How realistic are Xenomorphs (Aliens)

[primummobile]

Well, there were thousands of species of theropods and ornithopods and none of them evolved an erect stance. Only a few birds and mammals are erect, so it seems to evolve quite infrequently.

I wouldn't like to correlate an erect stance with sentience or sophonce without more data.

I don't think we would have developed intelligence if we did not have limbs that were not needed for locomotion.

And I just wanted to know your thoughts on the load-bearing abilities of an erect spine versus a horizontal spine.

[primummobile]

Well, there were thousands of species of theropods and ornithopods and none of them evolved an erect stance. Only a few birds and mammals are erect, so it seems to evolve quite infrequently.

I wouldn't like to correlate an erect stance with sentience or sophonce without more data.

I'm not speaking of all animals. No land animal on this planet with anything even approaching intelligence has any more than four limbs. The most intelligent animals are all able to walk upright, even for only a short distance, so their hands can be freed to use as tools. The exception is the elephant, but they have a trunk with digits. How succesful do you think humans would have been if we had our brains in the bodies of dogs?

[ZunarJ5]

I'm not speaking of all animals. No land animal on this planet with anything even approaching intelligence has any more than four limbs. The most intelligent animals are all able to walk upright, even for only a short distance, so their hands can be freed to use as tools. The exception is the elephant, but they have a trunk with digits. How succesful do you think humans would have been if we had our brains in the bodies of dogs?

First, I want to say that I agree with you for the most part on your stance regarding the probability of humanoid-like intelligent life in the universe.

I did just want to point out that crows and ravens are among the most intelligent animals on earth and have only their beak with which to manipulate tools.

[ravens_cry]

I did just want to point out that crows and ravens are among the most intelligent animals on earth and have only their beak with which to manipulate tools.

They also use their feet to a degree I believe.

[primummobile]

First, I want to say that I agree with you for the most part on your stance regarding the probability of humanoid-like intelligent life in the universe.

I did just want to point out that crows and ravens are among the most intelligent animals on earth and have only their beak with which to manipulate tools.

Yes, I should have probably said "mammals" instead of "animals". Thanks for the correction.

[eburacum45]

I would, as always, caution against the use of the word 'humanoid' when describing aliens. Even bipedal aliens with two arms and some sort of head-like arrangement are likely to look very different to anything on Earth; the fact that they have some remote resemblance to humans will probably make them look more unsettling, rather than more familiar.

[Jeff Root]

Why not the word 'humanoid'? Do you have an alternative?

-- Jeff, in Minneapolis

[eburacum45]

I wouldn't call a velociraptor or a tyrannosaur humanoid, but they would almost certainly resemble a human much more closely than most bipedal alien species.

[primummobile]

I really don't want to rehash this, but I believe I said 'humanoid-like'. I think I specifically said it would be more likely for intelligent life to resemble us, even superficially, than it would be for intelligent life to resemble a squid leaving a slime trail on the ground.

It was just a thought experiment and that's all. I was just assuming a terrestrial creature that is intelligent. And again, I never made the claim it was likely for them to resemble us. I said that it was probably not as unlikely as some may think. If you've ever listened to people like Carl Sagan or his disciples, they are so anti-geocentric that I think it clouds their judgement sometimes and so they take it to the opposite extreme. I've read that there is virtually no chance of there being similar beings elsewhere in the universe. I think that's taking it too far, and I gave the reasons why I think that.

A velociraptor may have had a branch diverge into the Gorn instead of birds. The Gorn I've seen are all pretty humanoid-looking to me.

[Noclevername]

I really don't want to rehash this, but I believe I said 'humanoid-like'. I think I specifically said it would be more likely for intelligent life to resemble us, even superficially, than it would be for intelligent life to resemble a squid leaving a slime trail on the ground.

It was just a thought experiment and that's all. I was just assuming a terrestrial creature that is intelligent. And again, I never made the claim it was likely for them to resemble us. I said that it was probably not as unlikely as some may think. If you've ever listened to people like Carl Sagan or his disciples, they are so anti-geocentric that I think it clouds their judgement sometimes and so they take it to the opposite extreme. I've read that there is virtually no chance of there being similar beings elsewhere in the universe. I think that's taking it too far, and I gave the reasons why I think that.

