Six Feet Over: Adventures in the Afterlife by Mary Roach Read Free Book Online Page A

historic import of the sea urchin. * In 1875, a German biologist named Oskar Hertwig watched a sea urchin sperm nose its way into a sea urchin eggand fuse with it to form a single nucleus, right there under his microscope. It took civilized man six thousand years to figure out how life begins, and the honors go to humble Oskar and his amorous echinoderms.
    Scientists had long suspected that human generation had something to do with eggs—most everyone who owned a chicken suspected this—and they knew it had to do with intercourse and semen, but beyond that they were unclear on the specifics. This was largely because they couldn’t see the specifics. The sea urchin’s eggs offered two advantages: (a) they’re see-through, and (b) they’re fertilized outside of the female’s body, in the ocean or, in occasional cases, under some German dude’s microscope.
    This means that for six thousand years, there was lots and lots of entertaining speculation about the creation of new human beings. Some of the earliest and most thorough speculating was done by Aristotle. The learned Greek—who, I was interested to read, went through life with a lisp—decided that the man’s semen supplied the soul of the new individual. The spirit, in those days, was envisioned as a kind of vapor or breath, which was understandable given breathing’s obvious connection to being alive. Hence Aristotle’s name for the spirit: pneuma , which is Greek for “wind.” He believed it was this pneuma, carried in the semen, that orchestrated the creation of a budding human being. Upon arrival inside the uterus, the pneuma would set to work, building new life out of the materials it had on hand: menstrual blood, to be unpleasantly specific. Aristotle described the process as a sort of coagulation, using the apt if inelegant analogy of a cheesemaker’s rennet solidifying milk. It took seven days for the new entity to “set,” at which time the pneuma would infuse it with the first of three eventual souls. This vegetative soul, as it was called, was a sort of starter soul, a learner’s permit for humanexistence. You were a thing that eats and grows: more than a potato but less than a human.
    On the fortieth day, Aristotle theorized, the proto-human morphed into what he called the sensitive soul. By “sensitive,” he meant “relating to the senses,” for forty days is about when the embryo’s sense organs begin to appear. After some further, unspecified amount of time had passed, the pneuma would allow the newly minted sensitive soul to upgrade to a rational soul. Here was the black belt of humanness, the sort of spirit that rises above animal lusts and girly emotions and pays no heed to people who make fun of the way it says semen .
    And that’s pretty much what people believed for the two thousand years after Aristotle put the word out. The man who elevated the ovum to a leadership role in the proceedings was seventeenth-century English physician William Harvey. Harvey is best known for figuring out that blood circulates in a closed system of arteries and veins, a feat he managed by dissecting cadavers, including that of his sister. For his pioneering work in reproduction, you will be relieved to learn that Harvey left the womenfolk alone. Here he turned to a herd of deer that wandered, ever more warily, the grounds of his employer, King Charles I. As a student of Aristotle’s teachings, Harvey expected to find the requisite coagulated blob when he dissected the deer’s uteruses. He was astonished to instead find the beginnings of tiny deer: embryos and fetuses encased in sacs, which he mistakenly identified as eggs. The egg, Harvey felt, contained the makings of “all that is alive.” Semen was relegated to the role of a “contagion,” prompting human generation much as a virus does a cold.
    And how would the life force, the soul, get into the egg? Here science abandoned Harvey, and he fell back on religion: “It is given … by the