Allow me to explain...
Most of what makes us modern happened within the past 10,000 years. Contrary to what you might hear on shows like Ancient Aliens, the progress from old stone age to new stone age to iron age (sometimes by way of the copper and bronze ages) followed by the steel age and leading to the industrial age and then the information age follows a linear progression that can be evidenced globally. Here and there we see advances in technology within isolated populations, and some of them spread to other cultures while others simply fade out and are forgotten, only to be rediscovered elsewhere by some other population at a later date.
Now, homo sapien sapiens has been around for about 200,000 years. Before that, there were neanderthals and other archaic homo sapiens for an additional 150,000 years...and many of these species or subspecies had bigger brains than modern homo sapien sapiens.
Additionally, if homo erectus soloensis and the so-called "hobbit" are related and the new dates for soloensis are correct, then a population of homo erectus living in the the now-sunken continent of Sundaland may have had a more developed frontal lobe than the ancestors of homo sapiens had 260,000 years ago or more.
In fact, since archaic homo sapiens goes back over 500,000 years, we can safely assume that there have been species on the planet capable of complex thought since at least 500,000 years ago. If we were ever to do any underwater archeology in the once fertile coastlines of Sundaland, or if we were ever able to actually find more fossils of the hominids that we know were in India previous to Narmada Man, we might even find that advanced frontal lobes go back 750,000 years or more. In fact, the first controversial example of abstract thought shows up around a million years ago, not 40,000, the date that Eurocentrists once claimed.
Since it only takes 10,000 years to go from Stone age to Industrial age and only 100 years to go from Industrial Age to Information Age, our current level of technology, (or at least that of the late 1800s) could have happened at any time in the history of Homo for the past 500,000 to 750,000 years, provided that the culture which reached that level of technology left no or few traces of its technology.
Anyone who has seen the recent TV programs showing what would happen if every human being disappeared tomorrow such as "After Us" realizes that there would be no trace of anyone having ever used metallurgy in less than 25,000 years.
Additionally, the most desirable real estate on earth during the ice age is now underwater (Sundaland), leaving only what would have been uninhabited mountain ranges at the time(Java, Borneo, etc.).
So what does this have to do with USOs and visiting extraterrestrials, might you ask?
Well, since we still don't quite know whether light speed itself is even possible, and since we don't yet have any good ideas about how a craft might survive the rigors of deep space travel, and since statititions have shown that finding the planet Earth is highly improbable for aliens at any level of technology, the desire to physically come here even more so....it follows that even theories like the more radical versions of AAH(Aquatic Ape Hypothesis), Atlantis, and even Hollow Earth and Creationism are still infinitely more probable than interplanetary travel having occured in our planet's past!
In fact, interplanetary travel is no more a possibility than inter-dimensional travel or time travel as far as our current understandings are concerned.
Recently, Michio Kaku has proposed that an alien culture might send out mechanized drones to find life on other planets, leaving "trip-wires" on Moons to alert them to a planets ascension to the Space Age. This increases the probability of an extraterrestrial visitation, but not until the 1960s...at least as far as we know!
Therefore, statistically speaking, the chance of aliens having visited our planet before 1960 are less than the chance for the existence of fairies, elves, and unicorns!
Even if they did find irrefutable evidence of high tech USOs operating in our ocean and don't reason that the government has reached that state of technology (after all the US Gov did have a version of google earth 50 years before the public did), then there are still better explanations for the technology than aliens.
In fact, even if they found a new species of hominid in a submerged USO, it would still be more logical to assume we shared a common terrestrial ancestor with it than to believe that it is from another planet. Maybe the Hollow Earth Theorists, Edgar Allen Poe, and various Native American legends are correct and there is a race of hominids living in the vast unexplored caverns of the earth. Maybe the earliest of the AAH theorists are right and one branch of our semi-aquatic ancestor stayed in the sea, having achieved a civilization far greater than ours on Sundaland in the remote past. Hell, maybe USOs are operated by a form of whales that retained arms for tool making, being that some claim that they are smarter than humans!
As ludicrous as all of this sounds, it's no more far-fetched than interstellar travel, as far as our current understandings are concerned. Not even 5% of the species that have existed on Earth are represented in the fossil record. Most of our planet's formerly prime real estate is now under water. A fossil of a chimpanzee has never been found in the wild, although we know that they exist. 25% of the US has not even been field surveyed, and there are vast areas of the Earth that will never be explored. There are places on land we cannot get to without destroying because our of lack of fur and our lack of immunities, and there are places under the sea where strange species exists that we will likely never get to. Most of the evidence of man's past is beneath the sea along the former coasts, and we are doing pretty much nothing to explore it.
Even if we found that a species of hominid found on a USO had DNA different than any other species on earth, and that DNA was equally distant from every species on Earth, it would still not be evidence of interplanetary travel... because inter-dimensional travel is equally impossible according to our current understanding.
So what's my point? I'm just pointing out that the bias on these popular alien shows borders on journalistic criminality. I understand that the ratings go down when the real scientists appear on their television programs, but at least they could get some other fringe theorists with equally plausible whacky explanations to provide a counterpoint.
When every mystery is followed by "We can't figure it out ...therefore Ancient Aliens!" and you know that they are talking about "aliens" of the interplanetary, material, travelling variety... it reeks of jumping to conclusions and makes little sense when there are so many other explanations, mainstream and otherwise, that can be found with a simple google search.
If an alien were to come out of the sea and make contact with the president, appearing on the 6 o'clock news tomorrow with proof that their DNA was different from any DNA on Earth, I wouldn't necessarily be surprised that some species in the vast universe had finally proven that light speed or inter-dimensional travel were possible and had therefore made themselves an engine to get here. I'm just saying that even if the reports of USOs are genuine, It's no more likely that they are extraterrestrial or extra-dimensional than it is that they are perfectly terrestrial and simply unknown to us.
And my main problem with Ancient Aliens is that man's technological advancement has proven to be largely linear over the past 10 thousand years at least, right up through the 1800s, and therefore if any aliens visited Earth in the past as anything more than casual observers we don't seem to have benefited from it as much as Ancient Aliens seems to make out. Even things like the Antykthera Mechanism and megalithic structures, though advanced for their time, would be as primitive to the creators of light speed and extra-dimensional travel as a homo habilis's hand-axe is to modern man. What's more, there are linear technological progressions from human cultures that ultimately result in things like the Antykthera Mechanism and megaliths, despite what Ancient Alien kooks spread about pyramids springing out of a Nile formerly inhabited only by grunting ape-men. there were underground mines along the Nile over 20 thousand years ago, and they aren't mining for Sitchin's gold but for flint and red ochre...the staples of paleolithic culture, not the culture of little green men from Sirius B!!
Man is not so stupid as to have to have an E.T. come down and teach him to do even the most mundane things, but Ancient Aliens would have you believe that our race wouldn't have ever been able to learn to wipe our own arses or rub two sticks together without alien intervention.
I'll have them know that I figure out things and try doing things differently with different tools and even invent new things all the time without consulting people from other planets...and since all the parts of my brain have been on this planet for at least 200,000 years I see no reason why my ancestors needed aliens, either. As far as the overall fossiland lithic record are concerned, the linear progression of man's technology has few, if any, missing links. they show that he did not need alien intervention in the least.
