25 January 2010

Sounds Teleological To Me

Aliens are likely to look and behave like us. (Richard Alleyne, Telegraph.co.uk, 1/25/10)
Prof Conway Morris believes that extraterrestrial life is most likely to occur on a planet similar to our own, with organisms made from the same biochemicals. The process of evolution will even shape alien life in a similar way, he added.
“It is difficult to imagine evolution in alien planets operating in any manner other than Darwinian," he said.

"In the end the number of options is remarkably restrictive. I don't think an alien will be a blob. If aliens are out there they should have evolved just like us. They should have eyes and be walking on two legs.

"In short if there is any life out there then it is likely to be very similar to us."
Note that "Darwinian" here seems to mean "destined to produce symmetrical bipeds with heads."

37 comments:

erp said...

Tail optional.

Susan's Husband said...

It's really hard to know. One can make good argument for parsimonious results via evolution (e.g., 2 legs because that's the fewest you need) but perhaps that's just a result of selection bias.

We know that the pre-Cambrian explosion gave rise to a very diverse set of body forms, only a few of which prospered over that age. Were the winners lucky or expected?

Peter Burnet said...

Truly an astounding article. Darwinism explains the physiology of aliens, assuming they exist, which they probably don't.

I wonder what Darwinism has to say about the evolution of leprachauns.

Hey Skipper said...

(e.g., 2 legs because that's the fewest you need)

As it happens, two legs makes for the most efficient means of terrestrial locomotion there is.

Not as fast as four, but given enough time, two will always run four to ground.

It is also hard to imagine precise depth perception without binocular vision.

Another way to look at this is through parallel evolution: essentially all terrestrial predators have eyes in front: wolves, bears, raptors.

Presumably Darwinism explains that because the vision requirements to be a predator are the same, no matter whether the predator is a bird or a human.

So, taking that one example, there are good reasons to expect an intelligent alien species to have paired in front, and very close to the brain, which won't be small.

Form follows function.

Peter Burnet said...

"Four legs good, two legs better!"

--Squealer the Pig.

Susan's Husband said...

Why is efficient locomotion important to evolving sentience?

We must also consider that things like binocular vision are not parallel but perhaps because a common ancestor had that basic configuration and evolution got "stuck" in a local minima, alternatives having been lost in the Cambrian.

My view is that you're probably right but I think it's very difficult to step away personally biased view of how things turned out here.

Brit said...

Also there are limits on what parallel evolution could tell you about alien evolution, because even parallel evolution still took place on Earth - there are so many unknowns when considering other planets.

Harry Eagar said...

Conway Morris is a careful thinker about evolution. His book about the Burgess Shale critters was very good.

This may not have been his finest moment.

The general proposition that Darwinian evolution will be a feature of any living system seems sound.

Speculation about how it would work out in detail seems to me like debating the Drake Equation. Not enough information.

Number of legs has long fascinated me. What is the distinguish character of these two series:

0, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 88, 100, 200

vs.

1, 3, 18 . . . 87, 89 . . . 99, 101 . . . 199, 201 . . .

There's some doubt about the numbers higher than around 15, but roughly, the first is the number of functional legs of existing critters, and the second is the number of legs not observed.

Beyond 12 or so, it is hard to imagine that the results are the result of anything but chance.

However, if I were going to start speculating about other intelligent life forms, my starting point would be: Could there be intelligent plants?

That is, assuming that intelligence is energetically expensive, could you afford to make, rather than consume, your own energy? I suspect not.

Hey Skipper said...

SH:

Why is efficient locomotion important to evolving sentience?

Good question, which I hadn't adequately considered.

Having given it more consideration, it isn't. After all, based upon first hand experience I think porpoises are sentient, but while their locomotion is very efficient, it sure as heck doesn't require legs.

We must also consider that things like binocular vision are not parallel but perhaps because a common ancestor had that basic configuration and evolution got "stuck" in a local minima, alternatives having been lost in the Cambrian.

Except that it is also worth considering that prey animals strongly tend to have their eyes towards the sides of their heads, providing vision that is more panoramic than binocular.

Since an alien planet must have prey and predators, then that planet will also have animals with appropriately placed eyes. And since any sentient alien is likely to be a predator, then biomechanics will likely result in any such alien having eyes on the front of its head.

