American Indian prehistory as written in the mitochondrial DNA: a review.

Native Americans have been divided into three linguistic groups: the reasonably well-defined Eskaleut and Nadene of northern North America and the highly heterogeneous Amerind of North, Central, and South America. The heterogeneity of the Amerinds has been proposed to be the result of either multiple independent migrations or a single ancient migration with extensive in situ radiation. To investigate the origin and interrelationship of the American Indians, we examined the mitochondrial DNA (mtDNA) variation in 87 Amerinds (Pima, Maya, and Ticuna of North, Central, and South America, respectively), 80 Nadene (Dogrib and Tlingit of northwest North America and Navajo of the southwest North America), and 153 Asians from 7 diverse populations. American Indian mtDNAs were found to be directly descended from five founding Asian mtDNAs and to cluster into four lineages, each characterized by a different rare Asian mtDNA marker. Lineage A is defined by a HaeIII site gain at np 663, lineage B by a 9-bp deletion between the COII and tRNA(Lys) genes, lineage C by a HincII site loss at np 13259, and lineage D by an AluI site loss at np 5176. The North, Central, and South America Amerinds were found to harbor all four lineages, demonstrating that the Amerinds originated from a common ancestral genetic stock. The genetic variation of three of the four Amerind lineages (A, C, and D) was similar with a mean value of 0.084%, whereas the sequence variation in the fourth lineage (B) was much lower, raising the possibility of an independent arrival. By contrast, the Nadene mtDNAs were predominantly from lineage A, with 27% of them having a Nadene-specific RsaI site loss at np 16329. The accumulated Nadene variation was only 0.021%. These results demonstrate that the Amerind mtDNAs arose from one or maybe two Asian migrations that were distinct from the migration of the Nadene and that the Amerind populations are about four times older than the Nadene.     

Genetic variation of the mitochondrial DNA genome in American Indians is at mutation-drift equilibrium.

Several surveys have found evidence for founder effects in Amerindian mitochondrial DNA because of the existence of rare Asian morphs in high frequencies in some Amerindian populations and the occurrence of several new morphs not seen elsewhere in the world. These reports, however, do not address whether or not the present genetic variation in the mtDNA genome in Amerindians has reached the steady-state distribution predicted by the mutation-drift theory of population genetics. The present work suggests that in three Amerindian populations (Pima, Maya, and Ticuna) a steady state has apparently been reached, and hence the initial founder effect has probably dissipated during the evolution of Amerindians in the New World. This result is consistent with the genetic variation in nuclear genes in similar populations, shown through surveys of protein variation in earlier work and, more recently, in studies of restriction fragment length polymorphisms.     

Dramatic founder effects in Amerindian mitochondrial DNAs

Southwestern American Indian (Amerindian) mitochondrial DNAs (mtDNAs) were analyzed with restriction endonucleases and found to contain Asian restriction fragment length polymorphisms (RFLPs) but at frequencies very different from those found in Asia. One rare Asian HincII RFLP was found in 40% of the Amerindians. Several mtDNAs were discovered which have not yet been observed on other continents and different tribes were found to have distinctive mtDNAs. Since the mtDNA is inherited exclusively through the maternal lineage, these results suggest that Amerindian tribes were founded by small numbers of female lineages and that new mutations have been fixed in these lineages since their separation from Asia.     

Genome-wide analysis in brazilian xavante indians reveals low degree of admixture

Characterization of population genetic variation and structure can be used as tools for research in human genetics and population isolates are of great interest. The aim of the present study was to characterize the genetic structure of Xavante Indians and compare it with other populations. The Xavante, an indigenous population living in Brazilian Central Plateau, is one of the largest native groups in Brazil. A subset of 53 unrelated subjects was selected from the initial sample of 300 Xavante Indians. Using 86,197 markers, Xavante were compared with all populations of HapMap Phase III and HGDP-CEPH projects and with a Southeast Brazilian population sample to establish its population structure. Principal Components Analysis showed that the Xavante Indians are concentrated in the Amerindian axis near other populations of known Amerindian ancestry such as Karitiana, Pima, Surui and Maya and a low degree of genetic admixture was observed. This is consistent with the historical records of bottlenecks experience and cultural isolation. By calculating pair-wise F(st) statistics we characterized the genetic differentiation between Xavante Indians and representative populations of the HapMap and from HGDP-CEPH project. We found that the genetic differentiation between Xavante Indians and populations of Ameridian, Asian, European, and African ancestry increased progressively. Our results indicate that the Xavante is a population that remained genetically isolated over the past decades and can offer advantages for genome-wide mapping studies of inherited disorders.     

