No Such Thing as an Antelope

There is no such thing as an antelope.

Or at least that's true in the same sense that there's "no such thing as a fish". Which is to say that, obviously, antelopes exist but they aren't a scientifically definable group of animals. Or that, if they were, that group wouldn't map closely to what the regular English word "antelope" is supposed to mean.

The word entered English during the Rennaissance, and descends, via Latin, from the Greek "ανθολοψ". That first appears in the 4th century (so not old enough to be Ancient Greek, as such) and referred at the time to a mythical beast said to live along the Euphrates that had horns so sharp and serrated that it used them to cut down trees. We don't know why the Byzantine Greeks called it this, but there's not some "lope" that it's "ante" to (nor, to use most other European languages, is it an anti-lope); it's just a coincidence that the word sounds that way. For all we know, they were borrowing a word from some other, older language spoken somewhere out east.

Rise of the One-Toed Horses

The horse family contains, depending on your definition, just seven or eight living species of wild animal. If you count them separately, you can add the two domesticated species to those (that is, the horse and the donkey) but that's it. Moreover, all of these species are so closely related to one another that they can interbreed, albeit usually to produce sterile offspring, and so are traditionally placed into a single genus: Equus.

The genus is noted for its members having just one toe on each foot. The story of how this happened, and the number of toes became reduced, is one of the most frequently repeated in mammalian evolution, although the detail may be more complex than is sometimes presented. The story of how the genus evolved since that point, however, is much less so.

Boys or Girls?

Generally speaking, a newborn mammal is equally likely to be male or female. The sex ratio in the resulting population may not always be a perfect 50/50 if one sex has a shorter life expectancy than the other, but it's still going to be pretty close. There is a sound reason for this, and it's called Fisher's Principle, after geneticist and mathematician Ronald Fisher, who promoted it in the 1930s (although he probably wasn't the first to have thought of it).

The argument runs like this. Let's say that a particular species produces more females than males. Then males will have more mating opportunities than females, and will, on average, have more offspring. If a mutation then arises in a given individual that makes her more likely to give birth to sons, she will tend to have more grandchildren, many of whom will carry that mutation. Since they will also have an advantage, the mutation will spread through the population... until males are more common, at which point it's preferable to have more female offspring, and so on. 

The Rarity of Gophers

What exactly does it mean to say that a species is "rare"? The general idea, of course, is that it must have a lower total population than some species that is "common", and we can certainly argue over where to draw the line between the two. But, even then, rarity can manifest in different ways and that may have an effect on our perception of it.

Take the tiger for example. Today, this is undeniably a rare animal, and it's internationally listed as an endangered species. But go back two hundred years, and tigers were found across southern Asia from the easternmost parts of Turkey to the Russian Far East. They stretched from the deserts of Central Asia to the jungles of Java. But even then, if you'd gone to any of these places, the chances of actually meeting a tiger weren't all that high. Tigers are big predators, and they need a wide area to find enough food to eat. So they may have had a high total population (certainly compared with today) but they weren't exactly abundant in any given locality. Does that count as being "rare"?