Anthropologists have long sought to pin down the exact location of the proverbial “Garden of Eden” — the region of our planet where the earliest Homo sapiens emerged.
Over the last two decades, a combination of genetic evidence and data from the fossil record led scientists to conclude that the first members of our species evolved in Eastern Africa about 200,000 years ago.
But a new discovery suggests a more complex narrative for the origin of humans.
In a pair of papers published on Wednesday in Nature, an international team of researchers describe 22 human fossils from northwest Morocco that are approximately 300,000 years old.
According to the authors, it is the earliest evidence of Homo sapiens ever discovered — by a long shot.
The unexpected location of the find, coupled with previous discoveries of early human remains dating back to 260,000 years in South Africa and 195,000 years in Ethiopia, cast doubt on the story that the first members of our species evolved in a single region of the African continent, study authors said.
“Our results challenge this picture in a number of ways,” said Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology in Germany, who led the work. “There is no Garden of Eden in Africa, or if there is a Garden of Eden, it’s Africa. The Garden of Eden is the size of Africa.”
This is the first almost-complete adult mandible discovered at the Jebel Irhoud site. The shape of the bone and the teeth clearly assign it to the root of our own lineage, the study authors said.
Not all of the fossils cataloged in the papers are new discoveries. Six of the 22 specimens were first unearthed in the 1960s as the result of barite mining operations at Jebel Irhoud, the archaeological site that is located between Marrakesh and Morocco’s Atlantic coast.
At the time of the initial discovery, scientists concluded that the fossils were about 40,000 years old. However, that date didn’t sit right for many researchers.
“The previous age estimate on the Jebel Irhoud hominin never made sense,” said Curtis Marean, an archaeologist at the Institute for Human Origins at Arizona State University in Tempe, who was not involved in the new work.
The shape of the fossilized bones looked too primitive for their supposed relatively young age, Marean said. In addition, the plant and animal evidence found in the same location as the bones didn’t match the environmental conditions that would have been present in the area 40,000 years ago.
Hublin and his colleagues also felt that the fossils had been inaccurately dated and wanted to do something about it. They visited Jebel Irhoud several times throughout the 1980s and ’90s, and officially resumed excavations there in 2004.
The researchers believe that the site was once a cave that likely provided shelter for small bands of early humans who came to the area to hunt gazelles and zebra. Their flint tools, sharpened into pointed forms that were likely spear heads, appear to be made from material collected at least 15 miles away.
“This suggests they visited high-quality locations to collect flint and then carried it around to places like Jebel Irhoud where they could stop and retool their weaponry,” said Shannon McPherron, an archaeologist at the Max Planck Institute for Evolutionary Anthropology who worked on the study.
Over the course of the team’s work, they discovered 18 additional hominin bones, as well as stone artifacts consistent with the dawn of the Middle Stone Age. They also found gazelle and zebra bones that suggested the animals were deliberately butchered and cooked over a fire.
Their biggest stroke of luck came when they found several burned pieces of flint artifacts buried alongside the fossils. The team was able to date the burned flint using a process called thermoluminescence. This allowed them to determine that the fossils were about 300,000 years old, making them the oldest Homo sapien remains ever found.
“That was a big ‘Wow!’ ” Hublin said. “The new dates convinced us that this material represented the very root of our species.”
Among the newly discovered fossils were an adult skull comprising a distorted braincase and fragments of a face, and a nearly complete adult lower jawbone. There was also one maxilla (which comprises the upper jawbone and the sinus cavity), as well as several teeth and other bits of skeleton.
Further analysis revealed that the 22 specimens came from a total of five individuals — three fairly young adults, one teenager and a child between 7.5 and 8 years old.
To be clear, these 300,000-year-old Homo sapiens were not our anatomical twins. Far from it.
The authors write that these early humans had a strange mix of characteristics — some that would be very familiar to us, while others are extremely primitive. For example, their faces were similar enough to the faces of modern humans that if you saw these individuals walking down the street, you would probably not take notice, Hublin said. However, the shape of their braincase suggests they had a large but much more primitive brain than we have today.
This implies that different parts of the human anatomy evolved at different rates, the researchers said.
“Some things were fixed early in a modern way and others took a lot longer to reach the modern condition,” Hublin said. “In short, the story of our evolution over the past 300,000 years is mostly the evolution of our brains.”