By "scientific," I assume you mean "irrefutable" or something along that line. Nothing is irrefutable, so let's set aside that term and simply look at what evidence exists with regard to the ability of oral tradition to preserve information from the past. Whatever is said, let's also remember that a written document does not necessarily "preserve historical facts." Every primary source requires scrutiny to determine how the subjectivity of the author may have shaded whatever was written. People are imperfect witnesses to history, and what they write is inherently flawed. All sources of information, whether written, oral, or elements of material culture, require care and assessment to determine what they are telling us about the past and how they are doing that.
In my forthcoming book, The Folklore of Cornwall: The Oral Tradition of a Celtic Nation I take up the question of how well oral tradition passes on stories from the past. It appears that the degree to which oral tradition preserves information from the past depends on the value placed by various cultures on that sort of preservation: while some stress the idea that stories must be passed on exactly as they are heard, other cultures place more value on modifying stories. So whatever is said about how well oral tradition "preserves historical fact" must first be understood within the cultural context. In other words, the first step in answering your question is to realize that the answer depends on which culture we are considering.
In my book, I compare the Cornish storytellers with those of Ireland. The Cornish were interested in modifying stories, always seeking to present something new. The Irish storytellers prided themselves in preserving stories exactly as told. (Alan Dundes observed similar differences among various cultures in North America; see his The Morphology of North American Indian Folktales (Helsinki: FF Communications No. 195, 1964).) That said, while the Irish storytellers prided themselves for their ability to tell a story exactly as it was told, George Denis Zimmermann, The Irish Storyteller (Dublin: Four Courts Press, 2001), suggests that storytellers might claim that after hearing a folktale once, they could repeat it exactly as it had been told, but they "were probably deceiving themselves.… Still, a gifted Irish storyteller was often said to repeat exactly what he had heard, and could sincerely believe that he did."
The best way to answer your question is to say that some cultures were very good at preserving stories from the past - and this could include information about the past. Even among those cultures, which maintained they preserved stories exactly as heard, drift in the oral narrative probably occurred. The stories one can gather, therefore, must be treated with caution. That does not mean that they must be disregarded. If we were to disregard all sources that must be treated with caution, we would disregard everything, written or oral. All sources require caution. What is important to understand when approaching oral tradition is that it requires its own sort of caution. Nothing should be taken at face value, but oral tradition can be impressive in what it preserves.
In addition to what the always amazing u/itsallfolklore has provided, I'd also like to link to some other threads provided by my friend and mod colleague u/snapshot52 -- hopefully they may pop in later if you have questions, but I know their schedule is very full right now. u/snapshot52 writes for us about history from the perspective of an indigenous person, being Nez Perce themself.
The thread that might speak most to your question is this one, about reconciling apparent contradictions in oral sources: https://www.reddit.com/r/AskHistorians/comments/8jf834/monday_methods_indigenous_sources_reconciling/
But these also might be interesting to you:
and
https://www.reddit.com/r/AskHistorians/comments/7kz79d/monday_methods_an_indigenous_pedagogy/
There's a lot of reference to the historiography of Oral tradition in the book Secwépemc People, Land, and Laws, and references the Supreme Court of Canada Delgamuukw decision of 1997.
https://scc-csc.lexum.com/scc-csc/scc-csc/en/1569/1/document.do
Which also cites the Report of the Royal Commission on Aboriginal Peoples
Which assesses the admissibility of Canadian Indigenous Oral Histories in court, and establishes a framework by which to authenticate and verify oral history so that they can be deemed admissable, and be held as real evidence in a court of law (as opposed to being treated as Hearsay, which they had been previously).
Some interesting parts:
"It would be perverse, to say the least, to use the refusal of the province to acknowledge the rights of its aboriginal inhabitants as a reason for excluding evidence which may prove the existence of those rights. Second, this rationale for exclusion places aboriginal claimants whose societies record their past through oral history in a grave dilemma. In order for the oral history of a community to amount to a form of reputation, and to be admissible in court, it must remain alive through the discussions of members of that community; those discussions are the very basis of that reputation. But if those histories are discussed too much, and too close to the date of litigation, they may be discounted as being suspect, and may be held to be inadmissible. The net effect may be that a society with such an oral tradition would never be able to establish a historical claim through the use of oral history in court."
"Notwithstanding the challenges created by the use of oral histories as proof of historical facts, the laws of evidence must be adapted in order that this type of evidence can be accommodated and placed on an equal footing with the types of historical evidence that courts are familiar with, which largely consists of historical documents. This is a long-standing practice in the interpretation of treaties between the Crown and aboriginal peoples: Sioui, supra, at p. 1068; R. v. Taylor (1981), 62 C.C.C. (2d) 227 (Ont. C.A.), at p. 232. To quote Dickson C.J., given that most aboriginal societies “did not keep written records”, the failure to do so would “impose an impossible burden of proof” on aboriginalpeoples, and “render nugatory” any rights that they have (Simon v. The Queen, [1985] 2 S.C.R. 387, at p. 408). This process must be undertaken on a case-by-case basis. I will take this approach in [1985] 2 R.C.S. 387, my analysis of the trial judge’s findings of fact."