Clarifying Prehistoric Parasitism from a Complementary Morphological and Molecular Approach.

This paper reports an approach to the identification of prehistoric parasitic infection, which integrates traditional morphological methods with molecular methods. The approach includes the strengths of each method while mitigating the limitations. Demonstrating the efficacy of this approach, we provide a case study from a 1,400 year old desiccated fecal sample from La Cueva de los Muertos Chiquitos, archaeological site, near Rio Zape, Durango, Mexico. Traditionally prepared microscope slides were processed via microscopy and tentative ascarids were identified. Information regarding the parasites' developmental stage was recorded. DNA was then extracted directly from the slide material. From this DNA extract, a small segment of the 18S ribosomal RNA gene variant that is specific to Ascaris, and its phylogenetically close relatives, was targeted for PCR amplification and sequencing. Phylogenetic analysis of the DNA sequence best matched a member of physalopterids, rather than ascarids, with a single exception of a match to Contracaecum spiculigerum. Subsequent extractions, amplifications and sequencing of the original rehydrated coprolite material confirmed these results. The C. spiculigerum sequence represented a phylogenetic anomaly and subsequent analysis determined the sequence was an error in the BLAST database, likely attributable to misidentification of juvenile specimens prior to sequencing and submission. Physaloptera are a difficult genus to identify morphologically and can carry major health burdens. They may be underreported in humans, in part, because of morphological similarities to the more common human parasites belonging to ascarids. We conclude that integrating traditional morphological methods with molecular methods can help resolve this issue, in both contemporary and prehistoric populations.

Brief communication: DNA from early Holocene American dog.

We present the oldest genetically identified dog in the Americas, directly dated to 9,260 ± 170 Cal. B.P. The DNA was extracted from an occipital condyle imbedded in a human paleofecal sample from Hinds Cave in southwest Texas. A 368 base pair fragment of the mitochondrial genome control region was sequenced. These data were analyzed with comparable data, which included other ancient dogs and extant dogs, wolves and coyotes from around the world. Compiled with published data, our results characterize ancient American dogs within clades rooted by Eurasian wolves. In the Americas, these data provide no evidence of local interbreeding with wolves. This is a departure from the genetic pattern in other areas of the world where interbreeding with local wolf populations is apparent. Our discovery of domestic dog bone in a human paleofecal sample provides the earliest direct evidence for human consumption of dogs in the New World. These data support the hypothesis that dogs were a food source for early Paleoamericans.