The irony of this thread is heartbreaking.

I've spent somewhere close to six months repeatedly showing you scientific evidence that commercial ancestry tests are unscientific mumbo jumbo.

Your reaction?

You label me a science denier.

So you should really try and answer your own question.

In my opinion there are two different phenomena that contribute to stupidity in this day and age. Those two are the imposter syndrome, and then the dunning-kruger effect.

The imposter syndrome is when a person who is accomplished or well-educated in a certain field, doesn't see themselves as an expert - even though other people would label them experts. Sometimes, when being asked a question regarding their expertise, they will downplay their knowledge on the subjects.

And example could be if you were to ask a neurologist a question regarding cardiology. Cardiology is not a neurologists expertise, however they are certainly able to give an educated answer on many questions concerning cardiology. Even if the neurologist didn't know the answer to the question, his guess would be far better than mine.

Then there is the dunning-kruger effect, which is the psychological effect of thinking you know more than you do, or that you are more able than you are. Basically, people might see themselves as experts in a subject they have very little knowledge or experience in. Imagine a relatively common, normal guy - maybe a plumber, who finds a book about cardiology. After he read this one book, he feels like an expert in the feel, because of his newly gained knowledge.

If there would be held a debate between the plumber and the neurologist on a cardiology topic, the neurologist might downplay his views, while the plumber is overly confident in his views. If there is an audience, they might side with the plumber - since his confidence is convincing. They aren't even able to make an educated judgment, since they likely know nothing about cardiology.

This is how all the debates go on the internet. Some fool says something overly confident, and people jump on the train, because they are equally foolish.