There are many candidates for ageless organisms, such as the hydra or the lobster, and some that have been revealed to in fact age in recent years as research costs fall far enough to allow these niche questions to be answered. Bacteria, for example, do age, but that was only conclusively established comparatively recently. Aging is not a large field in comparison to the life science mainstream, which is one of the reasons why there are so many unanswered questions relating to aging in various species.
Here is a fairly typical example - a collection of lower species that may or may not age, probably does so in a very different way to higher organisms, and where the process is largely unstudied.
Pale green and vaguely ruffled, like calcified doilies, lichens grow all over the tombstones and the old stone walls that fringe properties in this part of the world. Most people barely notice them. But Dr. Pringle, a mycologist at Harvard, believes they may help answer one of science's greatest questions: Is immortality biologically possible?
For eight years, Dr. Pringle, 42, has been returning to this cemetery each fall, to measure, sketch and scrutinize the lichens, which belong to the genus Xanthoparmelia. She wants to know whether they deteriorate with the passage of time, leaving them more susceptible to death.
Lichens are not individuals but tiny ecosystems, composed of one main fungus, a group of algae and an assortment of smaller fungi and bacteria. [While] lichens are communities, Dr. Pringle is largely interested in the fungi. Mycologists, the scientists who study fungi - not the most glamorous corridor of biology - have long assumed that many of these organisms don't age.The clear exception is yeast, a single-cell fungus that does senesce and that researchers use as a model to study aging. But most multicellular fungi, the assumption goes, don't senesce.
No one has ever proved that, though, or even collected much data.