WhiskeyX:
"The evidence would appear in the form of critical differences versus similarities in the etiology of their structures and functions, ranging from energy usage and chemical pathways to homochirality for just two of innumerable examples." There's no reason to presume (or assume) that if we discover evidence of life on, let's say Mars, that such life didn't originate on Earth and travel to Mars via some rock from a meteor impact.
There's no particular reason to presume the reverse.
What we know for certain today is that whatever precursors of life, if any, arrived on Earth 4+ billion years ago found a happy-home here and evolved continuously ever since.
WhiskeyX: "There is no reason why Life could not have originated on another planet 8 billion years ago orbiting around a star which subsequently which obliterated itself and the planet in a supernova."
Of course, no dispute: all that is possible, I'm only saying, until there is convincing evidence, it cannot be presumed, or assumed.
WhiskeyX: "More than 55 years ago I argued that exoplanets must exist in numbers far greater than the stars by implication of the laws of physics, despite the fact no exoplanets had yet to be discovered.
I predicted it was only a matter of time and better technology before we would discover those exoplanets implied by the laws of physics."
Fifty-five years ago I was an avid reader of many sci-fi books, all of which assumed there were numerous distant stars with earth-like planets.
Such predictions took no great genius, FRiend.
“There’s no reason to presume (or assume) that if we discover evidence of life on, let’s say Mars, that such life didn’t originate on Earth and travel to Mars via some rock from a meteor impact. There’s no particular reason to presume the reverse.”
That’s correct.
“What we know for certain today is that whatever precursors of life, if any, arrived on Earth 4+ billion years ago found a happy-home here and evolved continuously ever since.”
Yes, precursors to Life or Life itself.
“Of course, no dispute: all that is possible, I’m only saying, until there is convincing evidence, it cannot be presumed, or assumed.”
Yes, but the more important aspect of the issue are the many implied evidentiary reasons why extraterrestrial origin/s of Life on the Earth older than the Sun and Earth “cannot be presumed, or assumed” in the present absence of conclusive evidence for or against such conclusions. Just because we have not yet been able to explore the evidence and discover it does not mean the evidence implied by what little we do know won’t be there when we do finally obtain the means to discover it. Too many commentators adopt the logical fallacy that the absence of evidence due to limited observational capabilities is conclusive evidence the evidence does not exist.
“Fifty-five years ago I was an avid reader of many sci-fi books, all of which assumed there were numerous distant stars with earth-like planets. Such predictions took no great genius, FRiend.”
Agreed, you would have thought it “took no great genius....” It was a concept older than all of us today, yet it was still a much ridiculed prediction 55 years ago. A teacher invited I and another student to travel to a special evening university lecture by a noted professor in chemistry and organic chemistry regarding human interstellar travel to the exoplanets in other star systems. What was especially remarkable about the event was the way in which he trashed the ideas of human interstellar travel and any assumption that exoplanets must exist. The teacher, a WWII Army Air Forces combat veteran, was amused by my visible frustration listening to the professor carry on. Thanks to the 1950s era science fact and science fiction books I had been reading, I knew full well the professor was spouting nonsense. Interstellar travel was theoretically possible using asteroids as generational interstellar transports and exoplanets were and still are inherently implicit alongside the physics forming any star from a nebula. Despite the obvious evidence and logic, the concept of exoplanets remained controversial even among the professors of acaddemic science who should have known better 55 years ago. The teacher who invited us to attend the lecture was pleased to see us young students challenge the university professor’s conclusions.