Nuances and
Environments of Hydro-Carbonic Life
Hydro-carbonic life may
mean the one that, like all life forms that exist on Earth, is based on a
specific chemical element – the carbon - and develops inside a specific solvent
- the water. In our planetary system, apart from our own planet, only on Mars
and on three Galilean satellites (Callisto, Ganymede and, above all, Europa) is
clearly possible to find traces that those life forms existed or may still
exist.
Mars and the
Galilean Oceans
On Mars,
it’s thought that, in a distant past, liquid water flowed over the surface,
which eventually enabled the emergence of primitive
living entities.
The Meteorite of
Antarctica
In 1984 it was found in
Antarctica a meteorite (the ALH84001) that was proved to be proceeding from
Mars due, for instance, to the fact that its air pockets had a very similar
composition to the Martian atmosphere. The meteorite, with an
estimated age close to the age of Mars itself, unveils signals of having been
enshrouded in a liquid environment and displays chemical and physical
properties that possibly denounce an ancient biological activity. Finally, in
the meteorite there were found tiny structures whose shape resembles the living
being that existed on the primitive
Earth. Given its smallness it is, nevertheless, impossible to
analyse in detail its initial molecular frame. For instance, it wasn’t found
any measurable trace of cell membranes. Several factors, like the dimension of
the fossils (too small for being able to store the quantity of information
required by a living entity, according to some investigators) have awaken some
negative reactions about the biological nature of the characteristics that are
observed in the meteorite.
ALH84001: tubular structures with 1 / 1000 of the
thickness of a human hair, which are possible fossils of bacterial life that
once existed on Mars (Videnskaben eller Gud - DR Multimedia)
Mars Today
Today, Mars is a cold
planet (so cold that the existence of liquid water, essential for the
development of life, became impossible) with a very rarefied atmosphere,
vulnerable to the lethal ultraviolet rays and to the solar wind. The
atmospheric composition (95% carbon dioxide and 3% nitrogen) is unsuitable for
an animal life as we know it, but it isn’t unconformable with life forms that
don’t need oxygen for their metabolic reactions, as it is the case of the most
primitive organisms of Earth. Until today, there were never found any traces of
biological activity by the probes that have explored Mars.
Galilean Oceans
On the other hand, it’s
very probable that three galilean satellites (Europa
and, not so likely, Ganymede and Callisto)
host oceans of liquid water under the icy crusts. Therefore, there is a real
chance that life exists in such environments. However, there isn’t yet any
proof that this hypothesis is correct, because life, if it exists, is hidden
under these ice covers.
Models of the crust of Europa, one of them proposing
the existence of an ocean of liquid water (José António Penas)
Oasis of Life in
the Universe
The life as we know it has
the chance of occurring, in the whole Universe, in extremely limited zones, at
a determined distance (ecosphere) from simple stars (not multiple), with
average dimensions and formed from clouds with a reasonable level of
metallicity.
Simple Stars vs. Multiple
Stars
The double system formed
by stars with mutual orbits hardly may harbour a planetary
system, because the gravitational
disturbance that would result from it would prevent the accumulation of
matter in big planets (as it happened, for example, in the region of the asteroids,
due to the unstabilizing influence of Jupiter).
After some time, even the planets that could eventually form would be thrown
out to the interstellar space or would take a collision course with one of the
stars.
However, it may happen
that stars that are extremely close or extremely far away from each other can
be surrounded by relatively stable planetary systems, which would make them
possible targets for the search of extraterrestrial life.
New Suns
The temperature, diameter,
luminosity and life expectancy of a star (characteristics that are all
interconnected) also determine the chances for the appearance of life on the
planets that eventually exist around them.
The Sun is an average star, with a
surface temperature of roughly 6000 ºK, a diameter of about 1,4 million km and
a life expectancy of approximately 10 billion (10 000 million) years.
