Demography, fitness and evolution are a united thing!
Stages: can be behavior, epigenetics, morphology.
Why is so much variation in initial fitness components? Is it adaptive or stochastic?
Fitness is a property of a group, not an individual!
Staged model: immature, no breeding effort, failed breeding, one fledgling, two fledglings Make a Markov chain on this! They get a pretty good match using this simple model with no hidden structure. (Steiner & Tulijapurkar 2012 PNAS)
Can calculate mean age at death, variance, and lifetime reproduction.
What is needed to identify selective processes? Need stable population, moderately strong selection, and a large sample size.
E. coli not dividing equally. One can track old and new pole. Microfluidic device. Track cells at beginning and end. Data: age at death, age at last division. They see Gompertz logistic pattern like in humans. Caused by appearance of protein clusters perhaps?
Stochastic variation is very important for understanding these processes. Hamilton says that as age increases, we have decreased selection. Stage-based models do a better job of describing selection across age.