Demographic History of Indigenous Populations in Mesoamerica Based on mtDNA Sequence Data

The genetic characterization of Native American groups provides insights into their history and demographic events. We sequenced the mitochondrial D-loop region (control region) of 520 samples from eight Mexican indigenous groups. In addition to an analysis of the genetic diversity, structure and genetic relationship between 28 Native American populations, we applied Bayesian skyline methodology for a deeper insight into the history of Mesoamerica. AMOVA tests applying cultural, linguistic and geographic criteria were performed. MDS plots showed a central cluster of Oaxaca and Maya populations, whereas those from the North and West were located on the periphery. Demographic reconstruction indicates higher values of the effective number of breeding females (Nef) in Central Mesoamerica during the Preclassic period, whereas this pattern moves toward the Classic period for groups in the North and West. Conversely, Nef minimum values are distributed either in the Lithic period (i.e. founder effects) or in recent periods (i.e. population declines). The Mesomerican regions showed differences in population fluctuation as indicated by the maximum Inter-Generational Rate (IGRmax): i) Center-South from the lithic period until the Preclassic; ii) West from the beginning of the Preclassic period until early Classic; iii) North characterized by a wide range of temporal variation from the Lithic to the Preclassic. Our findings are consistent with the genetic variations observed between central, South and Southeast Mesoamerica and the North-West region that are related to differences in genetic drift, structure, and temporal survival strategies (agriculture versus hunter-gathering, respectively). Interestingly, although the European contact had a major negative demographic impact, we detect a previous decline in Mesoamerica that had begun a few hundred years before.     

The Role of Social Stratification in the Aztec Empire: A View from the Provinces

This paper explores the role of social stratification in the regional organization of the Triple Alliance, or Aztec empire. Unlike previous interpretations that see military coercion as the main force integrating the empire, I argue that the primary integrative factor was collusion between rulers of the core states and the nobility of the provinces, who gained economic rewards for their participation in the tribute empire. The common interest of the Mesoamerican nobility transcended political boundaries. The fundamental social and economic cleavage in Postclassic Mesoamerica was not between the Triple Alliance states and the provinces, as many have argued, but rather between the nobles and the commoners. The proposed model is supported through examination of the provincial polity of Cuauhnahuac in western Morelos, Mexico.     

Kingship in the Late Preclassic Maya Lowlands: The Instruments and Places of Ritual Power

The Maya of Central America constitute the only truly literate pre-Columbian civilization. Analysis of ancient Maya hieroglyphic texts and accompanying images dating from the Classic period (A.D. 200–900) documents the presence of a central and pervasive institution of governance: ahaw. The material symbol systems of the Lowland Maya of the protoliterate Late Preclassic period (350 B.C.-A.D. 100), as evinced in monumental decorated buildings and in portable art, suggest that these Maya innovated ahaw, the institution of kingship. The authority of ahaw rested upon direct descent and spiritual communion with the ancestors of all Maya, the Ancestral Heroes. Along with noble lineage, ahaw claimed charismatic power through the performance of shamanistic ritual. The Late Preclassic antecedents of the shamanistic parameters of ahaw are discussed in light of Classic and Postclassic ritual expressions.     

Bioarchaeological investigation of ancient Maya violence and warfare in inland northwest Yucatan,Mexico

This study investigates evidence of changes and continuities in ancient Maya violence and warfare in inland northwest Yucatan, Mexico from the Middle Preclassic (600–300 BC) to the Postclassic (AD 1050–1542) through bioarchaeological analysis of cranial and projectile trauma. It is hypothesized that the frequency of violence increases before the Classic Maya collapse and remains high during the Postclassic period. It is also hypothesized that the flat, open terrain was conducive to warfare and resulted in higher trauma frequencies than in other parts of the Maya area. Results show that the frequency of cranial trauma decreases before the Classic collapse and increases in the Postclassic, partially matching the expected chronological trends. The frequency of cranial trauma does not differ significantly from other Maya regions but the pattern does: for all periods, males have more healed injuries than females and they are concentrated on the left side of the anterior of the skull. Some injuries appear to be from small points hafted in wooden clubs. In addition, projectile trauma is evident in a scapula with an embedded arrowhead tip, the first such case reported in a Maya skeleton. Overall, these results suggest greater reliance on open combat and less on raids in this region compared with other parts of the Maya area, possibly due to the flat, open terrain, though the identification of perimortem trauma in both women and men indicates surprise raids on settlements were also practiced. Am J Phys Anthropol 154:140–151, 2014. © 2014 Wiley Periodicals, Inc.     