Dimensions and
Characteristics of the Stars
The life expectancy of the
largest stars (hot, blue and very bright) would be
excessively short for advanced life forms to have enough time to evolve.
In the case of the much
more abundant red dwarfs (small, cold and dim), the planets
that would be inside the ecosphere (where the water could exist under a liquid
form) would be so close to the star that the powerful tidal forces would end up
forcing them to always show the same hemisphere to the star, as it happens in
the case of the Moon relation with the Earth.
One hemisphere (the enlightened) would be scalding and the other (the dark)
would be permanently frozen. This situation would prevent the development of
life forms. The global circulation of atmospheric air would,
nevertheless, reduce the thermal differences between both hemispheres, to the
point of allowing the existence of life.
It’s also important that
the star doesn’t have a variable brightness, because that would constantly
unbalance the temperature of the planets orbiting it.
Metallicity
The disk that enshrouds
the star shall display a minimum proportion of elements heavier than hydrogen
or helium (metals), because life relies on them (carbon, nitrogen, oxygen) and
the habitats where life arises are composed by this kind of elements (planets like
Earth, composed by elements like iron, magnesium and
silicon).
The absence of very heavy
elements like iron, nickel, copper or zinc also represents an enormous
challenge for the development of a technological civilization. It’s thought
that the stars of the Population I, with high metallic
content, compose 10% of the stars of our galaxy.
Galactic Ecosphere
The position of the star
inside the galaxy is also important in what concerns to the chances of life
development in a planet orbiting it. The orbital speed around the galactic
centre doesn’t vary whatever the distance at which they are from the latter,
but the orbital speed of the arms is higher in the outer regions of the galaxy,
so that they don’t disrupt and, therefore, they are kept cohesive and united.
For the existence of
proper conditions for the appearance of life it’s necessary that the distance
at which the planet is from the galactic
centre is similar to the one where the orbital speed of the
stars and the orbital speed of the spiral
arms are equal. The Sun, which is found inside that “galactic
ecosphere”, crossed the arm of Sagitarius 4600 million years ago and only will
arrive to the arm of Perseus in 3300 million years from now.
Stars that are placed
farther away from the galactic centre orbit the galaxy more slowly than the
spiral arms and, therefore, cross them more often. Stars that are placed closer
to the centre orbit the galaxy more quickly than the arms, which ends up
resulting in similar crossings’ frequencies. When a star crosses a spiral arm,
it taker a higher risk of being targeted by radiation emanated from the
frequent supernovae that occur there, which may end up
becoming lethal. Therefore, it’s important to avoid close encounters with the
spiral arms and their supernovae.
Planets of Life
Since we imagine the
existence of a simple star, with average dimensions, reasonable metallicity and
revolving around the galactic centre at a suitable distance, it can be conceived
that a disk that is formed around it may contain a
planet with propitious conditions for the appearance of life as we know it. The
planet shall be placed at a suitable distance from the star, in order for the
temperature to allow the existence of water under a liquid form.
A Moon behind the Scene
It’s quite probable that
the existence of a satellite with a dimension comparable to the planet’s is a
fundamental factor, because it stabilizes the inclination of the rotation axis
concerning to the orbit plane (on Earth that inclination is about 23,5º). That
inclination determines the pattern of the climatic seasons on a planet.
If Earth
didn’t have a big mass satellite, the inclination of its axis could hugely vary
within an interval of a few million years (the Mars’
inclination varies between 10º and 50º), causing dramatic climatic changes.
When that inclination would be more pronounced, the seasons would be much more
bitter, which would make difficult the evolution of life into more developed
forms.
Because the appearance of
the Moon was probably caused by a casual event
(the collision of a smaller planet with the Earth), it’s rational to think that
life may, for that reason, be a relatively rare phenomenon in our galaxy.
The privilege of having a Moon (Mark S. Robinson)
Rotation Speed
Planets with slow
rotation, as Mercury and Venus,
without satellites, oscillate far less than Mars.
