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Lucy’s brain was part of the monkey, part of the human



Scans of the skull from Australopithecus afarensis.

Scans the Australopithecus afarensis Skull.
image:: Philipp Gunz, MPI EVA Leipzig

The famous The 3.2 million year old Lucy specimen has fascinated scientists since it was discovered in 1974. Lucy was a member of the species Australopithecus afarensiswho walked upright and probably used tools. New scans from the inside Australopithecus Skulls show that these extinct hominins surprisingly had ape-like brains that developed more like a human brain.

Our brain takes on a distinctive structure that distinguishes it from the brain of non-human apes, and it takes a long time to mature. Scientists have discussed when these traits developed during our evolution: did they adopt a human-like organization in old age? Australopithecus or during the development of later hominins? A new study appears to contradict previous claims and shows that Lucy’s brain would have been pretty ape-like – yet still shows human-like patterns in the way it develops.

“However, what is really fascinating is that the brain, although it looks very much like a monkey brain, has a human trait – that it grows over a long period of time,” said study author Philipp Gunz, a biological anthropologist at the Max Planck Institute for Evolutionary Anthropology. “This is really fascinating because it suggests that some of the unique modern traits in childhood learning and brain plasticity may already have deep evolutionary roots Australopithecus afarensis. “

The team analyzed two well-preserved ones Australopithecus afarensis Infant samples and six adults, including the famous Lucy fossil, use conventional CT scans and high-energy light CT scans generated at the European Synchrotron Radiation Facility, a particle accelerator in France. Scanning the inside of the skull creates a plaster cast, but using light instead of molding material. They used virtual reconstruction techniques to correct how skull damage might have affected the cast. In this way, they were able to create high-resolution images of the surface of the australopithecine brain.

Above all, the scans showed a feature that was previously not discovered in the brain of Australopithecine: the crazy sulcus. This is a cleft in the brain folds that is more prominent in chimpanzees than in humans and is usually not found in a cast of the inside of a human skull. The “clear” recognition of the characteristic in one of the infants Australopithecus Skulls and other wrinkles show that the entire surface of the brain looked much more like a monkey brain than a human brain. The team found no evidence that the Australopithecus The brain had started to change into a more human layout or even a larger size, the paper said released today in scientific advances.

The researchers followed the gypsum analysis with a study of the brain development of the young specimens. Previous research has shown that tooth development can be used to model the age of a sample at death, and in this case the two Australopithecus children were probably about two and a half years old when they died. They compared the estimated volume of the inner part of the skull of the children and adults to create a trajectory of brain growth. They calculated that Australopithecus had already developed a longer period of brain development – more human than chimpanzee-like in its time frame.

“We all tend to look at evolution on a continuum,” Jeremy DeSilva, associate professor of anthropology at Dartmouth, who reviewed the study, told Gizmodo. But “this idea of ​​everything that develops in step is destroyed by such a paper. It shows that, like everything else in human evolution, we have rather developed into a mosaic. modular fashion, where aspects of our anatomy developed at different speeds. “

In other words, the evolution from ape to human was not linear. Our pre-human ancestors may have adopted certain human-like traits while maintaining distinctly ape-like traits. DeSilva explained that, waist down, Australopithecus They looked very human, but above the waist they looked more ape-like.

C.A comparison of the skull fossils and the basin fossils suggests The Australopithecus needed help with childbirth, like people do, which would imply a social lifestyle, DeSilva said.

Although the study includes a large number of fossil specimens, Gunz Gizmodo explained that there is always a desire for more, especially given the small amount of data that anthropologists have to work with. Further fossils could confirm that these evolutionary patterns could be extended to the entire species and are not just the peculiarities of the few individuals that scientists have unearthed.

However, this paper confirms that evolution does not work as you can imagine from a cliched picture.


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