One interesting place that period doubling shows up that the article doesn't mention is in population ecology. I'm most familiar with the Tribolium work of Cons

One interesting place that period doubling shows up that the article doesn't mention is in population ecology. I'm most familiar with the Tribolium work of Constantino, Dennis, Cushing, and some other folks, which you can read an example of here[0]. Basically, the beetles have three life stages (four, actually - egg, larva, pupa, adult - but adding eggs in the model doesn't increase accuracy any so they leave it out for simplicity), and if you model the respective numbers of adults for a starting number of larvae, you can see truly chaotic behavior, including period doubling. It's fascinating work. [0] https://onlinelibrary.wiley.com/doi/full/10.1046/j.1461-0248.2001.00223.x https://onlinelibrary.wiley.com/doi/full/10.1046/j.1461-0248...