A recent finding was that mouse lemurs, with a brain 1/200th the size of that of a chimpanzee, performed approximately as well on a primate cognition test:
The test subjects included ring-tailed lemurs, black-and-white ruffed lemurs, and grey mouse lemurs, which vary greatly in diet, brain size, and social organization, both among themselves and with Old World monkeys and great apes.
The study, using the Primate Cognition Test Battery (PCTB), provides further evidence that brain size alone is not a predictor of intelligence, though that doesn’t mean there were no differences at all: Larger primates did better on spatial reasoning tests…
Although the Deutsches Primatenzentrum (DPZ) study is said to provide “provides important insights into the evolution of cognitive abilities in primates,” these insights are not spelled out. The obvious conclusion from the research is that all primates show a more similar level of intelligence than expected—except for humans, who are highly exceptional. And it’s not clear how to account for that according to conventional theories of evolution.Denyse O’Leary, “Lemurs, with brains 1/200 the size of chimps’, pass same IQ test” at Mind Matters News
Enough of this sort of thing will be a graveyard for many pop theories of evolution.
See also: Did the human mind originate in telling ourselves stories? A philosopher and writer tries to account for the jump from animal to human by wholly natural means.
Scientists clash over why octopuses are smart. New findings show, the brainy seafood breaks all the rules about why some life forms are smart.