Researchers have found that early humans such as the famous ‘Lucy’ were not as smart as the great apes. Using new methods, they have been able to determine that early humans did not have the same flow of blood to the brain as modern apes, which, they calculate, means that pre-humans could not have had the same level of intelligence, as say modern gorillas. As a result, of this study, our view of the evolution of early humans may have to change.

The research was carried out at the University of Adelaide in Australia. It was led by Professor Roger Seymour an evolutionary biologist. Mirage News reports that it was “conducted in partnership with the Evolutionary Studies Institute of the University of the Witwatersrand”. This study sought to estimate if pre-humans were as intelligent as modern great apes, by measuring the flow of blood to the cognitive part of their brains rather than by the size of their craniums.

Blood Flow and Brain Activity

The team sought to measure the brain metabolic rate (BMR), by estimating the rate of blood flow, in early humans. According to the Proceedings of the Royal Society , this “may be a better correlate of cognitive ability than brain size alone”.

This is because it measures the synaptic activity, which is “indicative of both the brain's rate of metabolism and its level of intelligence” reports the Daily Mail . The team had to develop a new equation to measure the flow of blood in cranial cavities.

Brain blood vasculature as a function of blood flow. The new study shows great apes have more flow of blood to the brain then early humans. (Daniel Mietchen / CC BY-SA 2.5 )

According to Mirage News this “measured the rate of blood flow to the cognitive part of the brain, based on the size of the cavities in the skull that passed the supply arteries”. The holes in “96 great ape skulls and 11 Australopithecus fossil skulls ” were measured, according to UPI.com.

Lucy’s skull, the cavities for arteries are smaller than great apes. (Tadias Magazine / CC BY-SA 2.0 )

Among the great apes studied were gorillas and bonobos. This allowed the experts to compare the rate of blood flow in the internal carotid arteries (Q˙ICA) of great apes and the extinct pre-human species known as Australopithecus.

Great Apes Are Smarter Than Early Humans

According to the Daily Mail based on the new methodology “blood flowed less rapidly to Australopithecine brains than those of modern great apes”. Researchers found that the holes that once held arteries that carried blood to the brains of these early humans were surprisingly small. They were smaller than would have been expected given the size of their brain.

Roger Seymour stated “the study shows that cerebral blood flow rate of human ancestors falls well below the data derived from modern, non-human primates” according to UPI.com. This is despite the fact that the Australopithecine brain was the same size as the modern gorilla brain.

An endocast of the Australopithecus afarensis brain. (Tim Evanson / CC BY-SA 2.0 )

Indeed, the flow of blood to a gorilla’s brain was twice that of early humans. The Proceedings of the Royal Society states that the “extant non-human great apes have a significantly greater absolute cerebral blood flow, and by inference metabolic demand”, meaning that the great apes were probably more intelligent than early hominids.

Based on the statistical estimates, it would seem that modern gorillas and even smaller apes such as the orangutan were more intelligent than pre-humans such as the famous ‘ Lucy’. This is the “ fossil remains of a female Australopithecus afarensis, one of the oldest early humans ”, according to the Daily Mail .

Lucy was found in 1974 in Ethiopia and is believed to be 3.2 million years old. Based on the latest study, it would appear that she was not as intelligent as modern species of great ape . We know that gorillas are very intelligent, such as the famous Koko who learned many signs in sign language while in captivity.

This Challenges Notions of Evolution

Traditionally it had been thought that because early humans had bigger brains that they were more intelligent, leading to the conclusion that they were better able to adapt to their environment and this is what made them so successful. Seymour is quoted as saying that the study “cast doubt over the notion that the neurological and cognitive traits of recent great apes adequately represent the abilities of Australopithecus species ,” according to Irish News.com .This may mean that theories on the cognitive superiority of early humans, compared to modern primates are all incorrect.

Australopithecus afarensis skull and modern human. (GIFTagger / Public Domain )

This research may indicate that early humans' cognitive abilities evolved not due to any innate physical or mental advantage. Rather the development of the human brain may be due to other factors. It is possible that the social organizations of pre-humans stimulated the growth of their brains and led to superior mental functioning and abilities such as language.

This could revolutionize our understanding of human evolution. The results of the findings of the research are published in the Proceedings of the Royal Society (Biological Science) .

Top image: A reconstruction of the head of an Australopithecus afarensis. Source: Tim1965 / CC BY-SA 2.0 .

By Ed Whelan