Facts[]
Altough Alfred Russell Wallace, co-discoverer of evolution, accepted the results of skull measurements, he rejected racist ideas about intelligence. This was because he had mathematically proved that beyond a certain number of neurons (which all peoples are well past) more brain capacity is just redundancy irrelevant for intelligence.
It has been revealed that Stephen Jay Gould hoaxed the discovery of deliberate racist hoax about brain size, but nobody ever claimed racial differences extending to below the Wallace brain insurance, so it does not matter anyway. Paleoanthropologists traditionally draw the line between Australopithecus and Homo just below half modern human brain size, which fits neatly with modern studies of dementia, which shows that brain exercise can delay the onset of the first symptoms, but then the cognitive degradation goes much faster when it begins, and that cognitive degradation becomes inevitable at just below half the "normal" number of brain neurons!
Do not let studies of statistical correlation between IQ and brain size observed on digital tomographies fool you. Such correlation may simply be the result of nutrition or blood flow affecting both the velocity of learning and the growth of the brain, and formal IQ tests cannot distinguish between "brainpower" and experience. Also, the majority of people with subclinical or preclinical neurodeegeneration (not officially considered dementia) do not practice brain exercise, which lowers average IQ for small-brained people. This is supported by studies of people who had much of their brain (almost an entire hemisphere) removed as small children, and today that does not seem to affect their intelligence, showing that differences in brain size in humans (except extremely small brains, i.e. hydrocephalia) are not a CAUSE of any differences in intelligence.
This may seem illogical, but becomes logical when one considers how neural networks really work. Information is stored and processed in the connections between the neurons, and increasing the capacity does improve the precision of the system-but not indefinitely. At a certain number of neurons, the function is so precise that adding more neurons hardly matters at all. This is why there is a causality between brain size and intelligence in animals but not in humans.
Transcending all causality between brain size and intelligence is probably crucial for being able to ask questions and investigate causes of faliure. This is because if brain capacity constrains intelligence, possible answers are omitted, and mentally omitting answers makes question-asking pointless. Studies show that apes cannot investigate causes of faliure in tests at all, but they can rival or sometimes even surpass 7 year old human children in tests that does not involve any investigatuion of the causes of faliure (the "apes are like 3 year olds" thing is just a symptom of the confusion of brainpower with experience and merging them into a single total score that all formal IQ tests perpetrate). The ape inability to investigate causes of faliure is explained by the fact that their brain capacity (25-33% of human average, the difference between 25 and 33 depends on how you count) is below the "slightly below half" limit shown by the dementia studies.
Howewer, the fact that elephants have a humanlike number of neurons suggest that they may be intelligent anyway (and, by extension, that one hand is enough even for aliens to evolve intelligence). Their lack of complex culture may be due to the fact that their ancestors were spread across the world prior to becoming intelligent simultaneously in multiple places, making it impossible for them to avoid competition with each other. Proto-humans could, according to this theory, avoid competition because they became intelligent in one place (Africa) and spread out from there roughly 2 million years ago, (and of course it was important that they did not compete for the same food as the elephants). To test this theory, experiments analogous to the faliure cause investigation tests the chimpanzees failed should be adapted for elephants. If elephants pass the test, it means, in a cosmic sense, that one hand is enough to evolve intelligence (as long as it is free).
Conclusions[]
Ergo, while aliens and future supercomputers (though the supercomputers must be non-binary to be intelligent) may well be true thinkers, they will never be able to look down at humans as if humans were insects or even chimpanzees.