Prominent British Royal Society astronomer Lord Martin Rees thinks that ET will turn out to be AI:

Human technological civilisation only dates back millennia (at most) – and it may be only one or two more centuries before humans, made up of organic materials such as carbon, are overtaken or transcended by inorganic intelligence, such as AI. Computer processing power is already increasing exponentially, meaning AI in the future may be able to use vastly more data than it does today. It seems to follow that it could then get exponentially smarter, surpassing human general intelligence.

Perhaps a starting point would be to enhance ourselves with genetic modification in combination with technology – creating cyborgs with partly organic and partly inorganic parts. This could be a transition to fully artificial intelligences.

AI may even be able to evolve, creating better and better versions of itself on a faster-than-Darwinian timescale for billions of years. Organic human-level intelligence would then be just a brief interlude in our “human history” before the machines take over. So if alien intelligence had evolved similarly, we’d be most unlikely to “catch” it in the brief sliver of time when it was still embodied in biological form. If we were to detect extraterrestrial life, it would be far more likely to be electronic than flesh and blood – and it may not even reside on planets.

Martin Rees, “Seti: why extraterrestrial intelligence is more likely to be artificial than biological” at The Conversation (October 18, 2021)

He’s hardly alone. Many theorists anticipate that extraterrestrials will have become artificial intelligences before we encounter them:

Indeed, an increasing number of futurists, astrobiologists, and SETI experts are starting to think that advanced intelligence eventually transitions into a digital mode of existence. Living as digital beings within powerful supercomputers, post-biological aliens (or future posthumans) will demand unhindered access to powerful and efficient means of information processing—a hypothetical mode of existence known as “dataism.”

GEORGE DVORSKY, “HIBERNATING ALIENS COULD EXPLAIN THE GREAT SILENCE” AT GIZMODO

Harvard astronomer Avi Loeb, thinks that advanced extraterrestrials might have engineered the Big Bang, finely tuned as it is. That raises the question of how we can be sure that we are not just an ET’s simulation. Two other approaches to ET as AI have been 1) the smart machines destroyed the extraterrestrials who invented them. (Adrian Kent) and 2) ET exists but evolved into virtual reality at a nanoscale (John M. Smart).

In his article at The Conversation, Rees considers these possibilities and more. He recommends changing the assumptions of the Drake Equation to reflect the fact that “the lifetime of an organic civilisation may be millennia at most, while its electronic diaspora could continue for billions of years. If we include this in the equation, it seems there may be more civilisations out there than we thought, but that the majority of them would be artificial.”

And, he warns, “Some electronic “brains” may simply have a quite different perception of reality. Nor can we predict or understand their motives.”

There is, however, one major impediment to this view: Rees and colleagues assume that artificial intelligences can be creative thinkers. But the evidence so far is against that view. Creativity is not necessarily a matter of just ramping up the technology. By their very nature, computers compute but creative thinking is largely non-computational. We should keep that in mind when we encounter breathless media releases claiming to have overcome the problem.

Also, the claim that artificial intelligence can simply evolve into artificial superintelligence stumbles on the No Free Lunch theorem.

So if the extraterrestrials did turn out to be artificial intelligences, there is a good chance they wouldn’t have independent ideas at all*. They would simply reiterate indefinitely the programs they were designed to execute. We can but hope they’d be friendly ones.

*That’s one way we can know that we aren’t an AI’s simulation: We can engage in non-computational thinking.

You may also wish to read:

Does creativity just mean Bigger Data? Or something else? Michael Egnor and Robert J. Marks look at claims that artificial intelligence can somehow be taught to be creative. The problem with getting AI to understand causation, as opposed to correlation, has led to many spurious correlations in data driven papers.

Did the smart machines destroy the aliens who invented them? That’s the Berserker hypothesis. A smart deadly weapon could well decide to do without its inventor and, lacking moral guidance, destroy everything in sight. Extinction of a highly advanced civilization by its own lethal technology may be more likely than extinction by natural disaster. They could control nature.

The aliens exist—but evolved into virtual reality at a nanoscale. That’s the Transcension Hypothesis, the latest in our series on science fiction hypotheses as to why we don’t see extraterrestrials. On this view, after a Singularity the ETs become virtual intelligences, exploring inner space at an undetectably small scale.

and

How can we be sure we are not just an ET’s simulation? A number of books and films are based on the Planetarium hypothesis. Should we believe it? We make a faith-based decision that logic and evidence together are reasonable guides to what is true. Logical possibility alone does not make an idea true.