There's a mismatch between the title and description: title reads as if proving a specific causal pathway (gut microbiome) is required to resolve YES, however description just mentions that Roundup needs to be a "contributor". It would also help what are the criteria for a "contributor" - if observational studies (akin to the many "chocolate/coffee/... causes/prevents cancer" out there) are enough that's much lower bar than say "a consensus of the scientific community"...

This is a good point. Something proven to cause X does not mean it's the only thing that causes X. This is what is meant by "contributor" - direct causal link. It would be good to have some standard proxy for "scientific consensus" - perhaps FDA regulation would be a a better benchmark than results of studies.

For the time being, edited question description to "will be proven to decrease testosterone levels"