Animal Immortality

Some animals with amazingly long lifespans compared to ours, including one that can survive potentially forever, the "immortal jellyfish":

Animals with the Longest Lifespans

The most incredible is the glass sponge, possibly living up to 15,000 years. Corals and giant barrel sponges are not far behind. Other animals on the list, while impressive, fall within more imaginable ranges, e.g., Greenland sharks (400), ocean quahogs (225), and giant tortoises (possibly up to 250). It's noteworthy that all the most long-lived creatures aside from the bowhead whale (200) are invertebrates or cold-blooded vertebrates. What stops us from attaining such venerable ages? Elephants, at the bottom of the page, have about the same maximum lifespans as humans.

The Wikipedia article on the glass sponge goes into great detail about its biology and ecology but doesn't speculate why it can live so much longer than most animals:

Hexactinellid

"Biological immortality" enables some rare species to avoid aging and thus theoretically live forever. In practice, though, they're not truly deathless, since they can succumb to disease or predators.

Here's a page about the jellyfish with that extraordinary gift:

Immortal Jellyfish

In response to stress, it can hit a "reset button" and revert to its immature polyp stage. The regenerated polyp grows into an adult genetically identical to its previous incarnation. This process of "transdifferentiation," in which "an adult cell, one that is specialized for a particular tissue, can become an entirely different type of specialized cell," is being studied by scientists in search of new ways to "replace cells that have been damaged by disease." Suppose a sapient creature had a similar life cycle? If we did, would we recognize it as a type of "immortality" we'd want? Would memory and learned skills carry over from one phase of the cycle to the next? Bacteria, reproducing by fission, are technically deathless, but if they had individual identities, would that individuality be preserved through their descendants? In musing on the immortal jellyfish, the article raises the question, "If all of an organism’s cells are replaced, is it still the same individual? The genes are the same, of course."

If we consider the issue from that angle, however, almost all the cells in our bodies get replaced throughout a lifetime, too, many of them over and over. Nevertheless, we think of ourselves as the same persons, with continuity of memory, experience, and identity.

Margaret L. Carter

Carter's Crypt

Quest for Longevity

The cover story of the January 2023 NATIONAL GEOGRAPHIC, a 35-page article titled "The Science of Living Longer and Better," explores several different approaches, both theoretical and practical, to the goal of extending the human lifespan. The genetically programmed maximum age for us seems to be around 120 years. However, very few people make it that far.

Numerous drugs enable mice to live as much as 60% longer than normal. Why don't they work on people? Why do certain animals such as naked mole rats and some bats live significantly longer, in proportion to their size, than we do? Why do Greenland sharks live at least 250 years, maybe longer? Altering a single gene in a certain species of roundworms doubles their lifespan while keeping them youthfully energetic, but we're more complicated than worms. Why do people in some societies tend to enjoy longer, healthier lives than the average? Environment? Diet? Exercise? Other lifestyle factors? Some scientists have tried promising drug therapies on themselves, with mixed results. Animal studies show life extension outcomes from severe restriction of calorie intake, but, again, such a regimen hasn't produced similar effects on human subjects. Anyway, personally, if I could lengthen my lifetime by a decade or two that way, I wouldn't bother; adding on years of semi-starvation would be no fun.

Stipulating the natural human upper age limit as about 120 years suggests that the Howard Families project in Robert Heinlein's METHUSELAH'S CHILDREN couldn't work the way the novel portrays it. By the date of the novel, the 22nd century, the typical Howard Families member lives to 150, retaining the appearance and vitality of a person in the prime of life. This situation exists before rejuvenation therapies are invented later in the story. Simply interbreeding bloodlines of naturally long-lived people couldn't extend their maximum ages past the 120-year limit if genes for such extension don't already exist. Moreover, real-life super-centenarians, however vigorous, still look their age, not so youthful they have to adopt new identities to avoid unwelcome attention. The only way the "Methuselahs" of Heinlein's novel could survive and remain young-looking to the age of 150 would be if Lazarus Long had already spread the mutated gene responsible for his apparent immortality through most of the Howard population. (Given the character of Lazarus as portrayed in the later book TIME ENOUGH FOR LOVE, that hypothesis seems not unlikely.) That explanation wouldn't work for the early generations such as Lazarus's own mother and her contemporaries, though. There's no plausible way mere selective breeding for a century or so could produce human beings who live over 100 years with the appearance of well-preserved middle age.

So if we want lifespans like Heinlein's characters, we'll have to develop futuristic technologies similar to those speculated about in the NATIONAL GEOGRAPHIC article. Even so, surpassing the natural limit of 120 years would seem to require something radically beyond those techniques, maybe direct alteration of DNA—such as the hypothetical "cellular reprogramming" mentioned in the article.

Margaret L. Carter

Carter's Crypt

Surplus of Time

Occasionally I read a humorous manga series called MISS KOBAYASHI'S DRAGON MAID. The heroine saves the life of a dragon who, in gratitude, decides to take human form and become the heroine's personal maid. In a recent issue, another dragon who happens to be visiting remarks that dragons have a "surplus of time" because of their long lives. Therefore, to him, consorting with humans and exploring their culture is merely a "whim."

Paranormal romance often includes friendships and romantic attachments between human characters and long-lived or immortal ones. Often one side effect of the extreme disparity of the characters' lifespans is skimmed over or left unmentioned: Can somebody such as a vampire, a "Highlander" immortal, a pagan deity, or a very long-lived extraterrestrial truly "love" a human partner in the sense ordinary mortals understand that emotion? The immortal or long-lived person may look upon the human lover as more like a pet, particularly since the immortal has lived through a vast realm of experience unknown to the short-lived partner.

With proper care, a domestic rabbit may live eight to twelve years, a ferret five to nine. Some large dogs typically don't live longer than nine or ten years. Of course, human pet owners love their dogs, rabbits, or ferrets, but can one have the same relationship with a creature whose lifespan is about a tenth or less of one's own as with a human partner? Likewise, an immortal may cherish his or her human lover yet realize in the back or his or her mind that the relationship will last a small fraction of the immortal's lifetime. After the human "pet's" death, the love relationship and the sadness at its loss will eventually fade to a wistful memory.

I've encountered quite a few books and movies that highlight the problem of a human lover's growing old while the nonhuman partner remains eternally youthful. Fewer works seem to tackle the more basic issue of the emotional effect widely different lifespans would have on such a relationship. The commitment required of the human partner must inevitably be deeper than that offered by the nonhuman character. Once in a while I have come across a vampire romance in which the human character doesn't want to be transformed, and the vampire's attitude is something like, "I can spare a mere sixty or seventy years to make you happy." How would a human lover feel about being viewed in those terms?

Of course, in a story that tackles this issue, the long-lived hero or heroine would have to be the exception, a character who somehow comes to value his or her human partner as more than a pet. What elements in a cross-species relationship could draw this character outside the normal comfort zone of his or her kind?

Margaret L. Carter

Carter's Crypt