January 27, 2009
Bipedal Aliens: What Evolution Can Tell Us About Extraterrestrials and Vice Versa
Michael Shermer over at Scientific Blogging:
If we ever do make contact with an extraterrestrial intelligence, what
will it look like? Hollywood has had no shortage of examples for films
and television shows that feature aliens, but they are almost always
bipedal primates who speak English with a funny accent. This
depiction is more the result of wardrobe budget constraints and the
flexibility of actors than it is the imagination of writers...
My explanation — that the chances of an ET turning out to be a bipedal primate are close to zero — is not one shared by all scientists. None other than the Oxford evolutionary biologist Richard Dawkins wrote to Josh Timonen, the videographer who filmed and produced this piece:
My explanation — that the chances of an ET turning out to be a bipedal primate are close to zero — is not one shared by all scientists. None other than the Oxford evolutionary biologist Richard Dawkins wrote to Josh Timonen, the videographer who filmed and produced this piece:
I would agree with him in betting against aliens being bipedal primates and I think the point is worth making, but I think he greatly overestimates the odds against. Simon Conway Morris, whose authority is not to be dismissed, thinks it positively likely that aliens would be, in effect, bipedal primates. Ed Wilson gave at least some time to the speculation that, if it had not been for the end-Cretaceous catastrophe, dinosaurs might have produced something like the attached.
Dawkins then presented this page from Promethean Fire: Reflections on the Origin of Mind
by
Charles J. Lumsden and Edward O. Wilson, based on the paleontologist
Dale Russell's evolutionary projection of how a bipedal dinosaur might
have evolved into something like us had the dinosaurs not gone extinct.
by
Charles J. Lumsden and Edward O. Wilson, based on the paleontologist
Dale Russell's evolutionary projection of how a bipedal dinosaur might
have evolved into something like us had the dinosaurs not gone extinct.Posted by Robin Varghese at 09:06 PM | Permalink
Comments
COSMIC ARROGANCE? I THINK NOT.
Great article by Michael Schermer.
Inevitability of bipedalism, let alone homo sapien (or aliens like us), always bothered me. Carl Sagan is famous for saying that it was akin to cosmic arrogance for us to assume we were the only life form in the universe. True enough, but I don't think it is without humility to regard the convergence of our form, consciousness, and intelligence as unique. Contingencies of structural biology may presuppose evolutionary outcomes of high probability. However, the likelihood of those contingencies is another matter. Prothero stated is this way: “Once groups of organisms are established and develop a body plan and set of niches, biological constraints are such that convergence and parallelism can be expected. But the issue of who gets this head start in the first place may be more a matter of luck and contingency that has nothing to do with adaptation.”
I'm in favor of Gould's conclusion: "Replay the [evolutionary] tape a million times from a Burgess beginning, and I doubt that anything like Homo sapiens would ever evolve again.”
Jacob Bronowski, in the last episode of his "The Ascent of Man" series on PBS, said the following about the possibility of other conscious and intelligent life in the universe (I quote from memory): "If we define life as a process of change [I really don't like this definition of life] there is no reason why we should necessarily recognize it, or that it would recognized us." I hypothesize that Bronowski would not have supported the SETI project. I'm not so sure I think it is worthwhile either.
Posted by: Norman Costa | Jan 28, 2009 12:54:04 PM
Good article...but Norman, I take your point and hey, Bronowski has always been a favourite with me (I kind of prefer him to Sagan, and I really like Sagan-just to scale it for you) but isn't the point of SETI to find out if there's anybody that we could talk to? Sure, the universe could be full of hyper-intelligent, aquatic lifeforms that are really good at math, poetry and music but clueless about radio. They're the world's greatest basement, rec-room band; brilliant but no airplay. Worse than hypothetical, we can't even begin a conversation much less figure out what they're saying.
It's about seeing if there's anybody out there that digs amateur radio and thinks prime numbers are cool. Okay, it's very niche but what's a galaxy for? SETI is a crapshoot wrapped in a lottery. Just like life.
