Category Archives: PHILIPPINES

A new clue to human evolution’s biggest mystery emerges in the Philippines

New clue to human evolution’s biggest mystery emerges in Philippines

Denisovans are an elusive bunch, known mainly from ancient DNA samples and traces of that DNA that the ancient hominids shared when they interbred with Homo sapiens. They left their biggest genetic imprint on people who now live in Southeast Asian islands, nearby Papua New Guinea and Australia.

New clue to human evolution's biggest mystery emerges in Philippines
Ayta people in the Philippines, shown here, belong to a group of ethnic communities that includes one with the highest level of Denisovan ancestry in the world, a new study finds.

Genetic evidence now shows that a Philippine Negrito ethnic group has inherited the most Denisovan ancestry of all. Indigenous people known as the Ayta Magbukon get around 5 per cent of their DNA from Denisovans, a new study finds.

This finding fits an evolutionary scenario in which two or more Stone Age Denisovan populations independently reached various Southeast Asian islands, including the Philippines and a landmass that consisted of what’s now Papua New Guinea, Australia and Tasmania.

The exact arrival dates are unknown, but nearly 200,000-year-old stone tools found on the Indonesian island of Sulawesi may have been made by Denisovans (SN: 1/13/16). H. sapiens groups that started arriving around 50,000 years ago or more then interbred with resident Denisovans.

Evolutionary geneticists Maximilian Larena and Mattias Jakobsson, both at Uppsala University in Sweden, and their team describe the new evidence on August 12 in Current Biology.

Even as the complexities of ancient interbreeding in Southeast Asia become clearer, Denisovans remain a mysterious crowd. “It’s unclear how the different Denisovan groups on the mainland and on Southeast Asian islands were related [to each other] and how genetically diverse they were,” Jakobsson says.

Papua New Guinea highlanders — estimated to carry close to 4 per cent Denisovan DNA in the new study — were previously thought to be the modern record-holders for Denisovan ancestry. But the Ayta Magbukon display roughly 30 per cent to 40 per cent more Denisovan ancestry than Papua New Guinea highlanders and Indigenous Australians, Jakobsson says.

That calculation accounts for the recent mating of East Asians with Philippine Negrito groups, including the Ayta Magbukon, that diluted Denisovan inheritance to varying degrees.

Genetic analyses suggest that Ayta Magbukon people retain slightly more Denisovan ancestry than other Philippine Negrito groups due to having mated less often with East Asian migrants to the island around 2,281 years ago, the scientists say.

Their genetic analyses compared ancient DNA from Denisovans and Neandertals with that of 1,107 individuals from 118 ethnic groups in the Philippines, including 25 Negrito populations. Comparisons were then made to previously collected DNA from present-day Papua New Guinea highlanders and Indigenous Australians.

The new report underscores that “still today there are populations that have not been fully genetically described and that Denisovans were geographically widespread,” says paleogeneticist Cosimo Posth of the University of Tübingen in Germany, who was not part of the new research.

But it’s too early to say whether Stone Age Homo fossils found on Southeast Asian islands come from Denisovans, populations that interbred with Denisovans or other Homo lineages, Posth says. Only DNA extracted from those fossils can resolve that issue, he adds. Unfortunately, ancient DNA preserves poorly in fossils from tropical climates.

Only a handful of confirmed Denisovan fossils exist. Those consist of a few fragmentary specimens from a Siberian cave where Denisovans lived from around 300,000 to 50,000 years ago (SN: 1/30/19), and a roughly 160,000-year-old partial jaw found on the Tibetan Plateau (SN: 5/1/19). 

Fossils from the Philippines initially classed as H. luzonensis, dating to 50,000 years ago or more (SN: 4/10/19), might actually represent Denisovans. But a lack of consensus on what Denisovans looked like leaves the evolutionary identity of those fossils uncertain.

Larena and Jakobsson’s findings “further increase my suspicions that Denisovan fossils are hiding in plain sight” among previously excavated discoveries on Southeast Asian islands, says population geneticist João Teixeira of the University of Adelaide in Australia, who did not participate in the new study.

Denisovans may have genetically encompassed H. luzonensis and two other fossil hominids found on different Southeast Asian islands, H. floresiensis on Flores and H. erectus on Java, Teixeira suspects. H. floresiensis, or hobbits, survived from at least 100,000 years ago to around 60,000 years ago (SN: 6/8/16). H. Erectus arrived on Java about 1.6 million years ago and died out between 117,000 and 108,000 years ago (SN: 12/18/19).

