Let's play Sherlock

Here's the rules;
Present something real and factual that provides the clues needed, then pose a question related to the clues.
It can be any category.
Answer than provide your own puzzle.
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Here's my example and first attempt.

Insects do not have a respiratory system the same as other animals. Instead of lungs and blood to carry oxygen, they have openings, spiracles, in their body's that are connected to a network of ducts that provide air/oxygen directly to the organs and cells. This internal HVAC system limits the size insects can grow because as their size increases, the amount of internal ducting required grows exponentially to the point that there would literally be more ducting than anything else in an insect say twice the size of a Goliath beetle.
So by virtue of how an insect's pulmonary system works, they are limited in potential size.

Here's the question to be deduced;

Considering the above facts, explain why/how they have found dragonfly fossils that are about 36" long with huge wingspans as well as other enormous insect fossil's.

 

And you want this to work, right?

 

Well I guess the only games that work here are the lame one liner games that don't need much brainpower....

still surprised nobody even tried to answer.

 

I am not a science person. Would the air in their world be better than our current air. (less pollutants?)

 

The large wings help direct higher amounts of oxygen into their internal "ducts"

?

 

Well I guess this idea crashed and burned.....

Spectacles was on the right track.
The hypothesis was that there may have been higher concentrations of oxygen in the atmosphere at the time. Subsequent testing of ice cores confirmed that the periods in which enormous insects are found coincide with periods when there was a greater percentage of oxygen present in the atmosphere.
More oxygen available made it much easier for the insects to extract oxygen thereby reducing the need for as large and complex of a respiratory system like we see presently.

 

Thanks for the explanation - though far too taxing for many (including me) that have more questions than answers to muse upon - methinks