The Uto‐Aztecan premolar among North and South Amerindians: Geographic variation and genetics

The Uto‐Aztecan premolar (UAP) is a dental polymorphism characterized by an exaggerated distobuccal rotation of the paracone in combination with the presence of a fossa at the intersection of the distal occlusal ridge and distal marginal ridge of upper first premolars. This trait is important because, unlike other dental variants, it has been found exclusively in Native American populations. However, the trait's temporal and geographic variation has never been fully documented. The discovery of a Uto‐Aztecan premolar in a prehistoric skeletal series from northern South America calls into question the presumed linguistic and geographic limits of this trait. We examined published and unpublished data for this rare but highly distinctive trait in samples representing over 5,000 Native Americans from North and South America. Our findings in living Southwest Amerindian populations corroborate the notion that the variable goes beyond the bounds of the Uto‐Aztecan language family. It is found in prehistoric Native Americans from South America, eastern North America, Northern and Central Mexico, and in living and prehistoric populations in the American Southwest that are not members of the Uto‐Aztecan language stock. The chronology of samples, its geographic distribution, and trait frequencies suggests a North American origin (Southwest) for UAP perhaps between 15,000 BP and 4,000 BP and a rapid and widespread dispersal into South America during the late Holocene. Family data indicate that it may represent an autosomal recessive mutation that occurred after the peopling of the Americas as its geographic range appears to be limited to North and South Amerindian populations. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Possible migration routes into South America deduced from mitochondrial DNA studies in Colombian Amerindian populations

Mitochondrial DNA haplotype studies have been useful in unraveling the origins of Native Americans. Such studies are based on restriction site and intergenic deletion/insertion polymorphisms, which define four main haplotype groups common to Asian and American populations. Several studies have characterized these lineages in North, Central, and South American Amerindian, as well as Na Dene and Aleutian populations. Siberian, Central Asian, and Southeast Asian populations have also been analyzed, in the hope of fully depicting the route(s) of migration between Asia and America. Colombia, a key route of migration between North and South America, has until now not been studied. To resolve the current lack of information about Colombian Amerindian populations, we have investigated the presence of the founder haplogroups in 25 different ethnic groups from all over the country. The present research is part of an interdisciplinary program, Expedición Humana, fostered by the Universidad Javeriana and Dr. J. E. Bernal V. The results show the presence of the four founder A-D Amerindian lineages, with varied distributions in the different populations, as well as the presence of other haplotypes in frequencies ranging from 3% to 26%. These include some unique or private polymorphisms, and also indicate the probable presence of other Asian and a few non-Amerindian lineages. A spatial structure is apparent for haplogroups A and D, and to a lesser extent for haplogroup C. While haplogroup A and D frequencies in Colombian populations from the northwestern side of the Andes resemble those seen in Central American Amerindians more than those seen in South American populations, their frequencies on the southeastern side more closely resemble the bulk of South American frequencies so far reported, raising the question as to whether they reflect more than one migration route into South America. High frequencies of the B lineage are also characteristic of some populations. Our observations may be explained by historical events during the pre-Columbian dispersion of the first settlers and, later, by disruptions caused by the European colonization.     

Native American Mitochondrial DNA Analysis Indicates That the Amerind and the Nadene Populations Were Founded by Two Independent Migrations

Mitochondrial DNAs (mtDNAs) from 167 American Indians including 87 Amerind-speakers (Amerinds) and 80 Nadene-speakers (Nadene) were surveyed for sequence variation by detailed restriction analysis. All Native American mtDNAs clustered into one of four distinct lineages, defined by the restriction site variants: HincII site loss at np 13,259, AluI site loss at np 5,176, 9-base pair (9-bp) COII-tRNA(Lys) intergenic deletion and HaeIII site gain at np 663. The HincII np 13,259 and AluI np 5,176 lineages were observed exclusively in Amerinds and were shared by all such tribal groups analyzed, thus demonstrating that North, Central and South American Amerinds originated from a common ancestral genetic stock. The 9-bp deletion and HaeIII np 663 lineages were found in both the Amerinds and Nadene but the Nadene HaeIII np 663 lineage had a unique sublineage defined by an RsaI site loss at np 16,329. The amount of sequence variation accumulated in the Amerind HincII np 13,259 and AluI np 5,176 lineages and that in the Amerind portion of the HaeIII np 663 lineage all gave divergence times in the order of 20,000 years before present. The divergence time for the Nadene portion of the HaeIII np 663 lineage was about 6,000-10,000 years. Hence, the ancestral Nadene migrated from Asia independently and considerably more recently than the progenitors of the Amerinds. The divergence times of both the Amerind and Nadene branches of the COII-tRNA(Lys) deletion lineage were intermediate between the Amerind and Nadene specific lineages, raising the possibility of a third source of mtDNA in American Indians.     

