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The next factor in the Drake equation measures the \textbf{probability of life evolving into "intelligent life".} Intelligence gives a clear evolutionary advantage and therefore it might represents a common pathway of life. Broadly speaking on Earth intelligent life has appeared at least a couple of times (\href{http://en.wikipedia.org/wiki/Cetacean_intelligence}{cetacean intelligence}). However we need to consider that the transition from simple microbial life to complex animals was a very long process. On Earth it took more than 3 billion years for life to evolve from single-celled bacteria to Homo sapiens. Therefore the same reasoning used for estimating $f_l$ might argues for a small value, $f_i<<1$. $f_i<<1$, but it is very hard to come up with a precise number.  Note that this perspective is quite different from the very optimistic view of Frank Drake, who argued that life likely always evolves into intelligent life, that is $f_i \sim 1$. To communicate with other intelligent life life,  a civilization has to develope develop  some sort of technology. If again we consider Earth's case, this happened for humans but not, for example, for dolphins. The factor \textbf{$f_c$ measures the fraction of civilizations that develop communicative technology}. As intelligence and curiosity seem to go hand-in-hand, it seems conceivable that all intelligent lifeforms might eventually evolve towards a technological, communicative form. $f_c = 1$ Putting these factors into the Drake equation we get   $N \approx \frac{2}{3} \frac{1}{4} f_i \,  L \approx L$. Note $.   This states that the number of communicative civilizations in our Galaxy is just the product of the chance of emergence of intelligent life times the average lifetime of a civilization's communicative phase.  %Note  this is basically the same result that Frank Drake obtained in 1961! The difference is that this has been obtained %obtained  only making assumptions on the factors $f_i$,$f_l$ and $f_c$, since the other terms in the equation are %are  now established. %\href{http://en.wikipedia.org/wiki/Fermi_paradox}{Fermi}