I find it difficult to believe life elsewhere does not exist, in some form. Billions of stars in just our galaxy alone. Billions of galaxies, most with at least as many stars as ours. What are the chances this little backwater planet in the "suburbs" of one galaxy is the only one anywhere with life on it?
I've been interested in this for many years, after reading "Chariots of the Gods" about 1972. Stone figures depicting quite human looking individuals wearing what can only be described as either a diving suit or a space suit. Drawings and rock carvings that depict objects that look almost identical to some of the UFO's described in modern times. Tales in various religious books and legends of many civilizations describing interactions with beings that can be thought of as extraterrestrial, and in some cases specifically described as star people or coming from the stars. Some Native American legends say exactly that. The "Kachinas" they believe in are also called star people in some cases.
Then there are the many architectural enigmas that cannot be explained. The standard mainstream explanation is that the stones used in some of these structures, weighing 80 tons or more, were transported there using slave labor and wooden rollers made of logs. But what would happen if you set a slab of rock weighing 80 tons on a dozen logs? Most likely it would crush the logs. If they were able to support the weight, it would sink into the ground. Then how do you get them to a location 20 miles away and several thousand feet higher in elevation?
Tiahuanaco, in south America, is at 12,500 feet above sea level. Some of the stones are over 100 tons. A row of faces carved from stone is found around one building, representing every race known on the planet plus a couple that are identical to what most people describe as the well known "grey" aliens. The site is estimated to be 17,000 years old.
http://www.ancient-wisdom.co.uk/Boliviatiahuanaco.htmLook up Puma Punku sometime. Huge granite stones with perfect right angles, surfaces so perfectly flat a machinst's straight edge won't show any daylight under them, estimated to be almost as old as Tihuanaco and also 12,000 feet above sea level, above the tree line, and 60 miles from where many of the stones originated.
Another item I saw on a documentary not long ago is a cone shaped core found I think in Egypt, with tool markings of a mechanical drill on it. Spiral, evenly spaced, and nothing we have today could cut it as fast (in distance per revolution) as it was done.
So who did it? Certainly not prehistoric man with nothing more durable than copper tools...