I was watching fire in the sky, and while Travis Walton was on a spaceship my first thought was ‘why is the atmosphere breathable in there’. On earth I think the CO2 concentration is something like 0.04%. If it gets too high our blood goes acidic and we have panic attacks.
Oxygen concentration is fairly set on earth, I think if it gets below 17% people have symptoms. Plus if it is too high it becomes flammable. Either way, oxygen is what we breathe because it was given off as a waste material billions of years ago. The odds that an alien species would also breathe oxygen seem low, as what are the odds their plant would have an oxygen rich environment? As I said, the only reason ours is oxygen rich is because that was the waste material cyanobacteria produced (before they polluted themselves to death).
Plus alien atmospheres could have carbon monoxide, which would be highly toxic to us.
Also the aliens look like primates. What are the odds of that? I thought most animals have a single jointed arm and leg bone that bends a certain way because we are descended from a certain kind of fish a few hundred million years ago who had 4 limbs that bent a certain way. The odds that aliens would have single jointed 4 appendages and be bipedal with elbows and knees that bend in the same direction seem very low. Not to mention the other similarities (wrists, hands, fingers, feet, toes, etc).
I don’t know why so many animals have similar faces. A face that is a left/right mirror image with the eyes on top, then two nostrils, then a mouth below that with ears on the side. That seems similar across a lot of species, and I assume it is because one of our descendants looked like that but I don’t know which one or if there are any real benefits to that kind of facial structure. Maybe the eyes being on bottom is superior.
Plus weather could be different, so maybe they would be built differently. If there was more cold, or more wind that would affect physiology.
Also if the aliens are so much more technologically advanced than us, why can’t they wipe memories properly? Shouldn’t a species potentially millions of years more advanced than us be able to properly wipe a memory so it cannot be retrieved?
Also I read some stories where people claim aliens can make solid objects permeable. So a person can pass through a wall for example. If so, why would they need to abduct anyone? Couldn’t they just put implants in people in their sleep from a distance?
Convergent evolution is a thing. Compare the marlin (fish), ichthyosaur (reptile), and dolphin (mammal). If there’s water oceans full of life out there I wouldn’t be surprised if there’s vaguely fish-shaped creatures in them.
But I wouldn’t expect aliens to have gone through our peculiar evolutionary history, or share our environment. An intelligent race from a high gravity, low temperature planet based on something weird like ammonia probably wouldn’t look like humans. Most smart aliens are probably something more Lovecraftian than human, like the Mi-go or the Great Race of Yith. Or just think of all the other animals on Earth that could’ve been super intelligent like elephants or raccoons or something.
It also depends on what you mean by human shaped. I don’t think having extra limbs changes it much, or an upside down face. What if it’s more like a centaur? Or if it’s head is where our torso is? Shades of gray.
I haven’t seen the movie in question, but I’ll take a stab at a reply anyway.
Well, if aliens brought humans on board a spaceship and didn’t want to kill them outright they’d probably make some effort to replicate our atmosphere. It’s no different than when people take fish out of a lake or ocean with the intention of studying them/keeping them without killing them. Actually, the usual practice is to take some of the water the fish is in along with the fish, maybe the aliens scooped up some Earth atmosphere, too? Or maybe just replicated it.
True. Actually, 19% is considered the minimum for long term health. That’s at one atmospheric pressure, at higher concentrations you can get by with a lower percentage of oxygen. On the flip side, at lower pressure you require a higher concentration of oxygen. That’s why people climbing Mt. Everest frequently use 100% oxygen - the pressure on the mountain summit is so low that even 100% oxygen concentration isn’t quite enough.
Er… um… well, yes, many species evolved that used the waste product known as oxygen although we don’t breathe it because it’s a “waste material”, we breathe because it’s abundant in Earth’s atmosphere and our ancestors evolved to use it.
Oxygen metabolism has the advantage of providing a great deal of energy vs. the non-oxygen metabolisms we know about. There are very, very few multicelluar animals that get by on non-oxygen respiration. It may be that an oxygen based energy metabolism is needed to provide the energy for large, complex multicelluar life and/or intelligence. Or maybe not, we just don’t know.
