Papua New Guinean Genomes Reveal the Complex Settlement of North Sahul.

The settlement of Sahul, the lost continent of Oceania, remains one of the most ancient and debated human migrations. Modern New Guineans inherited a unique genetic diversity tracing back 50,000 years, and yet there is currently no model reconstructing their past population dynamics. We generated 58 new whole-genome sequences from Papua New Guinea, filling geographical gaps in previous sampling, specifically to address alternative scenarios of the initial migration to Sahul and the settlement of New Guinea. Here, we present the first genomic models for the settlement of northeast Sahul considering one or two migrations from Wallacea. Both models fit our data set, reinforcing the idea that ancestral groups to New Guinean and Indigenous Australians split early, potentially during their migration in Wallacea where the northern route could have been favored. The earliest period of human presence in Sahul was an era of interactions and gene flow between related but already differentiated groups, from whom all modern New Guineans, Bismarck islanders, and Indigenous Australians descend. The settlement of New Guinea was probably initiated from its southeast region, where the oldest archaeological sites have been found. This was followed by two migrations into the south and north lowlands that ultimately reached the west and east highlands. We also identify ancient gene flows between populations in New Guinea, Australia, East Indonesia, and the Bismarck Archipelago, emphasizing the fact that the anthropological landscape during the early period of Sahul settlement was highly dynamic rather than the traditional view of extensive isolation.

Testing for Betel Nut Alkaloids in Hair of Papuans Abusers using UPLC-MS/MS and UPLC-Q-Tof-MS.

Betel nut is the fruit of Areca palm, growing in Papua New Guinea. Mixed with limestone and stick mustard, arecoline and guvacoline, which are present in betel nut, are hydrolyzed into arecaidine and guvacine, respectively. As part of the study on dietary habits of Papuans residents, our laboratory was asked to analyze the four alkaloids in hair to document long-term exposure. Hair samples were collected from 19 adult subjects (males = 11; females = 8), by some of the authors, and were sent to the laboratory for analysis. The four alkaloids have very similar chemical structures. In order to accurately identify the drugs, two methods were developed. First, the compounds were identified using an ultra-high-performance liquid chromatography system coupled to time-of-flight mass spectrometry. Then, they were quantified by an ultra-high-performance liquid chromatography system coupled to tandem mass spectrometry. After decontamination with dichloromethane, hair samples were cut into very small segments and 20 mg were incubated in methanol for 2 h 30 min in an ultrasound bath. After cooling, the methanol was evaporated to dryness in presence of 20-µL octanol to prevent volatilization. Nicotine-d4 was used as an internal standard. Linearity was observed for concentrations ranging from the limit of quantification to 20 ng/mg for arecoline, arecaidine, guvacine and guvacoline. Measured concentrations were in the range 60 pg/mg to 18 ng/mg for arecoline (n = 19), 14 pg/mg to 2.5 ng/mg for guvacoline (n = 11), 63 pg/mg to 3.8 ng/mg for arecaidine (n = 11) and 100 pg/mg to 3.2 ng/mg for guvacine (n = 6). There was no correlation between concentrations of arecoline and arecaidine (ratio from 0.01 to 0.18) and guvacoline and guvacine (ratio from 0.06 to 3.50). However, the identification of these substances in hair is a good marker of consumption of betel nut and allows us to document a local practice that remains difficult to evaluate just by questioning.