In 1931, geologists excavated skull fragments from a fossil bed along the Solo River in Java, an Indonesian island under Dutch colonial rule. Over the next two years, they uncovered 10 more skull specimens and two pieces from a tibia. The geologists identified the bones as belonging to a previously undiscovered ancient human, Homo soloensis.
Solo Man, as the specimen came to be known, has been a point of curiosity among archaeologists ever since its discovery. The hominid resembled ancient human lineages more closely than modern-day humans, even though researchers found it in a relatively young fossil bed.
For many years, scientists wondered if Solo Man had coexisted, peacefully or tumultuously, alongside modern humans on the island of Java.
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The scientific community almost missed out on the opportunity to test and investigate the remains of H. soloensis after the fossils’ initial discovery. In 1942, Japanese forces overtook Batavia, present-day Jakarta, where the collection was kept. Famed archaeologist Gustav Heinrich Ralph von Koenigswald hid the collection from the invaders for the next three years, at one point swapping the skulls for plaster casts for fear of plunder.
One skull piece, however, was sacrificed. Japanese officials ordered Koenigswald to send the specimen to the Emperor as a birthday present soon after the initial invasion. Koenigswald reluctantly packaged up the skull along with some “less important material” and sent it away.
A year after the end of the Japanese occupation, in 1946, an archaeology student traced the fossil and returned it to the rest of the collection in New York.
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H. soloensis, the species name initially given to Solo Man, is now considered a misnomer. Solo Man actually belongs to a far older human lineage — Homo erectus. In many ways, this makes the hominid even more remarkable.
Members of H. erectus migrated to Europe and Asia around 1.8 million years ago. Solo Man likely evolved from “Java Man,” the oldest H. erectus specimen found on the island. Java was the southeast terminus of the H. erectus migration, making Javaan H. erectus the furthest-traveled member of the species.
To date, Solo Man is the last-known surviving member of H. erectus. The hominid outlived its cousins throughout Africa, Asia and Europe.
Attempts at dating Solo Man fossils produced widely varying results. The Dutch geologists who made the discovery thought that the fossils were less than 150,000 years old due to the other fossils found at the site. In the ‘80s, ‘90s and 2000s, researchers used varying techniques to try to pin down Solo Man’s age. All of the results placed the fossils at around 70,000 years to 40,000 years old. If the findings were true, this would mean that Solo Man likely lived alongside prehistoric Homo sapiens, who likely migrated to Southeast Asia around 60,000 years ago.
However, an extensive analysis of fossils from the region, published by an international research group in 2019, revealed that Solo Man was older than previously thought — 117,000 years to 108,000 years old. So, Solo Man did not overlap with H. sapiens in Southeast Asia. But, the hominid probably coincided with other ancient humans in the area, such as the ancient pygmies discovered on the Indonesian island of Flores.
As we continue to unfold the narrative of human history, we owe an immense debt of gratitude to the efforts of these dedicated scientists who saved these fossils. Nearly 80 years later, they are still producing insights into the history of H. erectus.