|Photograph by Bill Curtsinger, National Geographic|
Even between humans, there are differences that are hard to handle at first exposure. When someone is first exposed to a way of life different from what they have always lived with and is left tongue-tied, we call it culture shock. When everything is different, from the clothing to the language to the greetings to the table manners, it can be difficult to adjust and make us uncomfortable and suspicious. Sometimes it can lead to bitterness, and even violence. If we can get so distraught over the differences in our own species, how much stronger would that be if a space ship landed and the people who came out had bug eyes and tentacles?
There is a trope in science fiction—largely due to lack of special effects technology in early TV—that intelligent aliens will look like us, with two arms, two legs, two eyes, and a mouth that has the physical capability to speak English. But this is not realistic at all. Just look at the animal kingdom of Earth. Apart from a few select species of monkey and ape, none of the millions of varieties meet all those criteria. And look at the runner-ups for intelligence: monkeys and apes, sure, but also mice, elephants, pigs, and dolphins (and probably more; animal intelligence is a relatively new field of study). Given the right environments for natural selection, Earth’s rulers of intellect could have come in any number of different shapes and sizes. So why should we expect creatures from another evolutionary tree entirely to look like us?
The next obvious question is language. Between different human groups, all it takes to pass the language barrier is learning and practice, but there is no guarantee that we will even be able to pronounce the sounds that aliens make. Heck, their communication might not even involve sound at all. And though we could probably rig up a computer to translate, there is no guarantee that we will be able to understand them even then. Human language is very abstract, and the aliens might be abstract in different ways. In the Star Trek: The Next Generation episode “Darmok,” the crew run into an alien species that they cannot understand even with their universal translator, because the species talk completely in myths and legends. Of course we probably will figure out how to communicate with any intelligent creatures sooner or later, but it is possible that they conceptualize the world in ways that are completely different from the way we do.
One major possible avenue for this is sight. Stars emit a thermal blackbody spectrum of light in the shape of a Poisson curve. On the horizon, our sun looks red, orange or yellow, but straight up without much atmosphere in the way, it looks white. This is because the sun’s light peaks in the middle of the visible part of the spectrum, and to our eyes all colors added together equal white. Well that is a nice coincidence, that our eyes are designed to take full advantage of our star’s light, right? Well, it is actually no coincidence at all. Evolution favors that which is best adapted to the environment, and so creatures with eyes that are better suited to sunlight will survive better and pass on their genes. The same logic, however, would apply to evolving eyes around any star, so we would expect that cone cells or something like them will develop to center around their sun’s peak emission wavelength. Eyes are incredibly useful, since the universe is full of light, and we have lots of evidence that they evolved multiple times here on Earth, so we can reasonably assume that most aliens would have eyes. Whether they would see the same colors in their minds’ eyes as we do is a fair question, but if they did, then life from a blue star would see our sun as red and life from a red star would see our sun as blue. If the creatures are from a star different enough from our own, their visible spectrum and ours might not overlap at all!
In the same vein, our computer and TV monitors are specially designed for human eyes. We have only three color receptors: red, green, and blue. It is more than likely that alien creatures will have different receptors, and our screens will look like gibberish to them. Although it probably would not be difficult to make a screen translator.
Aliens might have senses that we don’t. They might be sensitive to magnetic fields, like birds. Or imagine a creature that somehow grew ridiculously large, say, several miles across. Such a creature might evolve a gravitational wave sense (though it is difficult to imagine a scenario in which such a sense would be useful enough to be selected for). Or consider the rate at which we perceive time passing. There is no reason to assume this is an absolute. Some creatures might experience time so slowly that a day to us feels like a month for them, or so quickly that crossing interstellar distances might feel like a drive to the supermarket.
|We have only just finished saying "good morning."|
Aliens might have wildly different morality. Much of what we as humans consider right and wrong is based on natural instinct. Take marriage, for instance. It is nearly universal across the globe and human history that two people join together in a commitment and live the rest of their lives together, cooperating and raising children. This is because it is embedded in our psychology that the most intimate and meaningful relationships we can have are between two people, and the healthiest childhood environments are with two loving parents. But if we look to the animal kingdom, monogamous commitments are hardly universal. Many creatures mate indiscriminately, generating as many offspring as they can and betting that some will survive. Ants and bees have hives, with drones, workers, and one queen (mother). Alien creatures who evolved intelligence with mating habits like these would certainly have their own institutions and rituals, which most of us would probably find disturbing and barbaric. Yet, with enough investment in diplomatic relations, we may be able to find common philosophical ground.
|Flemming! How are the twins? Still digesting their mother, thank you for asking.|
I have spoken about many of the ways that alien life might be different from us, but have not touched on the most mind-boggling possibility of them all: alternative molecular biology. On Earth, every living thing contains DNA as the instruction code that causes it to grow, function, and reproduce. But DNA is not the only molecule of its kind. There are also RNA and PNA that we know of, though it is doubtful that we could find planets full of life based on those. But the fact that alternative nucleic acids exist means that there might be more possibilities that we have not discovered yet. If life can be made up of alternative molecules to what we find on Earth, there is no telling what might have evolved. There might be creatures whose chemistry is based on a liquid so cold that they would not feel the difference between liquid water and molten lava. There might be creatures who feed off gamma rays. When dealing with such great unknowns as the potential configurations of life in the universe, there really is no way to know the limits of what is possible.
With all the stars in the universe, it is hard to imagine that our world is the only one where civilization has arisen. Think of a species on some other planet gaining sentience, bringing forth philosophers, scientists, and astronomers, and coming to understand their place in the universe. One of these creatures, a humble and curious artist, looks up at the stars and wonders if somewhere out there there is something like it living under a strange sky, breathing strange air, and living in strange homes it has built for itself out of the materials of the strange ground it treads upon. It watches strange sunsets, and sees love so familiar in the strange faces around it. These creatures, that the faraway alien dreams about with such wonder, are us. We don’t live in The World, we live on a planet around a star in a remote corner of the universe, and no matter how different the other inhabitants of this universe may be from us, this, we share in common.