Analysis of mtDNA variation in African populations reveals the most ancient of all human continent-specific haplogroups.

mtDNA sequence variation was examined in 140 Africans, including Pygmies from Zaire and Central African Republic (C.A.R.) and Mandenkalu, Wolof, and Pular from Senegal. More than 76% of the African mtDNAs (100% of the Pygmies and 67.3% of the Senegalese) formed one major mtDNA cluster (haplogroup L) defined by an African-specific HpaI site gain at nucleotide pair (np) 3592. Additional mutations subdivided haplogroup L into two subhaplogroups, each encompassing both Pygmy and Senegalese mtDNAs. A novel 12-bp homoplasmic insertion in the intergenic region between tRNA(Tyr) and cytochrome oxidase I (COI) genes was also observed in 17.6% of the Pygmies from C.A.R. This insertion is one of the largest observed in human mtDNAs. Another 25% of the Pygmy mtDNAs harbored a 9-bp deletion between the cytochrome oxidase II (COII) and tRNA(Lys) genes, a length polymorphism previously reported in non-African populations. In addition to haplogroup L, other haplogroups were observed in the Senegalese. These haplogroups were more similar to those observed in Europeans and Asians than to haplogroup L mtDNAs, suggesting that the African mtDNAs without the HpaI np 3592 site could be the ancestral types from which European and Asian mtDNAs were derived. Comparison of the intrapopulation sequence divergence in African and non-African populations confirms that African populations exhibit the largest extent of mtDNA variation, a result that further supports the hypothesis that Africans represent the most ancient human group and that all modern humans have a common and recent African origin. The age of the total African variation was estimated to be 101,000-133,000 years before present (YBP), while the age of haplogroup L was estimated at 98,000-130,000 YBP. These values substantially exceed the ages of all Asian- and European-specific mtDNA haplogroups.     

Mexican American ancestry-informative markers: examination of population structure and marker characteristics in European Americans, Mexican Americans, Amerindians and Asians

Markers with large differences in allele frequencies between ethnicities provide ancestry information that can be applied to genetic studies. We identified over 100 biallelic ancestry informative markers (AIMs) with large allele frequency differences between European Americans (EA) and Pima Amerindians from laboratory and database screens. For 35 of these markers, Mayan, Yavapai and Quechuan Amerindians were genotyped and compared with EA and Pima allele frequencies. Markers with large allele frequency differences between EA and one Amerindian tribe showed only small differences between the Amerindian tribes. Examination of structure in individuals demonstrated a clear separation of subjects of European from those of Amerindian ancestry, and similarity between individuals from disparate Amerindian populations. The AIMs demonstrated the variation in ancestral composition of individual Mexican Americans, providing evidence of applicability in admixture mapping and in controlling for structure in association tests. In addition, a high percentage of single-nucleotide polymorphisms (SNPs) selected on the basis of large frequency differences between EA and Asian populations had large allele frequency differences between EA and Amerindians, suggesting an efficient method for greatly expanding AIMs for use in admixture mapping/structure analysis in Mexican Americans. Together, these data provide additional support for the practical application of admixture mapping in the Mexican American population.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Amerindian and NonAmerindian Autosome Molecular Variability – A Test Analysis

Analysis of 404 microsatellites, and 2–9 site haplotypes obtained considering 17 loci, all of them widely distributed over the human chromosomes and retrieved from two large data banks, yielded basically the same results. Colonization of the Americas may have led to some loss of genetic variability, but the range of differences found among five Native American populations was two times higher than those found between the most variable Amerindian (Maya) and a control Yoruba sample. Differentiation within the continent and the relatively recent history of these groups should be always considered in any discussion of Native American genetic variability.     

