Following link goes to a paper by folks at Oxford published June 8, 2018 that reexamines assumptions in the parameters of the Drake equation from a SETI-type mindset. The point the authors make is that there are magnitudes of uncertainty for several Drake parameters, in particular regarding
abiogenesis. That uncertainty affects the equation in such a way that a scientifically responsible outcome
could be that there are no other civilizations in the galaxy, or even in the observable universe, other than we humans. They do go to pains in the paper to clarify that they are not saying outright there are no other civilizations. But rather, by properly taking into consideration the magitudes of uncertainty for specific Drake parameters, the true situation
could well be that no other civilizations other than earth's exists. Thus other civilizations are not a given. Evidently there are some supplements to the paper that are not included at the link. Darn.
Dissolving the Fermi Paradox
Abstract
The Fermi paradox is the conflict between an expectation of a high
ex ante probability of intelligent life elsewhere in the universe and the
apparently lifeless universe we in fact observe. The expectation that the
universe should be teeming with intelligent life is linked to models like the
Drake equation, which suggest that even if the probability of intelligent
life developing at a given site is small, the sheer multitude of possible
sites should nonetheless yield a large number of potentially observable
civilizations.
We show that this conflict arises from the use of Drake-like
equations, which implicitly assume certainty regarding highly uncertain
parameters. We examine these parameters, incorporating models of chem-
ical and genetic transitions on paths to the origin of life, and show that
extant scientific knowledge corresponds to uncertainties that span multi-
ple orders of magnitude. This makes a stark difference. When the model
is recast to represent realistic distributions of uncertainty, we find a sub-
stantial ex ante probability of there being no other intelligent life in our
observable universe, and thus that there should be little surprise when
we fail to detect any signs of it. This result dissolves the Fermi paradox,
and in doing so removes any need to invoke speculative mechanisms by
which civilizations would inevitably fail to have observable effects upon
the universe. [emphasis added]