Posted by: Pete Chapman | Jan 28, 2009 2:02:24 PM
Pete,
I've always been ambivalent about SETI. My comment, above, is the first time I stopped being ambivalent and put it in writing. I would never argue my point for the purpose of convincing others. The whole area is speculative, though fascinating, and the only thing I could offer is more speculation, and probably not that fascinating.
If it ever came to a vote and my ballot was decisive, I would not kill the program. As a scientist I know that negative results and non-findings are enormously valuable. The Michelson-Morley experiment is a case in point. Also, SETI would be valuable without positive results by advancing astronomy and radio astronomy, improving associated technologies, and supporting the training of graduate students and post docs. If I remember correctly, the discovery of pulsars was initiated by what proved to be a false indication of an intelligence-based radio signal.
Nanu Nanu.
Posted by: Norman Costa | Jan 28, 2009 9:52:14 PM
They're the world's greatest basement, rec-room band; brilliant but no airplay
Lovely analogy, Pete.
Norm: Shazbat.
Posted by: Carlos | Jan 28, 2009 10:35:06 PM
The diversity of life on earth has come up with so many different solutions to the demands of feeding and reproduction that its tempting to think that at least some of the biological solutions that one might find on another planet could be familiar. Flight, for example, developed independently in insects, pterasaurs, birds, bats and a variety of gliding fish, lizards, snakes and mammals. This shows that when some resource (like the air) is available then life is highly likely to produce some form that can exploit it, which somewhat weakens the argument that "Replaying the [evolutionary] tape a million times from a Burgess beginning" would mean that certain evolutionary solutions would never appear. The 'evolutionary tape' is constantly being played and replayed simultaneously in billions of different organisms. Every individual is a unique solution offered to the mill of natural selection. Consider the crow (there was a post about that turn of phrase a while ago) A social bird that is bright enough to use simple tools and drop nuts in the road so that cars will crack them. A crow can manipulate things quite well with its beak, but its not versatile as a pair of hands. The crow's ancestors became bipedal and "sacrificed" their forelimbs as wings that enabled them to flutter and glide among the treetops, while the forelimbs of man's ancestors lengthened and acheived grip to enable them to swing from branch to branch. 2 adaptational strategies for dealing with the same problem: how to get from one tree to the next.
One path led to flight, the other to space flight.
Posted by: aguy109 | Jan 29, 2009 5:42:05 PM
aguy109,
A disclaimer: I am not a biologist, let alone an evolutionary biologist. I endeavor to keep up with the 'big' topics in science, and have tried to do so since late high school. I teach psychological research methods and statistics to both undergraduate students and graduate students. I use a lot of references and examples in the 'hard sciences' and 'life sciences' to drive home the understanding of what science is, that psychology is also a science, and that I am training them to be scientists. This is a long way to say that I hope professional biologists in the audience will weigh in if I get it wrong.
The point you are focusing on is at the heart of the debate. I'll restate you position this way: diverse earth life forms that are striving to survive in an environment that is more or less the same (for example, terrestrial, or aquatic, or subterranean), will tend to exploit the same environmental elements (like a substantial atmosphere) for similar reasons (transportation), in somewhat similar ways. I continue to restate your position. Thus, ET life forms on a planet with a substantial atmosphere might exploit the elements of their environment in more or less the same manner observed on earth by developing the capability of flight.
If I've restated your position accurately, then I would disagree and say it is wrong. Here's why.
1. Biological (Darwinian) evolution deals only with the adaptation to local conditions of existing life forms. It does not explain the developmental of life forms from non-life forms.
2. Assuming that the transition of non-life forms to life forms may be observed elsewhere in the universe, there is no reason to expect the inevitability of structures, models, and templates that would look like the earliest proto-life forms on earth. These are what could be referred to as a first set of contingencies.
3. Even if there were similarities there is no inevitability that later basic body forms would look anything like ours. These are what could be considered later contingencies.
4. Prothero and Gould were both making the point 'inevitable' evolutionary outcomes rely upon prior contingencies. If these contingencies, themselves, are not inevitable, then it becomes pointless to even talk about inevitable outcomes of evolution.
