Casandra Rauser is the Assistant Director of Research Development for the School of Biological Sciences at the University of California, Irvine.
Michael Rose is Professor of Biological Sciences at the University of California, Irvine. He is the author of Evolutionary Biology of Aging, and was awarded the Busse Research Prize by the World Congress of Gerontology in 1997.
Rauser applied the “Page 99 Test” to their new book, Does Aging Stop?, and reported the following:
Opening up to page 99 immediately took me back to 2001 when it dawned on me that we could test a number of the competing evolutionary and heterogeneity theories of aging at the same time using fecundity instead of mortality. Up until that point, mortality had been the character of choice, as it is the most obvious character related to aging itself; but selection acts very similarly on fecundity, so why not study that?Learn more about Does Aging Stop? at the Oxford University Press website.
Page 99 describes some of the competing heterogeneity hypotheses for why several biologists had observed a slowing in late age mortality rate giving rise to plateaus in a number of different species in the early 1990’s. Many of these hypotheses were post hoc attempts at explaining away the observed data – data that didn’t seem to make much sense to anybody at the time. That is, mortality was supposed to continuously increase with age, but researchers were instead observing a slowing of mortality rates at very late ages when large cohorts of individuals were investigated.
Together we refer to these heterogeneity hypotheses to explain late age plateaus in mortality rates as “Vaupelian theory,” which had not been extended to include fecundity. On page 99 we verbally extend this theory to apply to fecundity, and explain that “regardless of the numerous conceivable lifelong heterogeneity in fecundity hypotheses, all of them have in common the ability to infer late-life fecundity patterns from attributes of young individuals in a cohort, just as demographic theories of late-life mortality hypothesize that mortality rates plateau because of individual heterogeneity effects that are present throughout life.”
So, all we had to do to test these theories was “simply” follow the individual fecundity patterns of thousands of female flies from one cohort over their lifetime; a task that in the end was, of course, not so simple. In fact, this most arduous task involved an army of undergraduate students, several sleepless nights, naps on the cot set up in the lab, numerous shots of espresso, and most importantly the counting of millions of fly eggs. In the end this much experimental evidence could not be ignored – all of our results failed to support any heterogeneity hypothesis that one could dream up, and added even more credence to evolutionary theories explaining the cessation of aging in late life.