Ancestors Marry with Five Ancient Humans

KOMPAS/AHMAD ARIF

A team of researchers collect blood samples from members of the Fanan indigenous community on Sunday, 12 March 2017, in Loran village, Aru Tengah district, Aru regency, Maluku. The blood collection was part of a genetic study to determine the origins of the Indonesian people.

JAKARTA, KOMPAS— The latest genetic analysis proved that the ancestors of modern humans (Homo sapiens) interbred with at least five ancient humans after leaving Africa for Eurasia (Europe-Asia).

The two archaic humans were Neanderthal and Denisovan, while the other three were not named and only traced with their DNA. Islands in Southeast Asia are the center of the new finding.

"Southeast Asia, especially Indonesia, plays a very important role in understanding the migration and the interbreeding of modern humans with archaic humans," Pradiptajati Kusuma, genetic researcher at the Eijkman Molecular Biology Institute, said in Jakarta on Thursday.

A recent study by João C Teixeira and Alan Cooper of the University of Adelaide\'s Australian Center for Ancient DNA (ACAD), published in the July 2019 edition of the National Academy of Sciences (PNAS), confirmed the finding.

The research has mapped the location of "interbreeding” by analyzing the composition of these archaic genes in the human genome in various parts of the world.

"Each of us carry traces of genetics from the mixing with early humans," said the study\'s first author, João Teixeira of ACAD, in a press release on Monday. "All these archaic groups of humans were scattered and genetically diverse and survive within us."

He cited that all human populations now have Neanderthal DNA of around 2 percent. That is, the interbreeding of the Neanderthal with the ancestors of modern humans occurred once they left Africa from 50,000 to 55,000 years ago in the Middle East. Neanderthals first came out of Africa and their evolution was separate from modern humans 360,000 years ago.

The ancestors of modern humans then walked east and met at least four other groups of early humans.

The position of ancient Indonesia

The ACAD researchers\' study emphasized the importance of the position of Indonesia in the past in the migration and mixing of modern humans with early humans. Previous research from the collaboration of researchers at the Eijkman Institute and researchers from a number of countries published in the journal Cell, 11 April 2019, said that the DNA of Southeast Asians had the most diverse primordial human genes, namely D0, D1, and D2.

The D1 variant was only found in Papuans and it surroundings so that the population had the most complete and highest Denisovan composition. According to Pradiptajati Kusuma who participated in the study, Papuans experienced multiple genetic mixing with Denisovan. The Denisovan D1 gene entered in Papua 30,000 years ago and Denisovan D2 about 46,000 years ago.

"The Southeast Asian Islands were inhabited by many archaic humans when modern humans first arrived in this region, 50,000 years ago," Teixeira said. Three other groups of archaic humans inhabited in this area (Southeast Asia), then modern human ancestors mixed with them before they become extinct.

Using additional information from the reconstruction of migration routes and recordings of fossil vegetation, the researchers reconstructed the locations of the interbreeding, namely in the southern part of Asia between modern humans and ancient human groups named "Extinct Hominin 1".

The subsequent interbreeding occurred with early humans inhabiting the Southeast Asian Islands. The locations were in the southern Philippines, in Sunda exposure between Kalimantan and Java (now the Java Sea), and around Flores. This human group is called "Extinct Hominin 2".

KOMPAS/AHMAD ARIF

A medical worker takes a blood sample on from Menti Gentar, the head of the Orang Rimba indigenous community, on Thursday, 10 March 2016, in in Lower Makekal. The Pintas Tuo Community Health Center in Muara Tabir district, Tebo regency, Jambi, assisted the Eijkman and Warsi Molecular Biology Institute in conducting its genetic health research into the indigenous forest tribes of Bukitduabelas in Jambi.

The study showed the journey of modern humans out of Africa to various parts of the world was very complex. "The Southeast Asian islands were occupied a number of groups of archaic humans. They may live isolated from each other for hundreds of thousands of years before modern humans came," Teixeira said.

Shortly after the arrival and the interbreeding with modern humans, these archaic humans became extinct. They were extinct and replaced by modern humans who occupied almost all corners of the earth which were still unknown.

A number of previous studies, for example Reich (2014), found that the addition of archaic human genes to modern humans helped our ancestors adapt to the environment and the key to disease immunity. For example, the chain of the BNC2 gene that we inherited from Neanderthals helped the ancestors of Europeans live in the cold.

Meanwhile, a study from Pradiptajati et al. showed that the Denisovan gene chain was the key to the adaptation of Papuan ancestors. The Denisovan gene chain in Papuans are TNFAIP3 and WDFY2. The Denisovan gene increased resistance to certain viruses and bacteria. (AIK)