No such luck for our bug-eyed Malagasy friends, which live in the arid, scrubby southwestern region of the giant island. “Once they reach the end of the season,” Dr. Karsten said, “they’re done,” and they will drop from the trees with the papery grace of autumn leaves.

Assuming the execution orders are somehow part of the chameleon’s program, researchers might be able to identify the specific genetic or hormonal assassins in lizard cells, find their analogues in human cells and put a cap in them.

The new work also underscores the growing use of so-called life history theory to trace the history and contours of life on Earth.

Scientists have determined that many essential features of an animal’s portfolio are linked, among them whether at birth it looks fetal and helpless like a newborn kitten or precocious and competent like a neonatal giraffe; how big the average litter is; the speed with which the animal reaches sexual maturity; the length of time between births; and the pace at which an adult ages.

Try to improve or optimize one of these parameters and you end up paying somewhere else along the line. “One of the most robust things to come out of life history theory is that trade-offs exist,” said Steven N. Austad, the author of “Why We Age” and a professor of cellular and structural biology at the University of Texas Health Science Center.

“If you increase the number of young, the cost is often accelerated aging. If you get something that lives longer, you get costs early in life, with lower fertility and even sterility.”

Image WAITING The Furcifer labordi species spends most of its life span in the egg. Credit... Kristopher B. Karsten

Selective pressures in the environment push species toward one life history course or another. One example is that if you’re a species in which the great majority of adults end up being killed by predators or disease, it’s best to invest your resources in breeding early and often and not to bother worrying about long-term needs like a robust DNA repair system. And so it is that rodents beloved by carnivores everywhere have high fecundity and relatively poor longevity.