Aliens?
My opinion is that they can only be humanoids like us.
And I will explain why The universe is teeming with Earth-like planets.
By one estimate, there may be more than 70 billion in our Milky Way galaxy alone.
With so many potentially habitable exoplanets, many believe it's inevitable that life, from
intelligent to microbial, could have colonized most of them.
A realization that is usually followed by the question: What might aliens look like?
Honestly, no one knows.
Perhaps life on other planets evolved without physical form or with no fixed form - perhaps
some aliens are nothing more than sentient clouds, or who have mutable bodies that can
alter to suit the needs of the moment.
Maybe they can sail through space unaided, and use stellar radiation for a food source
and a sensory array, detecting changes in the radiation the same way bats detect sound
waves.
Who needs eyes and ears when your entire being resonates?
Or perhaps, putting fantasies aside, we can reason about it to try to arrive at a more
rational answer?
There are plenty of creatures here on Earth that are so astoundingly different from us
that we can barely comprehend them.
Try watching an octopus pull itself through a tiny crack in a glass tank sometime, or
look at a praying mantis up close.
There is nothing that resembles us except the group of Primates from which we originated...
So why would aliens be similar to us?
Let's try to understand it by reasoning about what little we know about our planet.
Basically, life on Earth has three biochemical requirements: it is carbon-based, it needs
water, and it relies on DNA to pass genetic information to its offspring.
But it would be very “Earth-centric” of us to assume that life everywhere in the universe
follows these same rules when it could be based on completely different principles.
Let’s take a look at the first requirement - carbon.
On Earth, all living things are made up of large amounts of carbon.
There are a couple of reasons for this: Carbon is great at bonding with other atoms, is relatively
stable, is available in large quantities, and can form complex biological molecules
required by organisms.
However, it is possible that other elements can take its place - the most popular alternative
being silicon.
Scientists including Stephen Hawking and Carl Sagan have discussed this possibility, with
Sagan even coining the term “carbon chauvinism” to describe our preconception that carbon
must be the basis of life everywhere.
If it does exist, silicon-based life would look nothing like what we have on Earth.
For one, silicon requires much higher temperatures to reach a highly reactive state.
The planetary environment in which life evolves obviously matters.
Gravity, for example, is a key factor that influences the development of all organisms.
Aside from limiting the size of land animals, gravity also forces several very specific
adaptations.
We can see evidence of this right here on Earth.
Organisms that made the transition from water to land had to develop limbs and complex skeletons
because they no longer had the buoyancy of water to offset the force of gravity.
Although a planet’s gravity does need to fall within a certain range (high enough to
maintain an atmosphere but low enough to not absolutely squash everything), this range
is still a large spectrum under which life can exist.
Let’s imagine a hypothetical situation where Earth’s gravity is doubled.
While this wouldn’t necessarily force all complex life on land to resemble a stocky,
turtle-like creature, the likelihood of bipedal humans would go down drastically.
Even if we managed to keep our two-legged method of movement, we would certainly be
much shorter and have larger bones to accommodate the stronger force of gravity.
Meanwhile, an Earth with half the gravity would likely have the opposite effect.
Land animals would require less muscle and weaker skeletons to cope with gravity, and
life, in general, would be taller and larger.
While we can theorize about the general characteristics of high- or low-gravity life, there’s no
way to predict more subtle adaptations.
Such adaptations would alter the appearance of alien life even further.
Similar to gravity, the atmosphere is another key factor for both the emergence of life
and its characteristics.
For example, arthropods that lived during the Earth’s Carboniferous period some 300
million years ago were significantly larger than their modern counterparts, thanks to
the higher atmospheric oxygen content - up to 35 percent versus today’s 21 percent.
Specimens from this time period include the giant dragonfly with a wingspan of up to 75
centimeters, the giant scorpion which was 70 centimeters long, and the absolutely terrifying
millipede that could grow to a staggering 2.5 meters.