But the slowness that characterizes their rotations is also a brake to the
process of biological evolution, because it provokes the existence of huge
daily thermal amplitudes (because nights and days are both very long). It’s
thought that a requisite for the existence of life on a planet is that its
rotation lasts less than one week.
A gravity equivalent to at
least one half of the terrestrial gravity is important for retaining a
minimally dense atmosphere, so that this one may perform a protective role
against the lethal radiations and may assure the existence of a greenhouse
effect that keeps the temperature of the planet at levels that are high and
stable enough.
Orbital Eccentricity
Finally, it’s obvious that
a planet susceptible of hosting biological activity shall have a nearly
circular orbit around its star, so that the seasonal differences of the
temperature are not destructive.
Different Worlds
In what different types of
planets could happen the existence of life?
Low Gravity
In a planet
smaller than Earth and with a weaker gravity, the atmosphere would be thinner
and dryer, being the greenhouse effect less efficient there. For
that reason, the temperatures would vary more strongly between day and night.
As the living creatures would weigh less in such a planet, they could grow so
much that they would reach very big dimensions when compared with the earthlings.
Just like in the dry
regions of Earth, the animal and vegetable life on this hypothetical planet
would have to create adaptation mechanisms to low humidity conditions, as the
capability for storing water and a reduced body area exposed to evaporation. On
Earth’s deserts, the leaves of the plants (like the cactuses) assume the shape
of spines and the skin properties of the dromedaries make the sweat very
difficult.
Life on a low gravity planet (Adolf Schaller)
High Gravity
On a big planet, one with
a stronger gravity than Earth’s, the humidity and the density of the
atmospheric air would be very high. Given the higher gravity of such planet,
the living creatures inhabiting it would necessarily have to be smaller and
more muscular, in order to be able to bear their own weight. The gravity would
also make improbable the existence of flying animals. Because these organisms
live in a so humid biosphere, most inhabitants are adapted to aquatic or swampy
conditions. The planet will need to be farther away from its star than the
Earth is from the Sun, so that the greenhouse
effect caused by the thick atmosphere can be counterbalanced
and, therefore, it can be avoided an evolution analogous to the one that
occurred on Venus.
Life on a high gravity planet (Adolf Schaller)
Gas Giants
It’s possible that even in
a gaseous planet, like Jupiter, some types of
life forms can emerge. There is an intermediate layer in the atmosphere of
Jupiter (below the freezing layers and above the scalding depths) that has
thermal conditions similar to the ones that exist on Earth. Some of the
ingredients essential to life (like the hydrocarbons or the water) are present
in the atmosphere of this planet, as well as in the other giant planets’
atmospheres. Therefore, there is some hope that living organisms may eventually
live there.
A possible inhabitant of
such a planet would be a giant creature that floats as a balloon and that feeds
from atmospheric organisms. Smaller animals, with limbs and capabilities for
manipulating the environment, could live inside those giant creatures, fit into
a symbiotic relationship (the giant creature would serve as a solid holder for
the smaller creatures, while the latter would serve the giant by doing jobs
inside and outside its body).
Life on a gaseous giant planet (Adolf Schaller)
Genetics and
Intelligence
The living beings evolve,
over the span of several million years, according to what the theorists call as
natural selection. The genetic characters, transmitted between succeeding
generations through the DNA, explain why are we so similar to what our
ancestors were millions of years ago or to what are the inhabitants living is
so distant places as Australia (aborigines), Kalahari Desert (khoisan), Peru
(amerindians), Japan or Scandinavia: because we share the same genetic
inheritance.
The double helix of DNA
Mutations
The genes are,
nevertheless, subjected to casual mutations, so the genetic information of an
individual may not be a perfect copy of the information inherited from his
parents.