Brit:

Also there are limits on what parallel evolution could tell you about alien evolution …

Absolutely.

But I am thinking in terms of biomechanics more than evolution.

It is very likely that anything more than extremely primitive life is carbon based and requires liquid water. Consequently, any aquatic lifeforms are going be shaped by hydrodynamics: given various combinations of size and speed, their simply aren't very many different ways to build a fish.

Similarly, brains and eyes have to be close together.

Also, nearly all animals and insects have a similar body plan symmetry: left and right are mirror imaged, but not front and back or top and bottom. Absent spiders, all that I can think of off hand have two eyes (presuming a compound eye counts as one)

So, given how widespread that is on Earth, there is probably pretty good reason to think that any sentient alien will have a large brain - body mass ratio (meaning it must have a head to contain the brain), be bilaterally symmetric, and have binocular vision with eyes very close to the brain.

I am sure my thinking is polluted by experience, but given the widespread nature of certain core characteristics, it is hard to see how many of them could be any different than they are.

Peter Burnet said...

What Brit said. Don't you need a savannah and tall grass to set an evolutionary course for bipedal humans? Without them, who is to say we wouldn't all still be quadripeds, or, even more intriguing, blobs?

Hey Skipper said...

Peter:

What Brit said. Don't you need a savannah and tall grass to set an evolutionary course for bipedal humans?

I don't think Prof Morris makes that claim. Rather, this sums it up pretty well: extraterrestrials will most likely have evolved just like "earthlings" and so resemble us to a degree with heads, limbs and bodies.

I take that to mean that evolution is just as universal a process as gravity is a force, and that the functional constraints on life forms means they must have body plans similar to those on earth (which include blobs.)

Further restricting the list to technologically capable beings adds more restrictions. Dolphins and elephants are sentient, but have no, or limited means, with which to manipulate things.

So it is really hard (for me, anyway) to imagine such a being without something like hands on arms. Two of those is far more useful than one; three hardly more than two; etc. Given all the tradeoffs, two seems far more likely.

Bipedal? Well, hands are most useful when specialized, which suggests that such a being would not use arms as legs.

Anyway, given how evolution here on earth has settled upon a very small number of body plans across a wide variety of life forms, it suggests to me that the range of fit solutions is not very wide.

Peter Burnet said...

I take that to mean that evolution is just as universal a process as gravity is a force

So are you saying the survival imperative has now been decoupled from environmental pressures? Whether hunters or hunted or unthreatened vegetarians, something would still have pushed us to two legs?

Hey Skipper said...

Peter:

No, I'm saying fitness cannot exist independently of physics.

Step away from humans for a bit. A bird doesn't get to be any shape: its wings have to be at the side, not top and bottom. The centers of gravity, lift, and drag all have to be very close together. So the design constraints mean anything that functions like a bird is likely to look a lot like a bird, no matter what planet it is on. It can't look like anything else and still fly, because no matter what planet it is on it will still have to deal with gravity, air, and Reynolds number.

Despite having followed very different evolutionary paths, birds and bats are structurally similar.

Is there some larger reason for two legs? SH has a point -- it could be pure luck of the draw that collapsed the plethora of Cambrian body plans to just a few, so what we see today isn't required, but purely contingent. So we could have ended up with four legs and two arms.

However, based on my limited engineering knowledge, I think the reason so few body forms survived the Cambrian is that they are demonstrably superior in engineering terms: they just work better.

For a ground dwelling animal larger than insects (I am excluding snakes), four is better than two, and six offers nothing four can't provide. Any technologically capable animal will require at least two hands, but if the starting point is four legs, then the result will likely be bipedal locomotion and two arms.

Hey Skipper said...

Oh, and like erp said, tail optional.

Bret said...

What if gravity were slightly greater or lesser than on Earth? What if the atmosphere was a different composition? Wouldn't factors like that have a significant effect on the physiology of life forms?

Peter Burnet said...

Skipper:

I think the reason so few body forms survived the Cambrian is that they are demonstrably superior in engineering terms: they just work better.

Work better at what, if not at surviving in the local environment? AOG makes the argument that evolution is parsimonious--you evolve what you need to survive and no more--so are we now to assume that two eyes or two legs are equally "needed" throughout the universe? What possible meaning could your word "work" have in this across-the-board analysis?

