Since the original description and naming ofAscaris lumbricoidesfrom humans by Linnaeus in 1758 and later ofAscaris suumfrom pigs by Goeze 1782, these species have been considered to be valid. Four hypotheses relative to the conspecificity or lack thereof (and thus origin of these species) are possible: 1)Ascaris lumbricoides(usually infecting humans) andAscaris suum(recorded mostly from pigs) are both valid species, with the two species originating via a speciation event from a common ancestor sometime before the domestication of pigs by humans, or 2)Ascaris lumbricoidesin humans is derived directly from the speciesA. suumfound in pigs withA. suumthen existing as a persistent ancestor after formation ofA. lumbricoides, or 3)Ascaris suumis derived directly fromA. lumbricoideswith the persistent ancestor beingA. lumbricoidesandA. suumbeing the newly derived species, and finally, 4)Ascaris lumbricoidesandA. suumare the same species, this hypothesis being supported by studies showing both low morphological and low genetic divergence at several genes. We present and discuss paleoparasitological and genetic evidence that complement new data to evaluate the origin and evolution ofAscarisspp. in humans and pigs, and the uniqueness of the species in both hosts. Finally, we conclude thatAscaris lumbricoidesandA. suumare a single species and that the nameA. lumbricoidesLinnaeus 1758 has taxonomic priority; thereforeA. suumGoeze 1782 should be considered a synonym ofA. lumbricoides.

Paleoparasitological studies using microscopy showed that Ascarisand Trichuris trichiura are the human intestinal parasites most found in archaeological sites. However, in pre-Columbian South American archaeological sites, Ascaris is rare. In this work we standardized a molecular methodology for Ascaris diagnosis directly from ancient DNA retrieved from coprolites. Using cythochrome b gene (142 bp) target, ancient DNA sequences were retrieved from South American samples, negative by microscopy. Moreover, the methodology applied was sensitive enough to detect ancient DNA extracted from 30 Ascaris eggs from an European coprolite. These results revealed a new scenery for the paleodistribution of Ascaris in South America.

A molecular paleoparasitological diagnostic approach was developed for Enterobius vermicularis. Ancient DNA was extracted from 27 coprolites from archaeological sites in Chile and USA. Enzymatic amplification of human mtDNA sequences confirmed the human origin. We designed primers specific to the E. vermicularis 5S ribosomal RNA spacer region and they allowed reproducible polymerase chain reaction identification of ancient material. We suggested that the paleoparasitological microscopic identification could accompany molecular diagnosis, which also opens the possibility of sequence analysis to understand parasite-host evolution.