Early humans still had large monkey-like brains, according to a new study that found that modern humans evolved to have our “advanced” thinking organs relatively recently between 1.7 million and 1.5 million years ago.
This means that the unique brain of modern humans (Homo) evolved more than 1 million years after Homo the genus arose, and after the first Standing man migrated out of Africa, according to the study, published online Thursday (April 7) in the journal Science.
The finding overturns an earlier view that human front lobe ̵
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Because brains are made of soft tissue that does not fossilizeinstead, the researchers examined fossil endocastes or the skull that housed the brain to determine how the organ changed over time.
To do this, the researchers compared the structure of “primitive” or “early” brains with the structure of a modern human brain and looked at the endocastes of man’s closest living relatives, big monkeys, including 81 chimpanzees, 27 bonobos, 43 gorillas and 32 orangutans, along with the endocastes of 110 modern humans. They then analyzed the endocastes of nearly 40 ancient human skulls, including those from Australopithecus sediba, Standing man and mand Nalediand determined how “primitive” or advanced their brains were probably by comparing them to the great ape and modern human endocast.
When researchers devised this research project in the late 1990s, the task felt unattainable because they had no objective ways of interpreting brain structure from endocastes, studied co-lead researcher Marcia Ponce de León, a paleoanthropologist at the University of Zurich. WordsSideKick.com in an email. But then it moves in computed tomography (CT) and other imaging technologies allowed researchers to “quantify brain-endocast ratios in living species,” she said. If it were possible to determine brain structures from endocasts of living species, her team could certainly deduce brain structures in CT scans of fossil skulls, she thought.
The detailed endocastes revealed imprints of the gyri and sulci or folds and furrows of the distant brains as well as the vascular structures around the brain, the researchers found. It was arduous work to analyze these imprints. “It was a hard job that needed a lot”gray matter‘involvement,’ shot study co-lead researcher Christoph Zollikofer, a paleoanthropologist and neurobiologist at the University of Zurich.
As the team slowly came through the fossil endocasts, the evolutionary shifts unfolded, such as a region that inches further toward the back of the brain over time. “For example, a posterior replacement of the precentral sulcus over the evolutionary period reliably indicates that the Broca region in front of it was expanded during human development,” Zollikofer said. “This region and its surroundings are particularly interesting because in modern humans they are involved in speech production and other higher cognitive abilities.”
After comparing the fossil endocasts with the great apes and modern humans, the team’s analyzes showed that the earliest members of Homo had a brain with a large ape-like frontal lobe.
“The earliest peoples of our family Homo had rather primitive ape-like brains, like their ancestors, australopithecines, “said Ponce de León. This includes fossils associated with Homo and early Standing man, the researchers said.
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When did Homo brains become ‘modern’?
That earliest Homo remain On record, fossils from Ledi-Geraru in Ethiopia date to 2.8 million years ago, but they have no preserved brains. For the next 1 million years thereafter, no one is preserved Homo endocasts, according to Amélie Beaudet, a paleoanthropologist at the University of Cambridge in the United Kingdom who was not involved in the study but wrote a statement about it in the journal Science.
This gap of 1 million years intensified the mystery of when Homo‘s advanced brain developed. But analyzes of Standing man skulls helped unlock this finding, the researchers said. Especially a group of five Standing man skulls known as the Dmanisi individuals, named after an archeological site in Dmanisi, Georgia, were key; of approx. 1.8 million year old skulls were well preserved and belonged to people who died between adolescence and old age.
“The Dmanisi fossils are very important because they show us that about 1.8 million years ago it was early Homo had a primitive brain similar to that of Australopithecus and of great apes, ”Zollikofer told WordsSideKick.com in an email.
But having a monkey-like frontal lap did not stop Standing man from having an extraordinary existence. “These primitive-brained people were able to leave Africa, cope with the harsh climatic conditions of Eurasia, produce a variety of tools, be involved in meat procurement and provide support to older group members,” Zollikofer said.
The Dmanisi individuals are thought to be among the early populations of Homo who left Africa. It was not until about 1.7 million years ago, in Africa HomoThe complex frontal lobe probably began to form, according to researchers who found evidence of the reorganized brain area in Homo skulls from Africa and Southeast Asia dating to 1.5 million years ago and younger. E.g, Standing man individuals who lived less than 1.5 million years ago, whose remains were found in Southeast Asia, had endocasts that were signs of modern Homo frontal patches, the researchers said.
This finding shows that a complex frontal lap “was once considered a hallmark of the earliest Homo in Africa … developed relatively late, “and was not necessary for the spread of early humans out of Africa, the researchers wrote 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.
“Focuses on a strong dichotomy between ‘our’ lineage Homo and former ancestors (e.g. Australopithecus as ‘Lucy’ from Ethiopia) is a remnant of the days when there were fewer fossils available and human evolution was considered a simple linear process from various early ancestors to us modern humans, “Spoor told WordsSideKick.com in a e-mail. ” In this context, the origin of the genus Homo was considered a biological revolution, associated with making stone tools and having a larger, more complex brain. ”
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Scientists have since learned “that stone tools were made as early as 3.3 million years ago (long before the expected origin of Homo) and species and specimens of the genus Homo unless brains have been discovered, “Spoor said. The reality is that different aspects that characterize us as modern humans emerged at different times and not necessarily as a neat package in a ‘special moment’. “
Why did the Homo brain change?
It’s still a mystery why Homo brains evolved to have a sophisticated frontal lobe, but researchers have a few ideas. Perhaps it is an occurrence of the so-called “Baldwin effect” when an ability to learn a new behavior can lead to changes to genetics and phenotype or appearance, Zollikofer said. In this case, it is possible that brain structures responsible for language and other complex cognitive tasks grew in an environment that was foreign and needed proto-language-like communication, he said.
“We hypotheses a positive feedback between cultural innovation and evolutionary brain reshaping, “Zollikofer explained. Having said that, even though early brain structures were” in place “about 1.5 million years ago,” we do not know if these early Homo populations had a modern human-like language, “he said. Instead, early humans probably had” a kind of proto-language that – in the sense of brain-culture coevolution – favored the development of these brain structures, and these brain structures favored the development of proto-language. “
Originally published on WordsSideKick.com.