A recent conference report on the buildup of complex organic molecules from some mauled "Ursuppe" raised expectations about alien life, so possibly about ETI's too. As long ago as at the dawn of modern physics, Huygens even wrote a book about that. But would alien civilisations nessessarily develop advanced technology and sciences? I doubt this. Even Kant estimated that the discovery of science needs, aside intelligence whose advancement may be an automatic result of any evolutionary process, some set of special "synthetic apriories". Nicolai Hartmann, a forgotten but interesting neokantian philosopher, later described a "categorial dynamics" analyzing the development of such basic concepts. The emergence of science in our history seems to me as caused by a series of singular events which could easily have been disrupted for ever. Aside the idea of science and it's relation to mathematics as mental model, the invention of a scientific community was IMO such a singular event. Perhaps it is an invention by Descartes? When I read some weeks ago in his texts, I had the idea that he first estimated the minimum lenght of research for reaching his goals (ca. 500 years until an understanding of the mind-body problem) and looked for means to extend his personal life for achieving that by himself. The concept of a scientific community with it's special way to communicate according to certain standarts was perhaps only a substitute he propagated when it dawned him that he would never harvest the fruits of the tree he planted.
Conc. Seti, one reads often about how messages sent should be cleverly encrypted for reaching only clever aliens. I guess that would communicate only - like communicative complicatednesses in general - a sickness of the mind behind the message. Communicating existence only would be very little and civilizations detecting that would wonder why we don't tell something more of interest. Most interesting would be astronomical data from our satellites and details of our biology and ecosystems. Only a detailed understanding of biology would make an understanding of anything involving culture possible. So the IMO only reasonable way to proceed would be to transmit such data for a very long time and see if that attracts responses (like cheese in a mousetrap). The signals would have to be detectable for civilizations able to undertake such data exchanges over centuries. But such data would be of interest for a civilization only because our universe and the biologies in it are the single source of really interesting information. If more developed civilizations have other and easier to handle with sources of that, they would lose an interest in the physical universe and would invest nothing in Seti.
Perhaps we are for communication purposes just too weird in comparison with the universe's average ETI? This idea of lucubrating black holes may fit better. Perhaps one should look for "TI's", not "ETI's", but unfortunately the real TI became extinct ca. 10,000 years ago. That's what two well known neurologists published some time ago, speculating about findings at the beginning 20th century indicating the existence of a very large brained version of homo sapiens in south africa ca. 70,000 -10,000 years ago. Their reconstructions show them with a ca. 30% overall bigger brain, ca. 50% larger prefrontal cortex, than modern humans. It is amusing to wonder about the implications, if that becomes verified by further diggs some time. Those „Boskops“ - the real "TI's" - would have differed from us as we do from the homo erectus.