A lot of times, that may
end up being negative for the new organism. On other occasions that can be
positive for the organisms, providing it some adaptation and/or environmental
manipulation capabilities that are superior to their species mates’. They shall
have more chances of surviving and living long enough so that they can transmit
that new information to a larger number of descendants. As time goes by, these
new organisms will end up becoming more numerous and shall be subjected to
subsequent mutations that, like the first one, will drive to the improvement of
the species. On the contrary, the least adapted species will end up perishing
while facing their competitors or predators. To this process is given the name
of natural selection.
Intelligence
The intelligence is an
important characteristic in the self-preservation of an animal. It is,
therefore, a key factor in the natural selection of species. The most
intelligent creatures have a better capability for thinking about how to avoid
or turn the problems around and how to be successful about getting the next
meal. That means that the creatures with larger brains tend to survive more
easily and tend to dominate the creatures endowed with smaller brains. On Earth,
they were the increasingly more intelligent animals those who dominated the
environment across the eras: the invertebrates first (specially the
arthropods), the fish and the reptiles, then the dinosaurs, the mammals and,
finally, the humans.
Life on land, more
strongly than life in the sea, may favour the development of the intelligence.
The obtainance of food on land demands higher skills than its obtainance in the
sea and the climatic variations are more strongly felt on land, which requires
higher adaptation capacities.
Besides living on dry
land, an animal with an intelligence similar to the human’s will, probably,
have an aspect similar to ours. This is called convergent evolution, which is a
phenomenon that is, namely, responsible for the similar physical shapes of
animals that are genetically very different (like the dolphins and the fish).
That happens for the simple fact that they live in the same kind of environment
(the water). A humanoid shape brings advantages for the creatures that invest
on intelligence, because it sets free the front limbs (arms and hands) for the
manipulation and construction of tools and, therefore, for the development of a
civilization. It’s also thought that if the
head was placed in any space other than above the neck, the body versatility
would be inferior to a humanoid creature’s. It’s possible that if the dinosaurs
had never become extinct by the catastrophe that occurred 64,7 million years
ago, the most intelligent creature on Earth today would be a human-shaped
reptile.
The Intelligent ET
A civilized alien, no
matter how exotic its mind may be revealed, shall share with the humans the
following capacities:
1.
Capacity to subdivide
complex problems into simple problems;
2.
Capacity to describe a
reality or an object based on parts and relations, to perceive and explain the
change (cause-effect);
3.
Capacity to accumulate
experience about similar problems (memory);
4.
Capacity to employ
efficiently the scarce brain resources (economy);
5.
Capacity to organize the
work before taking care of the details (planning);
6.
Capacity to solve the
problems with the objective of improving its own welfare.
The Intelligence on Earth
Although they are not
endowed with the intellectual capacities of the human being, animals like the
dolphins (which belong to the family of the cetaceans that also includes the
whales) seem to have ideas, ethical codes and complex languages, among other brain
capabilities. Others, like the chimpanzees,
are able to use tools in order to reach their goals (but they are not able to
produce them), and they are also able to communicate through gesture language
and to discover solutions for complex problems. It’s known the experience where
a chimpanzee is faced with the defiance of reaching a banana hanging from the
ceiling and, to attain that goal, he piles up a set of boxes, building a tower
and climbing to its top.
Dolphins and chimpanzees
are, like the humans, endowed with a rational brain, called neo-cortex,
responsible for the creative abilities and abstract thinking. Like the superior
mammals (which include the humans), all the other mammals
and birds are endowed with a limbic system that
commands the primary emotions (joy, grief, fear, aversion, surprise, anger), social
emotions (love, hate, etc), the feelings resulting from those emotions, as well
as some functions related with memory and the stability of the basic conditions
of the body. This part of the brain was possibly developed more than 200
million years ago (at the time when the first mammals were emerging).
Because the emotions and
the memory are concepts closely related with the emergence of the
consciousness, we can tell that it essentially exists in mammals and birds.
