The Fermi Paradox: Are We The First?

This is a possible consequence of the “too rare” solution, that we may be the first ones to emerge in our galaxy, or even all of the Universe that we can observe. However, this solution only requires rarity before our emergence, and not after.

But considering when we emerged, it is hard to point to what might make our emergence rare before when we emerged and common afterward. An obvious possible limiting factor is metallicity, the abundance of elements heavier than hydrogen and helium, what astrophysicists call metals. Old and exploding stars have gradually been enriching the interstellar medium with metals, giving later-forming stars more and more of metals. However, Earth-sized exoplanets have been detected orbiting stars with a wide range of metallicities, sometimes much less than the Sun’s (An abundance of small exoplanets around stars with a wide range of metallicities | Nature). This makes it unlikely that the Solar System was the first planetary system with habitable planets.

Then there is time to emerge, something that is rather curiously long compared to generation times, especially of prokaryotes. One might also expect prokaryotes’ great population sizes to make their evolution especially fast, but that does not seem to be the case. Looking among autotrophic prokaryotes, the primary producers among them, cyanobacteria can have doubling times of 6 – 12 hours, and methanogens doubling times of 3 – 10 hours. Heterotrophs like that favorite lab bacterium Escherichia coli can grow even faster, with a generation time as little as 15 minutes. For a generation time of 24 hours, this means nearly 400 billion generations in 1 billion years.

Much of that time seems to be spent in evolutionary stasis, with little or no phenotypic or selectively-visible evolution, with nearly all evolution being selectively neutral. The Fossil Record of Cyanobacteria | SpringerLink notes that many of them fit into five taxonomic families of present-day ones: “As documented by the essentially identical morphologies, life cycles, and ecologic settings of such fossils and their modern counterparts, members of these families have exhibited extreme evolutionary stasis over enormous segments of geological time.”

This raises the question of what does the timing of evolutionary events. It seems rather slow for something internal, and external triggers are only sometimes apparent, like colonization of new environments and ecological niches, and mass extinctions of previous populations.

But if the Earth’s biota is typical of evolution times, then it means that there is plenty of time for other biotas to evolve and diversify. An Earthlike planet of a Sunlike star that formed a billion or two before the Earth will have plenty of metals (in the astrophysical sense), but that much time of head start over the Earth’s biota.

So I conclude that this solution of the Fermi paradox is rather unlikely.


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