Frankly, we don’t know if oxygen-producers and oxygen-users are a common feature in the universe or not. Heck, we don’t even know if life is a common feature of the universe or limited to just one planet. However if you’re speculating on intelligent, alien life then guessing it breathes oxygen isn’t unreasonable as we know there is at least one such species in the universe.
There are plenty of cyanobacteria still around, they didn’t “pollute themselves to death”.
True, but CO isn’t toxic even to all life forms here.
Pretty damn low, actually, but if they’re using human actors in the movie that ups the odds of them looking primate since there’s only so much you can do with make up and a rubber suit.
If by “most animals” you mean “land vertebrates” yes, that’s true. However, “most animals” are not in fact “land vertebrates” but rather other types, like arthropods and the various worms and fish and cephalopods like octopus and squid and insects and sea urchins and… well, everything else that’s not a plant or fungus or bacteria sort of thing.
Again, if they’re using human actors that presents obstacles to something more exotic.
If they’re using CGI then there are limits of imagination. Also, it can be hard to get a human audience to relate to a squid-thing.
The concept here is “bilateral symmetry” and is freakin’ common in the world of the living. It extends from microscopic critters like tardigrades on up through the animal kingdom. It apparently evolved multiple times as the Ulitmate Common Ancestor of all the animal phylums probably didn’t have it (there are animal phylums that have radial rather than bilateral symmetry - think starfish, as an example)
There does seem to be some advantage to putting major sensory organs on the front end of an animal, given that that arrangement appears over and over again. However, even on Earth bits can move around. Whales, for example, have their “nostrils” on the top of their heads and we call them “blowholes”. Some insects have their “ears” located somewhere other than their heads. (Vertebrates have their ears on the sides of their heads because the bones of the inner ear evolved from jawbones, so the proximity and location remains. Insect hearing organs evolved differently.) So, partly you have a bias generated by being and mostly looking at large land vertebrates. You are correct that an alien species may well have a different configuration of sense organs/mouth/breathing organs/etc. However, again and again major sense organs seem to get placed near the front and near the mouth so there may, in fact, be some advantage - not universal, though, as there are exceptions even on our planet.
That depends. Maybe so completely wiping a memory will screw up the brain/intellect of the [del]victim[/del] individual so only partial memory wiping is possible without essentially destroying the individual. Since we don’t, ourselves, have memory-wiping tech we can’t know. Although we do have memory preventing tech, medications that prevent your brain from converting short-term memory into long term memory (essentially, the memory is never recorded) but that doesn’t mean aliens would automatically have access to or know about those particular pharmaceuticals.
Um… maybe those people making those claims have no real understanding of alien tech?
I wonder what wild the hell wild animals think when we capture and tag them, then release them again into the wild? We don’t wipe their memories, although the sedation we use sometimes might well make for very hazy, trippy memories for the animal. Maybe the aliens don’t care about memories, maybe the memory issues are a side effect of something else?
It’s not the concentration of oxygen that matters to us so much as the partial pressure. (Low pressure environments can kill you from oxygen deprivation, even if the concentration is pretty high).
We rely on oxygen mostly as an electron acceptor (when we burn organic molecules for energy, we convert them from high energy reduced forms to low energy oxidized forms). There are other potential electron acceptors that could work, and there are a few life forms out there that use sulfate or nitrate as electron acceptors. (And, of course, alcoholic fermentation is a process by which yeast uses a simple organic molecule as an electron acceptor, resulting in production of ethanol).
Oxygen and CO2 level have both varied quite a lot over time in the last billion years or so;
so we can’t rely upon a familiar level of either gas in an alien atmosphere. If the planet concerned exists at the outer edge of the habitable zone of their star, then the carbon dioxide level required to maintain liquid water might be so high that it would be toxic to humans.
It seems very, very unlikely that any humanoid alien species would evolve in the universe within travelling distance of Earth. But just possibly a sufficiently advanced species could manufacture an artificial body with any degree of resemblance to humanity.
