I can't find that definition of the word anywhere, not on dictionary.com or Merriam-Websters, or the link you gave me. Dictionary.com says the opposite: "a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact."
I'm trying to be honest with you and put things in terms that you, as a non-scientist, will understand. In science there is not absolute proof, no ultimate truth, no such thing as a "fact." But that confuses the non-scientist who does not understand the difference between a type one and type two statistical error. In science we accept that there are always unknowns, always room for new information, always some level of error. The general public doesn't understand this and want's absolutes.
I looked up "Scientific Theory" to see if it might have a different definition, and according to Wikipedia, a scientific theory is "a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation"
So, I'm guessing that you meant "scientific theory".
When I say "theory" I always mean "scientific theory."
This definition has its limitations as well, if it only involves explanations of the natural world.
That's a limitation? Say whatever you want about the unnatural world, it is irreverent to this conversation.
It also causes a problem: which theories are actually scientific theories, and how strong is the data behind them? Is the Siberian Land Bridge theory a scientific theory, or is it just a theory?
I'd say it qualifies as a scientific theory, (a powerful explanation for a broad set of observations, strongly supported by many different lines of evidence). It is possible for there to be completing theories.
What kind of testing can prove whether or not someone arrived by ship or by land?
Diet, herbivore and plant vs. seafood, that's at the root of the current competing theories. I support the idea that both theories are correct (and that at the present time the coastal route appears older).
You seem to want the Siberian Land Bridge to be either fact or fantasy. The "fact" is that the oceans were lower during the Pleistocene and that that resulted in there being a dry path from Asia to Alaska. Now, does that "fact" translate automatically in a theory that people used that land bridge to get from Asia to Alaska? No, it does not. That "fact" permits posing the hypothesis that that people used that land bridge to get from Asia to Alaska. Now comes the attempt to falsify that hypothesis. Paleo-climate analysis shows that air masses that swept over it were so dry they brought little snowfall, preventing the growth of ice sheets. Grasses, sedges and other cold-adapted plants where there as shown by preserved specimens under a layer of volcanic ash and in the frozen intestines of large herbivores. There are numerous evidences of large mammals that could have also been used for food. So all of the pieces come together, clearly none contradict, so we have a theory. There are other data that, while not contradicting, per se, point to another possibility: the Coastal Route theory. I'll not go into the specifics of the data, that not germane here, suffice it to say that there are two well developed theories that are not mutually exclusive, and that the data for the coastal route may indicate that it came first. But what if there were convincing evidence (there isn't) that boat building was unknown at time? That would falsify the Coastal Route theory and, with a single stroke, eliminate it from consideration. Such is the clear case with the BoM, our knowledge of the flora and fauna of the post-Pleistocene New World falsifies the BoM just as surely.
You also mentioned the pleistocene extinction; what kind of testing can be done to give anyone a sense of confidence when any particular species went extinct? Does it explain why some species would go extinct on one continent and not the other?
More than seventy genera in North America were lost, almost all are terrestrial animals, and large in size. The extinctions included elephants, horses, camels, ground sloths, all but one pronghorn, several ovibovids, most peccaries, and the giant beaver”. South America also lost elephants and sloths, in addition to horses, some camels, glyptodonts, and a rhinoceros-sized giant rodent species. In terms of when each species was lost, you look through the existing fossils and report the youngest. You look through sediment beds of known ages and see were the species of interest disappears. Without getting into the details here, the human overkill theory seems to be holding sway for the extinctions both in the New World and in Australia. In any case, well predating the alleged times of the BofM. There was an extinction in Europe, though much less pronounced. While the rapidly shifting Ice Age climate is thought to have played a part all over the world, the primary factors seems to have been the introduction of humans into environments is which the fauna had no co-evolved.
I think you are selling me snake oil.
When you think something is snake oil it tastes that way even if it's champagne. It's your confirmation bias showing.