An excess of male over female deaths is characteristic of modern national populations, whereas in some high-mortality societies female mortality exceeds that of males. Among the Semai Senoi, a Malaysian Orang Asli ("aboriginal") population, women experienced higher mortality than males in the decades before 1969. This differential occurred in all age classes older than 15 years so that the sex ratio progressively increased with age. A recent (1987) restudy of the Semai population found that sex-specific differential mortality is much reduced. A comparison of the 1969 and 1987 life tables shows a sharp shift in the sex ratios of mortality for the post-15-year-old age classes (the geometric means of age classes 15-44 were 0.768 in 1969 and 0.997 in 1987) so that male and female expectations of further life at age 15 are now nearly identical. In contrast to the best-known cases of high female mortality (mostly in South Asia), Semai sex differential mortality does not include the childhood ages. The Semai have traditionally been relatively sexually egalitarian, and sex bias in care has not occurred. Analysis of sex-specific causes of death for the pre-1969 population suggests that maternal mortality is the major cause of the excess female deaths. The reduced number of maternal deaths seems largely due to better health care, particularly the availability of hospital services. Interestingly, the reduction in female mortality has occurred simultaneously with increased fertility, and overall mortality has continued at relatively high levels (eO less than 36). Thus, rather than forming a component of a unitary demographic transition, declining sex differences in mortality can be accounted for by a specific factor, better maternal care.
A population genetic study was undertaken to provide gene frequency data on the additional blood genetic markers in the Semai and to estimate the genetic relations between the Semai and their neighboring and linguistically related populations by genetic distance and principal components analyses. Altogether 10 polymorphic and 7 monomorphic blood genetic markers (plasma proteins and red cell enzymes) were studied in a group of 349 Senoi Semai from 11 aboriginal settlements (villages) in the Pahang State of western Malaysia. Both the red cell glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (PGD) loci reveal the presence of polymorphic frequencies of a nondeficient slow allele at the G6PD locus and a fast allele at the PGD locus. The Semai are characterized by high prevalences of ahaptoglobinemia and G6PD deficiency, high frequencies of HP*1, HB*E, RH*R1, ACP*C, GLO1*1, PGM1*2+, and GC*1F and corresponding low frequencies of ABO*A, HbCoSp, HB*B0, TF*D, CHI, and GC*2. Genetic distance analyses by both cluster and principal components models were performed between the Semai and 14 other populations (Malay; Javanese; Khmer; Veddah; Tamils of Malaysia, Sri Lanka, and India; Sinhalese; Oraon; Toda and Irula of India; Chinese; Japanese; Koreans) on the basis of 30 alleles at 7 polymorphic loci. A more detailed analysis using 53 alleles at 13 polymorphic loci with 10 populations was carried out. Both analyses give genetic evidence of a close relationship between the Semai and the Khmer of Cambodia. Furthermore, the Semai are more closely related to the Javanese than to their close neighbors--the Malay, Chinese, and Tamil Indians. There is no evidence for close genetic relationship between the Semai and the Veddah or other Indian tribes. The evidence fits well with the linguistic relationship of the Semai with the Mon-Khmer branch of the Austro-Asiatic language family.
Associations among seven apolipoprotein B (APOB) gene polymorphisms [C-T promoter site; Leu-Ala-Leu signal peptide (SP) insertion/deletion; AG C,G site at codon 71; AG A1,D site at codon 591; XbaI site at codon 2488; AG H,I site at codon 3611; and AG T,Z site at codon 4154] were investigated in 195 members of an Orang Asli (aborigine) population from western Malaysia. Frequencies of the rare alleles for all these polymorphisms turned out to be low when compared with European but not Asian populations. The AG H,I site was not polymorphic. The highly polymorphic sites are in linkage disequilibrium among themselves, as shown by their delta values: SP 24,27 and AG C,G, 0.68; SP 24,27 and AG A1,D, 0.71; XbaI and AG C,G, 0.64; XbaI and AG A1,D, 0.57; SP 24,27 and XbaI, 0.48; and AG C,G and AG A1,D, 0.68. Ten unequivocal haplotypes on the basis of six sites (excluding the promoter polymorphism) were observed, and they represent 80% of the sample. The frequency of haplotype SP27,G,A1,X-,I,T, defined by the common homozygotes at all the sites for the APOB gene was 0.7, compared with 0.22 in Europeans. The ancestral haplotype SP27,G,D,X-,I,T was present at low frequency (0.01) in both the Orang Asli and Europeans. A cladogram constructed on the basis of haplotypes in the Orang Asli shows two different lines of evolution and that other haplotypes evolved by subsequent mutations on the ancestral haplotype.
