As we approach the millennium, some two thousand years after the birth of Christ, it is tempting to reflect on time in the widest scientific sense in order to attempt to break free of Judea-Christian cultural residue and its somewhat stultifying, apocalyptic tone.
Studying stars, slime molds, and bacteria broadens our experience of time. If, curiously, our thoughts of eternity and the origins of life and the universe occur only in the present, so the living presence of you, your friends, your pets, plants, and countryside tell a tale of eons. Earth is no more a rock with some life on it than you are a skeleton infested with cells: Space and time are consolidated, condensed on living matter. To keep something alive, in vernacular English, is to maintain its process. This is what living matter does via cell self-maintenance and reproduction. When a person smiles, for example, we get a glimpse of the hard white compound of the teeth, which chemically is the compound calcium phosphate. The skeleton that flashes through is part of the bony support and skull casing of a specific sort of mammal, the bipedal human, whose evolutionary ancestry can be traced from arboreal primates to four-legged tree mammals to mammal-like stem reptiles and from there to amphibians, fish, and beyond. Prior to fish we find symmetrical aggregates of cells, pre-Cambrian forms such as the Ediacaran fauna in the fossil record. All plants, animals, fungi, and slime molds (technically, a kind of protoctist) are composed of cell colonies or clones. The cells in question all have nuclei with chromosomes in them and oxygen-using structures outside the nucleus called mitochondria. Plants and animals with their tissues made of aggregate cells with nuclei can ultimately be traced back to free-living cells with nuclei. And these free-living nucleated cells, familiar from high school biology as amoeba and paramecium, dwelled primarily in the salt water of the ocean—where calcium was a constant threat to their well-being. Calcium ions must continuously be exported from nucleated cells, potassium ions imported. And, in the billions of years of evolutionary time available for living innovation, what seems to have happened is that certain lineages of marine cells became adept not only at exporting their calcium waste but making use of it. Seashells and smiles—the cycling center of nature spins beauty from waste. Over evolutionary time, houses can be constructed from solid cellular waste. Over evolutionary time, luxuries and innovations become necessities; they become integral to the bodies that produce them.
Or contemplate the mitochondria, the oxygen-using inclusions found outside the nucleus in all your cells. All the mitochondria in your body, which provide you with metabolic energy to read this page, come from your mother: The father’s mitochondria are found only in the head, not the tail of the generation-crossing wriggling sperm—the tail which breaks off after fertilization. But these female-derived cell parts span not only the human and animal ages, linking you to Eve and ape hominids ancestral to our species: Genetic evidence also suggests beyond a reasonable doubt that they were engulfed by cells billions of years ago, when oxygen was just beginning to accumulate in the atmosphere. Oxygen gas in the atmosphere originally built up because a mutant strain of photosynthetic bacterium learned to splice hydrogen atoms from water to make its body; the result of this was oxygen gas as a waste—a waste that poisoned virtually all cells on the surface of the planet. But another mutant evolved that not only tolerated the volatile, burn-causing gas, but made use of it to power its internal metabolism. This was the respiring bacterium. Mitochondria in your cells have a curious habit of reproducing on their own timetable, and in precisely the manner of bacteria. DNA evidence confirms the reason: They are latter-day bacteria, bacteria that have evolved for so long in a living environment that they can no longer live on their own. Different sorts of bacteria—the mitochondria forerunners, colorful bacteria found today as chloroplasts in plants and as rhodoplasts in seaweed, and a larger host form poisoned by oxygen—seem to have teamed up symbiotically. We encompass not only the depths of time but many different bodies.
Although the millennium is but a blip on the map of deep time, our contemplation of the future is informed by our understanding not just of the recent but of the ranging past. The past is prologue, as Shakespeare said. When we contemplate the networking of the internet, the tendency or individuals to curb their reproduction and devote themselves to group pursuits, or the attempt to deal with global pollution, we can look not to the recent but to the evolutionary past. And looking we find. The early Earth found its equivalents of corporate mergers and the World Wide Web in the rampant genetic exchange and symbioses of bacteria. Birth control and virtual sex have their precedents in the tendency of all crowded organisms to moderate their reproduction—an unconscious form of planning necessary to stave off the death knell of overpopulation. And the attempt to deal with global pollution has its precursor in the smile and the shell. From a view that encompasses the depths of the recesses of deep time, the millennium is nothing.
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