Geographical patterns of genetic divergence in the widespread Mesoamerican bumble bee Bombus ephippiatus (Hymenoptera: Apidae)

Bumble bees (Bombus Latreille) are an important group of social insects, well recognized throughout northern temperate regions as important pollinators of wild and agricultural plants. Little is known about the biology of this group in southern portions of the Americas, especially in Mesoamerica, a region of geological and ecological complexity from Mexico through Central America. One ubiquitous Mesoamerican species, Bombus ephippiatus, is enigmatic. Like many other Bombus, this species is homogeneous in body structure yet exhibits striking intraspecific color pattern polymorphism across its range, leading to uncertainty about its genealogical boundaries. It has been grouped taxonomically with B. wilmattae, a species narrowly restricted to southern Mexico and northern Guatamala. Furthermore, the relationships between these two taxa and a third species, B. impatiens, found only in America north of Mexico, have been controversial. Our phylogenetic analysis of DNA sequences from mitochondrial COI and nuclear PEPCK and CAD resolves the phylogeny of these three taxa as (B. impatiens, (B. ephippiatus, B. wilmattae)). Additional data from eight nuclear microsatellite markers reveal complex patterns of genetic divergence and isolation among populations of B. ephippiatus across its extensive geographic range, providing evidence for multiple independent evolutionary lineages. These lineages correspond not only to geographic and habitat variation across their range, but also to distinct color pattern groups present in the species. Knowledge of the phylogeny and genetic divergence of the B. ephippiatus group will provide a framework for understanding evolutionary and ecological origins of color pattern polymorphism in bumble bees, as well as providing insight into geographical factors enhancing speciation in Mesoamerica.     

Earliest Mexican Turkeys (Meleagris gallopavo) in the Maya Region: Implications for Pre-Hispanic Animal Trade and the Timing of Turkey Domestication

Late Preclassic (300 BC-AD 100) turkey remains identified at the archaeological site of El Mirador (Petén, Guatemala) represent the earliest evidence of the Mexican turkey (Meleagris gallopavo) in the ancient Maya world. Archaeological, zooarchaeological, and ancient DNA evidence combine to confirm the identification and context. The natural pre-Hispanic range of the Mexican turkey does not extend south of central Mexico, making the species non-local to the Maya area where another species, the ocellated turkey (Meleagris ocellata), is indigenous. Prior to this discovery, the earliest evidence of M. gallopavo in the Maya area dated to approximately one thousand years later. The El Mirador specimens therefore represent previously unrecorded Preclassic exchange of animals from northern Mesoamerica to the Maya cultural region. As the earliest evidence of M. gallopavo found outside its natural geographic range, the El Mirador turkeys also represent the earliest indirect evidence for Mesoamerican turkey rearing or domestication. The presence of male, female and sub-adult turkeys, and reduced flight morphology further suggests that the El Mirador turkeys were raised in captivity. This supports an argument for the origins of turkey husbandry or at least captive rearing in the Preclassic.     

The Postclassic to Spanish-Era Transition in Mesoamerica

The Postclassic to Spanish-Era Transition in Mesoamerica . Susan Kepecs and Rani Alexander, eds. Albuquerque: University of New Mexico Press, 2005. 260 pp.     