In a previous study of Southeast Asian genetic variation, we characterized mitochondrial DNAs (mtDNAs) from six populations through high-resolution restriction fragment length polymorphism (RFLP) analysis. Our analysis revealed that these Southeast Asian populations were genetically similar to each other, suggesting they had a common origin. However, other patterns of population associations also emerged. Haplotypes from a major founding haplogroup in Papua New Guinea were present in Malaysia; the Vietnamese and Malaysian aborigines (Orang Asli) had high frequencies of haplogroup F, which was also seen in most other Southeast Asian populations; and haplogroup B, defined by the Region V 9-base-pair deletion, was present throughout the region. In addition, the Malaysian and Sabah (Borneo) aborigine populations exhibited a number of unique mtDNA clusters that were not observed in other populations. Unfortunately, it has been difficult to compare these patterns of genetic diversity with those shown in subsequent studies of mtDNA variation in Southeast Asian populations because the latter have typically sequenced the first hypervariable segment (HVS-I) of the control region (CR) sequencing rather than used RFLP haplotyping to characterize the mtDNAs present in them. For this reason, we sequenced the HVS-I of Southeast Asian mtDNAs that had previously been subjected to RFLP analysis, and compared the resulting data with published information from other Southeast Asian and Oceanic groups. Our findings reveal broad patterns of mtDNA haplogroup distribution in Southeast Asia that may reflect different population expansion events in this region over the past 50,000-5,000 years.
DNA samples were extracted from six prehistoric human remains, found on the Malay Peninsula, dating to the Paleolithic and the Neolithic periods. Nucleotide sequences of mitochondrial DNA were determined by the polymerase chain reaction-direct sequencing method. A phylogenetic tree between prehistoric and present humans was constructed based on the nucleotide sequence data. Mitochondrial DNA phylogenetic relationships and ethnoarchaeological evidence suggest that there is a continuity beetween the pre-Neolithic humans and the present Semang and that the Neolithic humans in this area might be an ancestral group of the Senoi.
We determined the allelic (X+/X-, M+/M-, and E+/E-) distribution frequencies of the XbaI, MspI, and EcoRI restriction fragment length polymorphisms (RFLPs) in the apolipoprotein B gene in a control group of 374 healthy Chinese, Malays, and Indians and in a hyperlipidemic cohort of 131 Chinese patients. Covariability between the RFLPs and serum lipid, lipoprotein, and apolipoprotein concentrations was also studied. We found a lower frequency (average 0.0829) of the X+ allele and higher frequencies of the E+ (average 0.9452) and M+ (average 0.9772) alleles in our study population compared with frequencies reported in other populations. The 3 polymorphic sites did not contribute to significant variations in lipid levels (p > 0.1 in all cases). Also, there was no significant variation in genotype frequencies between the control subjects and the hyperlipidemic subjects. Despite their relative close proximity within the APOB gene sequence, the 3 polymorphic sites did not show any significant linkage disequilibrium. However, the presence of the X+ cutting site was in linkage disequilibrium with the Del allele of the 5' insertion-deletion polymorphism and the E-allele was in linkage disequilibrium with the 3' VNTR located near the 3' end of the coding region of the APOB gene.
Apolipoprotein H (APOH) (beta-2-glycoprotein I) polymorphism has been studied in 1159 Asians. The sample included 872 Chinese, 179 Asiatic Indians (Dravidian), 91 Filipinos, and 17 Malays. APOH polymorphism was determined by isoelectric focusing of sera in thin-layer polyacrylamide gels containing 3 M urea followed by immunoblotting. The frequencies of the three alleles--APOH*1, APOH*2, and APOH*3--were found to be 0.031, 0.900, and 0.069 in the Chinese; 0.061, 0.866, and 0.073 in the Dravidian Indians; 0.055, 0.923, and 0.022 in the Filipinos; and 0.088, 0.882, and 0.029 in the Malays. The phenotypic distribution was at Hardy-Weinberg equilibrium in all the populations.
A marked seasonality of births for the two main ethnic groups of peninsular Malaysia, far exceeding the cyclic fluctuations in births in the United States and Canada, was reported for the 1960s. A 36% excess of births over the average monthly number was observed among Malays each January. Among the ethnic Chinese in Malaysia a regular periodicity in the numbers of births was also found, but it was far less marked and the peak occurred in October or November. The peaks in both groups were due in large measure to conceptions that correlate with religious observances or holidays. Here I report on cyclic birth patterns in peninsular Malaysia for the period 1970-1985. Rapid economic development has occurred during this time and has brought with it demographic changes, such as a massive rise in contraceptive use and a decline in birth rates. These demographic changes have been accompanied by the loss of the pronounced seasonal pattern of births among the Malays. The seasonality of Malay births is now of roughly the same magnitude as the seasonality in the United States and Canada, whereas seasonality of births among the Chinese in Malaysia remains essentially unchanged.
