Telomeres shorten over time in mammals, are lengthened by telomerase, and this all seems to be important for aging, cancer and age-related disease. But many of the important details are still up for debate, even as companies are working on telomere-based therapies. This paper caught my eye as illustrative of the complexities that bedevil any sort of biological research. Given a brace of storm-petrels, what can you determine about telomeres and longevity? As it turns out, even the fundamental points are a challenge: "Given that telomeres generally shorten with age, it was surprising to find that in a population of a long-lived seabird, Leach's storm-petrel, telomeres appear to lengthen with age. This unique finding suggested that the longest-lived individuals are able to elongate telomeres, an interpretation we call the Elongation Hypothesis. Alternatively, the Selection Hypothesis states that the longest-lived individuals start with the longest telomeres and variation in telomere length decreases with age due to the selective disappearance of individuals with short telomeres." The Selection Hypothesis wins, but "the oldest adults also show little or no accumulation of short telomeres over time, a pattern unknown in other species. Long telomeres are thought to provide a buffer against cellular senescence, and be generally indicative of genome stability and overall cell health." Biology is always more complex than you'd like it to be.