So is extraterrestrial life similar to the Earth’s?

extraterrestral lifeVision of an alien by Helen S. Cooper in a scientific article from an Oxford team

UK researchers have used Darwin’s theory of evolution to reflect on how extraterrestrial life might be. And they suggest that it might resemble Earth’s life forms more than we could imagine.

We never meet an alien. But, when we imagine them, they are always otherworldly. So different from the human being as the works of fiction (both movies and books) suggest it. From our favorite ET, flat-faced friend who likes to ride a bike as much as any kid, to the slimy, bad and ugly creatures in the sci-fi Alien: Covenant (2017). And as long as we don’t meet them (they might be walking among ourselves, as in the Men in Black, 1997), we continue to look out there on other planets and even in other solar systems, to imagine them and even to predict what they might look like, to prevent us from passing by without realizing it. So a team of UK researchers decided to use Charles Darwin’s theory of evolution to reflect how life can be born in other ‘corners’ of the Universe and what it resembles. Spoiler alert: It may be more like Earth’s than we think.

“Making predictions about aliens is not an easy task”, says in the scientific article titled Darwin’s aliens, published in the International Journal of Astrobiology. And, if it’s true that it’s quite complicated, it is also true that the belief in the existence of extraterrestrial life, not necessarily intelligent, has adepts in the scientific community. Especially with the discovery of extra-solar planets, in particular, Earth-like rocky ones, located in the zone of habitability. Thus, at the right distance from their star to have a mild temperature that allows liquid surface water to exist. Like the ‘seven sisters of Earth’, discovered last year in orbit of a ‘sun’ 40 light-years away from us (which in cosmic terms is really not that much).

Going back in time, the first extra-solar planet was detected in 1995, about 22 years ago, by Michael Mayor and his doctoral student Didier Queloz, both from the Geneva Observatory in Switzerland. That’s how we discovered that the planets of our solar system are not the only ones in the Universe. Later, already in the 21st century, the first rocky-planet was found around the star mu Arae, 50 light-years away. But ten times the size of the Earth, there was still a long way to go, until the discovery of a ‘sister’ of Earth. Now the list of all extra-solar planets, from gaseous to rocky monsters already goes on about 3500, all in our galaxy, the Milky Way. The rocky are the ones that interest us the most, because they have, as far as we know, more conditions at the start, together with other factors, for life to evolve.

On another hand, there is also a project to search for intelligent extraterrestrial life. SETI came to be a program of the NASA space agency in the 1990s and is now managed by the SETI Institute, a private entity based in California (USA). It was founded more than 50 years ago by Frank Drake. He calculated, thanks to a mathematical formula, that there should be some ten thousand intelligent civilizations in the Universe. This number may even seem exaggerated, but there are estimated hundreds of billions of galaxies. Why, then, would our planet be so unique that there’s no life, yet simple, outside of it?

Illustration by Helen S. Cooper of a possible evolution, in an alien world, of a simple molecule, capable of replicating itself, until it becomes a complex organism composed of several parts with distinct functions

In fact, humanity has been dreaming about aliens for a long time. Our favorite ET was born in 1982 by Steven Spielberg. And the film Contact (1997), an adaptation of the novel by the same name of the famous Carl Sagan, where Jodie Foster is a SETI scientist, celebrates this year its 20th anniversary.

And long before that, for example, the former British Prime Minister Winston Churchill had begun writing, on the eve of World War II in 1939, an 11-page article (which was only completed in the 1950s) on this great mystery, without forgetting to emphasize the importance of liquid water. In the essay Are We Alone in the Universe?, Churchill said: “There may be extra-solar planets large enough to hold a surface with water and, with some luck, an atmosphere.”

It’s because it’s so essential to life as we know it that scientists follow so closely the ‘track‘ of liquid water on Mars, where it is known to have been abundant. Or because they look with special interest to the moons Europa (of Jupiter) and Enceladus (of Saturn), frozen to the surface but with oceans of liquid water hidden in its interior.

Why does the giraffe have a long neck?

Geological conditions necessary aside, we also know that the life known on Earth is made from six essential chemical elements: hydrogen, carbon, oxygen, nitrogen, phosphorus, and sulfur. These compounds mostly form the molecules of the cells. Therefore, at the outset, when we look for extraterrestrial life is also by this gauge that we rule. Another gauge we can use to predict how extraterrestrial life might be is, now suggested by the Oxford scientists (UK), the theory of evolution through Charles Darwin’s natural selection.