The effects of breast-feeding on infant health and mortality, particularly in the developing nations, are a matter of controversy and importance. The Malaysian Family Life Survey (MFLS) of over 1200 women has recently been the source of a great deal of valuable information on the influence of breast-feeding and interacting social variables on the incidence of infant mortality. Accuracy of reporting of breast-feeding duration is a key issue in the validity of studies of breast-feeding and infant mortality. This paper presents an illustrative analysis of the quality of breast-feeding data from the Malaysian Family Life Survey, using logit model schedules. Lesthaeghe and Page derived a logit model schedule of breast-feeding, summarizing empirical experience. This family of model breast-feeding duration curves is similar to the logit model life tables developed by Brass, and was intended for similar applications. To verify the MFLS retrospective breast-feeding reports, the observed median duration and variability were calculated for ethnic group/cohort subsets, and expected duration distribution curves were generated from the model using these observed parameter values. The expected curve generated from the model fit the observed curve of breast-feeding discontinuation extremely closely. Thus it is unlikely that any significant distortion of the pattern of discontinuation of breast-feeding occurred in data collection. Extensions of this method of data quality checking to other duration distributions are suggested.
The Austronesian Diaspora is a 5,000-year account of how a small group of Taiwanese farmers expanded to occupy territories reaching halfway around the world. Reconstructing their detailed history has spawned many academic contests across many disciplines. An outline orthodox version has eventually emerged but still leaves many unanswered questions. The remarkable power of whole-genome technology has now been applied to people across the entire region. This review gives an account of this era of genetic investigation and discusses its many achievements, including revelation in detail of many unexpected patterns of population movement and the significance of this information for medical genetics.
The primary focus of this article is on the so-called negritos of Peninsular Malaysia and southern Thailand, but attention is also paid to other parts of Southeast Asia. I present a survey of current views on the "negrito" phenotype--is it single or many? If the phenotype is many (as now seems likely), it must have resulted from parallel evolution in the several different regions where it has been claimed to exist. This would suggest (contrary to certain views that have been expressed on the basis of very partial genetic data) that the phenotype originated recently and by biologically well-authenticated processes from within the neighboring populations. Whole-genome and physical-anthropological research currently support this view. Regardless of whether the negrito phenotype is ancient or recent-and to the extent that it retains any valid biological reality (which is worth questioning)-explanations are still needed for its continued distinctiveness. In the Malay Peninsula, a distinctive "Semang" societal pattern followed by most, but not all, so-called negritos may have been responsible for this by shaping familial, breeding, and demographic patterns to suit the two main modes of environmental appropriation that they have followed, probably for some millennia: nomadic foraging in the forest, and facultative dependence on exchange or labor relations with neighboring populations. The known distribution of "negritos" in the Malay Peninsula is limited to areas within relatively easy reach of archaeologically authenticated premodern transpeninsular trading and portage routes, as well as of other non-negrito, Aslian-speaking populations engaged in swidden farming. This suggests that their continued distinctiveness has resulted from a wish to maintain a complementary advantage vis-à-vis other, less specialized populations. Nevertheless, a significant degree of discordance exists between the associated linguistic, societal-tradition, and biological patterns which suggests that other factors have also been at play.
The so-called negritos adapt not just to a tropical forest environment but also to an environment characterized by perturbations and fluctuations. As with other hunter-gatherers in the region and, indeed, throughout the world, they use both social and ecological methods to enhance their chances of survival in this changing environment: socially, they have developed networks of trading and marriage partners; ecologically, they maintain patches of key resources that are available for future harvesting. As evidenced in the case of the Batek (Orang Asli), patterns of forest structure and composition are sometimes direct outcomes of intentional resource concentration and enrichment strategies. While little of the above is controversial anthropologically, what has drawn some debate is the nature of the relationship with partner societies. Conventional wisdom posits relations of inequality between foragers and "others": foragers and farmers are often construed as hierarchical dyads where foragers supply products or labor to farmers in exchange for agricultural harvests and other trade goods. This kind of adaptation appears to be one of divergent specialization. However, there are cases, such as in the relationship between Batek and Semaq Beri, where both societies follow a roughly similar mode of adaptation, and specialization has not materialized. In sum, while not denying that hierarchy and inequality exist, I suggest that they have to be contextualized within a larger strand of relationships that includes both hierarchy and egality. Further, such relationships are part of the general portfolio of risk reduction strategies, following which access to widely scattered environmental resources, and passage from one location to another, is enhanced not by competing with and displacing neighbors but by maintaining a flexible regime of friendly exchange partners.