It’s not very developed in most of these animals (reduced to the core
consciousness, centred in the perception of one’s own organism and in the
instant moment) and is more developed on superior mammals and birds (which also
possess an extended consciousness, able to perceive the involving environment
in a past-future perspective). The core consciousness is aimed to favour the
attention concerning to determined "objects" (lacto-sensu) that
establish relations with the organism, while the extended consciousness is a
pre-requisite for the intelligence, which seems to deny the idea that there is
some kind of “intelligence” of the bees, as determined behaviours described
ahead could suggest. It’s thought that the consciousness has emerged as a form
of manipulation of the images (visual, sound and other) caught by the external
and internal senses of the organisms, aiming the forecast and the planning of
the actions concerning to an ultimate objective, which would be a trump card
for the survival of the conscious creature.
Besides birds and mammals,
the reptiles are also endowed with a more primitive component of the brain,
called reptilian brain or brain stem, which is responsible for the auto-preservation
mechanisms (like retraction) and aggressiveness. The emotions involved on these
mechanisms are background emotions (some movements and facial expressions) and
not primary or social emotions like love, grief or fear in its strict
definition. The brain stem manages the basic biological stability of the body
and the basic life support systems, e.g. breathing, heart rate, blood pressure,
temperature and sensing of other animals (preys or predators). So, it includes
mechanisms that instigate the physical reactions against external tensions.
Bodies with Intelligence
On Earth, the most
advanced class of animals concerning to intelligence and environmental
manipulation are the mammals. However, in other planets where the environmental
conditions were different, we could find another type of dominant animals.
In an entirely aquatic
planet, the dominating species could be an animal similar to an octopus, which
is a cephalopod mollusk, unfurnished of any
internal or external skeleton and very agile in the aquatic environment, where
it moves using its tentacles or expelling water jets. The development of the
intelligence could be, in such species, strongly favoured by the capacity to manipulate
the environment, which is granted by the tentacles, just as the progress of the
human intelligence was favoured by the bipedism
(locomotion on two feet) and liberation of the hands.
Cephalopod mollusk (James B. Wood)
On the other hand, in hot
planets, with a constant temperature (with a so quick rotation that it prevents
big daily thermal amplitudes), the reptiles
of the actual kind (cold blood vertebrates, unfurnished of hair or feathers)
may keep being the dominant animals. The Earth, which is a planet with a
relatively slow rotation (cold nights, hot days), is a hostile body for the
domination of the reptiles of the actual kind (although many scientists
advocate that the dinosaurs, which were also reptiles, were warm blood
animals). This kind of animals is condemned to a slow existence, in such an
environment.
The reptile that could dominate on Earth, today, in
the case that the dinosaurs had never become extinct (Dale Russell)
On a planet where the land
or marine food supply is scarce, the insects or other arthropods
(invertebrates endowed with a segmented external skeleton) will tend to
become the most intelligent animals. That will happen because the insects can
eat any kind of conceivable food and they can live in almost all kinds of
environments. Therefore, on a planet that would end up going through a
situation of catastrophic scarceness, this group of animals (the most adaptable
to the most adverse conditions) would end up assuming the dominating role.
The intelligent arthropod (ZetaTalk)
The Senses
How can we imagine the way
an alien feels the surrounding environment? What senses does he use, how he
does it and with which objectives? Maybe we can find part of the answer in the
terrestrial organisms. However, maybe we can go farther than that and try to
guess perceptions that are not found in any creature of this planet. Let’s do a
brief characterization of the known or hypothetical senses that a living
creature, terrestrial or not, may or might eventually have in order to be able
to manipulate the world.
Vision
The vision is the sense
through which light patterns are caught and interpreted.
The fact that an animal is
endowed with at least two minimally spaced eyes is an advantage, because it
provides it with a stereoscopic vision, able to resolve distances and to
create, this way, a tri-dimensional image. It provides the predators with the
capability for detecting the distance at which they are from their preys and,
following that, with the capacity to plan their hunting strategies.
