The answer isn't 42, but it's close...

[Jayhawker Soule]

Plug those numbers into the Drake Equation and you get about 1 civilization per galaxy.

Plug those numbers into the Drake Equation and you get history. Nothing else.

 

[beenherebeforeagain]

There is one method to extrapolate from a sample size of one that I find reasonable. Time. By slicing up our one example into aeons, we can estimate the probabilities to find certain characteristics. We have life on earth for about 4 out of 4 and 1/2 billion years. The chance of finding life on an earth like planet is about 80%. Out of those 25% have multicellular life. (1 billion years out of 4) Out of those about 0.2% have intelligent life. (2 million out of 1 billion) Out of those 0.005% have the technology that we can detect. (100 years out of 2 million)
Plug those numbers into the Drake Equation and you get about 1 civilization per galaxy.

And that's within about one order of magnitude from the estimate laid out in the article...

 

[beenherebeforeagain]

Forbes has an article...for me, behind a paywall...but the headline fits the thread...

"36 Alien Civilizations In The Milky Way? The Science Behind A Ridiculous Headline"