A velociraptor may have had a branch diverge into the Gorn instead of birds. The Gorn I've seen are all pretty humanoid-looking to me.

Well, let's look at Earth. The Cambrian Explosion produced multicelled life in every imaginable and some unimaginable forms. Of those, only a handful of animal types are alive today. One of those few lines of developments led to vertebrates, and to us. Now imagine if one slight difference in environment or mutation had not produced that specific line. All "humanoid" life would never have developed, and something else would have taken those niches. Alternately, suppose another line had survived and out-competed ours by just a little bit, then went on to become the dominant species; if cephalopods had developed, say, air-breathing just slightly before we did. Today some Squibbon scholar would be saying "well, it's unlikely that dry-skinned tetrapods could become sapient".

Evolution is a crapshoot. It uses whatever shape works for survival.

[primummobile]

Well, let's look at Earth. The Cambrian Explosion produced multicelled life in every imaginable and some unimaginable forms. Of those, only a handful of animal types are alive today. One of those few lines of developments led to vertebrates, and to us. Now imagine if one slight difference in environment or mutation had not produced that specific line. All "humanoid" life would never have developed, and something else would have taken those niches. Alternately, suppose another line had survived and out-competed ours by just a little bit, then went on to become the dominant species; if cephalopods had developed, say, air-breathing just slightly before we did. Today some Squibbon scholar would be saying "well, it's unlikely that dry-skinned tetrapods could become sapient".

Evolution is a crapshoot. It uses whatever shape works for survival.

I don't think that it's entirely a crapshoot. Whatever form is the most efficient with the fewest resources (such as food for the mother) needed to develop is going to win out. Whatever form can survive the best on the fewest resources is going to be superior, with all other things being equal. If we had four legs we would probably be superior to what we are now, but we would need to consume more calories to survive which would have put us at a disadvantage to our two-legged counterparts back when it was a struggle to find food.

I've been through all of this earlier in the thread. I'm not saying that humanoid-like life is likely to be encountered. I'm saying that others have said that the chances are nil that it has devloped elsewhere. I'm just saying that maybe it's not nil. Maybe the probability is .0000000001 that it would develop as the dominant form of life on an earth-like planet. I realize that there are a lot of ways for life to evolve, especially given all the options. But given enough time, you are going to find organisms that are exceedingly fit to physically survive in their environment. Our shape is exceedingly fit to survive on Earth, and you'd be hard pressed to identify a more fit form for us to take.

It should also be noted that when I say 'humanoid-like' I'm not referring to something that would have to be a vertebrate. I think in my first post on this I said that legs are the most efficient method of land locomotion we have discovered. (if you don't have naturally occuring roads to travel) In addition, it seems that one leg would not be very useful and three legs are one more than you need, which would mean extra energy required to maintain that leg. Intelligence would need something with which to grasp and manipulate objects in their environment, which would be something like a hand. There are other ways, yes, but a hand is the most universal tool for grasping objects. Some animals may evolve vacuum pressure to pick up objects, but as soon as something with a hand came along it would out-compete them. I also said that vital organs spread throughout the body would not be advantageous because the loss of a body part could mean death. A one-legged woman can still reproduce. If you heart was in your leg, losing a leg and surviving would not be an option.

My definition of humanoid-like was any being with a center mass, something like a head, something like two arms with hands, and something like two legs. Because its arms would need to be free to manipulate the environment it would probably walk upright.

It's also likely that life developed independentally many times in the early Earth. I don't think it likely that the first self-replicating molecule just happened to be RNA and we stuck with that. But with that in mind, it could mean that RNA-DNA is a very efficient means of carrying genetic information compared to some of the other possibilities that may exist. Therefore, given the same intitial conditions, it's not outlandish to think that something similar to DNA would eventually evolve.

