Early humans still had large ape-like brains, according to a new study that found that modern humans had our ‘advanced’ thinking organs relatively recently, between 1.7 million and 1.5 million years ago.
This means that the unique brains of modern humans (Homo) has more than 1 million years after the Homo genus arises, and after the first Homo erectus migrated from Africa, according to the study, which was published online in the magazine on Thursday (April 7) Science.
The finding overturns a previous view that the frontal lobe of people – the part of the brain which processes complex cognitive tasks, including social thinking, use of tools and language – developed at the transition from Australopithecus on Homo, which happened about 2.8 million to 2.5 million years ago, the researchers said.
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Because brains are made of soft tissues that do not fossilize, the researchers rather examined fossilized endocastes, or the skull region in which the brain was housed, to determine how the organ changed over time.
To do this, the scientists compared the structure of ‘primitive’ or ‘early’ brains with that of a modern human brain and looked at the endocastes of the closest relatives of man, the great apes, including 81 chimpanzees, 27 bonobos, 43 gorillas and 32 orangutans, along with the endocasts of 110 modern humans. They then analyzed the endocastes of nearly 40 ancient human skulls, including those of Australopithecus sediba, Homo erectus and Homo naledi, and determined how “primitive” or advanced their brains probably were by comparing them to the great ape and modern human endocastes.
When the researchers devised this research project in the late 1990s, the task felt unattainable because they had no objective ways of interpreting the brain structure from endocastes, studied co-lead researcher Marcia Ponce de León, a paleoanthropologist at the University of Zurich, said Live Science by email. But then, progress computed tomography (CT) and other imaging technologies have allowed researchers to ‘quantify brain-endocast relationships in living species,’ “she said. If it were possible to determine brain structures from the endocastes of living species, her team would certainly be able to deduce brain structures in CT scans of fossilized skulls, she thought.
The researchers found that the detailed endocast revealed prints of the gyri and sulci, the folds and furrows, as well as the vascular structures surrounding the brain. Analyzing these prints was arduous work. ‘It was a difficult task, which many’gray matter‘involvement’, joked Christoph Zollikofer, a co-principal investigator of the study, a paleoanthropologist and neurobiologist at the University of Zurich.
As the team slowly moves through the fossil endocasts, they see evolutionary shifts unfold, like one region that dives further to the back of the brain over time. “A backward shift of the precentral sulcus over evolutionary time, for example, reliably indicates that the Broca region expanded before it during human evolution,” Zollikofer said. “This region and its environment are particularly interesting because they involve modern people in speech production and other higher cognitive abilities.”
After comparing the fossil endocasts with those of the great apes and modern humans, the team’s analyzes revealed that the earliest members of Homo has a brain with a large ape-like frontal lobe.
“The earliest population of our genus Homo had very primitive ape-like brains, like their ancestors, the australopithecines, “said Ponce de León. This includes fossils associated with Homo habilis and early Homo erectus, the researchers said.
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When did Homo brains become ‘modern’?
The earliest Homo stay over on record that fossils of Ledi-Geraru in Ethiopia date from 2.8 million years ago, but they did not preserve the brain stones. For the next 1 million years there is no conservation Homo endocast, according to Amélie Beaudet, a paleoanthropologist at the University of Cambridge in the United Kingdom who was not involved in the study but wrote an opinion piece about it in the journal Science.
This 1 million year gap has reinforced the mystery of when Homo‘s advanced brain develops. But analyzes of Homo erectus skulls helped unlock this finding, the researchers said. In particular a group of five Homo erectus skulls known as the Dmanisi individuals, named after an archaeological site in Dmanisi, Georgia, were the most important; the approximately 1.8 million year old skulls were well preserved and belonged to individuals who died between adolescence and old age.
‘The Dmanisi fossils are of great importance because they show us that they were early about 1.8 million years ago Homo had a primitive brain, similar to that of Australopithecus and of great apes, ‘Zollikofer told WordsSideKick in an email.
But having a monkey-like frontal lobe did not stop Homo erectus of an extraordinary existence. “These people with primitive brains were able to leave Africa, cope with the difficult climatic conditions of Eurasia, manufacture a variety of instruments, be involved in meat procurement and provide support to elderly group members,” Zollikofer said.
The Dmanisi individuals are thought to be among the early population of Homo who left Africa. It was only about 1.7 million years ago in Africa HomoAccording to the researchers, the complex frontal lobe probably began to form, which found evidence of the reorganized brain region in Homo skulls from Africa and Southeast Asia dating from 1.5 million years ago and younger. For example, Homo erectus individuals who lived less than 1.5 million years ago, and whose remains were found in Southeast Asia, indicated endocasts that are modern Homo frontal lobes, the researchers said.
This finding shows that a complex frontal lobe was once a feature of the earliest Homo in Africa … developed relatively late, “and it was not necessary for the spread of early humans from Africa, the researchers write in the study.
This finding “is interesting and important, but … not necessarily controversial,” said Fred Spoor, a paleontologist at the Center for Human Evolution Research at the Natural History Museum in London, who was not involved in the study. .
Focus on a strong dichotomy between ‘us’ genus Homo and earlier ancestors (e.g. Australopithecus as’ Lucy ‘from Ethiopia) is a remnant of the days when there were fewer fossils available, and the evolution of man was seen as a simple linear process from different early ancestors to modern humans,’ Spoor said in an e email told WordsSideKick. that context, the origin of the genus Homo was seen as a biological revolution related to the making of stone tools and a larger, more complex brain. ‘
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Researchers have since learned “that stone tools were made 3.3 million years ago (well before the expected origin of Homo) and species and specimens of the genus Homo with smaller brains was discovered, “Spoor said.” The reality is that different aspects that characterize us as modern people have emerged at different times, and not necessarily as a neat package at a ‘special moment’. ‘
Why has Homo’s brain changed?
It remains a mystery why Homo brains have evolved into a sophisticated frontal lobe, but scientists have some ideas. Perhaps this is an example of the so-called “Baldwin effect”, when the ability to learn a new behavior can cause changes genetics and phenotype, or appearance, Zollikofer said. In this case, it is possible that brain structures responsible for language and other complex cognitive tasks have grown in an environment that is conducive and requires prototal-like communication, he said.
‘We hypothesize a positive feedback between cultural innovation and evolutionary brain reorganization, “Zollikofer said.” Even if brain structures for early language were ‘in place’ about 1.5 million years ago, ‘we do not know if it’s early. Homo populations had a modern human-like language, “he said. Instead, early humans probably had a kind of prototal that – in the sense of brain culture evolution – favored the evolution of these brain structures, and these brain structures evolution of proto-language. “
Originally published on Live Science.