Research orientation

My research is focused primarily on the genetic and environmental risk factors for type 2 diabetes in American Indians, a population disproportionately affected by this disorder.  I investigate these factors using statistical genetics methods.  In my secondary research, I use paleopathology and skeletal biology to examine the use and treatment of domesticated dogs in prehistory. These disparate research areas are connected by my interest in the relationship between biological variation, cultural practices, and the environment.   

My anthropological genetics research is broadly focused on the factors contributing to complex phenotypes (traits) in living humans.  Variation in complex phenotypes is influenced by the combined effects of multiple genetic and environmental factors and their interactions.  "Environment" includes age, sex, and lifestyle variables such as diet or smoking.  Most phenotypes are complex, for example, stature, handedness, or susceptibility to diabetes and many other diseases of public health importance.  The identification of genetic and other complex disease risk factors is essential to understanding biologic pathways and for developing disease treatments and interventions.  

The specialized statistical methods that I use to identify and characterize the genetic and environmental components of complex phenotypes include linkage analyses, which are used to map variation in phenotypes to chromosomal regions represented by genetic markers, and tests for association between phenotype variation and single nucleotide polymorphisms (SNPs) within genes.

Ongoing genetics research

In collaboration with several Native American communities in Oklahoma and with the OU Molecular Anthropology Laboratory, I am using statistical genetics methods and information from Native American families to investigate type 2 diabetes risk factors in American Indians. Type 2 diabetes is an endocrine disorder characterized by insulin resistance, impaired insulin secretion, and hyperglycemia. American Indians and Alaska Natives have an age-adjusted diabetes prevalence more than twice that of non-Hispanic whites. A combination of genetic, epigenetic and environmental factors may underlie this disparity. The specific aim of the study I am currently involved with is to use candidate gene sequencing to identify novel and common variants that contribute to type 2 diabetes risk in American Indians. My long-term goal is to identify genetic and environmental risk factors for type 2 diabetes that are of use in the development of culturally appropriate intervention and treatment strategies. 

Previous genetics research

My postdoctoral research focused on the genetic and environmental components of quantitative variation in hemostasis (blood clotting) phenotypes. Data were from families participating in the San Antonio Family Heart Study (SAFHS), an investigation of cardiovascular disease in low-income Hispanic families. Cardiovascular disease is the leading cause of death in this population. The hemostasis phenotypes are risk factors for cardiovascular diseases. Using a variance components-based approach and after accounting for measured covariates including age, sex, medications, and lifestyle factors, I found that genetic factors contributed significantly to variation in each of the hemostasis phenotypes, with additive genetic effects explaining between 20 and 60 percent phenotypic variation. Significant genetic correlations occurred between type 2 diabetes and several hemostasis phenotypes, suggesting that the same genes that influence cardiovascular disease risk pleiotropically contribute to type 2 diabetes risk. In a related project, I used genome-wide linkage scans to identify a significant quantitative trait locus (QTL) for thrombin-activatable fibrinolysis inhibitor (TAFI) on chromosome 13q.

In addition to my research on complex disease risk, I investigated the genetic components of normal variation in hand, foot and eye preference, using data from the San Antonio Family Diabetes/Gallbladder Study. There has been considerable interest among anthropologists and others in the evolution of human handedness because of its proposed link to the evolution of lateralized language centers in the brain. However, the factors contributing to side preference are poorly understood. I found a weak but significant heritability for self-reported handedness and other side preferences, indicating that genes are an important component of laterality. Genome-wide linkage scans revealed QTLs for hand preference and eye preference on chromosomes 12q and 22pter, respectively.

Skeletal biology research

I use skeletal biology and paleopathology to investigate the use and treatment of dogs by Native Americans in prehistory. Deliberate dog burial, both within and outside of human graves, was common in the Midwest, Midsouth and Southeast during the Archaic period (8000-3000 BP). Typically, Archaic peoples in these regions were highly mobile hunter-gatherers. A post-Archaic decline in the number of dog burials may reflect changes in the functional and/or cultural roles of dogs in Native American societies as sedentism increased and food production intensified. Although there has been considerable speculation about dog use in prehistory, much of our current understanding is based on ethnographic analogy rather than on direct evidence. I used data from 455 dogs from Archaic through early historic period archaeological sites in Alabama, Kentucky, Tennessee, and Illinois to investigate geographic, temporal, and other variation in dog health, size, and demography. I found that during the Archaic period, dogs that were buried in human graves were significantly older than dogs buried elsewhere. In contrast, a dog's sex, size, and life experience as indicated by skeletal and dental pathologies did not play a role in its co-burial with humans.

Male dogs outnumbered females in all time periods and in all geographic regions, potentially due to differential burial by sex or to an overrepresentation of males in the living dog population. More males would occur where females were culled for food and/or to control the population size, or where male dogs were more highly valued and given better care. Dog size was similar between geographic regions, and in contrast to earlier studies, I found no significant size increase over time. Patterns of variation in dental pathology supported regional and temporal differences in dog diet and activity. For example, the relatively greater number of carnassial and molar tooth abscesses in Archaic dogs from Kentucky and Tennessee versus Alabama suggested that the Alabama dogs had less access to plaque-promoting foods including carbohydrates. High frequencies of vertebral, rib, and skull fractures in all time periods and across geographic regions was consistent with abuse by humans, dog fights, and/or hunting injuries. The frequency of skull and rib fractures increased over time. Dogs in all geographic regions and time periods exhibited multiple pathologies consistent with use as beasts of burden.