Without looking up the Drake Equation, here's a rough estimation of the problem.
Ignoring all extinct species, there's an estimated 8.7 million unique species of plants and animals currently on Earth. So let's do some dumb estimating and say that there's a one in 10 million chance of "intelligent" life evolving on a planet that supports life. (I will not address the controversial issue of whether or not human life is actually intelligent.)
So whatever estimation is used for the number of habitable planets in our galaxy, Only 0.00001% of those planets might have intelligent life. Next, you must factor in how many of the intelligent species develop technology capable of interstellar communication, and when do they do it? Humans have existed for a few million years, but we have only had radio for a hundred years. With the development of technology comes the risk of self annihilation. We humans have had the ability to destroy ourselves for roughly 60 years. How much longer we go is anybody's guess, but given that life on our planet has existed for roughly 3.5 billion years, and the planet will become uninhabitable in another 5 billion (when the sun changes modes), the time window is pretty small. It's likely that life needs some elements that were less available in the early universe, so let's assume that it's only possible on planets of third-generation stars like ours. Also consider the speed-limit of EM propagation (C). There are only 76 stars within 100 light years of us. It's unlikely that intelligent life exists in any of those systems, but if it did, the inhabitants (if they were listening) would just now be able to hear us. Assuming we survive our technological revolution/evolution for another 100 years, we might get a message from a nearby system. Before then, we might receive some communications from systems farther away, but how long does a technological civilization use radio with simple modulation schemes that we would recognize as something other than noise? Maybe in less than a hundred years, we will have gone through radio, optical, and then quantum communications technology. It's likely that other technological civilizations (if they exist) are using communication technology that is incompatible with ours.
I'm not sure if Drake considered all of these things, but it looks pretty bad for us with regard to our ability to confirm the existence of extraterrestrial intelligence any time soon.
Ignoring all extinct species, there's an estimated 8.7 million unique species of plants and animals currently on Earth. So let's do some dumb estimating and say that there's a one in 10 million chance of "intelligent" life evolving on a planet that supports life. (I will not address the controversial issue of whether or not human life is actually intelligent.)
So whatever estimation is used for the number of habitable planets in our galaxy, Only 0.00001% of those planets might have intelligent life. Next, you must factor in how many of the intelligent species develop technology capable of interstellar communication, and when do they do it? Humans have existed for a few million years, but we have only had radio for a hundred years. With the development of technology comes the risk of self annihilation. We humans have had the ability to destroy ourselves for roughly 60 years. How much longer we go is anybody's guess, but given that life on our planet has existed for roughly 3.5 billion years, and the planet will become uninhabitable in another 5 billion (when the sun changes modes), the time window is pretty small. It's likely that life needs some elements that were less available in the early universe, so let's assume that it's only possible on planets of third-generation stars like ours. Also consider the speed-limit of EM propagation (C). There are only 76 stars within 100 light years of us. It's unlikely that intelligent life exists in any of those systems, but if it did, the inhabitants (if they were listening) would just now be able to hear us. Assuming we survive our technological revolution/evolution for another 100 years, we might get a message from a nearby system. Before then, we might receive some communications from systems farther away, but how long does a technological civilization use radio with simple modulation schemes that we would recognize as something other than noise? Maybe in less than a hundred years, we will have gone through radio, optical, and then quantum communications technology. It's likely that other technological civilizations (if they exist) are using communication technology that is incompatible with ours.