A better understanding of the biochemistry of long-lived, large species may in the near term lead to ways to better prevent cancer: more cells means more cancer risk, so every species larger and more long-lived than humans must have evolved better than human cancer suppression mechanisms. Elephants evolved many copies of tumor suppressor TP53, for example, while some whales appear to make use of other mechanisms to maintain cancer risk at a low enough level to ensure long lives and evolutionary success. That said, as for all of areas of interest arising from studies of the comparative biology of aging, it remains unclear as to the practical costs and feasibility of adapting cellular mechanisms from species A for use in species B. On a case by case basis this may be a prospect for the next twenty years, or it could require a century or more of progress towards reliable engineering of the human genome and cell biochemistry.
The first observations documenting the extraordinary longevity of whales were from the counts of annual ear plug lamina of fin whales (Balaenoptera physalus) and blue whales (Balaenoptera musculus) taken by Japanese whalers. Although most individuals had fewer than 20 lamina, a few specimens had more than 100 annual growth layers. From these data, the oldest blue and fin whales were documented to be at least 110 and 114 years, respectively. At the time, these were the oldest documented nonhuman mammals. Corroborating these ages is more recent evidence of great longevity in bowhead whales (Balaena mysticetus). Archaeological artifacts recovered from the blubber of bowheads taken in the modern Indigenous subsistence hunt include several stone or metal and ivory harpoon points last used in the 1880s. In 2007, a whale was taken in the traditional hunt and found to have an explosive Yankee Whaler harpoon tip embedded in its blubber last manufactured in 1885. These artifacts suggested that bowhead whales lived at least 130 years.
After the recovery of these artifacts, researchers used aspartic acid racemization (AAR) of the eye lens and then a new aging method to estimate the ages of whales taken in the subsistence hunt. In one instance, an individual's AAR-estimated age of 133 years corresponded closely to the 120-year-old whaling artifact recovered from its blubber, validating extraordinary AAR-estimated ages. AAR estimated ages of several individuals exceeded 150 years, and one individual, otherwise healthy, was estimated to be 211 years old. This was older than the documented ages of fin and blue whales by a century and would have likely been considered a laboratory error in the absence of the corroborating archaeological evidence.
From the standpoint of physiological scaling, these superannuated ages should not be unexpected. Whales are the largest living animals, and body size is highly correlated with longevity. There are three confounding issues in current whale age estimation, and all likely result in considerable downward bias on expected life span at the species level. First, although most toothed whales and some baleen whales have tissues with countable annular growth layers, many do not or, if they do, the archives are incomplete or difficult to count in very old individuals because of tissue remodeling, tooth wear, and/or thinning of the oldest annual layers. Second, it is unclear whether we could detect superannuated individuals in most whale populations today. Industrial whaling, which for most species ended only 60 years ago, would have required any individuals now aged over 100 years to have survived at least 40 years of intense whaling, and any individual over 150 would have had to survive 90 years of that same intense hunt. Last and closely related to the previous point, most methods of aging whales require lethal sampling.
Most whale populations have recovered or are recovering from industrial whaling, and although the populations are healthy, they have been growing for the past 60 years and are thus composed almost exclusively of individuals born after 1965. To detect very old individuals today using laminated tissues, AAR, or new molecular clock aging methods would still require extremely large sample sizes before detecting a single superannuated individual. Consequently, we believe that it is reasonable to hypothesize that now estimated baleen whale life spans are biased low.
Link: https://doi.org/10.1126/sciadv.adq3086
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