160,000-year-old fossilized skulls found in Ethiopia are the oldest anatomically modern humans

(ORDO NEWS) — Fossilized skulls of two adults and one child discovered in the Afar region of eastern Ethiopia have been dated at 160,000 years old, making them the oldest known fossils of modern humans, or Homo sapiens.

The skulls, excavated near the village of Herto, fill a large gap in the human fossil record – an era at the dawn of modern man, when the facial features and meninges that we today consider human first appeared.

The fossils date back to the exact time when biologists using genes to chart human evolution predicted that a genetic “Eve” lived somewhere in Africa and gave rise to all modern humans.

“We lacked intermediate fossils between prehumans and modern humans, between 100,000 and 300,000 years ago, and that’s where the Herto fossils fit in,” said paleoanthropologist Tim White, a professor of integrative biology at the University of California at Berkeley and one of the leaders of the team that led the study. excavations and site analysis. “Now the fossil evidence matches the molecular evidence.”

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“With these new skulls,” he added, “we can now see what our direct ancestors looked like.”

“This set of fossils is amazing,” said team member F. Clark Howell, UC Berkeley Distinguished Professor of Integrative Biology and co-director of the UC Berkeley Human Evolutionary Research Laboratory, along with White. “This is truly a revolutionary scientific discovery.”

Howell added that these anatomically modern humans predate most Neanderthals and therefore could not have descended from them, as some scientists have suggested.

The international team is led by White and his Ethiopian colleagues Berhane Asfaw of the Rift Valley Research Service in Addis Ababa, Ethiopia, and Gidai WoldeGabriel of Los Alamos National Laboratory in New Mexico. The findings will be presented in two papers in the June 12 issue of Nature.

The research team also found the skulls and teeth of seven other hominids, hippo bones with traces of stone tools, and more than 600 stone tools, including hand axes. They all belong to the same deposits and, therefore, to the same epoch.

“These were people using complex stone technology,” White said. “Using chipped hand axes and other stone tools, they butchered the carcasses of large mammals such as hippos and bison, and no doubt knew how to process plants.”

They lived long before most specimens of another early hominid, the Neanderthal, or Homo neanderthalensis, which White says is irrefutable evidence that Homo sapiens did not evolve from these short, stocky creatures. More like cousins, Neanderthals split off from the human tree over 300,000 years ago and died out around 30,000 years ago, possibly driven to extinction by modern humans.

“These well-dated and anatomically diagnosed Herto fossils are unmistakably not Neanderthals,” said Howell, co-author of the Homo erectus paper detailing hominids and an expert on early modern humans.

“These fossils show that human-like humans evolved in Africa long before the extinction of European Neanderthals. Thus, they convincingly prove that there was never a Neanderthal stage in human evolution.”

Since Herto’s fossils represent a transitional period between more primitive hominids from Africa and modern humans, they provide strong support for the hypothesis that modern humans evolved in Africa and subsequently spread into Eurasia.

This hypothesis contradicts the theory that modern humans originated in many areas of Europe, Asia and Africa from other hominids who migrated out of Africa at a much earlier time.

Fossil evidence, says Asfau, “clearly shows what molecular anthropologists have long been saying is that modern Homo sapiens evolved out of Africa.”

These fossilized skulls from Herto show that modern humans lived approximately 160,000 years ago with full-fledged features of Homo sapiens. The “African Natives” hypothesis has now been tested… (and) we can definitively state that Neanderthals had nothing to do with modern humans. They are dead.”

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Fossil skulls

Three fossil skulls remain in Ethiopia, but the research team compared their replicas to many Neanderthal and earlier hominin skulls, as well as modern humans. Many of the skulls of modern humans were taken from a worldwide sample of skeletal remains held in the collection of the Hearst Museum of Anthropology at the University of California, Berkeley.

The most complete of the three new fossil skulls is probably male, slightly larger than the extreme size observed in modern Homo sapiens, however, it has other characteristics within the range of modern humans – in particular, less pronounced brow ridges than prehomo sapiens, and more high cranial vault.

Because of this similarity, the researchers assigned the fossils to the same genus and species as modern humans, but added a subspecies name to them – Homo sapiens idaltu – to distinguish them from modern humans, Homo sapiens sapiens.

Idàltu, which means “elder” in the Afar language, indicates the antiquity and individual age of an adult male. The man, although he was probably in his 20s or 30s, had badly worn upper teeth and a brain size slightly larger than average for living humans.

Scientists tracking evolution through changes in mitochondrial DNA, which is passed down from mother to daughter, have suggested that humans got their mitochondrial genes from an ancestor mother nicknamed “Eve” who lived in Africa about 150,000 years ago. Other scientists studying the male Y chromosome have come to similar conclusions. Herto’s new fossils belong to a population that lived at that time.

