Underwater Fossils Surface to Reveal a Lost World of Archaic Humans
Scattered across the newly created island, scientists have uncovered more than 6,700 fossils of fish, reptiles, and mammals dredged from the deep, including the remains of two hominin skulls.
This is the first discovery of ancient human fossils between the islands of Indonesia. The bones belong to Homo erectus – the longest surviving of all our human relatives.
Until now, the only evidence of H. erectus in the region was confined to the island of Java. But as it turns out, this population was not so isolated after all.
More than 130,000 years ago, when sea levels were 100 meters (328 feet) lower than today, it seems that H. erectus left the island of Java and lived among the valleys and plains of sunken 'Sundaland'.
Sunda is the name for the largest drowned shelf in the world, and while it is now a shallow sea, in the past, it was occasionally a land bridge between the Asian mainland and the islands of Borneo, Sumatra, and Java.
This means that H. erectus may have even come into contact with other human species living in Asia at the time, like Neanderthals or Denisovans.
"Homo erectus could disperse from the Asian mainland to Java," says lead author and archaeologist Harry Berghuis from Leiden University in the Netherlands.
"This makes our discoveries truly unique. The fossils come from a drowned river valley, which filled up over time with river sand. We have been able to date the material to approximately 140,000 years ago."
At that time, experts suspect Sundaland resembled the African savannah. The fossils found on the artificial island included hippos, crocodiles, elephants, Komodo dragons, rhinos, big cats, and hoofed, ruminant animals, similar to bison or buffalo. Most are now extinct.
Given the dry habitat of this prehistoric ecosystem, it is likely that H. erectus stuck to the rivers in Sundaland, which would have provided a perennial source of drinking water and fish. Experts suspect the hominin may have also taken advantage of large game that visited the waters.
"Among our new finds are cut marks on the bones of water turtles and large numbers of broken bovid bones, which point to hunting and consumption of bone marrow," says Berghuis.
"We didn't find this in the earlier Homo erectus population on Java, but do know it from more modern human species of the Asian mainland. Homo erectus may have copied this practice from these populations. This suggests there may have been contact between these hominin groups, or even genetic exchange."
That's an interesting hypothesis, but further evidence is necessary.
Past fossil finds on Java have led scientists to believe this island was the last stronghold for H. erectus – a hominin that journeyed out of Africa and across Asia in a decidedly impressive two-million-year run. By 400,000 years ago, however, H. erectus had gone extinct in Asia and Africa. Yet the species persisted on Java until around 108,000 years ago.
It's a big win pulling the remains of H. erectus from the seabed off the coast of Java, but the fossils were found between a small and narrow strait separating two islands.
How much further afield H. erectus travelled from Java is a mystery.
"The answers may very well be at the bottom of the sea," write the authors.
The research was published in four installments in Quaternary Environments and Humans here, here, here, and here.
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