5. The word 'exploit' turns around the understanding of biological evolution so that it is pointing backwards. For example, one often hears evolutionary adaption described this way: Birds developed feathers and wings so that they could fly; or, in order to fly, birds had to develop wings. The words 'exploit', 'in order to', and 'so that they could' imply an intentional element in evolutionary biology, or some kind of direction to evolution. Direction in evolution is exemplified by the now famous graphic showing the temporal sequence of human evolution starting with a mole and ending with homo sapien. We look back and see progress and direction in evolution when in fact there are no such things. This was the fundamental flaw in Pierre Teilhard de Chardin's attempt to reconcile Darwinian evolution with Christian faith. He gave evolution a direction which ended in an omega point, Christ.
6. Thus, each subsequent evolutionary adaptation to local conditions is preceded by mutation and natural selection, not by exploitation, intention, directionality, or purpose. Coming to grips with Gould's dashing of the thought that there is no reason why we should be here, or that we could ever be here again, can be an Herculean undertaking. For some, it's as difficult as the universe is vast.
Posted by: Norman Costa | Jan 29, 2009 9:37:47 PM
Norman,
Thank you for spending so much time to respond to my commment. You may very well be right in what you say. I was just thinking, in the backgound, that
a) life has to be carbon based, as no other element can form such long, complex chain and ring molecules
b) life needs some kind of long memory molecule (like DNA-RNA) that both replicate and hold data
c) some kind of energy transfer system, like in the Krebbs cycle, would be needed with molecules like Adenosine tri phosphate giving up and receiving energy in small steps. It seems unlikely that rapid energy release (such as fire) could be used within a biological system
d)There would have to be water!
As for point 3 about body forms, I think there a good biomechanical arguments that 4 legs is the optimum number for
land animals above a certain size.
However, I dont think there is anything inevitable about an INDIVIDUAL mutation or event in biological evolution. My point is that there is a statistical likelyhood that evolution will tend to fill available niches. I recall seeing some very simple computer simulations of natural selection ( without any directionality or purpose present in the algorithm) that demonstrate just that.
Posted by: aguy109 | Jan 31, 2009 6:45:08 PM
this is thought provoking.
aguy109 - I'm not familiar with these biomechanical arguments for limb number. Could you summarize / link? Incidentally, I'm practically certain that b/c are true, and would agree that carbon is wonderful. That said, d. sounds implausible to me!
Posted by: D | Jan 31, 2009 7:05:54 PM
THE STUFF OF STARS
Yes! This is thought provoking, and worth the time to discuss.
I agree, in part, with a[not just any]guy109 (sorry, I couldn't resist that) about carbon. Carl Sagan, in his Cosmos series, said "I'm a carbon bigot. I freely admit it." He supported his 'bias' with the fact that carbon is so plentiful in the universe. I agree with him on this. Carbon probably affords great opportunity for life - maybe even inevitability. However, I don't understand that "life HAS to be carbon based." [emphasis mine]. Could we get to the moons Europa or Titan and look out the space ship portal and see a silicon-based giraffe walk by? This is not a rhetorical question. Others, who know a lot more than I about physics and chemistry, have to answer that.
There is enough evidence to support the notion that the precursors to earth's lifeforms, heavy elements and various complex molecules, are produced in enormous quantities in the fabrication factories of novae and supernovae. So there is a reasonable expectation, if only expressed in statistical probability from an hypothesized near-infinite number of trials, that earth-similar pre- and proto-life structures will emerge. However, this is where the issue of contingencies begins. You would still have to go quite a distance up the evolutionary chain of non-inevitable contingencies before your get to the 'inevitable' development of any adaptive structure.
When I took biology and genetics in college, the definition of life on earth included two absolute requirements that have been dispatched, recently, with great finality: sunlight and photosynthesis. This is why I am hesitant about definitions of life (earth-bound or not) that use the 'must haves', 'has to bes', 'optimums', and other absolute requirements that come from less than two hundred years of scientific knowledge. Carl Sagan and Edwin Salpeter have speculated about ammonia-based lifeforms that may exist in the upper atmosphere of Jupiter. These are their floaters, sinkers, and hunters. I saw a science on program on TV that speculated about extraterrestrial lifeforms on planets with far greater mass than the earth, resulting in an enormous gravitational field. They came up with a gila monster-like creature that had six fat short legs. Think of an elephant whose legs are about one-quarter their normal length.