On the other hand, what you said is true. Life doesn't need to be the most fit to survive and pass along its genes. It merely needs to be fit enough to survive and pass genes. That means that probably almost all of the time we would expect to find life quite different from what we have here. All I'm saying is that given enough time, you're bound to get organisms that are more fit than what came before. Given my belief that the humanoid form is very fit for intelligent organisms, I don't think it's unreasonable to say that we probably aren't the only humanoid-like organisms in the universe. Of course, that's assuming that intelligent life has developed elsewhere.

I think you're reading more into what I'm saying than what I am really saying. But unless you're talking to me about electrical engineering, scuba diving, or motorcycles I'm usually pretty non-committed in what I say. My speculation is much more along the lines of what could happen rather than what does or is likely to happen. In this case, I'm saying that humanoid-like life developing elsewhere from similar initial conditions isn't as impossible as some would believe.

[ravens_cry]

I don't think we are that likely to see complex tool using intelligence that doesn't have some kind of manipulator.
A manipulator could be a tentacle, a trunk, a hand like appendage, a prehensile tail, a claw beak combination or something else entirely.
I wonder how common a centauroid body plan will be, a centauroid being a creature whose manipulators did not evolve from a locomotive limb. For example, an elephant's trunk.

[Noclevername]

My speculation is much more along the lines of what could happen rather than what does or is likely to happen. In this case, I'm saying that humanoid-like life developing elsewhere from similar initial conditions isn't as impossible as some would believe.

Not impossible, no, but-- and I'm sure you've heard this argument before-- living things are like snowflakes, they melt if it gets too warm. Or something like that.

[primummobile]

Not impossible, no, but-- and I'm sure you've heard this argument before-- living things are like snowflakes, they melt if it gets too warm. Or something like that.

I thought they melt if they get wet.

[primummobile]

I don't think we are that likely to see complex tool using intelligence that doesn't have some kind of manipulator.
A manipulator could be a tentacle, a trunk, a hand like appendage, a prehensile tail, a claw beak combination or something else entirely.
I wonder how common a centauroid body plan will be, a centauroid being a creature whose manipulators did not evolve from a locomotive limb. For example, an elephant's trunk.

I agree with that. In fact, I think I used the example of an elephant trunk earlier in this thread.

[ravens_cry]

I agree with that. In fact, I think I used the example of an elephant trunk earlier in this thread.

Why bless my soul and whiskers, you did.

[JCoyote]

I don't think that it's entirely a crapshoot. Whatever form is the most efficient with the fewest resources (such as food for the mother) needed to develop is going to win out.

I initially agree with the idea but when I look at the Cambrian explosion a few things occur to me.

1: Establishment is strength. An established successful organism in its niche is hard to displace by different organisms that would share its niche. An organism could be more efficient, but if not initially present in large enough numbers could fail and go extinct. There is strength in numbers, breeding partners and territory control.

2: Failure to succeed in the environment is not purely based on body morphology. Some body formats may have been superior in some ways, but appeared in lineages with insufficient defense against disease, inadequate processing of useful available proteins, etc.

All I'm saying is it is more complex than just body shape, and once something succeeds even marginally it is hard to displace. I've said it before, nonlethal mediocrity is a valid outcome in selection.

[primummobile]

I initially agree with the idea but when I look at the Cambrian explosion a few things occur to me.

1: Establishment is strength. An established successful organism in its niche is hard to displace by different organisms that would share its niche. An organism could be more efficient, but if not initially present in large enough numbers could fail and go extinct. There is strength in numbers, breeding partners and territory control.

2: Failure to succeed in the environment is not purely based on body morphology. Some body formats may have been superior in some ways, but appeared in lineages with insufficient defense against disease, inadequate processing of useful available proteins, etc.

All I'm saying is it is more complex than just body shape, and once something succeeds even marginally it is hard to displace. I've said it before, nonlethal mediocrity is a valid outcome in selection.

I don't disagree with any of that. In fact, that's why I don't think there will be any significant steps in human evolution unless we leave the planet or most of us die off. We're too fearful of anything different to allow that to happen.

[SkepticJ]

. . . or how it sees with no eyes, is a mystery.

