Should we lower our standards?

Perhaps we should just search for extraterrestrial life, rather than focusing on advanced alien civilisations. That means any kind of life: single-celled organisms floating in oceans, moss clinging to rocks or the first hints of complex creatures moving around their environments. Sure, these kinds of life forms may not be as loud as intelligent life, but that doesn’t make them invisible. Indeed, one of the key features of any kind of life is the ability to throw a planet out of equilibrium.