So far as it’s about speculating on how aliens might be, Stuart West, from the Department of Zoology at the University of Oxford, and his team argue that we have opted for a very mechanistic approach, referring to the theories that say that all the phenomena that manifest in living beings are mechanically determined and, ultimately, essentially of a physicochemical nature. And two examples of this approach are given in the scientific paper. That we might predict that aliens will have eyes because ocular organs have evolved at least 40 times on Earth and are relatively universal. And that aliens would also be based on carbon, just like us, because it’s a very abundant element in the Universe.

“But there is no theoretical reason why aliens cannot be silicon-based and have no eyes”, they warn. On another hand, they point out that “natural selection does not depend on either a particular genetic system or a genetic material, elemental composition or specific planet type.” Researchers also say in the article, which even includes illustrations of possible aliens and their complexities, that “if there is heredity, variation, and differential success, natural selection occurs”.

Charles Darwin by Entomological Society of America

Now we know that when Darwin wrote his masterpiece, On the Origin of Species through Natural Selection (1859), he was far from knowing that living beings evolved from a molecule, now called Ida, which was copied itself, and then stored information in a genetic code. And that, later, Ida would give rise to Luca, who is the most recent ancestor shared by all life on Earth and have existed for more than 4000 million years. But Darwin already knew that life is very briefly a system of replication and that each individual, by transmitting his characteristics to his offspring, can lead to variations. Which now we know might be bad (inherit a genetic disease) or good (resisting a virus).

Darwin also knew that it’s the constant accumulation of such variations through natural selection that, when beneficial to the individual, gives rise to the most important modifications of structure. By which, in the wise words of the naturalist, “the innumerable beings on the face of this earth are enabled to struggle with each other, and the best adapted to survive”.

For example, why do giraffes have such a long neck? This is a question that still remains open in the scientific community. But one of the possible answers blames the natural selection: it was to reach the food increasingly high in the trees. Just as the giraffes have ‘adapted’ themselves to the environment (accumulating variations until they develop both a long neck and a powerful heart, capable of pumping blood two meters above the chest), aliens are probably also adapting to their surroundings. And if they need to reach a higher place to feed themselves, they are also likely to have long necks. Or, like humans, they might have built instruments to get there.

“Stuart West’s team — who is an author well-known for his studies on the evolution of organisms with very high cooperation systems, such as bees and ants — adopts an approach that is different from other authors who have looked more closely at the constraints [the environment of other planets], says the biologist Paulo Gama Mota, from the University of Coimbra. The proposed alternative is, therefore, to look not only at the environment but also at evolution. How might aliens have evolved? If we believe that extraterrestrial life is also subject to evolution through natural selection, then the four Oxford researchers think that it has most likely evolved similarly to life on Earth. “We can not predict evolutionary transitions, but, as far as we know, they are also likely to happen”, says the Portuguese biologist.

“If we are talking about a very recent planet, we can not expect very complex life forms. Taking life as an example on Earth, on a younger planet, one can expect life forms to be simpler because evolutionary transitions are not easy and happen relatively spaced in time. On another hand, it’s very difficult to predict life on a planet that has had more time than ours to evolve. And it’s possible that a planet with the same age of the Earth has intelligent forms of life”, highlights Paulo Gama Mota. “I would say that what we can expect is life forms that surely have systems of reproduction and where there are forms of competition, such as cannibalism and parasitism, for example, but also cooperation because it comes from natural selection.”

It is thus, with hope, that we are waiting for more news about stories of ‘sisters of the Earth’, aliens and the origin of species in other worlds. It will then be the perfect time to remember that one day, already far away, George Lucas imagined a system with two suns and that this fantasy of the planet Tatooine, home of Luke Skywalker, is not (since 2011) just another fantasy. There is actually a planet from which one can watch two sunsets. And, perhaps in a nearer future than we can imagine, the aliens cease to be science fiction, with or without long necks.

This is a translation of a Portuguese news, written by me and originally published in the newspaper Público

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Raquel Dias da Silva. Licenciada em Ciências da Comunicação - Área Opcional de Jornalismo e a frequentar o Mestrado em Comunicação de Ciência na FCSH-UNL, gosto de observar, desmontar fenómenos e partilhá-los através de histórias. Apaixonada por jornalismo (sobretudo cultural, ambiental e de ciência), alimento-me do que me faz pensar - teatro, livros e outros quebra-cabeças - e do que me deixa sem palavras - natureza, gastronomia, música e a arte de fotografar.