A new dating of the last known population of Homo erectus in Java

Skullcap of Ngandong Homo erectus
Skullcap of Ngandong Homo erectus

An article published in the journal “Nature” reports a research on the last known population of Homo erectus. A team of researchers carried out a new series of dating of fossil fragments and sediments present in the Ngandong site, on the island of Java, where the specimens attributed to that species were discovered concluding that that population lived between 108,000 and 117,000 years ago. Previous dating provided very variable results, a precise result can help understand the history of little men in Southeast Asia. That population could actually be the result of an interbreeding between Homo sapiens and another species of hominins, explaining some of its peculiar characteristics.

Between 1931 and 1933 various hominin bones belonging to 18 specimens were discovered at the Ngandong site, near a village along the Solo river, on the island of Java. They weren’t the first ones discovered in Java and subsequently attributed to the species Homo erectus but these ones (photo skullcap ©Ryan Somma) showed some peculiar anatomical features and the tools found at the Ngandong site were more advanced than the ones from the other sites on the island. This led over time to different classifications for these fossils up to that of Homo erectus soloensis.

The dating of the Ngandong fossils was complex because the site’s characteristics make the job difficult due to the geological complexity with various layers of sediment and because the information on the positions of the bones found was recorded vaguely compared to the precise paleontological work of subsequent decades. Remains of other animals were discovered on the same site but weren’t considered important and got lost. The result is that the various dating attempts provided very different results ranging from a minimum of 27,000 years to a maximum of 500,000 years.

The researchers who carried out this new study searched for all the existing information on the digging carried out at the Ngandong site and went looking for new fossils, finding a lot of fragments of animal bones, useful for new datings. Sediment samples were also taken from the site and further information was collected by conducting a geological analysis that provided chronological information about Ngandong in the context of the surrounding area.

A series of 52 datings was made on river sediments and fossils taken from the Ngandong site and the results indicate that the age of the site and of the Homo erectus nicknamed Solo men is between 108,000 and 117,000 years. It’s a period after that when, about 130,000 years ago, that environment changed from a vast prairie to a tropical rain forest. This remarkable change is considered a possible reason for the decline in the population of Java’s Homo erectus and it makes sense that the last population of that species lived between 13,000 and 22,000 years later.

Dr Kira Westaway of Macquarie University, one of this study’s lead authors, explained that the new estimate indicates that the Homo erectus of Ngandong might have met the Denisovans, another species of hominins known only thanks to a few bones that lugkily in Siberia got well preserved, to the point that it was possible to recover DNA fragments. There’s even the possibility that the population of Ngandong was the result of the interbreeding between the two species. Unfortunately, in an area like Java the conditions of temperature and humidity are not at all favorable for the conservation of DNA making the possibility of finding fragments still in the bones of Solo’s men unlikely.

If the dating made in this study is confirmed, it will be a help to research on the spread of hominins in Southeast Asia. In particular, it will offer important information on the history of Homo erectus, a species that’s one of Homo sapiens’ ancestor, but the ramifications of that history could also concern other species.

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