“In a certain sense, these genetic findings could not be seriously tested without good fossils from Africa,” says White. “Back in 1982, when Becky Kann and Allan Wilson at the University of California at Berkeley used molecules to study evolution, they concluded that the common ancestors of all modern humans lived in Africa 100,000 to 200,000 years ago. Over the past 20 years we were looking for good, dated fossil evidence of this antiquity.”

Previously found fossils were younger, from sites scattered throughout Africa, often poorly dated and incomplete. These include fossil skull fragments from the mouth of the Clasies River in South Africa dated to about 100,000 years ago, and Middle Eastern fossils from Qafzeh and Shul dated 90,000-130,000 years ago.

Some modern human fossils have been found in Ethiopia, including those from Omo that are about 100,000 years old, and those from Adum in Middle Awash that are about 80,000 years old.

Although these previous finds also appear to be Homo sapiens, the new finds from Herto are older, well dated, and more complete, lacking the common characteristics of more primitive human ancestors such as Homo erectus or Neanderthals.

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Opening

The fossil-rich site was discovered on November 16, 1997 in a dry and dusty valley bordering the Middle Awash River, near Kherto, a seasonal village. While scouting, White first noticed stone tools and a fossil skull of a slaughtered hippopotamus protruding from the ground.

When the team returned 11 days later for an intensive survey of the area, they found the most complete of the adult skulls, protruding from ancient deposits. It was exposed as a result of heavy rains and partially trampled on by herds of cows.

Part of the left anterior skull (braincase) of an adult was crushed and scattered, but the team was able to excavate the rest of the skull, minus the mandible, and reconstruct it.

The child’s skull, found nearby, was crushed and scattered due to being out in the open for many years. The team collected most of the skull fragments, over 200 in all, over a 400-square-foot area, and Asfaw painstakingly pieced them together over the course of three years.

Judging by the presence of unerupted teeth, the skull belongs to a child of six or seven years. Interestingly, both this skull and the skull of a second adult, too fragmentary for reconstruction, were found to have incision marks pointing to the ancient practice of fistfighting, White said.

There were marks on the child’s skull, indicating that, after death, the muscles were cut off from the base of the skull. The back of the base of the skull had been broken off and the edges polished, and the entire skull was smooth, as if the result of repeated manipulations.

On the second adult skull, parallel scratches were visible along the perimeter of the skull, apparently made by a stone tool that was repeatedly passed over the surface of the skull in a pattern different from that created during decapitation, in order to obtain food.

The burial rituals of Herto people differ from those of earlier hominids, some of whom cut flesh from skulls but apparently did not polish or decorate them with scratch marks. Changes similar to those seen on the Kherto skulls have been documented by anthropologists in societies, including New Guinea, where ancestral skulls are preserved and revered.

According to White, Herto’s skulls were not found along with other bones from the rest of the bodies, which is unusual, and this led the researchers to conclude that people were “moving their heads around the landscape.” They probably cut open the muscles and broke the bases of some of the skulls to extract the brain, but why, whether as part of a cannibalistic ritual, we cannot know.

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The team also found more than 640 stone artifacts, although they estimate that the entire area of ​​Herto contains millions of such artifacts: hand axes, scaled tools, cannonballs, flakes and rare blades. Noted African prehistorian J. Desmond Clark of the University of California at Berkeley analyzed many of them before his death last February.

Clarke and colleagues Dr. Yonas Beyene of the Ethiopian Cultural Heritage Research and Preservation Authority and Dr. Alban Defler of Marseille, France, concluded that stone tools are transitional between the Achaean period, characterized by the predominance of hand axes, and the later Middle Stone Age, in which flakes predominate.

“Accompanying fossil bones clearly show that the Herto people had a taste for hippos, but we can’t tell if they killed them or collected them,” says Beyene. “These artifacts are clues about the ancestors that made them.”

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Shore of an ancient lake

The first people in Kherto lived on the shores of a shallow lake formed after the temporary damming of the Awash River about 260,000 years ago. Hippos, crocodiles and catfish abounded in the lake, and buffaloes roamed the land.

The deposits and volcanic rocks in which the fossils were found have been dated to 160,000-154,000 years ago by a combination of the two methods. The argon/argon method was used by colleagues at the Berkeley Center for Geochronology under the direction of Paul R. Renne, Associate Professor of Geology at the University of California, Berkeley. VoldeGabriel of Los Alamos National Laboratory and Bill Hart of Miami University at Ohio used the chemistry of volcanic layers to correlate dated layers.

The Middle Awash research team consists of more than 45 scientists from 14 different countries who specialize in geology, archeology and paleontology. In this single area of ​​study, the team found fossils dating from the present to more than 6 million years ago, providing a clear picture of human evolution from ape-like ancestors to modern humans.

“Human fossils from Herto are at the top of the well-established African fossil sequence,” White said. “This is clear fossil evidence that our species evolved.”

The work was funded by the National Science Foundation and the Institute of Geophysics and Planetary Physics at Los Alamos National Laboratory in conjunction with the University of Miami Hampton Foundation for International Initiatives and the Japan Society for the Advancement of Science.

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