I think some similarities are almost virtually certain at the biochemical level. Water has important properties as a solvent. Amino acids are naturally occurring on comets, and lab experiments suggest would be naturally occurring virtually anywhere that could support life as we know it. Structures like DNA and RNA are also naturally occurring. Lipid bilayers around cells are almost a certainty in any water-based life form. Even cells themselves are very likely. Lots of research suggest that these are simply the available building blocks. There’s a decent chance that an alien could eat you and get nutrition from that.
Now, in terms of an alien atmosphere being safe for humans: Yeah, probably not all that likely. Humans live in a fairly narrow range of tolerances and plenty of life on Earth exists just fine in environments that would kill us. On the other hand, there are some good reasons why a life-bearing planet might have an atmosphere at least somewhat similar. I’d be willing to wager that there’s at least one Earth-based life form that could live in any atmosphere used by alien life.
In terms of physiology and anatomy: That’s a big debate on just how similar humans and aliens might look. There are good reasons for some of the structures we see on humans to be replicated in aliens.
For the face in particular: Eyes, nose and mouth being close together makes sense - you want to watch what you eat, right? Chemical senses are necessary even at the single cell level, so smell and taste as both givens (and, again, probably near the food intake organ.) Visual senses are useful enough that a planet full of blind creatures is almost inconceivable to me. (Unless, of course, the critters evolve without light. Like, say, under the ice sheets of Europa.) Same with sound. Putting the eyes and ears at the top of the body makes a lot of sense if you want to see over things without being seen yourself. You can see that this line of thinking makes a recognizable head likely, even if it’s just in the style of a crab.
For overall body shape: Symmetry has lots of advantages, so let’s assume that. Four limbs is lowest number of limbs for easy stability in walking, though we see from Earth life that more limbs can work. (They’re just energetically more expensive than four). An alien needs technology and that means something hand-like. Hand-like means either a bipedal form with four limbs, or something with more than four so that one pair can be dedicated for hands. (Tentacles might work, but there are some limitations compared to human-style limbs). So… overall body shape will probably not look very human, though we might argue that a human-like body shape is perhaps more likely than any other single option.
I would also suggest that intelligence is most likely to develop in either carnivores or omnivores. They have more energy available to fuel a brain and have an incentive to stay smarter than their prey. This assumption would tend to inform the body structure in many ways.
Of course, aliens that are willing to do genetic engineering on themselves could throw all this speculation out the window. At a certain level of biotech, you can look like anything you damn well please, regardless of how life originated on your planet. Since that tech is simpler than interstellar travel, who knows what we’d actually meet?
You ask about wiping memories: Frankly, I can’t imagine why aliens could wipe human memories at all. It’s not something we’ve figured out how to do to ourselves, and we’re not even positive it *can *be done in the way science fiction claims. Even with advanced tech, the aliens would have to know us extremely well to perform an operation like that.
The fact is, we just don’t know. Until we go out and collect some actual hard data, we’re left with more or less educated guesses. I think there are actually two questions going on here:
1 - how likely is it that intelligent life on any planet anywhere would evolve more or less like humanity, and
2 - out of all those intelligent life forms in the universe, how likely is it that those who chose to visit earth would be more or less human-like.
Again, this is speculation, but as to the first question, I think it’s more likely that there is a vast range of possible forms life can take, and the probability that any particular life form would share much similarity to earth humanity isn’t particularly high. I think the space of possible complex chemistries is just too vast for us to be able to say that our way of doing it is the best way or the most common way or whatever.
As to the second question, I think at that point, we’re applying a lot of filters that hugely increase the odds that alien life visiting us would share some of our features. In short, as has been suggested, only those life forms that are at least vaguely earth-like would be interested in earth.