For a complete visual
field, useful for the animals that constantly need to have precautions against
a predator that may appear from any direction, it’s necessary a much larger
interval between the eyes (in opposite sides of the head). However, this placement
of the eyes leads the animal to lose a great deal of the stereoscopic effect,
unless the animal has an even higher quantity of eyes.
For a night vision it’s
vital to have eyes furnished with large pupils, able to catch bigger quantities
of light. A night vision may also be helped by a layer of reflecting cells,
that can re-direct the non absorbed light in such a way that it gets a second
chance for being caught by the eye (as it happens in the case of the cats).
For a vision focused in a
vertical plane or in a horizontal plane (as in an eastern African savanna),
it’s important that the pupils assume the shape of thin gaps, oriented in the
direction in which the animal wants to focus the image.
An animal may also have
the need to see colours that are undetectable by the humans, like the ultraviolets
(which bees use to detect the nectar of a flower) or the infrareds
(which some snakes use to detect the heat emanated by their preys). One
possible (but not existent on Earth) vision of microwaves
radiation would be useful on a planet enshrouded in a thick and foggy
atmosphere.
There are on Earth birds
of prey with a visual resolution capacity much higher than the humans’, giving
them the capability for detecting preys from a very big distance. The birds
also tend to distinguish the colours in a more accurate way than the other
animals, because they have eyes containing photo-sensible pigments that react
according to the colour that is caught.
A less advanced form of
vision than the human’s is, for instance, the vision of the insects,
which possess multiple eyes that provide them with low-resolution images,
similar to mosaic photos. It’s, nevertheless, a form that gives them a refined
capability for detecting movement. Even less advanced is the vision of
determined animals that can barely distinguish anything else than variations
between light and darkness.
The eyes in the animal kingdom (Lani Hardage,
Christopher Tyler)
Mechanical Senses
The mechanical senses are
responsible for the detection of tensions, pressures and their variations
(waves and vibrations) in the environment.
Hearing
The hearing is the most
developed mechanical sense in most vertebrates,
being characterized by the detection of aerial or aquatic vibrations. Like the
vision, the audition of determined animals may also reach more advanced levels
than the human audition.
The existence of an ear is
an advantage, because it allows focusing the vibrations (sounds) in the channel
that leads to the eardrums, or in other words, to the organ that amplifies and
transmits them to the brain.
The existence of a pair of
ears is also a factor for the success, because it allows detecting where the
sounds are coming from (stereophony). This capability results from the analysis
that the brain does about the time interval that exists between the arrival of
a sound to the left ear and to the right ear.
The bats are specialized
on the detection of ultra-sonic frequencies (high frequency sounds),
transforming the ears in sonar instruments specialized on the detection of the
echoes of the sounds that they emit themselves. That provides them with the
capacity to perceive the presence of the preys and objects in dark
environments, just as a radar does. Other animals that use the sonar are the
dolphins. It’s also possible that an animal specializes its hearing on the act
of captivating specific frequencies.
The hearing organs aren’t
always located at the head. There are insects
whose ears are placed in different parts of the body, like the abdomen
(grasshoppers) or the front legs (crickets).
Hearing organs that are
less advanced than the humans’ are, for instance, the simple openings (without
ears) leading to the eardrums or, instead, surface membranes or thin hair that
vibrate with the flowing of the sound waves. The simplest hearing organ that
can be conceived is a primitive structure composed by nerves that are sensitive
to the waves proceeding from nearby sounds.
Touch
The touch is, like the
hearing, a mechanical sense. It’s the only human sense that uses all the body’s
surface as a sense organ, but it can be felt more intensely in specific zones
like the hands (humans), the antennas (insects)
or sensitive hair (cats’ moustaches).
Chemical Senses
On the other hand, the
smell and the taste are senses that represent the reaction to purely chemical
stimulus.