Susan's Husband said...

Bret;

Like gas giant aliens who live in the clouds? They're not going to have two legs :-).

I do think that Skipper's probably right, that if you start with a terrestrial planet you'll probably end up with something roughly humanoid.

Mr. Burnet;

By "work" Skipper means "out compete the other forms". I have intended for years to do a post on this -- I think that the Cambrian explosion followed by a collapse is a nigh inevitable phase of early multi-cellular evolution. The possibility of structurally different aliens comes down to how much luck there is in shake out. Skipper's argument is that because the basic physics are the same, we should expect the same basic designs to win. I have a lot of sympathy for that view, that one has to radically change the environment to get substantively different results.

erp said...

As usual, the great bard says it best and in the fewest words, "There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."

Our experience is limited to what we can imagine, but there are probably unimaginable (to us) things in a universe as vast as ours?

Be fun to be able to explore it.

Peter Burnet said...

AOG:

I think I understand--sort of. But if we are now moving away from the minutiae of a million just-so stories and dealing with sweeping universals about evolutionary competition that apply irrespective of local environments (except, of course, when they don't), surely the tautological objection to Darwinism has just gotten a lot stronger.

David said...

As erp suggests, now we're just playing in the sandbox of the Anthropic Principle.

Brit said...

But then again, it's not unreasonable to suggest, on the basis of parallel evolution, that on an alien planet very like earth then things would look like earthlings. This is what Morris appears to be suggesting, though it's almost, as David always loved to say, trivial.

Peter Burnet said...

it's not unreasonable to suggest, on the basis of parallel evolution, that on an alien planet very like earth then things would look like earthlings.

Perhaps, but that doesn't help the argument much, as it is just as reasonable to suggest, based upon the gazillions of random mutations, extinctions and different survival challenges that led us to where we are, that they wouldn't. I suppose that tends to happen when what you are arguing about doesn't exist.

As erp suggests, now we're just playing in the sandbox of the Anthropic Principle.

Damn, that is good, David, and deserves pride of place in the pantheon of erudite, casual and devastating put downs. I'm already working on a few variations to use against unsuspecting leftists who assume conservatives are all stupid:

As Harry suggests, now we're just swinging on the Jungle Jim of the cosmological constant;

As Brit suggests, now we're just frolicking in the wading pool of the multiverse theory;

As Skipper suggests, now we're just flailing in the boxing ring of the Fermi Paradox

I knew all those archives would come in handy one day.

Brit said...

Yes it is a tricky one, because we're not really sure any more how important natural selection is compared to other evolutionary factors. So this is as much a question about evolution on earth as speculation about other planets.

David said...

Surely, it's "Jungle Gym?"

Peter Burnet said...

Yeah, it is, but spare me that sniffy "surely" nonsense. You aren't fooling me, I know you had to Google it to make sure yourself.

Did you just buy a Park Avenue condo?

Harry Eagar said...

To go back to the heading, whatever it may be, it isn't any more teleological than limiting the number of planes that a crystal can grow in.

If -- let's posit -- an intelligent being has to be mobile, then there are only a finite number of ways to do that.

David said...

Peter:

Though I'm reluctant to correct you at this point, the proper response was, of course, "Yes, and don't call me Shirley."

David said...

Harry:

Any theory that says that, no matter what the starting point and after billions of years and millions of random mutations, you will end up with something more or less us (both physically and psychologically) will do until real teleology comes along.

Peter Burnet said...

there are only a finite number of ways to do that.

finite, adj.---One, with a few minor variations in colour and style.

David:

After years at this game, I find myself completely impervious to accusations I am a total lunkhead about Darwinism, but being caught out in a simple spelling mistake is simply more than I can bear.

erp said...

David, I didn't mean to say what you said I said, I only meant having a tail makes it so difficult to wear designer jeans and high heeled boots.

Hey Skipper said...

Peter:

But if we are now moving away from the minutiae of a million just-so stories and dealing with sweeping universals about evolutionary competition that apply irrespective of local environments (except, of course, when they don't), surely the tautological objection to Darwinism has just gotten a lot stronger.