If a 14-percent difference in oxygen content can have such a big impact on arthropod size,
we can imagine that an atmosphere where oxygen is extremely high or low could produce some
very unique creatures...
And we haven’t even touched on the possibility of life that doesn’t require oxygen at all,
which gives us an almost infinite number of atmospheric compositions to work with.
It just so happens that scientists have already found a multicellular organism that doesn’t
need oxygen right here on Earth, so the chances of life thriving on a planet with a totally
different atmosphere aren’t so crazy.
Organisms that evolved on such a planet would certainly look very different from us.
As mentioned above, water is another universal requirement for all life on Earth.
Water is necessary because it exists in a liquid form across a large temperature range,
is an effective solvent, acts as a transport mechanism, and enables chemical reactions
to take place.
But that doesn’t mean that other liquids can’t take its place elsewhere in the universe.
The most popular substitute for water as the basis of life is liquid ammonia, as it shares
many of water’s qualities, such as a high specific heat (the amount of heat required
to raise its temperature).
Another popular alternative is liquid methane.
Some scientific papers using data from NASA’s Cassini spacecraft suggest that methane-based
life could even exist in our own solar system on Saturn’s moon Titan.
Aside from the fact that ammonia and methane are completely different compounds from water,
they are also found in liquid form at much colder temperatures.
Given this, life-based on non-water solvents would look very different.
"Hey, guys, just a moment before we continue...
BE sure to join the Insane Curiosity Channel...
Click on the bell, you will help us to make products of ever-higher quality!"
The third key piece in the puzzle of life on Earth is a way to store genetic information.
For the longest time, we believed that only DNA was capable of doing this.
But it turns out there is an alternative here as well, and we don’t even need to speculate.
Scientists recently created a synthetic alternative to DNA called XNA - xeno nucleic acid.
Just like DNA, XNA can store and pass on genetic information and undergo evolution.
In addition to having an alternative form of DNA, alien life could also produce and
use different proteins.
All life on Earth uses a combination of only 22 amino acids to produce proteins, but there
are hundreds of naturally occurring amino acids, in addition to those that we can create
in a lab.
As such, alien life could not only have its own version of DNA, but also different amino
acids to produce different proteins.
Such fundamental differences on the molecular level could result in life that is unlike
anything on our planet.
Even after accounting for all of the different factors listed above, the power of random
chance cannot be understated.
As far as we know, there is nothing to suggest that all highly intelligent life must develop
a humanoid body form.
What if the dinosaurs were never wiped out?
Would one of them have developed human-like intelligence?
What if a completely different animal evolved into the most intelligent life-form on Earth
instead of us?
To be fair, we would probably have to limit the pool of potential candidates to the most
advanced animal groups - birds and mammals.
But this still leaves a myriad of possible species that could have developed levels of
intelligence comparable to humans.
Animals such as dolphins and crows are quite smart in their own right and could have very
well taken our place as the rulers of Earth.
The bottom line is that life can evolve in an endless number of ways, so the odds of
it producing intelligent beings that are similar to us elsewhere in the universe are astronomically
low.
Well, among experts this is one of the most shared opinions, but who is talking to you
at this moment absolutely does not believe that a dinosaur could have reached our level
of intelligence.
Nor could crows and dolphins, no matter how great their current mental abilities.
All the necessary physical architecture would be missing!
The point, in fact, is another ... we are talking about life "whatever" or intelligent
life?
In the first case, as we have seen, there is absolutely no limit to the ability of nature
to shape incredibly imaginative life forms.
But in the second one... and this is my opinion... evolution, even on other planets, should necessarily
come to design something very similar to us humans.
The one that comes into play in cases like this is the "convergent evolution"
Convergent evolution is the phenomenon of species independently evolving to be similar.
Usually, it results from the species adapting to similar situations, natural selection favoring
the same solution to the same problem posed by the environment.