Taste
The taste can be found in
parts of the body other than the tongue and the smell in parts other than the
nose. In many insects, the smell receptors are lodged in the
antennas or in mouth prominences.
Smell
The moths are among the
animals that possess a more accurate sense of smell, which in their specific
case has the purpose of detecting the pheromones exhaled by the females. When
the males receive them, they fly in the direction of the source with the purpose
of coupling. The smell can also be useful for detecting preys, as in the case
of the sharks that, this way, catch the smell of blood of the wounded and
vulnerable animals.
The Two Faces of the Same
Coin
The taste frequently acts
together with the smell and can be locates in places like trunks or external
prominences able to detect the flavour of a meal, even without touching it.
Therefore, we can consider the taste as an eventual substitute of the smell. In
insects, for instance, this sense exists in
organs located in the legs or in the tentacles.
Exotic Senses - Detection of Magnetic Fields
A sense that the humans
don’t have, but that some terrestrial animals like insects,
fish and birds
use to navigate and to orient themselves (particularly during migration
periods), is the detection of magnetic fields (namely, the magnetic poles). In
planets with stronger magnetic fields than Earth’s, this sense may
assume a much higher importance than it does on Earth.
Pain
The sense of pain, with a
nature that is not exclusively external like the ones previously mentioned, is
also a reaction of the nervous system against external or internal pressures.
The sensation of pain proceeds from the modified neurons that react to
determined substances by emitting electric stimulus.
The ability to feel pain
(including the psychological pain, as the anxiety) is an important aid
concerning to the survival chances of a living creature, because it leads them
to avoid the sources that provoke physical damage on them.
It exists in the superior
animals, particularly among the vertebrates
and the cephalopod mollusks, but quite doubtfully in
animals with a less developed nervous system, like the insects
(which miss a system of fibres sensitive to pain analogous to the
vertebrates’).
Temperature
The sense of the
temperature works also through receptors similar to the ones mentioned just
above and reacts in a similar way to the neurons that are responsible for the
pain. In the cold blood animals like the reptiles
(unable to control internally the body temperature) this sense has a
particularly important role.
Contrarily to the sense of
pain, it is a largely disseminated sense in the animal kingdom, from the most
primitive evolution stages.
Communication
The animals can
communicate through colours, shapes, movements, smell, touch stimulus and
sounds (prevalent among the humans). The signals can be exchanged between two
or more individuals of the same species or, more rarely, between individuals of
different species.
Chemical Communication
The chemical signals,
caught by the smell or the taste, are the most ancient and primitive in the
animal kingdom. Particularly relevant are the already mentioned pheromones,
secreted by some animals to communicate with an eventual receptor of the
opposite sex and to awake on them the sexual appetite.
Beyond the attractive
signals, there are also tranquillizing signals (for instance, for the purpose
of mutual identification of the members of the same community), repelling
(which are used to establish limits in what concerns to competitors) and
dissuasive (like the ones used by the wounded animals in order to warn their
mates about the danger).
Visual Communication
The colourations induced
by the nervous impulses were essentially developed among the cephalopod
mollusks. The emotive state of these animals is transmitted
through variations in the skin colour, revealing states of fear, anger or
sexual excitement.
It’s possible that some fish,
like the candlefish, use their capacities to emit light (from a luminescent
organ under each eye) in order to communicate with their species’ partners.
The candlefish, with bioluminescent organs in the head
and the body
Examples of shapes and
movements used for communication purposes are the erection of the feathers (birds),
hair (mammals) or extremities (spiders and crabs),
inflation of air bags (ballfish), etc. The body expansion reveals the intention
to frighten, while its reduction reveals submission. Some birds can display
colourful and exuberant plumage, like the peacock that opens its iridescent
tail into the shape of a fan, waving and showing it to its potential sexual
partners, with the purpose to attract them.
