#Intelligent Life

The Fermi Paradox, according to Wikipedia, is:

the apparent contradiction between the lack of evidence for extraterrestrial civilizations and various high estimates for their probability

as illustrated most popularly by the Drake equation. I don't specifically take issue with the way the Drake equation is formulated, but I do think there might be a better way than I've seen to estimate some of the factors. In particular, fᵢ, the fraction of planets with life that eventually develop intelligent life.

I've long been uneasy with assumptions that intelligent life must exist elsewhere in the universe, given how big it is. Is it really that big? My skepticism comes primarily from a career working in and with cryptography, which deals in truly huge numbers that are nonetheless of tremendous practical value in everyday life, such as in protecting your web browser's connection to the internet. Let's compare.

So numbers like 10²² don't impress me. They seem positively minuscule compared to some numbers I work with every day.

Now consider a simple model for determining how likely it is that intelligent life will develop, one in which there are a number of concrete but major steps that each need to go right for that intelligent life to emerge. To illustrate the model with a simple example, let's assume there is only one path and one outcome (the past 2 million years of primate history leading up to something closely resembling modern homo sapiens, maybe with more or fewer limbs, digits, different colored skin, proportion differences, etc.). Furthermore, let's assume there are 100 critical steps, such as developing opposable thumbs or the equivalent for building simple tools, brain centers for language development, problem solving, and decision making, taming fire for cooking to unlock nutrients in otherwise raw food (enabling more energy consumption and larger brains), etc.

Each of these steps either happened or it didn't, which means there are two options for each step. That means to get to where we are now, we'd have had to score exactly right on each of those 100 critical steps, meaning we'd have a probability of 1/2¹⁰⁰ of developing humanity, or about 1/10³⁰. Note that the number of stars in the observable universe is only 10²², and we don't know how many of those even have planets that might support life.

Obviously humans aren't the only possible intelligent life, so let's expand this to something a bit more realistic. Let's say there are many possible paths to intelligent life, but still a number of critical steps on each path. If you define the criteria for these critical steps as those that are truly critical and not merely cosmetic, I suspect the number of possible spaces of substantively different intelligent life forms is pretty small. If you consider the little green men from early science fiction, those beings are human-like in the sense of possession of large brains and being individual and autonomous rather than something utterly different like a hive mind. So I'll just pick a large number—1 million, or 10⁶—as the number of substantively different types of life form with completely different paths to development.

Under this assumption, the probability of developing intelligent life is now 10⁶x1/10³⁰ = 1/10²⁴. The reciprocal is still less than the number of stars in the observable universe.

There are a lot of assumptions in this admittedly shallow analysis. I don't know how many critical steps there were in the development of human intelligence; I pulled 100 out of my ass. I don't know whether they're all necessary, or if we only really needed some high enough percentage of them. Some of the steps on the path to human-like intelligence probably don't need to occur in a particular order, meaning I should be counting combinations in the denominator rather than strict sequences of developmental steps. I also don't know how many substantively different kinds of intelligent life might be possible. But this analysis is not trying to disprove the existence of intelligent life elsewhere, only to make it seem a bit less implausible that humanity is alone among intelligent species in the universe.

Alone right now. But that's an argument for another time.