Maybe not like primates, exactly, but the Law of Parsimony suggests that our planform is fairly logical. Like **dracoi **said, bipedal locomotion is very efficient, which is part of why we can run down most quadrupeds, eventually. Two arms are more efficient than one; sure, three or four can be handy at times, like when wrapping presents, but most of the time we can get away with two, and that’s what parsimony is all about. Hands with several fingers are much more useful than single tentacles, and for that matter muscles need firm attachment points–on internal or external skeletons–when lifting and moving a body outside of a supportive atmosphere like water. Which is why the Pacific Northwest Tree Octopus is so rare.
I second what dracoi said about the face and would add that when working with nerve impulses moving slower than a Bugatti Veyron it’s best to keep the trip short by keeping the brain very close to the sensors in a centralized communication unit.
The reason that I suspect that humanoid ‘erect bipeds’ will be rare in the universe is that they have rarely evolved on Earth. Just two quite small groups of erect bipeds have evolved on our planet (hominims and penguins); these species make up a tiny fraction of all lifeforms on our world. Unless advanced intelligence is positively correlated with erect bipedalism elsewhere in the galaxy I would guess that humanoids are comparatively rare.
Since cantilevered bipeds (like theropods and kangaroos) have been much more common in Earth’s history, we might expect cantilevered intelligent bipeds to be somewhat more common. However, it may be the case that the relatively numerous class of superearth planets are the most common host of intelligent life; in this case bipeds of any description are unlikely to thrive on such hi-gravity worlds.
I have often wondered about his myself. mainly because if it hadn’t been for the dinosaurs we could not have evolved as we did. We needed the comet that destroyed them.
On Earth we have only two general body plans for largish land animals: vertebrates and arthropods; maybe three if you count legless crawlers as a category by itself. So we really don’t know what other body plans might possible. Some science-fiction artists have tried to come up with truly innovative ideas; but really we just don’t know.
Read the rest of my post; the theropod dinosaurs were cantilevered bipeds, not erect bipeds, and evolved into birds, which are similarly balanced. Only penguins are truly erect among the birds, and they have no hands.
Cantilevered bipeds have tails that balance the weight of the body and head, which project forward; this may be a common bodyplan, at least as common as erect bipeds, and perhaps much more common (if the history of life on our world is anything to go by).
Gravity. The surface gravity of a superearth will be greater than that of our world, sometimes much greater; the erect biped form will have significant disadvantages compared to organisms with more legs. Bipeds will be smaller, and will have proportionally smaller brains, and risk circulation difficulties as their hearts try to pump blood against gravity.
Although the exact evolutionary origin of bilateral symmetry is somewhat murky, there is genetic evidence that it may have only developed once. All creatures with bilateral symmetry use a common genetic mechanism for determining overall body arrangement during development, which suggests a common origin, although it’s possible that the genetic framework developed first for another reason and was later re-purposed.
Starfish (and other echinoderms) go through larval stages in which they are fully bilaterally symmetrical, only developing radial symmetry later in life, and appear to have evolved from a fully bilateral ancestor. Corals, anemones, jellyfish, and other members of the phylum Cnidaria are on the other hand fully radially symmetrical at all stages of life and seem to have split off from other animal lineages before the development of bilateral symmetry.
Just how heavy do you think a bird tail is? It’s almost entirely feathers, and it’s to balance the bird in FLIGHT, not on the ground. Look at birds like wrens, which have almost no tail at all.
On earth, I imagine that the number of species in any of those categories is tiny, surely under 1% for any except maybe mammals, and probably them too.
If it’s 1% on Earth, it’s almost certainly less than that in other places.
What are the odds that the Members of the Federation look exactly like humans with skin and hair conditions? THAT’S the real mystery to me!
The bird has its feet well forward, balancing the weight of its head by placing half of its mass behind the centre line. To support a large brain in a bird-like body, the mass behind the centre-line would need to increase accordingly. Give the body a pair of arms as well that can engage with the mouth (presumably at or near the head) and you will need a heavier tail; sentient with arms could resemble velociraptors quite closely. Not really humanoid.
Note that crows and other corvids are already quite intelligent, and use their beaks for some very smart manipulation. I could see a fully sentient species of flying bird evolving from crows, using beaks as hands; but not really humanoid.