Late Holocene palaeoecology of Lago Verde: evidence of human impact and climate change in the northern limit of the neotropics during the late formative and classic periods

Multiproxy analysis (pollen, diatom, charcoal) on a 6 m core from Lago Verde (Sierra de Los Tuxtlas), shows evidences of environmental changes and human impact on the evergreen rainforest on the tropical lowlands of eastern Mexico during the last ca. 2,800 years. Prehistoric human occupation is recorded since the late Formative throughout the middle Classic (250 b.c.–ca. a.d. 800) by the presence of maize pollen, a low abundance of tropical arboreal taxa and a high abundance of herbaceous pollen and charcoal particles. This occurred under a scenario of very low lake levels from which dry conditions are inferred based on the dominance of aerophilous and periphytic diatom taxa. After ca. a.d. 800 the site was abandoned and forest regeneration started, at the same time higher lake levels, an indication of more humid conditions, were established. In the absence of human disturbance, tropical forest regeneration was rapid (ca. 200 years). Fluctuations in pollen composition during times of low human population at the site are related to climate variability, with the highest tropical forest diversity and lake levels recorded during the Little Ice Age. Modern human impact is also recorded and compared with the prehistoric deforestation event. Comparison with palaeoecological records from Yucatan and the highlands of central Mexico offers a Mesoamerican perspective of climatic variability giving evidence that the late Formative and early to middle Classic demographic expansion occurred under a scenario of climates dryer than present, with the Postclassic characterized by moister conditions. The end of the Classic (ca. a.d. 800–1000) is identified as a period of rapid climate change which marks one of the most important cultural transitions in Mesoamerica.     

Secular trend for stature in adult male Yucatec Maya to 1968

Statures for 64 adult male Yucatec Maya (18+ years old, sons of campesinos) were measured in 1968 and compared with mean statures presented in results for previous studies. There were no significant changes in mean stature since 1895. If the sample is divided into 5-year age groups, no secular trend is evident. Using osteological information from as early as the Late Preclassic, stature of adult Maya males has decreased 119 mm in a little more than 20 centuries (?0.06 cm/decade). Comparing the results with measurements from other Mesoamerican groups, only one – the Otomí – show evidence of significant secular change. It is possible that modern economic development schemes in Mesoamerica are too recent or ineffective to have had an effect on stature.     

On the origins,rapid expansion and genetic diversity of native Americans from hunting‐gatherers to agriculturalists

Given the importance of Y‐chromosome haplogroup Q to better understand the source populations of contemporary Native Americans, we studied 8 biallelic and 17 microsatellite polymorphisms on the background of 128 Q Y‐chromosomes from geographically targeted populations. The populations examined in this study include three from the Tuva Republic in Central Asia (Bai‐Tai, Kungurtug, and Toora‐Hem, n = 146), two from the northeastern tip of Siberia (New Chaplino and Chukchi, n = 32), and two from Mesoamerica (Mayans from Yucatan, Mexico n = 72, and Mayans from the Guatemalan Highlands, n = 43). We also see evidence of a dramatic Mesoamerican post‐migration population growth in the ubiquitous and diverse Y‐STR profiles of the Mayan and other Mesoamerican populations. In the case of the Mayans, this demographic growth was most likely fueled by the agricultural‐ and trade‐based subsistence adopted during the Pre‐Classic, Classic and Post‐Classic periods of their empire. The limited diversity levels observed in the Altaian and Tuvinian regions of Central Asia, the lowest of all populations examined, may be the consequence of bottleneck events fostered by the spatial isolation and low effective population size characteristic of a nomadic lifestyle. Furthermore, our data illustrate how a sociocultural characteristic such as mode of subsistence may be of impact on the genetic structure of populations. We analyzed our genetic data using Multidimensional Scaling Analysis of populations, Principal Component Analysis of individuals, Median‐joining networks of M242, M346, L54, and M3 individuals, age estimations based on microsatellite variation utilizing genealogical and evolutionary mutation rates/generation times and estimation of Y‐ STR average gene diversity indices. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc.     

