say that there are biological laws of convergence across similar worlds but we do see convergent evolution on Earth as you, yourself have pointed out. So again, while this is no positive proof, it certainly doesn’t argue against convergent evolution across similar worlds.

    5) Lastly, you say the universe is large. You say we don’t know everything about it. Then you say it is ‘bad practice to assume that intelligent life exists elsewhere.’

    But given that we have a ‘goldilocks’zone planet sampling of one, isn’t it equally unscientifically presumptuous to assume that there isn’t intelligent life elsewhere in the universe? The truth is we just don’t have a large enough sample to draw any valid statistical probabilities about evolution on other worlds.

    Your philosophical position is similar to a friend of mine’s who argued vociferously in 1993 that because we had no proof that any planets existed in the universe beyond our own solar system it was premature and foolish to speculate about them.

    Of course he has been proven quite wrong but not just philosophically but scientifcally. We know from spectral astronomy that the universe is homogenous. If star creation is consistent under the right circumstances everywhere then so should planetary formation also be.

    And if planetary conditions are similar for life, its existence should also be common in the universe. And if statistically, there are enough planets with life in the universe, then it also follows that intelligent life will exist throughout relative to it’s own probabilities.

    You say, ‘the universe is extremely large.’ I cannot stress what an understatement this is from a conceptual standpoint. We all know this at face value but I doubt most people understand intuitively what it really means.

    Look again at the Hubble Deep Field images of the universe and think again what it means to say that there is only one world in the universe with intelligent life, let alone life.

    There are some 200 billion stars in the Milky Way galaxy. If you gave every man woman and child on Earth 30 stars, there would be about 20 billion left over.

    Our galaxy is only the second biggest in the Local Group of 40 known galaxies.

    We are one small part of the Virgo Supercluster which contains over 1300 galaxies.

    There are estimated to be about 10 million superclusters in the universe.

    And even though the universe as far as we know is homogeneous, you still think it likely that on not one other planet or moon out of 10 million times 1 thousand times 200 billion chances over 13 billion years, life or intlligent life ever evolved? Statistically speaking, I think this is the improbable scenario.

    I agree with you that from what we know about the evolution of life and intelligence on Earth it would more likely be in the minority on living worlds than the majority.

    Because we don’t have the requisite data, belief or disbelief in extraterrestrial life for the time being must remain a philosophical issue though I believe it is statistically supported.

    I also can’t resist pointing out, however unscientific a sampling it is, that on the one world where we know intelligent life can exist, it in fact does. So what does that say about nature’s ability to generate life and intelligence in the universe?

    If you care, check out:

    Galaxy: Stuart Clark.
    300 Astronomical Objects: Jamie Wilkins
    Visions of the Universe: Raman Prinja
    Stargazer’s Guide to the Universe: Robin Kerrod
    Violent Universe: Kimberly Weaver
    Infinite Worlds: Ray Villard
    Pale Blue Dot: Carl Sagan
    A Journey Through Time: Jay Barbree

    • darwinaia Says:

      Hey Josh,

      Thanks for the extremely thoughtful comment, and sorry it’s taken me a while to reply. You raise some pretty good points; I’ll explain where I stand with regards to them. Of course, my views on this are philosophical/speculative in nature rather than scientific. I’m not trying to disprove your points here (they are quite good in general), but rather expanding on my own position a bit.

      I’ve had some training from a paleontological perspective, so I tend to view evolution on a linear scale, over time. With your 4th point, as far as the element of luck goes, the way I view it is as follows (just to clarify my position a bit): where luck plays in most importantly is early on, when early Chordates were developing. For some reason, they survived an extremely vulnerable period, and selective pressures allowed the group to diversify. Eventually, once you get a large-scale level of diversification, it becomes tough to exterminate such a huge group as the chordates. Part of what has allowed the chordates to prosper is fitness and a certain level of momentum, part of it is luck. Pikaia & co could have been easily wiped out. Later chordates, not so much.

      As far as the tetrapod body plan, what rubs me the wrong way a bit isn’t a vague 4-limbed presentation of aliens, but rather that these aliens seem to have run through an almost exact replication of evolution on Earth. Convergent evolution can explain some similarities of this magnitude on Earth (I’m thinking birds and bats, for example), but that is with extremely similar environmental and selective pressures. I view evolution in a relatively contingent light (not as deeply as Stephen Jay Gould did, however), so knowing the path tetrapod evolution has taken on Earth, and seeing the almost exact similarity between human and alien forms, suggests to me that convergent evolution must have taken place on an extremely large level, under pretty similar selective and environmental pressures. I just don’t see how a general progressive evolutionary trend (which would suggest a pathway towards intelligent tetrapods) is tenable when looking at the fossil record. Convergent evolution could take place on other planets similar to Earth, but that convergent? You’d need an almost dead-on match for Earth, with similar historical elements as well one would think. Of course, I could be dead wrong about that. Or such a planet could exist.

      As far as intelligence evolving elsewhere, what kind of intelligence are we looking for? Are we looking for human-type intelligence or some other form? Frankly, looking at the facts, I’d hazard a guess that life is relatively common throughout the universe (after all, look at the amino acid content of some comets, for example). But what evolutionary path would it take? As I imply in the last paragraph of my post, if selective pressures strongly favoring “intelligence” are present, then sure, intelligent life could exist elsewhere, or even be rather common. The big thing I’m arguing against here is the inference that this is necessarily the case. Possible, yes. But likely unlikely. I’m all for a rational look at things, and a deductive stance that argues tht intelligent life could exist. But the key thing I am arguing for is to emphasize the “could” part of the sentence. My issue is with a wholly progressive reading of evolution, not with the possibility of intelligent life existing somewhere in the universe besides here.

      By the way, thanks for the book suggestions. Pale Blue Dot is a great book (I read it a few years ago). I’ll have to check out some of the other ones you’ve suggested.

  4. carol colose Says:

    Awesome writing! i think we may be related somehow!

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