Tooth size of Ticuna Indians,Colombia, with phenetic comparisons to other Amerindian

This study reports on odontometric analyses of unadmixed, adult Ticuna Indians, Colombia, South America. This group is characterized by crown diameters intermediate in size relative to the known Amerindian range and, in turn, to the range in modern man. Sex dimorphism is absent in Ticuna tooth size; there is a strong retention of the M1 > M2 size sequence. The Ticuna are compared multivariately to other Indian groups reported in the literature, using the size and shape coefficients of L.S. Penrose. Tooth size clusters the groups into small, medium, and large-toothed classes, but does not yield a pattern attributable to known genetic or historical affinities. Shape coefficients distinguish Indians from non-Indians (Caucasian, Negroid, and Australian samples), primarily on the basis of I1–I2 proportionalities. Neither size nor shape discriminates between North and South American groups.     

mtDNA haplogroup X: An ancient link between Europe/Western Asia and North America?

On the basis of comprehensive RFLP analysis, it has been inferred that approximately 97% of Native American mtDNAs belong to one of four major founding mtDNA lineages, designated haplogroups "A"-"D." It has been proposed that a fifth mtDNA haplogroup (haplogroup X) represents a minor founding lineage in Native Americans. Unlike haplogroups A-D, haplogroup X is also found at low frequencies in modern European populations. To investigate the origins, diversity, and continental relationships of this haplogroup, we performed mtDNA high-resolution RFLP and complete control region (CR) sequence analysis on 22 putative Native American haplogroup X and 14 putative European haplogroup X mtDNAs. The results identified a consensus haplogroup X motif that characterizes our European and Native American samples. Among Native Americans, haplogroup X appears to be essentially restricted to northern Amerindian groups, including the Ojibwa, the Nuu-Chah-Nulth, the Sioux, and the Yakima, although we also observed this haplogroup in the Na-Dene-speaking Navajo. Median network analysis indicated that European and Native American haplogroup X mtDNAs, although distinct, nevertheless are distantly related to each other. Time estimates for the arrival of X in North America are 12,000-36,000 years ago, depending on the number of assumed founders, thus supporting the conclusion that the peoples harboring haplogroup X were among the original founders of Native American populations. To date, haplogroup X has not been unambiguously identified in Asia, raising the possibility that some Native American founders were of Caucasian ancestry.     

INTRASPECIFIC MOLECULAR PHYLOGENY IN THE YELLOW WARBLER (DENDROICA PETECHIA), AND IMPLICATIONS FOR AVIAN BIOGEOGRAPHY IN THE WEST INDIES

A phylogenetic analysis of mitochondrial DNA (mtDNA) restriction sites was used to examine the evolutionary history of populations of yellow warbler (Dendroica petechia) sampled from North America, Central America, South America, and the West Indies. Thirty-seven haplotypes were identified, and only one was found in more than one of these regions. Estimated sequence divergence among haplotypes ranged from 0.14 to 3.17%, and mtDNAs from North American migratory populations clearly were differentiated from those of most tropical sedentary populations. Parsimony analysis of haplotypes suggested multiple colonizations of the West Indies archipelago and of individual Caribbean islands. The inference of multiple colonizations has important implications for studies of avian ecology and evolution in this region.     

Diabetes, the ice free corridor, and the Paleoindian settlement of North America

Since the 1940s, many Amerindian populations, including some with mixed Amerindian ancestry, have experienced an epidemic of obesity and adult-onset diabetes (NIDDM). Obesity and NIDDM were apparently rare among Amerindian populations prior to that time. Though the evidence is equivocal, obesity and NIDDM seem to be rare today among Athapaskan Amerindians of the North American Arctic, sub-Arctic, and Southwest. It is hypothesized that the Amerindian genotype(s) susceptible to obesity and NIDDM arose from selection favoring "thrifty" genes during the peopling of North America south of the continental glaciers. "Thrifty" genes (Neel: Am. J. Hum. Genet. 14:353-362, 1962) allowed a more efficient food metabolism as hunter-gatherers from an unusually harsh mid-latitude tundra environment (the "ice free" corridor) adapted to more typical mid-latitude environments to the south. The early Paleoindian settlement pattern from Wyoming to Arizona and Texas indicates a relatively brief period of reliance on unpredictable big game resources in lower elevations and smaller game and gathered resources in higher elevations. This unusual "specialist" settlement pattern may have resulted from the early Paleoindian's unfamiliarity with gathered foods and small game in lower elevations. Athapaskan populations evidently moved south from Beringia sometime after the Paleoindian migration when the "ice free" corridor had widened and contained environments and resources more typical of subarctic latitudes. Thus, Athapaskan hunter-gatherers could gradually adapt to the resources of lower latitudes such that "thrifty" genes would not have been as advantageous. The interaction of recently introduced "western" diets and "thrifty" genes have evidently led to today's epidemic of obesity and NIDDM among Amerindians of Paleoindian ancestry.     

