There is this problem that often gets media attention from time to time but particuarly in the late 90's and that is frogs with deformities.
Now this story gives lots of insight into mass hysteria,and science as a way of knowing because it's a mystery with a surprise twist ending.
So in ponds across North America all of a sudden there was an increase in reports of the number of frog deformities. The media quickly picked this up because its disturbing and possibly because frogs look vaguely human with their legs being longer than arms.
There were a number of possibilties that were proposed. One category was genetic mutation. This includes everything to human causes such as mutagens and radiation from various sources one article irresponsibly floats the idea of the ozone layer being responsible. The other was that a negative mutation arose and was being passed around which genetically predisposed some to these mutations.
The second category were environmental disruptor chemicals. This had been seen before with cyclopamine being a naturally occurring plant alkaloid that causes midline deformities in livestock.
There were some environmental correlates that turned up which seemed to initially shed some light but ultimately led scientists down the wrong path. Turns out that deformities were correlated with high numbers of nitrogen compounds. And that these were usually isolated ponds near civilization. Aha! so it must be due to human effects and those damn overgrown golf courses.
The only problem was that raising frogs in high nitrogen tanks didn't cause these deformities in lab experiments. Genetic experiments failed to find any correlates between those deformed frogs and normal ones. For example cloning frogs is really easy and the clones raised in a lab didn't grow up with deformities.
It took a while but the cause for most was ultimately found. It turns out that a trematode worm parasite causes these. At first this would seem to be entirely natural.
However due to complex ecological interactions the high nitrogen compounds caused sudden and unseasonable blooms in algae which lead to increases in snails which hosted part of the trematode worm's life cycle which led to increased parasitism of frogs who acquired these deformites.