Halffter's Mexican transition zone (1962–2014), cenocrons and evolutionary biogeography

The Mexican transition zone is the complex and varied area in which the Neotropical and Nearctic biotas overlap. In a series of contributions, Gonzalo Halffter provided a coherent theory that explains how sets of taxa that evolved in different geographical areas assembled in this transition zone. Halffter's theory developed gradually, being refined and clarified in successive contributions from him and other authors. After a review of the historical development of the Mexican transition zone, including the characterization of the dispersal or distributional patterns recognized by Halffter, its relevance for evolutionary biogeography is discussed briefly. The Mexican transition zone in the strict sense includes the highlands of Mexico and Guatemala (Sierra Madre Occidental, Sierra Madre Oriental, Transmexican Volcanic Belt, Sierra Madre del Sur and Chiapas Highlands provinces), whereas northern Mexico and the southern United States are clearly Nearctic, and the lowlands of southern Mexico and Central America are clearly Neotropical. The distributional patterns recognized by Halffter are considered to represent cenocrons (sets of taxa that share the same biogeographical history, constituting identifiable subsets within a biota by their common biotic origin and evolutionary history). The development of the Mexican transition zone is summarized into the following stages: (1) Jurassic–Cretaceous: the four Paleoamerican cenocrons extend in Mexico; (2) Late Cretaceous–Palaeocene: dispersal from South America of the Plateau cenocron; (3) Oligocene–Miocene: dispersal from the Central American Nucleus of the Mountain Mesoamerican cenocron; (4) Miocene–Pliocene: dispersal from North America of the Nearctic cenocron; and (5) Pleistocene: dispersal from South America of the Typical Neotropical cenocron.     

Assessing the impact of ancient Maya animal use

Tropical forest animals are at high risk worldwide as a result of over-exploitation and forest clearing. Zooarchaeological studies of animal use by the ancient Maya of the southern lowland regions of Guatemala, Honduras, Belize, and Mexico provide long-term historical information on animal populations under conditions of human population growth and climatic change that is valuable to both archaeology and conservation biology. In this paper, zooarchaeological data from 35 chronologically defined faunal sub-samples recovered from 25 ancient Maya archaeological sites are used to assess the effects of ancient hunting on animal populations of the Maya region between the Preclassic and Colonial periods (2000 BC–AD 1697). The variations in species abundance are used as a proxy for describing changes in ancient Maya hunting practices and hunted animal populations, interpreted on the basis of hunting efficiency models from foraging ecology. A significant reduction in the proportion of large mammals, particularly Odocoileus virginianus, in zooarchaeological assemblages between the Late Classic (AD 600–850) and Terminal Classic/Postclassic periods (AD 850–1519) suggest that over-hunting during the Late Classic may have led to a reduction in availability of these animals to the ancient Maya hunters in the later periods. This finding is discussed in relation to important social and environmental variations to evaluate the impact of hunting and other factors such as forest clearance and climate on ancient animal populations in the Maya region.     

Delineating genetic relationships among the Maya

By 250 AD, the Classic Maya had become the most advanced civilization within the New World, possessing the only well-developed hieroglyphic writing system of the time and an advanced knowledge of mathematics, astronomy and architecture. Though only ruins of the empire remain, 7.5 million Mayan descendants still occupy areas of Mexico, Guatemala, Belize, El Salvador, and Honduras. Although they inhabit distant and distinct territories, speak more than 28 languages, and have been historically divided by warfare and a city-state-like political system, and they share characteristics such as rituals, artistic, architectural motifs that distinguish them as unequivocally Maya. This study was undertaken to determine whether these similarities among Mayan communities mirror genetic affinities or are merely a reflection of their common culture. Four Mayan populations were investigated (i.e., the K'iche and Kakchikel from Guatemala and the Campeche and Yucatan from Mexico) and compared with previously published populations across 15 autosomal STR loci. As a whole, the Maya emerge as a distinct group within Mesoamerica, indicating that they are more similar to each other than to other Mesoamerican groups. The data suggest that although geographic and political boundaries existed among Mayan communities, genetic exchanges between the different Mayan groups have occurred, supporting theories of extensive trading throughout the empire.     