Discrepancy between Cranial and DNA Data of Early Americans: Implications for American Peopling

Currently, one of the major debates about the American peopling focuses on the number of populations that originated the biological diversity found in the continent during the Holocene. The studies of craniometric variation in American human remains dating from that period have shown morphological differences between the earliest settlers of the continent and some of the later Amerindian populations. This led some investigators to suggest that these groups—known as Paleomericans and Amerindians respectively—may have arisen from two biologically different populations. On the other hand, most DNA studies performed over extant and ancient populations suggest a single migration of a population from Northeast Asia. Comparing craniometric and mtDNA data of diachronic samples from East Central Argentina dated from 8,000 to 400 years BP, we show here that even when the oldest individuals display traits attributable to Paleoamerican crania, they present the same mtDNA haplogroups as later populations with Amerindian morphology. A possible explanation for these results could be that the craniofacial differentiation was a local phenomenon resulting from random (i.e. genetic drift) and non-random factors (e.g. selection and plasticity). Local processes of morphological differentiation in America are a probable scenario if we take into consideration the rapid peopling and the great ecological diversity of this continent; nevertheless we will discuss alternative explanations as well.     

Founding Amerindian mitochondrial DNA lineages in ancient Maya from Xcaret, Quintana Roo

Ancient DNA from the bone remains of 25 out of 28 pre-Columbian individuals from the Late Classic-Postclassic Maya site of Xcaret, Quintana Roo, was recovered, and mitochondrial DNA (mtDNA) was amplified by using the polymerase chain reaction. The presence of the four founding Amerindian mtDNA lineages was investigated by restriction analysis and by direct sequencing in selected individuals. The mtDNA lineages A, B, and C were found in this population. Eighty-four percent of the individuals were lineage A, whereas lineages B and C were present at low frequencies, 4% and 8%, respectively. Lineage D was absent from our sample. One individual did not possess any of the four lineages. Six skeletons out of 7 dated from the Late Classic period were haplotype A, whereas 11 skeletons out of 16 dated from the Postclassic period were also haplotype A. The distribution of mtDNA lineages in the Xcaret population contrasts sharply with that found in ancient Maya from Copán, which lack lineages A and B. On the other hand, our results resemble more closely the frequencies of mtDNA lineages found in contemporary Maya from the Yucatán Peninsula and in other Native American contemporary populations of Mesoamerican origin.     

Reconstructing the population history of Puerto Rico by means of mtDNA phylogeographic analysis

The haplogroup identities of 800 mtDNAs randomly and systematically selected to be representative of the population of Puerto Rico were determined by restriction fragment length polymorphism (RFLP), revealing maternal ancestries in this highly mixed population of 61.3% Amerindian, 27.2% sub‐Saharan African, and 11.5% West Eurasian. West Eurasian frequencies were low in all 28 municipalities sampled, and displayed no geographic patterns. Thus, a statistically significant negative correlation was observed between the Amerindian and African frequencies of the municipalities. In addition, a statistically highly significant geographic pattern was observed for Amerindian and African mtDNAs. In a scenario in which Amerindian mtDNAs prevailed on either side of longitude 66°16′ West, Amerindian mtDNAs were more frequent west of longitude 66°16′ West than east of it, and the opposite was true for African mtDNAs. Haplogroup A had the highest frequency among Amerindian samples (52.4%), suggesting its predominance among the native Taínos. Principal component analysis showed that the sub‐Saharan African fraction had a strong affinity to West Africans. In addition, the magnitudes of the Senegambian and Gulf of Guinea components in Puerto Rico were between those of Cape Verde and São Tomé. Furthermore, the West Eurasian component did not conform to European haplogroup frequencies. HVR‐I sequences of haplogroup U samples revealed a strong North African influence among West Eurasian mtDNAs and a new sub‐Saharan African clade. Am J Phys Anthropol 128:131‐155, 2005. © 2005 Wiley‐Liss, Inc.     

mtDNA variation of aboriginal Siberians reveals distinct genetic affinities with Native Americans.

