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What is the chance of life emerging around a star like the Sun, about 12-13 billion years after our Universe was born?  A recent work looked at the past, and set a lower bound on the probability that one or more technological species have evolved anywhere and at any time in the history of the observable Universe \citep{Frank_2016}.  The authors conclude that is very likely that humanity is not the first technological intelligence that has evolved, so far, in the Universe. ``There have been aliens'' seems to be the conclusion of this work, although the Fermi paradox \href{https://www.authorea.com/25815}{Fermi paradox}  seems to point out that either intelligence is a very rare avenue of life and/or alien civilizations do not last very long, or that aliens like to play hide\&seek with us.