9 January 2020
Dyani Lewis
Dyani Lewis is a freelance science journalist based in Melbourne, Australia.
The oldest human remains in Southeast Asia – Java man – aren’t as old as we thought they were.
An Indonesian-Japanese team of scientists has overturned a decades-old estimate of Homo erectus remains from Central Java in Indonesia, shaving off several hundred thousand years from the age of the globe-trotting hominin, the first to disperse out of Africa.
The new estimate, published in the journal Science, puts Homo erectus at the fossil-rich Sangiran dome by around 1.3 million years ago, and certainly no earlier than 1.5 million years ago
That’s at least 300,000 years younger than a long-standing estimate from the 1990s, which suggested the oldest Homo erectus remains at Sangiran could be up to 1.8 million years old.
The age has remained controversial, though, because some studies have come up with much younger estimates for Homo erectus at Sangiran, ranging from 1.3 to 0.6 million years old.
To figure out whether the fossils were older or younger, Shuji Matsu’ura from the National Museum of Nature and Science in Tsukuba City, Japan, and colleagues used two separate dating techniques not previously used at the site.
“It was exciting to know which chronology would be supported by the new method,” says Masayuk Hyodo from Kobe University, a senior author on the study.
Uranium-lead dating, which measures the crystallisation age, and fission track dating, which measures the volcano eruption age, of zircon grains show that volcanic ash just below the fossil-bearing layers are just 1.3 million years old.
“The combination of uranium-lead and fission track is a really nice combination,” says Kira Westaway, who led a study revising the youngest erectus remains on Java
“It’s dating two different events, so if you get an agreement between the two, then you really know that you’re onto something,” she says.
The younger age of first appearance at Sangiran fits with other remains on Java that have been dated to 1.49 million years old.
It also puts to bed ideas that the birthplace of Homo erectus could have been in Southeast Asia. It now seems much more likely that Homo erectus arose in Africa and dispersed out through Georgia in the Caucasus, where the oldest Homo erectus remains aged 1.85 million years old have been found. From there, they dispersed into Asia.
“People say, ‘well, it’s only a few hundred thousand years, who cares?’ But it really is a big deal,” says Westaway.
