What is life like in the womb? Thanks to National Geographic, we’ve been able to refresh our memories with a beautiful book (In the Womb: Witness the Journey from Conception to Birth through Astonishing 3D Images) as well as a TV mini-series that makes use of the most advanced video technology to reveal human prenatal development. Now a new book (In the Womb: Animals) and series examine the prenatal life of our fellow mammals — and it’s weirder than I ever expected.
If you’re a professional zoologist, nothing here will surprise you. But I was amazed to learn that an elephant’s trunk is a hundred times more sensitive than our fingertips. It contains 40,000 individual muscles, while the entire human body requires only 639. And did you ever think about an elephant’s feet? Those enormous, calloused feet, which stomp around under the weight of maybe 11,000 pounds of elephant all day, are so sensitive that they can receive sound waves through the ground; elephants can “hear” through their feet. And while those massive feet look as flat as pancakes, the sole is actually spongy and convex (a design that Nike might want to study).
In the Womb: Animals is mesmerizing, and it can turn you or anyone you know into a veritable fountain of Wow Facts. Since the book is about gestation, it is also about sex, and there is a lot more variation in how animals mate than I’d ever suspected. The male elephant’s “curvy three-foot-long penis” never actually enters the female, and the male lemon shark doesn’t even have a penis. Perhaps irritated about being teased for this, he and some buddies grip the female in their jaws while assaulting her, a process that will leave her with scars, “and some females don’t survive mating at all.”
An aspect of this book that I particularly appreciated is the deftness of author Michael Sims’s prose. It doesn’t read like one amazing info-bit after another, though (as you can see) to a large extent that’s the material he has to deal with. The tone is conversational and lightly amusing. Discussing the prenatal development of a dog’s mouth, he writes that it is also the equipment he will use to bark, “that impressive tool dogs use to greet, notify, and threaten, as well as to torment writers who are trying to concentrate.”
On virtually every page a theory is proposed to explain why this or that odd feature evolved. “All female dogs go through a pseudo or phantom pregnancy.” This evolved so that unmated females could nurse the puppies of a mother dog needed elsewhere (e.g., to hunt). Puppy eyelids appear a month after conception, in order to seal the eyes shut against waste in the amniotic fluid. Dewclaws on a dog’s leg don’t really have a purpose any longer, but they indicate a five-toed ancestor; over time, dogs’ feet evolved so they could run faster, on tiptoe.
You don’t have to be an anti-Darwinist to recognize that some of these theories sound more theoretical than others. The tendency to wonder and guess is one of the human creature’s most endearing characteristics. Sometimes we seem to be in the land of Rudyard Kipling’s Just So Stories: This is how the leopard got his spots, this is how the rhinoceros got his skin, and this is how the dog got his dewclaw.
Some theories prompt obvious questions. Any mutation may, of course, occur; the question is how disadvantageous mutations could have become the prevailing mode. Why did baby kangaroos evolve to be born in a nearly fetal state and then struggle up to their mom’s pouch, when the usual pattern of remaining longer in the womb is so much safer? It’s great that a shark’s yolk sac, its prenatal food source, is able to turn into a placenta after it depletes — but why did it evolve to deplete prematurely, before the shark was finished developing? Why did the sand shark evolve so that the strongest fetus devours all its brothers and sisters in utero? Wouldn’t that inhibit rather than advance reproduction?
Scientists don’t claim to have all the answers; as Sims says, “all over the planet, human beings are amassing . . . facts and doing the best they can to interpret them. When nature reminds us that our explanations are approximate, we tweak them again.” This work of observing and theorizing is thrilling. “How exciting,” Sims writes, “to decipher old mysteries and discover new ones in previously uncharted territory — inside molecules, at the bottom of the sea, beyond our galaxy, and in the womb.”
And how awesome it is to recognize that human beings have evolved to find this knowledge exciting. As G. K. Chesterton said, the simplest lesson of the ancient cave drawings is that an observer has now “dug very deep and found the place where a man had drawn the picture of a reindeer. But he would dig a good deal deeper before he found a place where a reindeer had drawn a picture of a man.” This beautiful record of animal life in the womb is not produced by cats or crocodiles but by members of our own human race, the most curious (in all senses of the word) creature of them all.