The mtDNA variation of 411 individuals from 10 aboriginal Siberian populations was analyzed in an effort to delineate the relationships between Siberian and Native American populations. All mtDNAs were characterized by PCR amplification and restriction analysis, and a subset of them was characterized by control region sequencing. The resulting data were then compiled with previous mtDNA data from Native Americans and Asians and were used for phylogenetic analyses and sequence divergence estimations. Aboriginal Siberian populations exhibited mtDNAs from three (A, C, and D) of the four haplogroups observed in Native Americans. However, none of the Siberian populations showed mtDNAs from the fourth haplogroup, group B. The presence of group B deletion haplotypes in East Asian and Native American populations but their absence in Siberians raises the possibility that haplogroup B could represent a migratory event distinct from the one(s) which brought group A, C, and D mtDNAs to the Americas. Our findings support the hypothesis that the first humans to move from Siberia to the Americas carried with them a limited number of founding mtDNAs and that the initial migration occurred between 17,000-34,000 years before present.     

Linguistic and maternal genetic diversity are not correlated in Native Mexicans

Mesoamerica, defined as the broad linguistic and cultural area from middle southern Mexico to Costa Rica, might have played a pivotal role during the colonization of the American continent. The Mesoamerican isthmus has constituted an important geographic barrier that has severely restricted gene flow between North and South America in pre-historical times. Although the Native American component has been already described in admixed Mexican populations, few studies have been carried out in native Mexican populations. In this study, we present mitochondrial DNA (mtDNA) sequence data for the first hypervariable region (HVR-I) in 477 unrelated individuals belonging to 11 different native populations from Mexico. Almost all of the Native Mexican mtDNAs could be classified into the four pan-Amerindian haplogroups (A2, B2, C1, and D1); only two of them could be allocated to the rare Native American lineage D4h3. Their haplogroup phylogenies are clearly star-like, as expected from relatively young populations that have experienced diverse episodes of genetic drift (e.g., extensive isolation, genetic drift, and founder effects) and posterior population expansions. In agreement with this observation, Native Mexican populations show a high degree of heterogeneity in their patterns of haplogroup frequencies. Haplogroup X2a was absent in our samples, supporting previous observations where this clade was only detected in the American northernmost areas. The search for identical sequences in the American continent shows that, although Native Mexican populations seem to show a closer relationship to North American populations, they cannot be related to a single geographical region within the continent. Finally, we did not find significant population structure in the maternal lineages when considering the four main and distinct linguistic groups represented in our Mexican samples (Oto-Manguean, Uto-Aztecan, Tarascan, and Mayan), suggesting that genetic divergence predates linguistic diversification in Mexico.     

Mitochondrial DNA studies show asymmetrical Amerindian admixture in Afro-Colombian and Mestizo populations

The origin of the African populations that arrived on the Colombian coasts at the time of the Spanish conquest and their subsequent settlement throughout the country and interaction with Amerindian and Spanish populations are features that can be analyzed through the study of mitochondrial DNA (mtDNA) markers. For this purpose, the present study investigates the admixture between these populations by analyzing the markers defining the main (A, B, C, D) and minor (X) founder haplogroups in Native Americans, the principal African haplogroup (L), and additional generic markers present in Caucasian (I, J, K, H, T, U, V, W) and minor African lineages (L3). As part of an interdisciplinary research program (the Expedición Humana, furthered by the Universidad Javeriana and directed by J.E. Bernal V.), 159 Afro-Colombians from five populations in which they are the majority and 91 urban Mestizos were studied. No Amerindian haplogroups (A-D, X) were detected in 81% of the Afro-Colombians. In those samples with Amerindian lineages (average 18.8%, with a range from 10% to 43%), haplogroup B predominated. When analyzed for the presence of African haplotypes, Afro-Colombians showed an overall frequency of 35.8% for haplogroup L mtDNAs, although with broad differences between populations. A few Afro-Colombian samples (1.9%) had mutations that have not been described before, and might therefore be considered as previously unsampled African variants or as new mutations arising in the American continent. Conversely, in Mestizos less than 22% of their mtDNAs belonged to non-Amerindian lineages, of which most were likely to be West Eurasian in origin. Haplogroup L mtDNAs were found in only one Mestizo (1.1%), indicating that, if present, admixture with African women would bring in other, rarer African lineages. On the other hand, in an accompanying paper (Keyeux et al. 2002) we have shown that Amerindians from Colombia have experienced little or no matrilineal admixture with Caucasians or Africans. Taken together, these results are evidence of different patterns of past ethnic admixture among Africans, Amerindians, and Spaniards in the geographic region now encompassing Colombia, which is also reflected in much of the region's cultural diversity.