Proto-Uto-Aztecan: A Community of Cultivators in Central Mexico?

Authorities on the origin and history of Uto-Aztecan have held that speakers of the protolanguage were foragers who lived in upland regions of Arizona, New Mexico, and the adjacent areas of the Mexican states of Sonora and Chihuahua about 5,000 years ago. New lexical evidence supports a different view, that speakers of the protolanguage were maize cultivators. The Proto-Uto-Aztecan speech community was probably located in Mesoamerica and spread northward into the present range because of demographic pressure associated with cultivation. The chronology for the spread and differentiation of the family should then correspond to the chronology for the northward spread of maize cultivation from Mesoamerica into the U.S. Southwest, between 4500 and 3000 B.P. [ Uto-Aztecan, cultivation, Mesoamerican, historical linguistics, migration ]     

Tree squirrels: A key to understand the historic biogeography of Mesoamerica?

A multi-taxon historical biogeography approach (Brooks Parsimony Analysis) was used to estimate relationships among the Mesoamerican lowland and highland areas and the particular biogeographic history of Mesoamerican squirrels (Sciurus, Microsciurus and Syntheosciurus species). A total of 15 lowland areas and 12 highland areas plus 41 clades comprising 240 species (45,135 records) were employed to obtain Taxon-Area Cladograms and Area Cladograms. A single most parsimonious General Area Cladogram indicated a strong vicariant relationship between Southern Mexico and the remainder of Mesoamerica, and identified several vicariant nodes (Modern Chiapanencan Volcanic Arc, Honduras’ Great Central Depression, and Nicaraguan Depression) as well as historically independent highland areas. A secondary BPA in relation with Sciurus species showed several instances of post speciation dispersal or range expansion, lack of response to vicariant events, and, possibly, lineage duplication. The results obtained suggest that Mesoamerican biotas have been subjected to several major vicariant events, but the reticulated nature of some of its areas also indicates that dispersal (post-speciation dispersal and range expansion) had been important in the diversification of the Mesoamerican biota. This trend was also observed in the particular biogeographic history of Mesoamerican tree squirrels.     

Distillation in Western Mesoamerica before European Contact

Distillation in Western Mesoamerica before European Contact. Fermented beverages are almost universal among ancient human societies. Ethanol is an analgesic, disinfectant, and mind-altering substance, and can help to preserve and enhance the nutritional value of food. Fermentation has therefore played a key role in human cultural and technological development. In Mesoamerica, codices and colonial-era sources describe a variety of fermented beverages produced before European contact. Distilled beverages, in contrast, have not been invented in all cultures, and their production in pre-contact Mesoamerica remains controversial. We tested the hypothesis of Needham et al. (1980) that Capacha gourd and trifid vessels described by Kelly (1974) for the Early Formative (1500–1000 BCE) in Colima state, western Mexico, could have been used to produce distilled beverages. Experiments using vessel replicas, techniques, and materials (including agave ferment) available in this region during this period successfully produced ethanol-containing distillates. We propose the possible origin and development of a “Capacha-type Mesoamerican still” from bean pots or from steamer pots used during this period, and discuss the possible production of spirits as part of the prevailing agricultural and cultural system. Average gourd and trifid vessel sizes, their archaeological context, and the ethanol yields of the replicas suggest that, if used as stills, they were used to produce a prestige product for ceremonial purposes, with high social and cultural relevance.     

