Dr Meyer Rochow bio essay : "Hitching a ride"


Something to chew on

Many years ago on a Caribbean Cruise I met a man who had made a fortune with artificial teeth or, to be more precise, with developing chemicals for colour nuances between snow white and yellowish brown. I learned from him that human teeth display hundreds of subtle hues and of course jacket crowns or dentures need to resemble the natural teeth of a person.

Teeth, as we all know, hold important clues for the criminologist, but also for the palaeontologist studying distribution and evolution of vertebrates. Teeth are extremely durable; they are useful for seizing and chewing food and consist of bonelike material called “dentine” capped with the even harder “enamel”. Teeth in mammals can be categorized as incisors (the front teeth), canines (the corner teeth), and molars (the grinding teeth further back), but dolphins seem to lack dental specializations. Apart from their biting and chewing function, teeth may have other roles to play. In humans speech without teeth becomes slurred and difficult to understand. Baring of the teeth has signal function not only in humans, but many species, e.g., dog, monkey, horse, etc. Teeth in mole rats are used as “digging tools” to excavate the subterranean tunnels these rodents live in and large visible teeth may be a sexual characteristic as, for example, in boars, musk deer etc. In the pig deer (Babyrousa babyrussa) of Sulawesi, canine tusks of the male actually grow upward through the flesh of the snout and, continuing to grow, may even penetrate the animal’s skull!

Teeth can also be formidable weapons in defence, even if useless for biting and chewing: the tusks of elephants and hippopotamuses come to mind. But while the up to 80 cm long and six kg heavy tusks of the hippos are anatomically canines, those of the elephant are incisors. Incidentally, the world’s first plastic (namely celluloid) was invented by John Hyatt in 1865 to protect elephants, whose tusks, i.e. the ivory, was used to manufacture billiard balls for the increasingly popular cue sports like snooker etc. Some of the most complicated teeth are not found in mammals, but in snakes and certain deep sea fishes. Some venomous serpents possess hollow teeth with a canal inside for injecting or spitting venom, while some deep-sea fish may sport hinged and dagger-like teeth of grotesque proportions. And talking about fishes, sharks actually carry teeth not only on their jaws but much smaller ones, yet nonetheless proper little teeth, all over their body. Birds do not normally have teeth, but very occasionally reports of birds with a couple of teeth have been published, which serves as a reminder that the birds’ ancestors were indeed reptiles – and they did have teeth.

Although most mammals have two generations of teeth (milk and adult teeth), the proverbially lazy sloth produces only one set. A single over one metre long tooth is the rule in the Arctic narwhale male and a few mammals like the Australian platypus and anteaters have no teeth at all when adult. However, how silly zoological nomenclature can sometimes be shows the example of the armadillos: classified as “Edentata” (toothless animals), they actually possess more teeth than many other mammalian species. And toothless humans? Well, they are being helped by my acquaintance from the Caribbean Cruise.

thirst ship sheep sailor evolution

Let’s embark on another ship with this story!

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2016.
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