Within recorded history, most Southeast Asian peoples have been of "southern Mongoloid" physical type, whether they speak Austroasiatic, Tibeto-Burman, Austronesian, Tai-Kadai, or Hmong-Mien languages. However, population distributions suggest that this is a post-Pleistocene phenomenon and that for tens of millennia before the last glaciation ended Greater Mainland Southeast Asia, which included the currently insular world that rests on the Sunda Shelf, was peopled by short, dark-skinned, frizzy-haired foragers whose descendants in the Philippines came to be labeled by the sixteenth-century Spanish colonizers as "negritos," a term that has since been extended to similar groups throughout the region. There are three areas in which these populations survived into the present so as to become part of written history: the Philippines, the Malay Peninsula, and the Andaman Islands. All Philippine negritos speak Austronesian languages, and all Malayan negritos speak languages in the nuclear Mon-Khmer branch of Austroasiatic, but the linguistic situation in the Andamans is a world apart. Given prehistoric language shifts among both Philippine and Malayan negritos, the prospects of determining whether disparate negrito populations were once a linguistically or culturally unified community would appear hopeless. Surprisingly, however, some clues to a common negrito past do survive in a most unexpected way.
The Aslian language family, located in the Malay Peninsula and southern Thai Isthmus, consists of four distinct branches comprising some 18 languages. These languages predate the now dominant Malay and Thai. The speakers of Aslian languages exhibit some of the highest degree of phylogenetic and societal diversity present in Mainland Southeast Asia today, among them a foraging tradition particularly associated with locally ancient, Pleistocene genetic lineages. Little advance has been made in our understanding of the linguistic prehistory of this region or how such complexity arose. In this article we present a Bayesian phylogeographic analysis of a large sample of Aslian languages. An explicit geographic model of diffusion is combined with a cognate birth-word death model of lexical evolution to infer the location of the major events of Aslian cladogenesis. The resultant phylogenetic trees are calibrated against dates in the historical and archaeological record to infer a detailed picture of Aslian language history, addressing a number of outstanding questions, including (1) whether the root ancestor of Aslian was spoken in the Malay Peninsula, or whether the family had already divided before entry, and (2) the dynamics of the movement of Aslian languages across the peninsula, with a particular focus on its spread to the indigenous foragers.
Southeast Asia houses various culturally and linguistically diverse ethnic groups. In Malaysia, where the Malay, Chinese, and Indian ethnic groups form the majority, there exist minority groups such as the "negritos" who are believed to be descendants of the earliest settlers of Southeast Asia. Here we report patterns of genetic substructure and admixture in two Malaysian negrito populations (Jehai and Kensiu), using ~50,000 genome-wide single-nucleotide polymorphism (SNP) data. We found traces of recent admixture in both the negrito populations, particularly in the Jehai, with the Malay through principal component analysis and STRUCTURE analysis software, which suggested that the admixture was as recent as one generation ago. We also identified significantly differentiated nonsynonymous SNPs and haplotype blocks related to intracellular transport, metabolic processes, and detection of stimulus. These results highlight the different levels of admixture experienced by the two Malaysian negritos. Delineating admixture and differentiated genomic regions should be of importance in designing and interpretation of molecular anthropology and disease association studies.
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.
Anatomically modern hunter-gatherers expanded from Africa into Southeast Asia at least 50,000 years ago, where they probably encountered and interacted with populations of Homo erectus and Homo floresiensis and the recently discovered Denisovans. Simulation studies suggest that these hunter-gatherers may well have followed a coastal route that ultimately led to the settlement of Sahul, while archaeology confirms that they also crossed significant seas and explored well into the interior. They also adapted to marked environmental changes that alternated between relatively cool and dry conditions and warmer, wetter interludes. During the former, the sea fell by up to 120 m below its present level, which opened up a vast low-lying area known as Sundaland. Three principal alignments can be identified: the first involved the occupation of rock shelters in upland regions, the second has identified settlement on broad riverine floodplains, and the last concentrated on the raised beaches formed from about five millennia ago when the sea level was elevated above its present position. This cultural sequence was dislocated about 4 kya when rice and millet farmers infiltrated the lowlands of Southeast Asia ultimately from the Yangtze River valley. It is suggested that this led to two forms of interaction. In the first, the indigenous hunter-gatherers integrated with intrusive Neolithic communities and, while losing their cultural identity, contributed their genes to the present population of Southeast Asia. In the second, hunter-gatherers withdrew to rainforest refugia and, through selective pressures inherent in such an environment, survived as the small-bodied, dark-skinned humans found to this day in the Philippines, Peninsular Malaysia and Thailand, and the Andaman Islands. Beyond the impact of expansive rice farmers in Melanesia and Australia, hunter-gatherers continued to dominate until they encountered European settlement.