In the early 20th Century it was already clear that shit happens. However, not until nearly the end of that century did a consensus begin to arise regarding whose fault it was that shit happens. Actually, several contradictory consenses.
A few visionary scientists began to look for random correlations between various human activities and the shit frequency. They concluded that, with 73% confidence, shit was caused by humans sitting on toilets.
This proposition was soundly denounced by other scientists widely believed to be in the employ of toilet paper companies, waste management corporations and the plumbing industry in general. Their position was, loosely paraphrased, "Shit happens. D'oh!" (Others who had never appreciated The Simpsons preferred to say, "Shit happens. Duh!)
When pressed for a more detailed critique of the Anthropic Global Fecal Advance (AGFA) model, they explained that shit has been happening since the beginnings of life on Earth, and it was likely to continue until the end of same.
The AGFA proponents replied, "Yeah, and if people like you get their way that won't be long, because we'll all drown in shit!" The AGFA Deniers declined to comment.
Around the turn of the Millennium, popular enthusiasm for this issue reached such a fever pitch that every politician felt obliged to champion one side or the other, aggravating an already dramatic propensity for political polarization. Soon after that every scientist was pressed to "take a stand on shit" and declare for or against AGFA. Most complied.
By 2007 politicians around the world came together in Elizabeth, NJ, to draft the Elizabeth Accords, according to which the signatory nations promised to cut the shit by 20% within the next century. Almost every head of state shrugged and signed, knowing full well they would not be in office when the deadline approached.
In 2014 the United Nations formed an Intergovernmental Panel on Fecal Advance (IPFA) charged with polling all the world's scientists for their opinions on the issue. During the voting, fence-sitting scientists were excoriated by both sides and many lost their research funding and even their jobs; elementary particle theorists were especially persecuted, because they seemed unaware of the existence of shit.
In 2041 there was a nuclear war between the AGFA Alliance and everyone else. Life on Earth was exterminated, as the Alliance always predicted.