ETI. I think human evolution is a strong example of punctuated evolution. I think it shows the idea that evolution of intelligence is a steady preordained outcome given enough time is not supported by the one example we know of.

Australopithecus struggled to survive and evolved many dead ends. Their low level of mobility compared to Homo erectus meant more effective isolation of various populations. This unique ape line could have easily died out over millions of years as most of its branches indeed did before giving rise to the Homo genus.

Homo erectus evolved rapidly over a few hundred thousand years or less, was wildly successful spreading across the old world with high mobility, and then stagnated or evolved slowly for almost 1 million years. H.s. and H.n. then also evolved rapidly in relative isolation to eventually displace H.e.

Regards,
Mark