Creation narratives are usually 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 out with a Bang and once earth takes shape, the first organic molecules appear relatively quickly, less than a billion years later.
But at that point the story of life slows way down. Life remains in the form of single cells for the next two billion years. What was happening to our smallest and oldest ancestors all that time? Why did it take so long to move beyond the stage of one-only? Was evolution on hold?
What took so long was the creation of some of the building blocks for being alive. Portions of this creation echo the first chapters of Genesis. In the opening of the Bible, plant life emerges on the third day, including “fruit trees bearing fruit in which is their seed,” followed on 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. With a broad similarity, life as described by science evolved from the simplest cells to cells with a nucleus that enclosed the protected “seed” of DNA. This seemingly simple change set in motion the loss of one kind of immortality, the arrival of sex and death, and then a new kind of immortality. The process was slow because the changes were huge.
Science has a name for our first ancestor. LUCA, our “last universal common ancestor,” was a single-celled organism, a kind of bacteria, from which all life on earth today is descended. Inside LUCA was a floating coil of DNA, sections of which have been passed down to every living thing.
LUCA’s cell membrane protected its insides from the environment. With such protection, the genes could reproduce. Cells divided, with one set of genes in each new cell. The new cells were identical, a long line of Adam clones with as yet no Eve.
LUCA’s membrane enclosed only watery liquid and the genes. There were no other structures or major particles inside it. Gradually this emptiness filled. LUCA’s descendants absorbed other bacteria into themselves. These internal bacteria came to serve as cell nuclei. The genes that had floated around inside LUCA and other “Prokaryotes,” (“before a nucleus”) were now protected even more securely within this nucleus. The nucleus served as a seed that provided the DNA with a chemical environment of its own. Such cells with nuclei are called Eukaryotes (meaning “a true nucleus” and pronounced “you carry oats”). Seed-bearing Eukaryotes were much more energetic than their predecessors and eventually became hundreds of times larger and carried a hundred times more DNA.
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. Each would rub up against another Eukaryote and portions of their DNA sets would be inserted into the other. Primitive sex. With this exchange of DNA, genetic variation sped up. So did natural selection.
Later, some energetic, sexy Eukaryotes became multi-celled. 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”) to produce offspring. No longer was the parent reincarnated in a clone. It was left behind, and it aged and died.
As in the verses of Genesis, the co-mingling of different living things brought sex and death. Cellular life moved beyond Eden.
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 many might ask, how seriously should we take this idea that the continuity of our DNA actually amounts to immortality? Here is Harvard biology professor George Wald’s answer, in his famous 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.
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