The marsupial Tasmanian tiger (sadly extinct in 1936) and placental canids such as wolves
and dogs are perhaps the most striking example of convergent evolution.
Through this process, distantly related animals can evolve similar forms in response to shared
environmental challenges.
Despite having a last common ancestor at least 160 million years ago, these apex predators
– who are at the top of the food chain and are not preyed upon by other animals – had
nearly identical skull shapes with similar biomechanical properties.
And if two carnivorous predators, so different, united only by being both at the top of the
food pyramid, have ended up assuming almost the same features, then it is very likely
that also two alien species, one located on Earth and the other (for example) on a planet
of Alpha Centauri, arrived to dominate their environment thanks to intelligence, can show
similar body shapes.
And at this point, we could also try to make a list of all the characteristics necessary
for a species to develop an intelligence able then to open to science and technology.
There is one thing that is nearly certain: an alien life form will be symmetrical.
Everything we know of that grows follows a symmetrical pattern.
Cut a tree in half lengthwise, the branches and roots on one side would be fairly similar
to the other.
The same applies to humans and all living growth, even inorganic growth such as crystals
and galaxies.
Head?
If you define "head" as a bony enclosure for the brain as well as the location for eyes,
nose, and mouth, then it's likely.
The nose could be located above or below the mouth.
Above works better for swimming, but that's not a strict evolutionary requirement.
Mouth?
Must have means for ingestion of food.
All large animals have some means to capture and swallow food.
Some masticate it; others do not.
Teeth are rather common on Earth but other systems of eating are possible.
Arms?
You must have something with which to manipulate things.
Tentacles are unlikely because of their inability to perform fine manipulation.
They usually have suckers on them and a very different purpose than toolmaking.
The number of joints could be greater, and the direction of bend could be different.
Fingers?
You must have a way to grab tightly and a way to pick up small objects and twist and
turn them.
Two fingers are probably too few.
Five are perhaps too many.
Three or four is about right.
The three joints in our fingers are about right.
One would not do.
Two, as with our thumbs, is unlikely.
"Eyes?
Of course.
You have to see to build a civilization.
How many eyes?
One just will not do.
Inability to perceive distance will lead to rapid extinction.
Eyes being important, they will be recessed and capable of being covered, as necessary.
Our aliens are not likely to be bug-eyed, although we cannot totally rule that out.
Legs?
Certainly, but how many?
In our case, we adapted the forelegs for manipulation from animals with four legs.
No land animals with endoskeletons have more legs.
standing is not at all a natural position (and even less comfortable): it is a challenge
to the laws of gravity because it raises the center of gravity of the body and places it
in a position of perpetual instability.
The upright station requires, therefore, by the individual who has it, a considerable
expenditure of energy for the continuous search of the position of balance.
It also implies a series of risks such as immobility, or almost, in case of wounds or
fractures.
The real benefit is represented by the possibility to use the upper limbs as tools for gripping
and carrying objects of various kinds and at the same time to acquire, thanks to the
greater height, better control of the territory.
Intelligence could hardly develop in the absence of these physical characteristics.
Fur?
Hair?
Feathers?
Scales?
Something else truly alien?
The skin covering could be anything that makes sense.
Real feathers are not so likely.
Because feathers are used for flight, brains will be small.
Scales are unlikely because they are particularly well-adapted to cold-blooded creatures.
The presence or absence of a hair system depends more than anything else on the climate of
the planet of origin.
Ultimately, I think the belief of many that everything in evolution is absolutely random
and that the human species could have evolved from any other animal species is wrong.
There are stakes, there is an obligatory path.
The species that became extinct or "didn't make it" could never have developed our intelligence.
From that point of view, their evolutionary path was simply a dead end due to the lack
of the right physical characteristics.
And so I firmly believe that when and if we make eye contact with beings from other planets,
we will find that they are humanoids just like us.
Uglier, prettier... tall, fat, small, and stocky or slender.
But still humanoid.
What do you guys think?
Do you agree with me or not?