Is there any unimpeachable expert with absolutely certain 100% decisions or estimations, or is the nature of science that which cannot be proved, therefore certainty may only be temporary until something else is discovered?
Science works by eliminating wrong ideas because the evidence shows they are wrong. It does not and cannot absolutely prove any general statement. It is *always* possible new evidence will show modifications are required.
So, for example, Newton proposed a theory of gravity. That theory worked incredibly well for over 200 years, including the discovery of Neptune. But very small discrepancies were found between the Newtonian predictions and the observations of the motion of Mercury. When Einstein came around, he proposed a *different* theory of gravity that explained those anomalous motions of Mercury. But it *also* agreed with the Newtonian prediction *as an approximation*. In other words, Newton's ideas were 'wrong', but were a good approximation to the more accurate ideas of Einstein.
Now, in spite of being 'wrong', Newton's methods are still used today to get probes to other planets. Why? because they are a very good approximation, in spite of being wrong in detail. They are a good enough approximation to get those probes to other planets: the differences in prediction between Newton and Einstein are very, very small in this case.
This is a good lesson on how science changes: we can never *absolutely* know we have the right picture. But we *can* know that our picture gives the right answers to some degree of approximation. And, when our ideas are found to be wrong, the new picture that arises has to be a *better* approximation: it has to agree with the old ideas to the extent they were tested and give *better* results in other cases.
So, in spite of Newton's ideas being 'wrong', we don't go from Newton's ideas *back* to those of Ptolemy and Aristotle (which were used prior to Newton) because those were a *worse* approximation.
In the same way, the idea that species are basically static (no evolution) was the OLD idea that was common about 200 years ago. It was shown to be wrong and Darwin's ideas gave a mechanism for the observed changes. But Darwin wasn't the last word (there is no last word in science). So while his ideas were a good approximation, Darwin didn't know anything about genetics. So, later, the discoveries of genetics were integrated into the understanding of how species change (this occurred in the 1940-50s). Later, Gould and Eldridge discovered that in *some* cases, the changes between species could happen pretty rapidly (less than 50,000 years), so another modification to the overall viewpoint was adopted.
The goal is to get better and better approximations and thereby learn in more detail how the universe works. At no point can we be certain we have the 'one correct theory'. Instead, we look at the universe, hopefully with more and more refined methods giving more detail, and modify our ideas in response to this new information, getting better and better approximations as we do so.
The idea that species are static and that the Earth is less than 10,000 years old was the OLD idea that was found to be a very bad approximation. it is gone in scientific circles because it was shown to be such a bad approximation. And just like there is no longer debate about whether Ptolemy's ideas were correct, there is no longer debate about whether species are static *within science*.