First author of the paper is Mary Kelaita, a postdoctoral fellow at the University of Texas at San Antonio's Department of Anthropology. The howler monkey study was part of Kelaita's doctoral dissertation work at U-M's Department of Anthropology.
For years, anthropologists have attempted to infer hybridization among human ancestral species based on the fossil record, which represents only a snapshot in prehistory, and have concluded that hybridization is extremely rare, according to Kelaita and Corts-Ortiz. Given the utility of living primate models for understanding human evolution, the howler monkey study "suggests that the lack of strong evidence for hybridization in the fossil record does not negate the role it could have played in shaping early human lineage diversity," Kelaita said.
The authors conclude that the process of hybridization (defined as the production of offspring through the interbreeding between individuals of genetically distinct populations), the factors governing the expression of morphology in hybrid individuals, and the extent of reproductive isolation between species should be given further consideration in future research projects.
In their study, Kelaita and Corts-Ortiz analyzed different types of genetic markers, from both mitochondrial and nuclear DNA, to trace the ancestry of each howler monkey they studied. The use of molecular markers made it possible to approximate the relative genetic contributions of the parental species to each hybrid.
A total of 128 hybrid individuals were detected. Kelaita and Corts-Ortiz found that most were likely the product of several generations of hybridization or of mating between hybrids and pure individuals.
Subsequently, they performed statistical analyses on body measurements and found a large amount of morphological variation in individuals of mixed ancestry.
|Contact: Jim Erickson|
University of Michigan