Except when it comes to the Darwinian explanation for the history of life, which can't be questioned.
Everything can be questioned and tested - everything. But the ToE has been questioned and tested for 150 years and all that's changed are details. My personal opinion is that our understanding of how evolution actually works is still very naive. I think we'll find out that it's vastly more complicated and messy than we think it is now - and certainly how we discuss it here.
But to actually test it you have to first understand it and then work professionally in the field. It can't be successfully challenged by people with no understanding of it and disagree with it for purely religious reasons. You need scientific reasons with evidence to support it.
The ToE is real science so it can be falsified - all you have to do is provide the falsification. The simplest being a fossil found out of order in the fossil record. That's all it takes, one mammal in a rock older than mammals are found in. (In practice it would take a few to be conclusive, but if the ToE is wrong, that should be easy, you'd find no order in the fossil record.)
Apparently, accepting a flawed theory is better than saying "We don't know."
The problem you have is showing the *fatal* flaws.
There have been lots of flaws and there'll be many more, but none of them fatal and all add to our understanding. When science doesn't know, it says so. That all life on earth evolved is not something we don't know, it's now a fact accepted by all but those with religious reasons not to.
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"Science adjusts it's views based on what's observed. Faith is the denial of observation so that Belief can be preserved." - Tim Minchin, in his beat poem, Storm.