The instructions for opinion and analysis articles used to say:

“We look for fact-based arguments. Therefore, if you are making scientific claims—aside from those that are essentially universally accepted (e.g., evolution by natural selection explains the diversity of life on Earth; vaccines do not cause autism; the Earth is about 93 million miles from the Sun) we ask you to link to original scientific research in reputable journals or assertions from reputable science-oriented institutions. Using secondary sources such as news reports or advocacy organizations that do not do actual research is not sufficient.”

Now it says just “You should back up claims with evidence.” but opinion doesn’t mean anything goes.

https://www.scientificamerican.com/page/submission-instructi...