The Ticuna are an Amerindian tribe of Central Amazonas, a key location in theories of the peopling of eastern South America. The results of typing some 1760 members of the tribe with respect to 37 different genetic systems are reported, as are the results of HLA typings on a subsample of 129 persons. Salient findings include the following. (1) Except for a high frequency of LMs allele and an unusual combination of HLA allele frequencies, there are no notable findings with respect to the commonly studied polymorphic systems. A multivariate treatment of six of the most commonly studied genetic polymorphisms accords the Ticuna an 'average' position among Amerindian tribes. (2) There is much less intervillage heterogenicity than usually encountered in Amerindian tribes; this is attributed to recent high rates of intervillage migration due to religious developments. (3) A thus-far unique polymorphism of ACP1 was identified, the responsible allele having a frequency of 0.111. (4) In proportion to the size of the tribe, there was a relative paucity of 'private' genetic variants, the ACP1 allele being the only one. This discrepancy is attributed to a relatively recent numerical expansion of the tribe; effective population size over the past several thousand years is thought to have been well below what present numbers would suggest. (5) The thesis is again advanced that 'private variants' (alleles not occurring as polymorphisms of wide distribution) are more common in Amerindian than in Caucasian or Japanese populations.

Demographic data and genetic information concerning 40 genetic systems are reported for three populations of Macushi Indians, and have been compared to those already obtained for three other communities of this tribe. These are young populations (mean age, 19 years), with a low sex ratio (90), low percentages of non-Indian ancestry (1-2%) and of marriages between locally born persons (34). Intertribal unions (14%) are less frequent than among their neighbours, the Wapishana. Fertility is high (average of 8.2 children per woman who completed reproduction), but the variance in family size and the frequency of premature deaths relatively low for populations at this cultural level. This conditions the lowest Index of Opportunity for Selection (0.45) calculated thus far among South American Indians. No variation was observed in 20 genetic systems, limited variation in 3, and larger variability in the remaining 17. In 13 of the 29 comparisons (45%), the Macushi gene frequencies present values in the middle third of the range observed among South American Indians. The previously reported private genetic polymorphism of esterase A was encountered in one of the three villages. A comparison of the genetic distances between villages with and without this polymorphism, and a similar comparison for the villages of the neighbouring Wapishana, yields no clue as to the tribe in which this polymorphism originated.

The distributions of Gm(a, x, f, b, c, g, and t) and Inv(l) allotypic markers have been examined in 512 Chinese classified as to province of origin. The results indi cate a south to north cline, extending from southernmost to northern China in which Gm^ag changes from 0.12 to 0.55, Gm^axg from 0.04 to 0.15, Gm^abst from 0.04 to 0.12 and Gm^afb from 0.80 to 0.22. In contrast to the Gm system, there does not appear to be any significant regional variation in the frequency of Inv¹ among Chinese.

Immunoglobulin (Gm and Km) allotype and haplotype frequencies are presented for 1707 individuals from Northern Chile and Western Bolivia, subdividing them by ethnicity and altitude of residence. The haplotype distribution of Gm as well as Km loci in these populations suggest that in almost all of the ethnicity x altitude subdivisions of this population considerable admixture of Amerindian and Caucasian genes have occurred. The haplotype frequency heterogeneity and the analysis of departure from Hardy-Weinberg expectations demonstrate that while some local variation in haplotype frequencies at the Gm and Km loci exists in this region, there is no clear evidence suggesting that the pattern of variation is due to an adaptation to the hypoxia of altitude. We conclude that such differences in haplotype frequencies are probably due to random genetic drift and differential admixture of Amerindian and Caucasian genes that have occurred in the past.