Geographic ancestry patterns on Southeastern Asian islands and in Australia suggest that this region was settled by a genetically distinct Denisovan population from southern parts of mainland East Asia, Teixeira and his colleagues reported in the May Nature Ecology & Evolution.

700,000-Year-Old Stone Tools Point to Mysterious Human Relative

700,000-Year-Old Stone Tools Point to Mysterious Human Relative

A recent finding of stone instruments and other evidence has shown that in Southeast Asia hominins, our pre-human relatives – were in South East Asia hundreds of thousands of years earlier than we thought.

The 57 stone tools and an almost complete rhinocéros skeleton which shows signs of being butchered were found in the Philippines and date back 709,000 years.

Previously, the earliest evidence for hominin habitation in the area was found in Callao Cave, a river-floodplain on the northern island of Luzon. It’s only 67,000 years old.

Researchers found a 700,000-year-old site on the Philippine island of Luzon where unknown hominins butchered a rhinoceros. To avoid damaging the bones, the team dug them up with only bamboo sticks.

The tools found consist of 49 sharp-edge stone flakes, six cores – the stones from which the flakes are hammered – and two possible hammer stones. In addition, the site yielded a collection of skeletons: a stegodon, brown deer, freshwater turtle, and monitor lizard.

The rhinoceros skeleton was very interesting. Several of the bones had cut marks consistent with butchering, and the humerus bones seemed to have been hit with a hammerstone, possibly to access the rich marrow inside.

The tools weren’t made by humans – our oldest evidence of Homo sapiens is from about 300,000 years ago – but by a close ancestor. And their presence means we need to reconsider how humans and hominins spread through South East Asia.

Archaeologist Gerrit van den Bergh from the University of Wollongong in Australia says that hominins most likely spread through the region in several waves throughout the millennia.

He also believes that they probably travelled from north to south from China and Taiwan, rather than west to East from Borneo or Palawan through Indonesia, using the ocean currents and settling as they went.

Eventually, this migration could have landed on the Indonesian island of Flores to give rise to Homo floresiensis, also known as the “hobbit” for its small stature.

Evidence of hominins dating back 700,000 years has been found on the Indonesian island of Java. In addition, Homo floresiensis ancestors have been found on Flores from around the same time. Both of these finds are consistent with the new migration hypothesis.

Previously, it had been thought that hominins didn’t have boats, and therefore couldn’t have travelled by water to reach Luzon and the other islands of Wallacea, the group of islands separated from mainland Australia and Asia by deep oceans.

But the north-to-south migration hypothesis is supported by another fossil record: that of animals.

“If you look at the fossil and recent faunas you see that there is an impoverishment as you go from north to south. On Luzon, you find fossils of stegodons, elephants, giant rats, rhino, deer, large reptiles, and a type of water buffalo.

“On Sulawesi, the fossil fauna is already impoverished; there’s no evidence of rhinos or deer ever entering there. Then on Flores, you only had stegodons, Komodo dragons, humans, and giant rats, that’s all,” van den Bergh said.

“If animals did reach these islands by chance, by entering the sea and following the currents south, then you would expect the further south you go the fewer species you would find – and that’s what we see.”

If the animals didn’t have boats, the humans needn’t have either. However, they could have had rafts, used for fishing, or been caught up in debris and carried out to sea by tsunamis, which are relatively common in the area.

Who these hominins were is unknown, and will probably remain so without their bones to study. They could have been the ancestors of the owner of that foot bone hundreds of thousands of years later; they could have been Luzon’s version of Homo floresiensis; or they could have been a different group, perhaps even the mysterious Denisovans. But the discovery has archaeologists excited to keep digging to see what else they can find.

“There’s a lot of focus again in the islands of South East Asia because they are places where you find natural experiments in hominin evolution. That’s what makes Flores unique, and now Luzon is another place we can start looking for fossil evidence,” van den Bergh said.

“On Flores, we’re pretty certain they arrived about 1 million years ago based on stone tool evidence, but we don’t know when hominins first arrived on Luzon. Now we can go looking in older strata and see if we can find more artifacts, or even better, fossil evidence.”