Could alien civilizations already be using AI?

Possibly, but this remains speculative rather than established fact. Some researchers in astrobiology and SETI have argued that if advanced extraterrestrial civilizations exist, they may be likely to develop artificial intelligence and could eventually become predominantly machine-based.

The basic reasoning is that biological evolution is very slow on cosmic timescales, while technological progress can be very fast. On Earth, the jump from early radio communication to modern AI happened in a tiny fraction of the age of the universe, so some scientists think there may be only a short window in which a civilization is both biological and easy to detect before it develops more advanced machine intelligence.

This idea is sometimes discussed in terms of a postbiological or machine-intelligence-dominated future, but it is still a hypothesis, not a confirmed scientific conclusion. There is no empirical evidence yet that alien civilizations exist, much less that they use AI.

That is one reason SETI also looks for techno-signatures beyond radio signals, such as unusual heat waste, large-scale energy use, or megastructures like Dyson spheres.