|Scientists have long argued the period when the Homo erectus, one of the modern man's direct ancestors, disappeared after colonizing the ancient world. The last known site of these ancestors was a spot called Ngandong in Java, Indonesia / Photo by: Jaroslav Moravcik via 123RF|
Scientists have long argued the period when the Homo erectus, one of the modern man's direct ancestors, disappeared after colonizing the ancient world. The last known site of these ancestors was a spot called Ngandong in Java, Indonesia.
A new study puts this years-long debate to rest after an international team of researchers determined the age for the Homo erectus' last known settlement.
"This site is the last known appearance of Homo erectus found anywhere in the world," corresponding author, Russel Ciochon, said in the press release.
Last Known Appearance
The Homo erectus is the oldest known early humans that possessed modern human-like body proportions. It stands at a height ranging from 4’9” to 6’1” and weighs around 88 to 150 lbs, living mostly in Africa and Asia.
To determine the precise period for the site, the researchers time-stamped the area by dating animal fossils collected from the same bonebed where Homo erectus bones were found. They also dated the landforms around the site to determine the accurate record for the ancient humans' possible last stand.
Those landforms were mostly river terraces below and above Ngandong. The research team also dated stalagmites from caves in the Southern Mountains to determine when the mountains first emerged.
This process allowed them to establish the period when the Solo River started its course through the Ngandong site and determined when the river terrace sequence was created, a press release on the study states.
Analysis of the evidence gathered from and around the site resulted in 52 new age estimates. The final results suggest the last existence of the Homo erectus is dated between 108,000 and 117,000 years ago.
"You have this incredible array of dates that are all consistent," Ciochon said. "This has to be the right range. That’s why it’s such a nice, tight paper. The dating is very consistent."
The corresponding author noted that they merely dated the last occurrence of the hominid and not their extinction. However, there is no evidence that the Homo erectus lived later than the established period anywhere else.
Paleoanthropologist Susan Antón of New York University said the ancient species may have lived in Java 10,000 to 20,000 years earlier or later than estimated in the new report—considering the uncertainties in determining the precise ages of the Ngaondong fossils.
Ending Years of Uncertainty
If the findings hold after further investigation, the study will provide the definite last known occurrence of the Homo erectus anywhere in the world after years of confusion.
The Ngandong specimens analyzed were 12 skullcaps and two lower leg bones out of the 25,000 fossils uncovered during excavations from 1931 to 1933, which stirred the uncertainty about the formation process of the Ngandong sediment layers since their discovery. There was also confusion about the exact location of the fossils, leading to great contrasts in their age estimates.
For instance, a 1996 report dated the fossils between 53,000 and 27,000 years ago. Science News, a scientific bi-weekly magazine, says this finding implied that the hominid lived alongside Homo sapiens in Indonesia.
However, an analysis published in 2010 increased the estimated age and dated the Java fossils around 550,000 years ago.
It's unlikely that humans and the Homo erectus overlapped, Ciochon said. He noted that this is because evidence suggests humans in Indonesia first settled no earlier than 73,000 years ago. The last occurrence of the hominid was at least 35,000 years before that and after the species arrived in Java about 1.6 million years ago.
Meanwhile, paleoanthropologist Matthew Tocheri of Lakehead University said the new timeline supports the idea that at least three extinct Homo species occupied parts of Southeast Asia. This scenario would've occurred while Homo sapiens were beginning their journey out of Africa.
"Now we just need to figure out what exactly happened when Homo sapiens first arrived in Southeast Asia," Tocheri said.
An Iconic Species
The Homo erectus essentially disappeared after nearly two million years of wandering the Earth and settling in different continents. That long survival saw them sharing the planet with new groups of humans.
But this didn't last long, and the researchers believe climate change may have played a role in the species' demise.
Animal remains filled the bone bed at Ngandong specifically deer, the large bovid ancestors of water buffalo, and Java's banteng wild cattle. The Smithsonian said these mammals lived in open woodland ecosystems like those in Africa—and Ngandong's environment was similar to that.
"Then around 120,000 or 130,000 years ago, we know that there was a change in the climate, and this rainforest flora spread across Java," Ciochon explained.
"Homo erectus was not able to adapt. Other than Homo sapiens, no other early human was adapted to living in a rainforest," he added.
As far as history is concerned, the Homo erectus will always have a prominent place in the modern human family tree. Paleontologist and head of the Smithsonian's Human Origins Program Rick Potts even described them as "one of the iconic species in human evolutionary history."
"It’s perhaps the most important species that indicates how branchy the human family tree is, because Homo erectus persisted through all of those other species, including eventually Homo sapiens, coming into being from earlier populations of Homo erectus."