tl;dr Given the size of the universe, and statistics, it is extremely unlikely that we will see any extra-terrestrial intelligent life.
It was very unlikely that a child would get to a Gorilla in a Zoo (the story has been covered in many places such as this). We all make mistakes once in a while. Rarely though, a combination of unfortunate events or mistakes happen. In this case it was:
- A parent did not keep an eye on their child for a minute or two.
- The child made it into the gorilla area.
- The design of the zoo was not 100% perfect for blocking access to the gorilla by visitors.
Not too long ago, I made a very minor mistake that was due to my lack of judgement. No one was harmed at all, no one even noticed, it did not affect any one or anything. It was fixable (with either 20 minutes of time, or $30 payment). My error was statistically unlikely. It was from the combination of two events: lack of judgement. The second event is something that I do at most once every two weeks. The probability of two independents events is usually calculated by multiplying the probabilities of each event. For example, if one event has a probability of 10%, and the other event has a probability of 5%, then the probability of both events happening is 10% times 5%, which is equal to half of a percent.
Hence, the probability of the Gorilla and child event, should be really small. This can be somewhat seen by the many years in which such an event has not happened before. (Remember that many many people with kids go to the zoo all the time).
Now, is it likely that there is intelligent life in different planets than ours? yes, of course. However, when we consider how big the universe is, it is extremely unlikely that we will see any extra-terrestrial intelligent life. Just think about how long it took for a satellite to get anywhere near Pluto to take photos of it at a good enough resolution so that scientist can figure out things about it. Or, think about the distances required and the speeds needed to get there alive. For example, even though I can see the moon, it takes an gigantic amount of energy and effort to get a human there. It has been decades since I last heard of fast-speed trains that could do a 300 miles trip in 40 minutes. Considering that we do not have a network of such trains to help us move faster between cities, what is the likelihood that we will organize things to go to other planets? If such delay happens here, it is likely to happen in other planets having intelligent life. Hence, they will not be showing up any time soon either. (They are probably on the sofa watching their version of popular TV shows or something like that).
Thus, no extra-terrestrial intelligent life showing up on our skies any time soon.