How we were infected by parasites? Almost all modern hunter-gatherer tribes, such as pygmies from Central Africa, chavante from Brazil and San from South Africa, are infected with parasites, and their parasitic load is not very high. Most members of these tribes have a few helminths, but no one has too many parasites. However, the use of data on modern hunters and gatherers can mislead us. They live in a much more populous world than they did a hundred years ago, let alone sixty thousand years. They could also get parasites from sedentary peoples, who in turn got them from animals.
Our Primate relatives can better illustrate our own primitive parasitic load. In wild chimpanzees there is a real ecosystem consisting of intestinal helminths, blood flukes (schistosomes) and unicellular protozoa. In this case, also, no individual is infected with parasites in large numbers. As it turned out, the set of parasites peculiar to man is more like the set of parasites available in baboons, and not in chimpanzees. In all likelihood, this is due to the fact that the man lived in Savannah for a long time. In fact, parasites can tell us a lot about where we’ve been and who we’ve met along the way.
The reason we got quite large helminths, scientists usually called domestication of pigs and cows, but this was before the parasitologist of the us Department of agriculture Eric Hoberg more closely analyzed this issue. He concluded that human tapeworms are most closely related to the tapeworms of cats, dogs, and hyenas in Africa, rather than Eurasia, where humans have domesticated most animals. Human tapeworms diverged from their African relatives between one million and 2.5 million years ago — around the time our Homo erectus (“upright man”) ancestors, who had already learned to use tools and tamed fire, began to gather and may have hunted regularly in the Savannah. We have risen to a higher level of the food chain and, as if by some ecological rite of passage, have inherited the parasites of the higher predators.
And what did our anthropoid relatives face during their lives? There are more than three thousand species of lice infecting birds, rodents, ungulates and, perhaps, all who are covered with wool or feathers. (Among creatures who have no lice are oviparous platypus, scaly anteaters, and hairless dolphins and whales.) These tiny biting pests have been living in Primate hair for at least 25 million years. Gorillas and chimpanzees have their own unique species of lice, but humans have them, oddly enough, two species: one live on the head, and the other in the pubic zone. These two kinds of lice diverged from the same ancestor that lived on man? Not exactly.
In 2007, David reed of the Florida Museum of natural history stated that head lice are the closest relatives of chimpanzee lice. About six million years ago, humans and chimpanzees had common ancestors, consistent with the divergence of lice of the two species. The most recent common ancestor of gorilla and human lived about seven million years ago, but reed found that the divergence of pubic lice and gorilla lice occurred much later, about 3.5 million years ago. How could this happen? “We’ll never know if it was copulation or something more banal,” reed told the New York Times. However, this method of obtaining lice at least sheds light on another long-standing mystery: the question of when our family lost hair. To gorilla lice colonized the pubic area of a person, his family lice should be gone.
We know that the naked Primate eventually began to cover the body with clothing. Lice tell us again when it happened. The clothing is home to a subspecies of head lice. (This louse carries such a terrible epidemic disease as typhus.) And the head louse moved into its new niche (woven clothing) about 107,000 years ago.
When modern Homo sapiens left Africa about 60,000 years ago, the descendants of previous migrations still inhabited Eurasia: in the West, Neanderthals, with whom we had a common ancestor about 350,000 years ago; in the East, Homo erectus, who left Africa about 1.8 million years ago; in addition, it was recently established that Denisov people, close relatives of Neanderthals, also lived in the East. There was a slight interbreeding. From one to four percent of DNA of people outside Africa are derived from Neanderthals. The inhabitants of Melanesia and Southeast Asia have a slightly larger share of Denisov’s human DNA.
However, although our interbreeding was small, we always took one of these humanoid parasites. The biological “race” of human head lice, existing only in North and South America, differs significantly from the lice of the Old World. According to DNA analysis, this species of lice diverged from human head lice about 1.18 million years ago, long before Homo sapiens left Africa. David Reid believes that this insect came from ancient anthropoids that lived in Asia. Homo erectus and Denisov’s man died out, but their lice survived in the hair of those modern human pioneers who eventually made it to North America.
About 30,000 years ago, an unknown artist created exquisite drawings of buffaloes, horses, lions and hyenas on the walls of a deep cave in southern France. These amazing sketches in the cave of Chauvet, located near the town of Vallon-Pont-d’arc, not only drive modern artists crazy with their effortless skill, but also give an idea of a world in which there were many large animals.
In a lesser-known cave in the South of France, the grottoes of ARCIS-sur-cure, there are also drawings, albeit of lower quality. However, this cave tells us something else about life in those days. About 30,000 years ago, someone peed in the depths of one of the grottoes. Thirty millennia later, scientists discovered in fossilized excrement helminth eggs, which became by that time the most common worm infecting people: human Ascaris (Ascaris lumbricoides). According to some estimates, this large roundworm is now present in about 1.2 billion people (a sixth of humanity), mainly in developing countries. However, not so long ago, all people, including Europeans and Americans, were infected with these helminths.
Scientists again blamed the presence of these large worms in humans on domestic animals, in this case pigs, which have a similar species of helminths. However, as these fossilized feces show, we got this parasite about 20,000 years ago, before the domestication of wild pigs. Some believe that the excrement from the grottoes of ARCIS-sur-cure could have been left behind by a bear, which would have cast doubt on the idea. However, other data confirm the receipt of these helminths by humans in the Paleolithic era. In particular, Amerindians roundworm appeared nearly 4,000 years before the Spaniards brought pigs to America. Their ancestors migrated through Beringia before agriculture was born. Looks like we can take that responsibility off the pigs. We gave them our roundworms when we domesticated them, not the other way around.