Local origin and diversification among Lampornis hummingbirds: a Mesoamerican taxon

The huge biodiversity found in Mesoamerica is often explained by its geographic situation as a natural bridge between two large biogeographic regions. Often overlooked, however, are the high levels of speciation and diversification in the area. Here we assess the phylogenetic relationships within a Mesoamerican group of hummingbirds (Lampornis). We sequenced both mtDNA (1,143 bp of cyt b and 727 bp of ND5) and nuclear genes (505 bp of AK-5 intron and 567 bp of c-mos) for each of the seven recognised species and outgroups. We find two or three clades of similar age within this genus: L. clemenciae and L. amethystinus (singly or as each other's sister taxa) and a Central American clade. This Central-American clade presents a clear bipartition between northern (L. viridipallens and L. sybillae) and southern Mesoamerica, which is shared with many other Mesoamerican organisms. Our analyses suggest that L. hemileucus does not belong in the genus Lampornis. While we refrain to apply a time-scale to our data because of the lack of an appropriate calibration, our results indicate that the genus Lampornis predates the uprising of the Panama land-bridge, and that diversification among the isthmian species (L. castaneoventris and L. calolaema) is a very recent event. Our results strongly suggest a local Mesoamerican origin for this genus.     

Genetic structure of Mesoamerican populations of Big-leaf mahogany (Swietenia macrophylla) inferred from microsatellite analysis

While microsatellites have been used to examine genetic structure in local populations of Neotropical trees, genetic studies based on such high-resolution markers have not been carried out for Mesoamerica as a whole. Here we assess the genetic structure of the Mesoamerican mahogany Swietenia macrophylla King (big-leaf mahogany), a Neotropical tree species recently listed as endangered in CITES which is commercially extinct through much of its native range. We used seven variable microsatellite loci to assess genetic diversity and population structure in eight naturally established mahogany populations from six Mesoamerican countries. Measures of genetic differentiation (FST and RST) indicated significant differences between most populations. Unrooted dendrograms based on genetic distances between populations provide evidence of strong phylogeographic structure in Mesoamerican mahogany. The two populations on the Pacific coasts of Costa Rica and Panama were genetically distant from all the others, and from one another. The remaining populations formed two clusters, one comprised of the northern populations of Mexico, Belize and Guatemala and the other containing the southern Atlantic populations of Nicaragua and Costa Rica. Significant correlation was found between geographical distance and all pairwise measures of genetic divergence, suggesting the importance of regional biogeography and isolation by distance in Mesoamerican mahogany. The results of this study demonstrate greater phylogeographic structure than has been found across Amazon basin S. macrophylla. Our findings suggest a relatively complex Mesoamerican biogeographic history and lead to the prediction that other Central American trees will show similar patterns of regional differentiation.     

Phylogeography of Liquidambar styraciflua (Altingiaceae) in Mesoamerica: survivors of a Neogene widespread temperate forest (or cloud forest) in North America?

We investigate the genetic variation between populations of the American sweetgum (Liquidambar styraciflua), a tree species with a disjunct distribution between northeastern Texas and Mexico, by analyzing sequences of two chloroplast DNA plastid regions in Mesoamerica. Our results revealed phylogeographical structure, with private haplotypes distributed in unique environmental space at either side of the Trans‐Mexican Volcanic Belt, and a split in the absence of gene flow dating back ca. 4.2–1.4 million years ago (MYA). Species distribution modeling results fit a model of refugia along the Gulf and Atlantic coasts but the present ranges of US and Mesoamerican populations persisted disjunct during glacial/interglacial cycles. Divergence between the US and Mesoamerican (ca. 8.4–2.8 MYA) populations of L. styraciflua and asymmetrical gene flow patterns support the hypothesis of a long‐distance dispersal during the Pliocene, with fragmentation since the most recent glacial advance (120,000 years BP) according to coalescent simulations and high effective migration rates from Mesoamerica to the USA and close to zero in the opposite direction. Our findings implicate the Trans‐Mexican Volcanic Belt as a porous barrier driving genetic divergence of L. styraciflua, corresponding with environmental niche differences, during the Pliocene to Quaternary volcanic arc episode 3.6 MYA, and a Mesoamerican origin of populations in the USA.