Estephen J. Gould maintained that evolution does not have a purpose or direction, that if the film of life were rewound and projected again the result would be different.
Under this premise, anything can happen, or not. If life has appeared on other planets and follows the same evolutionary rules of natural selection, one would expect that, from this perspective, life would be very different from here. Will intelligence have appeared in these worlds? Is this something inevitable or the result of chance?
On Earth we have ecological “mini-planets”, like Madagascar or Australia. In these islands no intelligent animals appeared from lemurs or kangaroos. In fact, the animals in these places are different from other places, although there may be similarities.
It is also true that many cases of evolutionary convergence can be found, beings that, evolving separately, have arrived at the same anatomical solutions to survive the same environmental challenges. That separation may have been in space, but also in time. Thus, for example, multicellularity developed on several occasions and the same can be said of vision or flight.
Based on this idea, Simon Conway Morris, in his book "The Runes Of Evolution", comes to the conclusion that the map of life on Earth allows us to think that if there are aliens on an exoplanet, some of them must look like us .
According to Conway Morris, convergence is not common, it is that it is everywhere and governs every aspect of the development of life on this planet, from the proteins themselves to the elaboration of tools and passing through intelligence. According to him, this aspect has not been appreciated until now and that implies that it is inevitable once life emerges. Life would not be something random, but a predictable process according to a set of rigid rules.
If this professor of paleontology (University of Cambridge) is correct, on other planets where life has appeared there may be beings similar to terrestrial ones. Given the profusion of exoplanets being discovered, the odds of such a thing would not be zero, although the planet or planets in question can never be visited due to their remoteness.
“Frequently convergence research is accompanied by exclamation and surprise, described as unlikely, remarkable, and surprising. In fact, it is all over the place and that is a remarkable indication that evolution is far from being a random process. And if the results of evolution are at least widely predictable, then what applies on Earth will apply throughout the Milky Way and beyond, ”he says.
According to Conway Morris the aliens will have limbs, heads and bodies in such a way that they resemble us. Even on other planets with complex life, predators similar to sharks, carnivorous pitcher plants, mangroves, mushrooms and many other things that are on Earth will appear.
He argues that intelligence has appeared in other terrestrial creatures such as octopuses or birds when they have had to manipulate objects or have a social life. Since intelligence is an inevitable consequence of evolution on Earth, then it can also characterize extraterrestrial life.
According to him it can be shown that convergence has been present in every important step that has been taken in the evolution of terrestrial life, from the first cells, the appearance of tissues, sense organs, limbs and even the ability to manufacture and use tools.
Thus, for example, despite the fact that the octopus and the human are not related, the two have evolved eyes with a very similar design. But he also cites the case of collagen, which appeared in fungi and bacteria independently, the ability to get drunk that we share with fruit flies or the ability to feel disgust that we share with leaf-cutter ants.
He predicts that the Asian clouded panther (Neofelis nebulosa) would evolve into a species very similar to the prehistoric saber-toothed cat of the past, but that, unfortunately, this will not happen because it will become extinct because of us.
According to this researcher, all life navigates this evolutionary map under a predictable biology. "Biology travels through a story, but ends up in the same destination," he says.
This point is interesting, because then the evolution would be unpredictable in the short term with a historical behavior subject to a certain randomness, but it would be finalist or confluent and would tend to specific objectives, almost equal solutions for very similar problems.
Although there are a very large number of planets, Conway Morris admits that, by not knowing the origin of life, it is not possible to know if it is abundant or not, but that if life occurs, then it will evolve towards whatever it can and this means that something analogous to the human being will appear sooner or later with a high probability. He argues that, since it is already known that there are many planets in the habitable zone of its star, although intelligence only appears once in a hundred times, then intelligent beings like us have to be abundant.
But, as the Fermi paradox teaches us, he also admits that, despite this supposed abundance, we have not contacted any of those civilizations, so something is missing or has to go wrong. "We shouldn't be alone, but we are," he adds.
He adds that the idea that evolution could end up reaching the same solutions makes people feel uncomfortable, because they wonder how many ways there are to digest or hunt something and so on, a deduction that can make us believe that the possibilities exist in a astronomical number, but for all of them to really work in the end they are only an infinitesimally small fraction of all of them.
Simon Conway Morris became famous for being the paleontologist who reviewed the fauna of the Burguess Shale in the 1970s. Something that reflected Stephen J. Gould's book "The Wonderful Life." It is still a bit paradoxical that Conway Morris now speaks of a certain inevitability in evolution against the opinion of who made him famous. He is also known for having a theistic view of evolution, since he is a believer.
Although, without looking closely, neither are Gould's and Conway Morris's visions that opposite, since similarity is not the same as equality. Then it would be a matter of interpretation. In addition, Gould already mentions in his book "Full House" that complex life appears because there is no space in the niches of simplicity occupied by bacteria, so it is more or less inevitable that something like this will evolve. From this perspective, in the end, the most complex thing has to appear by evolution because it has no choice (they don't let you be simple) if enough time is given.
But in order for us to say something accurate about all this from a positivist scientific point of view, we would have no choice but to have more examples of well-documented biospheres (with their evolutionary history) from other Earth-like planets. Something that seems impossible, even if we have bioindicators that tell us that there is life on other planets, because we will not know what the organisms that make up that biosphere are like. We just can't travel there, whatever that is there.