The problem with your assertion presuming that it is possible to have both widely varying local environments and sentient life.

True, it is nearly impossible to prove a negative. But taking just one premise as given: life requires carbon and widespread liquid water, then local environments simply don't get to vary much. That means all the physical constraints that apply to earth must be similar elsewhere. Reynolds number doesn't matter much for humans, but it certainly did for our very distant aquatic ancestors. Since water is not compressible, a planet's gravity, so long as it is sufficient to retain an atmosphere has (SFAIK) essentially no effect on what body plans work (in an engineering sense) best.

Therefore, presuming life was aquatic to start -- and the reasons for that appear hard to avoid -- the body plans available from that beginning are going to be limited in precisely the same ways as on Earth.

This is nowhere close to a tautology: the universe of conceivable airplane/bridge/fish designs is far larger than the subset of possible designs.

Biomechanical limitations are inescapable. Exoskeletons do not work for anything much larger than will fit in your hand. Why? Can't breath. That upper size limit varies with O2 concentration, but not by a lot. Free oxygen seems to be necessary, which means CO2. Photosynthesis is the only known way to close that circle. But it doesn't provide sufficiently concentrated energy to support a brain. That means a sentient animal has to eat, which means an alimentary canal. Any environment capable of supporting a sentient being will also exhibit scarcity. Etc.

Given just one entering assumption, the list of consequent constraints within which evolution must occur gets very long very quickly.

It escapes me how teleology is even remotely involved.

Peter Burnet said...

Once upon a time, a new scientific theory was developed to explain the development of life. It was called Darwinism. It posited that life evolved as a result of a localized survival competition among millions of random genetic mutations. There was no reason for any of these mutations, no direction they led to, no purpose to it all and no reason to pre-suppose any one mutation would prove more beneficial than another--one had to await the outcome of the battle for survival to determine that. Indeed, the proponents of Darwinism became noticeably cranky when anyone suggested anything drove this genetic battle other than the objective survival challenges their hosts encountered in their actual, specific environments.

Then, gradually, this theory was repleaced by a completely different theory. Beginning with physics and moving slowly to biology, this new theory posited that the development of life was constrained tightly by many, many universal physical and biochemical laws, the provenance of which no one knew. The more these laws were studied, the more astoundingly fine-tuned they were seen to be, leading to tighter and tighter parameters that led progressively and inexorably to life as we know it today. Not only was the chance emergence of life itself calculated to be one in more of the number of atoms in the universe, gradually it became clear that the major features of life were constrained to the point of near-inevitability, and on a one-way trajectory. It was as if evolution had moved from a spontaneous neighbourhood pick-up game with no rules other than who could outmuscle whom, to a tightly refereed match with a common rulebook so thick, most of the players ended up being ejected from the game by higher authority rather than outmuscled.

They called this new theory Darwinism.

Peter Burnet said...

Surely you all know I meant "less than one in more than the number of atoms in the universe"? Surely.

Hey Skipper said...

Makes the same amount of sense either way.

Harry Eagar said...

David, there is nothing in the theory that says you get intelligent life, and so far as we have any evidence of, you can go 3 billion years without even advancing to anything more complicated than a bacterium.

However, if you do go toward intelligence, there are (perhaps, we don't know) not an infinite number of ways it could happen. Despite various airy speculations about silicon-based critters floating in hydrogen skies, it seems pretty likely to me that you're going to involve liquid water somehow.

We know zip about other kinds of life, but we know a lot about chemistry, and the unusual abilities of H2O and carbon suggest that it would be difficult to get a great deal of complexity from any system that couldn't use those.

joe shropshire said...

Sounds like ordinary hindsight bias to me. I can sympathize with the good professor not wanting to sound like a loon, but the way to handle this sort of thing is the way Percival Lowell (the astronomer who thought he saw canals on Mars) did. You may recall the story where William Hearst is supposed to have sent a telegram to Lowell : PLEASE WIRE 1000 WORDS IS THERE LIFE ON MARS, and Lowell supposedly wired back: NOBODY KNOWS NOBODY KNOWS NOBODY KNOWS, 500 times. That's a lot better than this guy just did.

erp said...

Obviously Professor Lowell wasn't trolling for a federal grant. Oh, for the good old days.