Extraterrestrials or aliens can called to any kind of life that doesn’t come from Earth; it’s officially the subject of study of astrobiology and the existence of extraterrestrial life is still hypothetical for science.Nevertheless the theory about the existence of aliens on the earth seems to have even more collective approval every day due to the undeniable amount of evidence. Extraterrestrials The term abduction comes from Latin (abdelius), it refers to humans being abducted by aliens and subjected to strange medical tests or experiments. In relation to this, there are numerous reports of people who claim to have been victims of extraterrestrial abductions, being abducted even from their own homes while they slept. Psychologists and specialists have been highly disconcerted by the incredible similarity in each of the stories made by the victims.It’s been speculated in relation to the extraterrestrial life forms, these speculations range from intelligent creatures to life forms in the bacterial scale. For some ufologists experts in the subject, our planet has been visited by at least three extraterrestrial races. Below we’ll describe the characteristics of each alien race.  “Gray alien”:  They’re very well known for being very thin with huge eyes and head. Contacted affirm that they arrived from the constellation of name "Orion" that is located in the star system called "Zeta Reticuli". It’s believed that most of these beings are clones and therefore lack feelings or empathy and soul, their behavior would be similar to a thinking machine.They are attributed responsibility in almost all confirmed abduction claims, experts claim that these beings are servants or subjects of the Reptilians. Reptilians: These extraterrestrials come from the constellation called Draco. These beings would walk erect, have a human appearance and live not only on their home planets, but also in caverns and tunnels within the Earth. According to researcher David Icke, they’ve hybridized with humans, which are controlled by pure-bred reptilians. The human-reptilian DNA of a hybrid allows them to transmute from the reptilian to the human form. Anunnaki: The Anunna or Anunnaki are a product of Sumerian mythology, a second category of gods. The Anunnaki inhabited the Dulkug or Du-Ku which would be the "sacred mountain". They are called the seven judges of the underworld of the dead.For ufologists and researchers, Anunnaki is the name attributed to these extraterrestrial beings, the same would be related to mythology due to an alleged alien intervention in antiquity.According to research done by David Icke, these reptoid beings are the intelligence behind the new world order. According to the writer and researcher Zecharia Sitchin, he said he succeeded in translating some Sumerian tablets, which would be related to a race of aliens or the so-called Anunnaki. Antique Sumerian tablets: More than a dozen copies of a mysterious text refers to the lists of Sumerian kings have been discovered in recent years by archaeologists in regions as unrelated as ancient Babylon, Susa, and Assyria. The best preserved example of this ancient text is called the Weld-Blundell Prism and is shown to the public at the Ashmolean Museum.The tablets of the Sumerian kings have baffled historians since they were discovered by modern humans. The text describes a fascinating period in the history of the so-called gods who ruled over humanity tens of thousands of years ago. The manuscript refers to eight kings who "descended from heaven” and ruled over a surprisingly long period of 241.200 years. Each of these kings ends with its period during the great flood that devastated the world's population.The translations made to the clay tablets by a researcher named Sitchin revealed that the Annunaki came to earth for precious metals, including gold, this alien race was looking for this metal to spread it in the atmosphere of its home planet , with the intention of increasing the temperature of its extremely cold climate.It’s said that the miners of their race began to reveal themselves and that the Annunaki genetically modified the "homo erectus" and mixed it with their DNA, turning it into "homo sapiens" to make them slaves and use them for the extraction of gold in the mines.