The modern brain is younger than originally thought, probably developing 1.5 million years ago, according to a study published on Thursday – after the first humans had already started walking on two legs and even started moving away from Africa.
Our first ancestors of the genus fag appeared on the continent about 2.5 million years ago, with primitive brains resembling monkeys, about half the size of those seen in humans today.
Scientists have been trying to solve a mystery as long as our home story was known: Exactly when and where did the brain evolve into something that made us human?
“People thought that these human-like brains actually evolved right at the beginning of the genre. fag, so about 2.5 million years ago “, paleoanthropologist Christoph Zollikofer, co-author of the study published in the journal Science, he told AFP.
Zollikofer and the study’s lead author, Marcia Ponce de Leon, examined skull fossils from Africa, Georgia, and the Indonesian island of Java, but found that evolution occurred much later, between 1.7 and 1.5 million years ago. follow.
Because the brain itself does not fossilize, the only way to observe their evolution is to study the traces it leaves inside the skull.
Scientists have created virtual images – known as endocasts – about what filled the skulls a long time ago.
In humans, the Broca area – part of the frontal lobe related to speech production – is much larger than the area corresponding to other large monkeys, said Zollikofer of the University of Zurich.
The expansion of an area results in the change of everything behind it.
“This backward change can be seen on fossil endocasts, when we look at fingerprints of brain fissures,” Zollikofer said.
‘Surprise’
Studying the skulls of Africa, the researchers were able to determine that the oldest – dating back more than 1.7 million years – actually had a frontal lobe characteristic of large monkeys.
“This first result was a big surprise,” Zollikofer said.
That meant that kind fag “Started with bipedalism” or walking on two legs and that the evolution of the brain had nothing to do with the fact that it was already bipedal.
“Now we know that in our long evolutionary history … the first representatives of our kind fag they were just terrestrial bipeds, with monkey-like brains, “said the paleoanthropologist.
However, the youngest African fossils, dating back 1.5 million years, have features of the modern human brain.
This meant that the evolution of the brain took place between the two dates, in Africa, according to the study.
The conclusion is supported by the fact that in the same period more complex instruments appeared, called Acheulean instruments, which have two symmetrical faces.
“This is not a random coincidence,” Zollikofer said, “because we know that those areas of the brain that expand during this time are those that are used for complex manipulative tasks, such as making tools.”
Two migrations from Africa
The second surprising result of the study comes from observations of five skull fossils found in present-day Georgia, dating to between 1.8 and 1.7 million years ago.
Particularly well-preserved specimens proved to be primitive brains.
“People thought you needed a big, modern brain to disperse from Africa,” Zollikofer said. “We can show that these brains are not big and not modern, and yet people have managed to leave Africa.”
Meanwhile, Java fossils, the youngest specimens in the study, showed modern features of the brain. Therefore, researchers believe that there was a second migration from Africa.
“So you first spray people with primitive brains, then things evolve into a modern African brain, and these people sprayed again,” Zollikofer explained.
“It’s not a new hypothesis … but there was no clear evidence. And now, for the first time, we have real evidence about fossils.”
© Agence France-Presse