Medicina

Ancient astronauts
According to certain authors, intelligent extraterrestrial beings called ancient astronauts or ancient aliens have visited Earth, and this contact is connected with the origins or development of human cultures, technologies, and religions. A common variant of the idea include proposals that deities from most, if not all, religions are actually extraterrestrials, and theirtechnologies were taken as evidence of their divine status.[1][2]
These proposals have been popularized, particularly in the latter half of the 20th century, by writers Erich von Däniken, Zecharia Sitchin, Robert K. G. Temple, and David Icke.[3] Ancient astronauts have been widely used as a plot device in science fiction, but the idea that ancient astronauts actually existed is not taken seriouslyby most academics, and has received little or no credible attention in peer reviewed studies.
Details
Proponents of ancient astronaut theories often maintain that humans are either descendants or creations of beings who landed on Earth thousands of years ago. An associated idea is that much of human knowledge, religion, and culture came from extraterrestrial visitors in ancient times, in thatancient astronauts acted as a “mother culture”. Other proposals include the idea that civilization may have evolved on Earth twice, and that the visitation of ancient astronauts may reflect the return of descendants of ancient humans whose population was separated from earthbound humans.[citation needed] These ideas are generally discounted if not ridiculed by the academic and skepticalcommunities.
Proponents argue that the evidence for ancient astronauts comes from supposed gaps in historical and archaeological records, and they also maintain that absent or incomplete explanations of historical or archaeological data point to the existence of ancient astronauts. The evidence is said to include archaeological artifacts that they argue are anachronistic or beyond the presumed technicalcapabilities of the historical cultures with which they are associated (sometimes referred to as "Out-of-place artifacts"); and artwork and legends which are interpreted as depicting extraterrestrial contact or technologies.
Mainstream academics, when they comment at all on such proposals, have responded that gaps in contemporary knowledge of the past need not demonstrate that such speculativeancient astronaut ideas are a necessary, or even plausible, conclusion to draw.[6] Academic researchers in related disciplines generally maintain that there is no evidence to support the proposals of ancient astronauts or paleocontact. Francis Crick, the co-discoverer of the double helix structure of DNA, however strongly believed in what he called panspermia, the concept that earth was 'seeded'with life, probably in the form of bluegreen algae, by intelligent extraterrestrial species, for the purpose of ensuring life's continuity. He believed that this could have been done on any number of planets of this class, possibly using unmanned shuttles. He talks at length about this theory in his book Life Itself.

Ancient aliens
Ancient alien theorists like Erich von Däniken believe that,thousands of years ago, extraterrestrials landed on Earth, where they were hailed as gods and helped shape human civilization. But what proof could possibly exist for such an encounter? Proponents of the theory point to two types of evidence: ancient religious texts and physical specimens such as cave drawings, stone sculptures and pyramids. Is your curiosity piqued? Here’s a quick introduction tosome of the most famous examples.
The Nazca Lines
Etched into a high plateau in Peru’s Nazca Desert, a series of ancient designs stretching more than 50 miles has baffled archaeologists for decades. Along with simple lines and geometric shapes, they include drawings of animals, birds and humans, some measuring more than 600 feet across. Because of their colossal size, the figures can only be...