Feeling Old? Envy the Lobster

The certainty of death is hard enough. But aging as a prelude—the wrinkling, weakening, deteriorating and the rest of the assault—can feel downright demeaning! Is there a benefit here for survival of the species, or for any species, that no one told me about before I reached 73?

lobster (anvilcloud.blogspot.com)

(anvilcloud.blogspot.com)

Not all species go through their version of this. The paths that organisms follow after maturity vary enormously. Some plants live for one year only, others come back every season. Bacteria clone themselves and don’t die from age at all but from hostile organisms and conditions in their environment. Seabirds age very slowly; as long as they can fly, they can stay ahead of most predators.  Lobsters don’t age; they can continue to grow and remain fertile for 45 years or more in the wild, dying only when they can no longer molt and grow a larger shell.

How and why the declines of aging are included in the final phases of some species’ lives is complex. Wikipedia’s “Senescence” introduces the range of theories and uncertainties. Here are three insights from the evolutionary perspective that make sense to me.

One is that certain harmful genetic mutations switch on later in life after an organism’s reproductive period has ended. Many cancers in humans do, for example. Because they don’t impact the number or health of the offspring, such genes do no harm to the persistence of the species and so they are unlikely to be lost over the generations. The diseases of the elderly get passed along by the young.

Even more unfortunately, some mechanisms in our bodies boost our health when we’re young and then come back to bite us when we get older. Digesting calcium, for instance, builds strong bones early on but helps clog and stiffen arteries decades later. As long as such a function improves our fitness to make and raise babies, whatever damage it does later on doesn’t matter much in the very long run.

A third way in which selection seems indifferent to the pains of aging is statistical: even if natural selection did reduce the ravages of aging and prolong the fertile period, the population of such organisms would still decline with age as accidents and predators took their inevitable toll. The body invests its resources where they are the most effective for the future, in youth and early reproduction, not in a comfortable old age.

In these ways and others, aging is linked to the importance of reproduction and the dangers of predators and other external forces. For primates, including me, we reproduce early because the big cats—leopards, jaguars, cougars, tigers—stalked us for millions of years in the forests and grass lands. And for most other species as well, the safest bet for species continuity is simple: reproduce early. Still, the exceptions are fascinating. Lobsters in their suit of armor run little risk from ancient predators, so they can reproduce throughout their lives without ever aging into genetic irrelevance.

So, armed with such insights, do I experience my weakening muscles, declining sexuality, distracted thinking,  and dulled senses with any less resentment? Yes, a little. Knowing that the decline has its place, even though it’s a melancholy one, in the evolution that brought me to being in the first place is some consolation.

 

Genesis for Non-Theists

Creation narratives are lively stories.  In the Bible, God creates the universe and earth in six days. In other traditions, creatures are dismembered, huge eggs hatch, birds create land. Even science’s own creation narrative starts with a Bang and once earth takes shape, the first organic molecules appear relatively quickly, within a billion years. 
 
But at that point the scientific story of life slows way down. Life remains at the stage of single cells for the next two billion years. What was happening to our smallest, oldest ancestors all that time? Why did it take so long to move beyond the stage of one-only? Was evolution on hold?
timeline

From “Oldest bacteria fossils” to “Multi-cellular eukaryotes” 2 billion years later, life on earth was single-celled.
(vector-clip-art.com)

What took so long was the creation of the building blocks for being alive. It’s a creation story with parallels to the first chapters of Genesis. Here’s the biblical sequence: plant life emerges on the third day, including “fruit trees bearing fruit in which is their seed,” followed over the next three days by creatures of the water, air, and land, including man and woman. A few verses later we read about the Garden of Eden and, symbolically, the beginnings of sex and death.

Here briefly is science’s version: life evolved from the simplest cells to cells with a nucleus that enclosed the protected “seed” of DNA. This change set in motion the end of one kind of immortality, the beginnings of sex and death, and the emergence of a new immortality.

The process was slow because the changes were huge.

LUCA
Like the Bible, science has a name for our first ancestor. LUCA, our “last universal common ancestor,” was a single-celled organism, a kind of bacterium, from which all life on earth is descended. Inside LUCA was a floating coil of DNA, sections of which have been passed down to every living thing.
Prokaryote

Our common ancestor, a cell with DNA but no nucleus
(shmoop.com)

LUCA reproduced simply by dividing, with one set of genes in each new cell. The new cells were identical, a long line of Adam clones without an Eve.

LUCA’s membrane enclosed only watery liquid and the genes. Gradually LUCA’s descendants “ate” and absorbed other bacteria. Some of these bacteria turned into the nucleus of the cell that absorbed them. They became the container for the cell’s genes. Such cells advanced from  prokaryotes (before a nucleus) to eukaryotes (a true nucleus, and pronounced “you carry oats”). The nucleus was a seed, a seed that provided the DNA with a chemical environment of its own and helped grow more complex DNA and much larger cells.
Sex, Death…
cell

Cells get a nucleus–and more.
(biogeonerd.blogspot.com)

Early cells were, in their own way, immortal. The genes in both prokaryotes and early eukaryotes would reproduce and then the cell would split into two identical cells, as bacteria still do. Did such cells die? Eventually, but only from accident or the environment. In this Eden, cells did not get older. They became their own offspring and could theoretically live forever.