Is it necessarily true that a large creature would have large camera eyes? What about patches of compound eyes? Maybe evolved* phased arrays?

*Or not, in the case of the created Xenomorphs.

[publiusr]

With that dome for a head--I would think sound as vision

[SkepticJ]

The real answer, of course, is that the lack of eyes makes it creepier. Alien being a horror movie.

H.R. Giger's original art, Necronom IV, had eyes.

[Jeff Root]

Could you provide a link to an image of one of these
eyeless movie aliens? I'm confused now as to which
alien (or possibly aliens) you are referring to.

-- Jeff, in Minneapolis

[SkepticJ]

Could you provide a link to an image of one of these
eyeless movie aliens? I'm confused now as to which
alien (or possibly aliens) you are referring to.

-- Jeff, in Minneapolis

The movie is called Alien. It's from 1979. Starred Sigourney Weaver, Ian Holm, and others. Directed by Ridley Scott

It had a sequel called Aliens. 1986. Sigourney Weaver, Michael Biehn, Paul Reiser, and others. Directed by James Cameron.

The aliens, or xenomorphs, in these movies lack visible eyes.

The movie Prometheus is set in the same universe as the above two fine films, as are four other movies that aren't worth the film they were recorded on.

[Strange]

The real answer, of course, is that the lack of eyes makes it creepier.

Oooh. I had never noticed that before. The things you learn on BAUT/CQ.

[eburacum45]

With that dome for a head--I would think sound as vision

This would be more reasonable if the Alien were an aquatic animal. Dolphins use the 'melon' organ in their large domelike head as a lens to focus their sonar emissions. However I'm pretty sure this wouldn't work very well in air. The density of the air is much lower, so the focus of the lens structure would be all wrong.
According to this wiki page,
http://en.wikipedia.org/wiki/Melon_(whale)
one function of the melon is 'impedance matching'; specifically 'creating a similarity between characteristics of its tissue and the surrounding water, so acoustic energy can flow out of the head and into the environment with the least loss of energy'. The Alien's head would need to be quite differently arranged to match impedance with the surrounding air, and it would need big ears to recieve the echoes too.

[eburacum45]

The Xenomorph's stance has some differences to the normal human 'erect biped' stance,or so it seems to me; it often seems to move in a crouching fashion, and it has a long tail, which would probably impede a fully erect walking motion in any case. No doubt the 'crouching' is just another example of an attempt to make it look creepier, but when I saw the film on its first release the scariest moments came when the monster was mostly concealed; it could have been almost any shape for most of the film.

[ravens_cry]

I found the almost, but also certainly not, human teeth and jaw to be the scariest part, especially when connected to the lack of visible eyes.

[Joe13]

Totally unrealistic. They grow ridiciulously fast with very little if any nutrition.

Evolutiononaly it is possible for a creature to evolve that can grow that quickly, we have some examples on Earth like some types of insects.

[Seaumas]

Hey, if you want to be in the movies you have to look a little recognizable. Just kidding. They were probably designed with insects in mind. I'm sure an entymologist and an arachnidologist were involved with H.R. Giger back there drawing like mad. If you think they look too human, then check out a preying mantis.

[TooMany]

I don't think that it's entirely a crapshoot. Whatever form is the most efficient with the fewest resources (such as food for the mother) needed to develop is going to win out.

There is considerable evidence of convergent evolution that probably occurs for this very reason. Some things work better than others.

The eye of an octopus and the human eye have evolved independently but are remarkable similar.

The main difference in these eyes is that in an octopus, the nerves that do pre-processing and transmit signals from the retina to the optic nerve are behind the retina. In humans, the arrangement is opposite which results, for example, in our blind spot. So actually the octopus eye is more efficient. This difference is an accident of evolution. Such a major difference is unlikely to change. And yet other than this, the two "designs" are virtually the same.

I just read an article that says that it is possible that "comb" jellyfish have evolved muscles and nerves independently from other animal forms. The suspicion comes from major differences in genetic structures between these jellyfish and all other animals. If true, this may change some people's view about how random evolved systems are and demonstrate that multiple paths can lead to similar structures that evolve simply because they are effective.