The Drake equation, N = ( R* x fp x ne x fl x fi x fc) x L, is really an untested hypothesis and not really an equation. Also, it is based on the assumption that there are lifeforms that require similar conditions to those found on earth. This is fair enough, until you realize that the concept of contingencies is not part of the equation, nor is it implied or assumed by any of the terms. The Drake equation assumes a statistical inevitability of earth-like lifeforms, given similar earth-like conditions. If you introduce a term that assumes inevitable earth-like lifeforms are based upon contingencies that are not inevitable, then I hypothesize that the equation will resolve to near zero. If my hypothesis is shown to be supported, even I would be disappointed. Even with an abundance of life in the universe, we may still find ourselves unique and alone. Maybe that would give us an opportunity to contemplate Einstein's cosmic consciousness and Spinoza's God. After all, there seems to be no scientific disagreement that we are “The Stuff of Stars”.
Posted by: Norman Costa | Feb 1, 2009 3:12:42 PM
D,
I can't find a reference about the biomechanical advantages of being a quadruped, but I heard it somewhere.. The crude version goes like this:
If you build a table, the minimum number of legs (or points of contact with ground) for stability is 3. If the table starts walking, it first has to lift at least one leg off the ground, making it unstable, then has to lift the other 2 and hop foreword while the first supports its weight. The gait is possible, but very uneven. (3-wheeled cars are inherently unstable and unsafe, and very few have ever been marketed) 4 is the minimum number of legs for an even gait.
All bipedal animals (birds, bipedal dinosaurs, kangaroos and man) are derived from the quadruped body form. It seems improbable that the first animal to move on dry land on another planet would come ready with the balancing skills and specialized muscle structure required for bipedalism.
Why not 6 or more legs, like insects and millipedes? Because the latter are very small, they are constantly having to climb over things that are large relative to them (sand grains, pebbles etc) so they need extra points of contact in order to provide grip on these obstacles. Snakes face the same problem, and have lost their ancestral legs in order to gain multiple points of contact with the uneven substrate in which they live. For other large animals, the ground is relatively smoother and 4 legs are enough. The weight of an animal grows by a factor of a cube of its length, so large animals can’t manage with the spindly legs of a light spider. Extra, superfluous legs would encumber them and would be a metabolic waste. Spider monkeys and mice can hang from their tails (=5th limb), however, showing how flexibly natural selection creates adaptations.
Why does life need water and have to be carbon based? Chemistry is a pretty mature science, and it works the same way on any planet. Silicon atoms just don’t form long stable molecules. Water readily creates ions and is the best solvent, and also enables molecules to move around and interact with each other. NASA follows a “find the water” policy in its unmanned Mars missions, as necessary preliminary to looking directly for any living or fossil organisms.
You can speculate that ET life may take a form that we know nothing about, but that begs the question: then how could you look for it?
Posted by: aguy109 | Feb 3, 2009 4:54:53 AM
aguy109 - Thanks for the detailed response! I don't know how persuaded I am that there even need to be legs, let alone that there need to be four of them, but I better understand these considerations of dynamics now (especially the insect -> snake thing)
Posted by: D | Feb 4, 2009 10:42:20 AM
Thanks everyone! This was a great, thought provoking exchange, and not just a discontinuous collection of individual comments [though they can be interesting at times]. I hope we continue to have more of them here.
Posted by: Norman Costa | Feb 4, 2009 5:28:38 PM
CORRECTION
My point number 6, above, should read:
"6. Thus, each subsequent evolutionary adaptation to local conditions is preceded by mutation and natural selection, not by exploitation, intention, directionality, or purpose. Coming to grips with Gould's CONCUSION [NOT: dashing of the thought] that there is no reason why we should be here, or that we could ever be here again, can be an Herculean undertaking. For some, it's as difficult as the universe is vast."
Posted by: Norman Costa | Feb 4, 2009 5:44:10 PM
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