Commenter MeLo asked about the IQs of dolphins. According to Wikipedia, the tucuxi dolphin have an encephalization quotient of 4.56, meaning their brains are 4.56 times bigger than the statistically expected brain size for an animal their size (not to be confused with simple brain size/body size ratio which is a less accurate measure of intelligence).
The EQ of dolphins is larger than that of chimps (2.4) and they have IQs around 35, but smaller than that of Homo erectus (6.0), who likely had an IQ around 55. This suggests an IQ around 45.
To put these numbers in perspective, modern humans have an EQ of 7.61 (far and away the highest in the history of the World, if not the galaxy, and in some countries, our average IQ exceeds 100).
But the fact than IQ as high as perhaps 45 could have evolved independently in a lineage so divergent from humans is strong evidence that evolution is progressive and that intelligence is the ultimate adaptation: an ability to adapt itself.
And indeed, few animals have had to adapt as much cetaceans whose ancestors first adapted to the oceans, then evolved into successful land animals, only to have readapt to ocean life. Few organisms have travelled such a transformative evolutionary path, making dolphins especially evolved, adaptable and intelligent.
Because evolution is so incredibly progressive, I predict that if humans go extinct, and the earth remains intact, within 10 million years there will be another species, at least as intelligent as we are. It seems dolphins have already made it up to IQ 45 and chimps and even crows are not far behind; it’s only a matter of time before one of their descendants hit 100.
Because evolution is progressive and intelligence is perhaps the ultimate adaptation.