Cannibalism: A Perfectly Natural History(24)

But if the consumption of maternal epithelial cells in viviparous caecilians gave this admittedly strange behavior a cannibalistic slant, it was in the egg-laying species that the story really took off.

In 2006, caecilian experts Alexander Kupfer, Mark Wilkinson, and their coworkers were studying the oviparous African caecilian, Boulengerula taitanus, when they made a remarkable discovery. This species had been previously reported to guard its young after hatching, and the researchers wanted to examine this behavior in greater detail. They collected 21 females and their hatchlings and set them up in small plastic boxes designed to resemble the nests they had observed in the field. Their initial observations included the fact that the mothers’ skin was much paler than it was in non-moms and that hatchlings had a full set of deciduous teeth resembling those employed by their oviduct-munching cousins.

Intrigued, the researchers set out to film the parental care that had been briefly described by previous workers. On multiple occasions, Kupfer and Wilkinson observed a female sitting motionless while the newly hatched brood (consisting of between two and nine young) slithered energetically over her body. Looking closer, they noticed that the babies were pressing their heads against the female, then pulling away with her skin clamped tightly between their jaws. As the researchers watched, the baby caecilians peeled the outer layer of their mother’s skin like a grape . . . and then they consumed it.



Scientists now know that these bouts of “dermatophagy” reoccur on a regular basis and that the mothers’ epidermis serves as the young caecilians’ sole source of nutrition for up to several weeks. For their part, female caecilians are able to endure multiple peelings because their skin grows back at a rapid rate.

“The outer layer is what they eat,” Wilkinson said. “When that’s peeled off, the layer below matures into the next meal.”

In addition to the ability of the skin to quickly repair and replenish itself, the nutritional content of this material is yet another interesting feature in this bizarre form of parental care. Normally, the outermost epidermal layer, the stratum corneum, is composed of flattened and dead cells whose primary functions are protection and waterproofing. But when the researchers examined the skin of brooding female caecilians under the microscope, they noticed that the stratum corneum had undergone significant modification. Not only was the layer thicker, it was also heavily laden with fat-producing cells, which explained why the baby caecilians experienced significant increases in body length and mass during the weeklong observations. It also explained why mothers of newly hatched broods experienced a concurrent decrease in body mass of 14 percent. In short, dermatophagy is a great way to fatten up the kids, but for moms on the receiving end of their gruesome attentions, the price is steep.

Scientists now believe that the presence of dermatophagy in both South American and African oviparous species offers strong support for the hypothesis that these odd forms of maternal investment originally evolved in the egg-laying ancestor of all modern caecilian species. Consequently, when the first live-bearing caecilians evolved, their unborn young were already equipped with a set of fetal teeth, which took on a new function, allowing them to tear away and consume the lining of their mothers’ oviduct.





8: Neanderthals and the Guys in the Other Valley


Here is a pile of bones of primeval man and beast all mixed together, with no more damning evidence that the man ate the bears than that the bears ate the man—yet paleontology holds a coroner’s inquest in the fifth geologic period on an ‘unpleasantness’ which transpired in the quaternary, and calmly lays it on the MAN, and then adds to it what purports to be evidence of CANNIBALISM. I ask the candid reader, Does not this look like taking advantage of a gentleman who has been dead two million years.

— Mark Twain, Life As I Find It, 1871

In 1856, three years before publication of Charles Darwin’s On the Origin of Species, a worker at a limestone quarry near Düsseldorf, Germany, uncovered the bones of what he thought was a bear. He gave the fossils to an amateur paleontologist, who in turn showed them to Dr. Hermann Schaaffhausen, an anatomy professor at the University of Bonn. The bones included fragments from a pelvis as well as arm and leg bones. There was also a skullcap—the section of the cranium above the bridge of the nose. The anatomist immediately knew that while the bones were thick and strongly built, they had belonged to a human and not a bear. They were, though, unlike any human bones he had ever seen. Beyond the robust nature of the limbs and pelvis, the skullcap had a low, receding forehead and a prominent ridge running across the brow. These anatomical differences led him to conclude that these were the remains of a “primitive” human, “one of the wild races of Northern Europe.”

The next year, the men announced their discovery in a joint paper, but the excitement they hoped to generate never materialized. This was, after all, a scientific community that had yet to reject the concept that organisms had not changed since God created them only five thousand years earlier. It was no real surprise, then, when a leading pathologist of the day examined the bone fragments and pronounced them to be modern in origin, insisting that the differences in skeletal anatomy were pathological in nature, having been caused by rickets, a childhood bone disease. He blamed the specimen’s sloping forehead on a series of heavy blows to the head.

By the early 1860s, thanks to the publication of On the Origin of Species, there was increased interest in evolution, especially the topic of human origins. Now the concept of “change over time” was no longer alien, and in the newly minted Age of Industry, the idea of the survival of the fittest was not only palatable, it was profitable. By 1864, the rickets/head injury hypothesis had been overshadowed by the discovery of new specimens with identical differences in skeletal structure. Neanderthal Man became the first prehistoric human to be given its own name, a moniker derived from the Neander River Valley, where the presumed first fossils had been uncovered.11