Do aliens speak Similarlish or Differentlish?

The community of linguists felt proud for the attention it got with the appearance of the movie Arrival. Its plot involves linguists helping to establish communication with aliens, by managing to analyze and decode the language that the aliens use. The tasks involved are based on a variation on the theme of the linguistic relativism and on actual experiences of field linguists. It turns out that alien language is quite different, but the distance between the alien language and human languages is not of a different order than the distance between human languages can be. Surprising as this may be, in a recent conference, Noam Chomsky and Jeffrey Watumull went even further, saying: "To put it whimsically, the Martian language might not be so different from human language after all" - implying that the similarities are expected to be even greater. 

Weirdly, but not unexpectedly, this has led to a new round of all the same discussions between those linguists in whose rough estimation what's universal in language is much more than what varies and those in whose rough estimation what varies is much more than what's universal. One camp was all in favor of Chomsky and Watumull's view, and the other was outraged - because even human languages are not significantly similar to each other, so an alien language should also be very different. Both camps involve an assumption of commensurability: that the alien language is nearly as similar to human languages as human languages are to each other, i.e. that it is nearly as different from them as they are from each other.

Let me try to give several reasons why it is actually very unlikely that alien languages, if they exist, are comparable to ours, or even that aliens, if they exist, have a property that can be singled out and vaguely described as language.

First degree: hardware limitations

Human language is severely delimited by the media through which it is produced and transmitted. There are limitations of sound, limitations of our vocal tract, limitations of our auditory apparatus, which for instance do not allow language to go multi-channel with an equal distribution of information across channels, or which exclude the option of choral interaction, where a large group speaks and hears different content simultaneously, possibly also retrieving, updating and mutually relating different knowledge representations at the same time.

Another limitation comes from our cognitive processing capacities. Just to illustrate their limitations, we can think of a language in which we can use pronouns even for referents we mentioned last year without causing confusion, we can have an information-archiving mechanism (an extreme case of polysynthesis) that collapses complex sentences into strings of only several short morphemes, and we could mutually cross structural dependencies in an unbounded fashion (thanks to Gisbert Fanselow for this point).

This mismatch can go as far as there being aliens who can scan, read, compare and mutually update other subjects' brains, or rather minds to stay safe from anthropocentricity. And, further, save new mind-images in other individuals next to or instead of the existing ones. They could be able to highlight a segment of an image that they recommend for being scanned and retrieved (in one step, not via smaller units). Even just very weak versions of this option yield the notion of language obsolete and inapplicable.

Second degree: software limitations

Numerous open philosophical questions show the limitations of the type of logic and of rationality that humans have. We do not know if our logic is able to see the elephant, or it may only ever access its ear. We do not know if time is yet another dimension of space or there is something special to it. Consequently, we do not know if our unidirectional movement through time is a limitation of nature, or of our own species. And communication is a notion that fully builds on the unidirectional experience of time. We do not know if all the possible worlds apart from ours are just ideas, or they are all real, and what are, if any, the constraints that all worlds obey. Therefore we also do not know what kinds of information there can be, and how it can be exchanged.

What guarantees that aliens do not command a logic that allows them to 'walk' back and forth in time? That they do not operate completely different logics, or even minds not based on any logic but for instance on holistic images of the world or on something that we are not able to think? That they do not reside in more than one different world at a time, and may communicate between worlds? That they do not manifest immediate influence over worlds and events, rather than in terms of indirect causation and prediction? That they are driven by similar instincts such as identities, the imperative of survival, pleasant vs. unpleasant sensations, reproduction and devotion to the offspring, solidarity, greed? All these are preconditions for communication the way we think of it and the way it is thought in the movie. What guarantees that aliens would be able to conceive our idea of communication, let alone to try to engage in it, to understand our concepts necessary for it to take place?

We linguists

All in all, the range of possibilities, and the levels of probabilities of each of them, are such that it makes no sense to try to explore the imaginable and unimaginable scenarios. It is not impossible that aliens speak a language within, or not far outside the range exhibited by human languages, but the probability that it is so is likely closer to the probability that they happen to speak a language which indeed is spoken by humans too, for instance - English (a rather improbable scenario), than to the probability that they do not have any homologue of language, or that they have it, but it shares very little with human language (which is actually a class of infinitely many concrete scenarios of the of the kind of aliens speaking English). 
Even our immediate neighboring animal species do not have a language minimally different from ours - the communication they engage in is quite different from ours. Yet, we expect that aliens will come to our planet (even just assuming that they travel in space, and choose destinations is problematic), and talk to us in, mutatis mutandis, yet another human language. And all that ends up serving just as absurd ammunition for the fight who's right - those who start from the assumption that each language is a separate phenomenon, or those who start from the assumptions that all languages are underlyingly the same. Even if they share the ultimate goal of meeting halfway at some point.