![]() ![]() Fortunately Hoberg and his colleagues did. Finally, if we knew which other definitive hosts carry the tapeworm species most closely related to ours, we might learn something of the style of eating and obtaining meat practiced by our ancestors.Īs a paleoanthropologist who spent decades trying to track the lifestyle and origins of meat-eating, hunting and scavenging among early hominids, I regret that I never conceived of such an interesting and sound approach to these questions. If we knew which species were the intermediate hosts of tapeworms that are closely related to the human-specific tapeworms, we'd have a good idea of which prey species our ancestors ate. When did hominids first become definitive hosts for tapeworms? If we knew the answer to this question, we'd know when our ancestors began to eat animal flesh regularly enough for the human-specific tapeworms to evolve. Once in the definitive host's gut, the tapeworm larvae mature into adults and shed eggs, completing the cycle. The larvae then pass into the definitive host when it eats the infected intermediate host, either raw or inadequately cooked. In the body of the intermediate host, the tapeworm eggs develop into larvae that live in the host's flesh. The eggs are then ingested by an intermediate host, which is often a particular species of herbivore, such as a domestic cow, some antelope or a pig (domestic or wild). When the adult worms mature, they shed eggs, which pass out of the host's body in its feces. With the exception of the three taeniid tapeworms that are specific to humans, adult tapeworms in this study commonly live in the intestines of carnivores such as lions, hyenas or African wild dogs. For taeniids, this always involves taking advantage of a predator-prey relationship, in which a carnivore harbors the adult tapeworm and an herbivore hosts the infective larvae. The complicated life cycle of a tapeworm is magnificently adapted to its parasitic existence. ![]() The beauty of the system is that the host species actually infects itself as it goes about its daily tasks the tapeworm need do nothing except be at the right place at the right time. They co-opt the work of their host species, who unwittingly provide food and housing to the parasites at various stages in their lives. ![]() Tapeworms have their own charm and at the very least must be considered to have found a clever way to make a living. Since tapeworms must be ingested to pass from individual to individual or from species to species, the research team realized that the genetic and host differences among tapeworm species can be used to understand something about the changing dietary habits of a host species. All three are host-specific, meaning they can't survive as adults outside a human gut. Human beings are vulnerable to infestation by any of three species of taeniid tapeworms: Taenia saginata, T. Department of Agriculture, Nancy Alkire of the University of Colorado, and Alan Queiroz and Arlene Jones, both of the Natural History Museum in London, realized that the tight adaptational relationship between a particular species of tapeworm and its host means that tapeworms can reveal a great deal about the animals in whose guts they live.
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