Field of Science

Doggone seriously skeptical

The Dogon, a people living in Mali, are by some said to have obtained astronomical knowledge about the Sirius star system that they could only have gotten if Sirians came for a visit and told them. And article in eSkeptic shoots that story down, but I have a slight problem with one of the arguments used, involving evolutionary biology:
What about Sirius? It has a mass of 2.35 times the mass of the Sun. This means that it will have a lifetime on the stellar Main Sequence, which is where stars spend 90% of their lives, of about 1.2 billion years. By comparison, our own Sun was that old 3.4 billion years ago. The oldest traces of life on Earth go back to about that time. Obviously, no Earth-based species was flying to other stars back then!

Even if you allow for a much higher biological mutation rate on any Sirian planet compared to the Earth, it still isn’t enough time. Just when multi-cellular life would began, Sirius A would become a Red Giant, crisping any nearby planets
The point he is making is that life on planets no older than 1.2 billion years could not have evolved to be multicellular, complex, large, intelligent, and sophisticated enough to allow them to build spaceship and travel to Earth to meet the Dogons. But why exactly do people always assume that because it took so long for multicellular life to evolve on Earth, so must it necessarily be everywhere else, too? Seems to be that it's either probability calculation, meaning that we take how long it took here as some mean, and thereby estimate that the chance it would take a tenth or less of that time is very, very small. Either that, or it's an assumption that it necessarily takes that long because unicellular life goes through a number of prerequisite evolutionary stages that must are necessary before multicellular, complex life can evolve.

The first proposition is crazy because one datum does not tell you anything about the distribution it is drawn from. It is wrong to assume that the time it took on Earth is near the average time that sort of thing takes, and it gives no information about the variance.

There is no evidence for the second proposition whatsoever, either. No one presently knows what the requirements are for multicelluar, complex life to evolve, and there's no reasons to think that they necessarily take billions of years to evolve. On the contrary, recently much evidence has been amassed that evolution can be very fast (e.g. fungi and lizards).

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