Research has shown that, in general, human or animal intelligence is not based on brain size but on creature-specific organizational properties.2
Based on the diverse skull fragments and a few nearly complete crania, the defining features of H. erectus are a prominent brow ridge, a sloping forehead, reduced chin, more constricted temples than typical humans, larger teeth, forward-projecting jaw (prognathism), and cranial capacities on the lower end of the normal human-size spectrum.2 In fact, one could say that H. erectus skulls are shaped similarly to Neanderthal craniums except that instead of being larger compared to modern humans, their heads were on average generally smaller. However, H. erectus cranial volume is still within the same range as modern humans. Research has shown that, in general, human or animal intelligence is not based on brain size but on creature-specific organizational properties.2