No doubt if astronauts from Earth were to journey to some other
planet with civilized life, they would probably find beings who
looked very different from a human. But what is the chance that
somewhere out there exists extraterrestrials who very closely
resemble humans?
Some astronomers who have considered this question have guessed that
the chance of extraterrestrials looking like humans is basically
zero. Such thinkers have pointed out that human evolution was the
result of a long series of events stretching over millions of years,
and many of these events were due to blind chance. As the whole
series of events leading to the current human form is unlikely to be
repeated again on another planet, these thinkers reason, we should
not assume there are any extraterrestrials who look like us.
I'm not sure that this reasoning is very compelling, as it ignores
the fact that there are multiple ways to randomly wander about and
finally reach the same destination. If I leave Grand Central Station,
and randomly walk around New York City, finally arriving at the
Chrysler Building, it would not be right to reason that some other
person leaving Grand Central Station and wandering around would not
reach the Chrysler Building, on the grounds that he would have been
most unlikely to have followed my random path. The person might have
followed any number of other paths, and also arrived at the Chrysler
Building. Similarly, we can imagine a thousand different paths of
evolution which might lead eventually to the existence of some
organism resembling a human.
A better argument against the likelihood of extraterrestrials looking
like us is based on the sheer fact that there are so many different
ways in which the body of an extraterrestrial might look.
Extraterrestrials might have two legs, three legs, four legs, or five
legs. They might be blobs that move around like a jellyfish, or
aquatic creatures that swim. Or perhaps they could have wings. If
they have two legs, they might have two gigantic legs like a
Tyrannosaurus Rex, and only very small arms. Some argue that there
are so many possible combinations that we should assume there would
only be an extremely small chance (or perhaps no chance) that
extraterrestrials would look like us.
Such arguments have a certain degree of force, although I think those
who argue along these lines exaggerate their case. It is true that
there are many different types of organisms that could be produced by
evolution, but if an extraterrestrial planet were to have civilized
life, it would have to have some life form that met certain
characteristics. A civilized organism would have to have powerful
appendages capable of manipulating tools. That would mean a civilized
extraterrestrial presumably could not look like a horse or a
limbless blob or a limbless sphere or a shark (although an appearance
like a centaur could not be precluded). There are surely many
combinations that one could imagine for the body of a civilized
extraterrestrial, but the number of combinations is probably less
than a million. I would also argue that we should expect the simplest
types of body arrangements to be more commonly found across the
universe. If we had ten legs, ten arms, and five heads, it might be
right to say that a weird body arrangement such as ours must be very
rare. But as we have only two legs, two arms, and one head, we
should not assume that our type of body arrangement is all that rare
across the universe.
Another factor to consider is the huge number of planets on which
intelligent life could evolve. Our galaxy the Milky Way contains
perhaps 400 billion stars, and scientists recently estimated that
there may be as many as 60 billion planets in our galaxy which may have life. Our galaxy is only one of billions of spiral galaxies in
the universe. So even if it is very unlikely that civilized beings on
another randomly selected world would look like us, we should still
expect that there are many planets that have civilized beings that
look not very different from us. Given a sufficient number of
chances, even extremely unlikely things happen not just once, but
repeatedly.
But if man goes exploring the distant stars, should we expect to
someday find by chance civilized creatures that look rather like us?
No, we should not, not unless we were to visit thousands of stars.
The chance of another planet developing civilized life that looks
like humans is sufficiently low that we should not expect to find
humanoid creatures on the first few hundreds of planets that we
explore.
Somewhere out there probably exists creatures looking much like us,
but it may be eons before we ever get in touch with such beings
(unless we get help from some galactic social network that helps
civilized beings find out about the existence of other civilized
beings with a similar appearance). We should expect that the first
few dozens or hundreds of alien species that we communicate with in future ages
will look very, very different from us.
SBH (Single Blue Humanoid) seeks social interaction across the light years
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