[CarbineCaleb]

Capt: Some interesting stuff there - I know that for most mammals, evolution has ensured that fertility is a function of food supply - obviously a good strategy. This is accomplished by hormones whose levels track the feeding state of the animal and act to enhance or suppress ovulation. I think there may be multiple hormonal cues, but one of them has to do with the amount of fat on the animal. Therefore, you will naturally get an increase in predator population - if they are better fed, they will have more babies.

Same thing happens with humans, by the way - hormonal changes due to high fat levels seem to be capable of introducing pubescent changes and estrus earlier, for example, and very low levels of feeding - what we call malnutrition, can completely suppress menstruation. If you are poorly fed, you will have fewer or no babies.

Just as you said, the population of the response system cannot overlay directly on the driving system - there has to be some inherent lag between the two (a phase lag), that is characteristic of the reproductive cycle rates for the animals.

Like you, I have my doubts about the predator/prey cycle business with regard to bears. While bears can eat meat, my understanding is that they get about 2/3 - 3/4 of their calories from vegetable sources (like berries), and most of the rest is carrion found by scavenging in the wild. So I am not sure how tightly coupled they'd be to "prey" populations of any kind.

However, bear population changes, regardless of the causes for them, could definitely affect attack/fatality rates. More bears mean more encounters, and more encounters mean more fatalities. Likewise, more bears means increased competition for food, which will cause some of them to move to seek out new territory where there is greater opportunity.... that will invariably cause the nomads to encounter humans in their search.

What you would need would be the other data for the candidate causes to allow them to be overlaid and correlated. I don't think this shape is just random variation, anyway.

Keep me posted! ;-)
Caleb