Category Archives: Edentates

Double or Nothing

Nine out of ten Earthlings agree: Nothing beats a hot pair of twins. If you are already attracted to someone, the only thing that can possibly improve their overall hotness is discovering that there is two of them. In fact, that’s the best theory I’ve heard yet to describe why identical twins, as a phenomenon, are so popular in everything from DoubleMint Gum commercials to Playboy spreads: we singletons tend to objectify them as the same person with the advantage of having two bodies. But biologically speaking, does having a clone confer any advantage to you as an individual, or even to you as a species?

There are some questions better left unasked.

First, a primer on twinning. Dizygotic twins, otherwise known as fraternal — or, in the case of two females, which is more common, sororal — twins are the product of two separate eggs, and form in two separate placentas. In humans, having any kind of twin is a gamble — even a fraternal twin is five to seven times more likely to die in the womb than a singleton fetus, and at much higher risk of mental retardation, learning disabilities, respiratory problems, cerebral palsy, and a host of other health problems. But in the animal world, di- or polyzygotic young are the norm; we call them litters. In a cruel world, a species usually cannot count on only children to further itself, and so hedges its bets with siblings.

With dizygotic twins, it is possible to produce siblings with different genetic defects.

More rare in humans and other animals are monozygotic twins; that is, identical twins developed from a single egg and placenta. You might be a twin or know a twin who looks very different from his or her womb-mate, as environmental factors such as lifestyle choices and childhood illnesses cause certain genes to express themselves in one twin and not another. Identical twins may share the same DNA, but don’t bear the same fingerprints. I’m a singleton myself, but sometimes I imagine a hypothetical twin brother I might have had who works out, is a vegetarian, and hasn’t been drinking coffee daily since age 14. He is 6’1″, physically fit, has a normal haircut, and I secretly hate his guts.

Happy as he was for his brother Paul, Morgan Hamm had to wonder if he took the silver medal because he had eaten a second slice of birthday cake at age 9.

Twins in human reproduction seem to be a happy accident; after all, twins make up a mere 2% of the world’s population, with identical twins or triplets constituting only 8 percent of those, or 0.2% of all people. But what about species in which twinnage is fairly common? Can producing two or more genetically identical offspring be a successful reproductive strategy? At first glance, the animals that frequently have twins have little in common: ferrets, cats, sheep and deer all frequently bear twins, and polar bears almost exclusively do. But for popping out passels of identical bundles of joy, one mammal has the rest beat: the nine-banded armadillo, which as a rule produces litters of identical quadruplets.

Nothing beats a hot pair of twins, except two hot pairs of twins.

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Raiders of the Ark

To the builders of Ark Encounter, a state-sponsored theme park in Kentucky espousing that the flood in Genesis was a historical event: While carpenters you must have many, and animal handlers at least a few, I imagine you don’t have a proper biologist on your crew. Before you build a replica of the famous Ark, let me give you a few pointers that may help you with construction:

  • There are between 3 and 30 million species of animal on Earth. Perhaps more.
  • 40,000 of these are spiders, and perhaps 1 million of those species are beetles. Happy hunting.
  • The Ark was supposedly 300 x 50 x 30 cubits — a “cubit” being about 18 inches — which means the boat was roughly 450 x 75 x 45 feet, or roughly the same carrying capacity as 569 railroad freight cars. No doubt your carpenters and engineers already know this. What your engineers may not have accounted for is that 569 train cars filled with 1,600 tons of animals do not float.
  • Especially not when you include the aquarium. You may have thought that Noah at least got to ignore the aquatic animals, but unfortunately, when you flood the Earth with freshwater until it covers the mountains, neither most freshwater nor most saltwater animals can survive. The ocean’s salinity level would have been merely “brackish,” a mix of salty water and fresh which most aquatic animals cannot tolerate. So you’ll want to account for several trillion gallons of water in several wooden aquariums, including potable freshwater for yourself and the terrestrial animals.
  • Might want to reconsider the size of a “cubit,” huh?
  • The ark is typically pictured with a single pair of giraffes, their heads sticking out like a couple loaves of french bread in a grocery bag. There are at least five subspecies of giraffe. Please do not forget all your giraffe-holes.
  • There was undoubtedly a separate room for the Tasmanian devils and the honey badgers. Probably a dungeon, with restraints.
  • A giant panda consumes between 20 and 40 lbs of bamboo daily. Account for storage capacity for 6,300 lbs of bamboo for your pandas alone. The elephants will need 60 tons of food for themselves.
  • In Genesis 7:2-3, it says:

    Of every clean beast thou shalt take to thee by sevens, the male and his female: and of beasts that are not clean by two, the male and his female.

    Of fowls also of the air by sevens, the male and the female; to keep seed alive upon the face of all the earth.

    This means that only the “unclean” animals were taken in single pairs, while “clean” animals were taken 14 at a time. Given that there are roughly 10,000 birds on Earth, for example, that means your Ark has to account for 140,000 individual birds. Even squeezed tight, there is not enough floor space on your current Ark model for the 100,000 square feet of newspaper Noah needs to change every day.

  • Here’s a trickier question: Where did Noah keep the termites? As an “unclean” animal, perhaps there were only two of each species aboard, a queen and a male. But the paradox here is that a giant anteater, which primarily eats termites, will eat 30,000 in a single day. And as it lacks teeth of any kind, or hydrochloric acid in its stomach as most mammals have (the formic acid from its ant and termite prey works just as well), you have to feed the anteater termites. So, ignoring the pangolins, the tuandaras, the aardwolves, the numbats, and all other anteaters and ant-eaters, a single pair of giant anteaters would need 12.6 million termites to survive the 7-month journey. Seeing how the Ark is built entirely of wood, you can see how this might present a problem.

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  • The Subterraneans

    Underground! From rabbit warrens to nuclear fallout shelters, it’s a great place to hide out. If you’re a terrestrial vertebrate, the safest place you could conceivably be is underground, where you’re protected by a temperature-stable bunker, an ocean of dirt, rocks, and roots. But it’s one thing to dig a burrow, and another to spend all your time underground, swimming through the soil. If you’re a full-time tunneler, there are really just two body types you can evolve to fit: the “mole” model, and the “earthworm” model.

    Consider the difficulties of underground travel. You don’t want to be too large, or digging would be exhausting. You don’t want large eyes, which would be useless and become full of grit. You’ll need a keen sense of smell and touch, as you’re likely to be finding food by chemical and tactile signals rather than visual ones. This star-nosed mole from North America is a great example of the mole archetype: small, compact, wedge-shaped, with sealed-off eyes and ears, powerful front claws, and 22 fleshy appendages that are among the most sensitive touch receptors in the animal kingdom. Star-nosed moles are true swimmers; they breaststroke through soil, but are also quite adept at catching prey in the water. Moles are insectivores, related to that most ancient of mammals, the shrew. But thanks to the awesome power of convergent evolution, you don’t have to be related to the moles to become a mole.

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    Meditation on Slow Angels

    Something you may know about me: in college, I was a botany major. Something you may not know about me: in my junior year, my concentration was in canopy ecology. My grand plan was to go climb trees in the rainforest and inspect the animal life living in epiphytic bromeliads. (I am somewhat off-track.) But last week I found a book my dad bought second-hand and forgot to give me for Christmas, Life Above the Jungle Floor, a travelogue by a canopy ecologist working in Costa Rica, and have been enjoying ever since. And this brings me to my latest “weird animal” post:

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