Eukaryotes, however, found a new way to reproduce. One would rub up against another eukaryote and portions of their DNA sets would be inserted into the other—the original sex act. With this exchange of DNA, genetic variation sped up, at last. So did natural selection.
 
In the next step, sex became specialized. As some early organisms became multi-celled, such as algae, they reproduced not by division of the whole parent organism but, as with us, by means of specialized germ cells (not the disease kind of germ but the creative kind, as in the “germ of an idea”).
No longer was the parent reincarnated in a clone, as in bacteria. It was left behind, and it aged and died. As in Genesis, the co-mingling of different living things brought sex and death. Cellular life moved beyond Eden.
 
…and Immortality
So we have lost the immortality that the prokaryotes enjoyed. But we have found it in another, more complex form. Our immortality runs through the genetic line of our children and other blood  relatives. It turns out that it is not the body, the soma, that is the crucial package. It is the germ cells that carry the DNA forward. 
 
But is this an adequate and satisfying idea for us humans who dream of living forever? Is the continuity of DNA a meaningful form of immortality? Here is one answer from Harvard biology professor George Wald, in his 1970 lecture on “The Origins of Death.”
 
We already have immortality, but in the wrong place. We have it in the germ plasm; we want it in the soma, in the body. We have fallen in love with the body. That’s that thing that looks back at us from the mirror. That’s the repository of that lovely identity that you keep chasing all your life. And as for that potentially immortal germ plasm, where that is one hundred years, one thousand years, ten thousand years hence, hardly interests us.
 
I used to think that way, too, but I don’t any longer. You see, every creature alive on the earth today represents an unbroken line of life that stretches back to the first primitive organisms to appear on this planet; that is about three billion years. That really is immortality. For if the line of life had ever been broken, how could we be here? All that time, our germ plasm has been living the life of those single celled creatures, the protozoa, reproducing by simple division, and occasionally going through the process of syngamy — the fusion of two cells to form one — in the act of sexual reproduction. All that time, that germ plasm has been making bodies and casting them off in the act of dying. If the germ plasm wants to swim in the ocean, it makes itself a fish; if the germ plasm wants to fly in the air, it makes itself a bird. If it wants to go to Harvard, it makes itself a man. The strangest thing of all is that the germ plasm that we carry around within us has done all those things. …
I, too, used to think that we had our immortality in the wrong place, but I don’t think so any longer. I think it’s in the right place. I think that is the only kind of immortality worth having — and we have it.

The Immortal Jellyfish

The Immortal Jellyfish

There is a species of small jellyfish that will, when it is sick or injured, instead of dying, regenerate itself. It will sink “to the bottom of the ocean floor, where its body folds in on itself—assuming the jellyfish equivalent of the fetal position. The bell reabsorbs the tentacles, and then it degenerates further until it becomes a gelatinous blob. Over the course of several days, this blob forms an outer shell. Next it shoots out stolons, which resemble roots.” These stolons grow into new jellyfish.

The description is from Nathaniel Rich’s article, “Forever and Ever” in the New York Times Magazine (Dec. 2, 2012). Over two years, one lab colony of such jellyfish rebirthed itself ten times. The jellyfish’s official name is Turritopsis dohrnii and its not-surprising nickname is the Benjamin Button jellyfish. As different from us as it may look, our genetic makeups are surprisingly similar.

We view death as part of the definition of life, as a boundary that all living things share. But death, it turns out, is not absolute. The clichés that “you live and then you die” and “life is short” tap into more complexity than they were intended to. Bacteria , for example, divide in two: individual bacterium may be destroyed or die from illness, injury, or antibiotics, but most of them form identical clones, which then clone again and again. And as for life being brief, Buffalograss, a prairie plant resistant to weather extremes, sprouts underground stems which in some locations may have been growing for the last 15,000 years. Among individual plants, the Bristlecone Pine named Methuselah in California, is coming up on its 5000th birthday. And Wikipedia’s lengthy “List of Longest Living Organisms” begins with a note that “This list is incomplete.”

Today the immortal jellyfish is a specialty of Dr. Shin Kubota at Kyota University’s Seto Marine Biological Laboratory. Kubota spends much of his days feeding, caring for, and observing his wards. A prolific researcher, Kabuto is also spiritual and a little eccentric. His expressed goal is to become young again himself, even to achieve immortality, or at least to point a way towards a cure for cancer.

In what ways might our knowledge of rejuvenating jellyfish and other exceptions to the rule of death change our perspective on our mortality? Not surprisingly such reports encourage daydreams of life-prolonging gene splicings. But they also complicate and enrich our view of the vulnerabilities and persistence of living things.