The face and hands’
expressions are extensively used by the hominoid
primates. The gestures (hands’ expressions) are nowadays the
base of the deaf humans’ language, which is also used to each other hominoids.
Another interesting case
is the one about the bees that use a movement (a dance) to communicate to their
mates what’s the direction of a food source. It’s remarkable that this form of
communication seems to suggest the existence of intelligence in a so primitive
organism, as is this insect – the bees appear to be able to learn: in one
experience a food source was moved every day to a place located at a fixed
distance from the previous location. After some time, the bees were already
able to fly to the extrapolated direction, instead of flying to the direction
where they had found the food during the previous flight.
Touch Communication
The touch communication is
essentially reserved for the intimate individual relations. They may have the
meaning of an appeal (as the child that calls the mother), excitement (in
sexual intercourse) or tranquillization.
Sound Communication
The most simple sound
communication is used by the arthropods
(particularly, the insects), that rub structures of the external skeleton in
order to produce sounds. Two examples are the crickets and the grasshoppers.
On the other hand, the vertebrates
produce sounds through membranes that vibrate with the airflows (as the vocal
chords). The sound communication is far less developed among fish and only
slightly more among the amphibians (the coaking of the frogs) and the reptiles
(whistles, puffs and snores emitted during the period of sexual excitement).
The birds
dominate much better the sound communication, emitting their chirps from the
internal larynx, located in the lower end of the tracheas (close to the lungs).
On the other hand, the mammals emit the sounds from the external
larynx, using the air that flows from the interior and that provokes the
vibration of the vocal chords. They modulate the sounds in the oral-pharyngeal
cavity (in the region of the mouth) and some, like the humans, use their
tongues.
On the other hand, the
dolphins are even more advanced than the humans
over one aspect: since both nasal cavities function as two independent sound
organs, they can keep two completely separate conversations at the same time.
Bizarre Creatures
What kind of strange
characteristics may we find in an alien species?
Number of Sexes
It’s possible that they
are hermaphrodites (each individual possesses both sexes, at the same time) or
that they can change sex across their lifes, as it happens in some species of
fish. There may be more than two sexes, although only two are relevant for
procreation, as it happens among some social insects.
Psychological Time
They could have a notion
of the time flow different from ours, like the insects or other small sized
animals that, given their capability for processing fast the images that are
transmitted by the eyes, observe the world in a slow motion. The opposite
happens with the biggest animals (like the elephants) or with those that are
armoured well enough to protect themselves against the natural hazards (like
the turtles or the gastropod mollusks). Among the terrestrial animals, the time
perception is essentially determined by the temperature of the body and by the
adrenalin and the heart activity. The first one conditions the time perception
in a direct or inverse relation, so that the animal may inclusively enter a
lethargic state (during which that perception is much shortened) when the
temperature is excessively low or high. The production of adrenalin and the
increase of the heart beat provoke a lengthening of the perceived time, which
happens namely in situations when the survival of the organism is challenged,
as it happens in the case of a hunt.
Brains’ Network
We could know minds
connected in a network, like two or more computers. The idea of monitoring the
totality of the human brain is already ventured by some scientists. The biggest
difficulties about the materialization of that idea are the huge complexity and
dimension that characterize this organ. Between monitoring the brain and
connecting it to a network there will be only a small step. The dreams, the
thoughts, the knowledge, the feelings, all of them could be accurately
transmitted among two different brains.
Electroencephalography: computerized monitoring of a
human brain (BrainMaster)
Exotic Capacities
We could even find
creatures with powers that we consider exotic (like the extra-sensorial
perception or the psychokinesis) or other ones that not even the most advanced
imagination can conceive. They may reveal to us completely new ethical patterns
as well as new civilization goals or ways of thinking.
Conclusion
All the physical,
psychological or social nature of the aliens that we may find in the future may
be revealed to us as a complete surprise. Maybe even a still unchallenged
conjecture may fall: can life be based in elements
other than carbon?
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