The Toba supereruption in Sumatra, ∼74 thousand years (ka) ago, was the largest terrestrial volcanic event of the Quaternary. Ash and sulfate aerosols were deposited in both hemispheres, forming a time-marker horizon that can be used to synchronize late Quaternary records globally. A precise numerical age for this event has proved elusive, with dating uncertainties larger than the millennial-scale climate cycles that characterized this period. We report an astronomically calibrated (40)Ar/(39)Ar age of 73.88 ± 0.32 ka (1σ, full external errors) for sanidine crystals extracted from Toba deposits in the Lenggong Valley, Malaysia, 350 km from the eruption source and 6 km from an archaeological site with stone artifacts buried by ash. If these artifacts were made by Homo sapiens, as has been suggested, then our age indicates that modern humans had reached Southeast Asia by ∼74 ka ago. Our (40)Ar/(39)Ar age is an order-of-magnitude more precise than previous estimates, resolving the timing of the eruption to the middle of the cold interval between Dansgaard-Oeschger events 20 and 19, when a peak in sulfate concentration occurred as registered by Greenland ice cores. This peak is followed by a ∼10 °C drop in the Greenland surface temperature over ∼150 y, revealing the possible climatic impact of the eruption. Our (40)Ar/(39)Ar age also provides a high-precision calibration point for other ice, marine, and terrestrial archives containing Toba sulfates and ash, facilitating their global synchronization at unprecedented resolution for a critical period in Earth and human history beyond the range of (14)C dating.
Genetic research into Southeast Asia's "negritos" has revealed their deep-rooted ancestry, with time depth comparable to that of Southwest Pacific populations. This finding is often interpreted as evidence that negritos, in contrast to other Southeast Asians, can trace much of their ancestry directly back to the early dispersal of Homo sapiens in the order of 70 kya from Africa to Pleistocene New Guinea and Australia. One view on negritos is to lump them and Southwest Pacific peoples into an "Australoid" race whose geographic distribution had included Southeast Asia prior to the Neolithic incursion of "Mongoloid" farmers. Studies into Semang osteology have revealed some hints of Southwest Pacific affinities in cranial shape, dental morphology, and dental metrical "shape." On the other hand, the Andamanese have been shown to resemble Africans in their craniometrics and South Asians in their dental morphology, while Philippine negritos resemble Mongoloid Southeast Asians in these respects and also in their dental metrics. This study expands the scope of negrito cranial comparisons by including Melayu Malays and additional coverage of South Asians. It highlights the distinction between the Mongoloid-like Philippine negritos and the Andamanese and Semang (and Senoi of Malaya) with their non-Mongoloid associations. It proposes that the early/mid-Holocene dispersal of the B4a1a mitochondrial DNA clade across Borneo, the Philippines, and Taiwan may be important for understanding the distinction between Philippine and other negritos.
Six extant species of non-human great apes are currently recognized: Sumatran and Bornean orangutans, eastern and western gorillas, and chimpanzees and bonobos [1]. However, large gaps remain in our knowledge of fine-scale variation in hominoid morphology, behavior, and genetics, and aspects of great ape taxonomy remain in flux. This is particularly true for orangutans (genus: Pongo), the only Asian great apes and phylogenetically our most distant relatives among extant hominids [1]. Designation of Bornean and Sumatran orangutans, P. pygmaeus (Linnaeus 1760) and P. abelii (Lesson 1827), as distinct species occurred in 2001 [1, 2]. Here, we show that an isolated population from Batang Toru, at the southernmost range limit of extant Sumatran orangutans south of Lake Toba, is distinct from other northern Sumatran and Bornean populations. By comparing cranio-mandibular and dental characters of an orangutan killed in a human-animal conflict to those of 33 adult male orangutans of a similar developmental stage, we found consistent differences between the Batang Toru individual and other extant Ponginae. Our analyses of 37 orangutan genomes provided a second line of evidence. Model-based approaches revealed that the deepest split in the evolutionary history of extant orangutans occurred ∼3.38 mya between the Batang Toru population and those to the north of Lake Toba, whereas both currently recognized species separated much later, about 674 kya. Our combined analyses support a new classification of orangutans into three extant species. The new species, Pongo tapanuliensis, encompasses the Batang Toru population, of which fewer than 800 individuals survive. VIDEO ABSTRACT.
Tibetan high-altitude adaptation (HAA) has been studied extensively, and many candidate genes have been reported. Subsequent efforts targeting HAA functional variants, however, have not been that successful (e.g., no functional variant has been suggested for the top candidate HAA gene, EPAS1). With WinXPCNVer, a method developed in this study, we detected in microarray data a Tibetan-enriched deletion (TED) carried by 90% of Tibetans; 50% were homozygous for the deletion, whereas only 3% carried the TED and 0% carried the homozygous deletion in 2,792 worldwide samples (p < 10(-15)). We employed long PCR and Sanger sequencing technologies to determine the exact copy number and breakpoints of the TED in 70 additional Tibetan and 182 diverse samples. The TED had identical boundaries (chr2: 46,694,276-46,697,683; hg19) and was 80 kb downstream of EPAS1. Notably, the TED was in strong linkage disequilibrium (LD; r(2) = 0.8) with EPAS1 variants associated with reduced blood concentrations of hemoglobin. It was also in complete LD with the 5-SNP motif, which was suspected to be introgressed from Denisovans, but the deletion itself was absent from the Denisovan sequence. Correspondingly, we detected that footprints of positive selection for the TED occurred 12,803 (95% confidence interval = 12,075-14,725) years ago. We further whole-genome deep sequenced (>60×) seven Tibetans and verified the TED but failed to identify any other copy-number variations with comparable patterns, giving this TED top priority for further study. We speculate that the specific patterns of the TED resulted from its own functionality in HAA of Tibetans or LD with a functional variant of EPAS1.
Palmaris longus (PL) tendon is regularly used in reconstructive surgeries as a donor tendon because it is observed as an accessory muscle and has little practical use to the human hands. It is only found in mammals. For example, the orangutan has PL but it is absent variable in the higher class of apes such as gorillas and chimpanzees. The absence of PL in humans appears to be hereditary, but the genetic transmission is unclear. The main objective of this study is to determine the prevalence of PL tendon absence in pre-clinical medical students of UMS and to compare the lack between gender and ethnic groups. By using standard Schaffer’s test, we examined the presence or absence of PL tendon among the first and second-year medical students of UMS. Four additional tests, Thompson’s test, Mishra’s test I, and II, Pushpakumar’s tests were used to determine whether PL present or not. A total of 134 volunteers were examined, and 91.8% were right-handed, and 8.2% were left-handed. The overall absence (bilateral and unilateral) of PL tendon was 23.9%, whereas unilateral absent was 17.9%, and bilateral absent was 6.0%. The high prevalence of absence of PL tendon among females 25.5% compared to males 20.0%. Chinese and Indian have a higher incidence of PL tendon absence followed by Kadazandusun and Malay. In this study, there were different figures for each ethnic group. The prevalence of absence of PL varies depending on the populations.