The Drake equation is an often quoted probability argument used to estimate the number of potential active extraterrestrial civilizations in the Milky Way galaxy. Written in 1961 by Frank Drake as a mode of stimulating a dialogue at the first scientific meeting of (SETI). It is used to estimate the number of civilizations advanced enough to communicate via radio waves in the Universe, summarized it attempts to determine the odds of finding intelligent life in the cosmos.
Present day science estimates that the Milky Way contains roughly 100 billion planets, give or take a few million. So only about half the stars have a planet of their own. Those stars that have multiple planets will probably have at least one that lies within the goldilocks zone, where water can exist in liquid form on the surface. For now Mother Earth is the only world that we are certain harbors life, and among all the living things on our planet, Homo sapiens, one of several intelligent species on this world is the only species ever known to have developed advanced technology.
Assuming that 100% of the planets in their suns goldilocks zone will develop life in one form or another, and that at minimum 1% of those goldilocks planets will be able to evolve an intelligent species, 1% of that 1% will be able to communicate for a period of about 10,000 years. If we run those numbers through the Drake Equation, we end up with a value of 10. So 10 is all we get out of 100 Billion - what is often overlooked in the drake equation is the 10,000 year factor.
A provocative paper entitled "The Silurian Hypothesis" takes "Worlds before our Own" [Brad Steiger] to a new level. It is a scientific look at the possibility of there being an intelligent species that may have populated the Earth before the age of humans. One that would have been able to communicate via radio waves or some facsimile at some point in their history, before they vanished or moved on. References to an ancient race of intelligent reptilians is made. It is further implied that these reptilians / lizard people existed on Earth before mankind.
If an advanced, industrialized, intelligent species ruled Earth before Adam and Eve became fruitful and multiplied to take over the planet, would modern-day humans be able to detect their presence in our planets past ? That is the basis of "The Silurian Hypothesis".
Co-Author of the paper, Astrophysicist Adam Frank of Univesity of Rochester stated "Do we really know we were the first technological species on Earth?.... We've had an industrial society for only about 300 years, but there's been complex life on land for nearly 400 million years.... "
We are accustomed to thinking of extinct civilizations in terms of ancient Greece, the Pyramids, sunken temples and subterranean ruins. These remnants and artifacts from earlier human societies date back a few thousands of years at the most. If you want to traverse time on a grander scale it becomes increasingly complex. Farnk further states that "If humans went extinct today, any future civilization that might arise on Earth millions of years hence might find it hard to recognize traces of human civilization." No artifacts would last the millions of years we are talking about.
Fossilized bones are a possibility, but even if they are found, or have possibly already been found, would we recognize them for what they are ? The Silurian Hypothesis theorizes that a reptilian race may have been our predecessors - perhaps the Ubaid Lizard Men are depictions of some of the surviving remnants of this race. Perhaps our distant ancestors have / had contact of sorts with the remnants of this dieing civilization / If so then a trace of them would exist within our legends and lore.
Getting back to Adam and Eve becoming fruitful and [re]populating the Earth - who was their nemesis in the Garden of Eden ? - The serpent of course, but this 'serpent' was not a snake or even serpentine as per the mythos. Genesis states 'So the Lord God said to the serpent, 'Because you have done this,' Cursed are you above all livestock and all wild animals! You will crawl on your belly and you will eat dust all the days of your life." which implies that prior to his transgression he had legs and walked as opposed to slithered. [Genesis 3:14]
Legends of the Jews by Louis Ginzberg states that the serpent in Genesis could speak and walk upright on two legs. "Among the animals the serpent was notable. Of all of them he had the most excellent qualities, in some of which he resembled man. Like man he stood upright upon two feet, and in height he was equal to the camel." .. In Gods punishment of the serpent God is cited as stating ... "I created thee to be king over all animals, cattle and the beasts of the field alike; but thou wast not satisfied. Therefore thou shalt be cursed above all cattle and above every beast of the field. I created thee of upright posture; but thou wast not satisfied..."
Legends and lore from around the world bare witness to reptilians in one form or another, even the zulu tribe had legends of the 'Chitauri' a reptilian race that came to Earth in prehistory.
The Silurian Hypothesis attempts to take waste into account in looking for civilizations before our own. Long living Synthetic molecules which it is assumed an advanced civilization would have generated as well as radioactive waste or radioactive fall out. Unexplained Radioactive fallout exists in a few places, most notably Mohenjo Daro See: Nuclear War Ancient India
Are humans being cloned, is the great grandson of Dr. Frankenstein perpetuating the family legacy ? Well Dr. Frankenstein is fake, but human cloning apparently is not. There are multiple claimaints to Human Cloning. While it's true that some may fall into the realm of our old friend Dr. Frank N. Stein, others including a Canadian company with ties to a pseudo intellectual quasi religous sect known as the Raelians may be the real deal. The quasi religous sect is Raëlism and the company is called clonaid.
Ethnobotanist Terence McKenna took Timothy Learys advice back in the 60s to 'turn on, tune in and drop out' and he believes that eons ago some of our ape-like ancestors did just the same thing.
McKenna authored 'Food of the Gods ', an exploration of humanities harmonious history with plants, and their chemical properties. One of his theories was that Homo erectus ingested the same magic mushrooms while on their evolutionary journey, that enabled them to evolve into Modern Homo-Sapiens.