Random Mammal Generator

What the mammal generator does

You want an animal. For a class, a quiz, a drawing, a story, or because somebody said binturong and you need to know.

This gives you one. Pull a batch and you will meet a fossa, a pudu, a springhare and a numbat, and you are on this list too, which is worth sitting with for a second.

What follows is why the word exists. It turns out somebody chose it, in a specific year, for a specific reason, over better options. And the trait that actually holds the group together is not the one in the name. It is in your ear.

How to use it

1. Choose how many you want. One for a subject. Twenty to find out how few you recognise.
2. Press Generate. A fresh set every time.
3. Press Copy to take the set with you.

The name was an argument, not a description

Ask what makes something a mammal and most people say the same thing. Milk. Which is the answer the word gives you, since mammal comes from mamma, the Latin for breast.

Now notice the problem with it.

Half of every mammal on this list does not have functioning mammary glands. Males do not lactate. And the females only lactate for part of their lives, and only some of the time. So the trait the entire class is named for is present in roughly a quarter of the class at any given moment.

Meanwhile hair is on all of them, all of the time, from birth to death, male and female, whale and bat and you. Hair is the trait that actually behaves like a definition, and it was available. Linnaeus could have said Pilosa. The hairy ones. Nobody would have blinked.

He did not. In 1758, in the tenth edition of Systema Naturae, Carl Linnaeus threw out the term everybody had used since Aristotle, Quadrupedia, the four footed ones, and coined Mammalia instead. He was a conservative namer everywhere else. Look at his other classes. Insecta is about the segmented body. Amphibia is about where the thing lives. Vermes comes from the colour of an earthworm. All descriptive, all obvious, all boring. Mammalia is the outlier.

In 1993 a historian called Londa Schiebinger asked the obvious question, which is why, and she wrote the paper that answers it. It won a prize and it is one of those pieces of work you cannot unread.

Her argument is that the choice sits in its moment. Linnaeus was writing in the middle of a loud European argument about wet nursing, which was the ordinary practice of the well off handing their babies to another woman to feed. There was a campaign against it, tied up with ideas about what women were naturally for, and Linnaeus was personally in it. He wrote a pamphlet against wet nursing. He and his wife had seven children.

So the class of animals that includes every human being got named after the breast, in the same years its author was publicly arguing that women should be at home using theirs.

Schiebinger is careful and it is the care that makes it land. She does not say he sat down and did it on purpose. Her point is sharper than that. A scientist being innocent of what their work implies does not stop the work carrying the implication. Nobody voted on Mammalia. It just fitted the moment so well that it went into English and stayed, and here we all are, two and a half centuries later, filed under a body part on the strength of an eighteenth century argument about babies.

Every other name on this list describes an animal. The name of the list itself describes an era.

You hear with what used to be your jaw

So if the name is a poor definition, what is a good one?

Three bones. Not hair, not milk. Three tiny bones in the middle ear, and they are the thing every mammal has and nothing else does.

You have them right now. The hammer, the anvil and the stirrup, sitting behind your eardrum, the smallest bones in your body. The stirrup is about three millimetres long. Sound hits the drum, the drum shoves the hammer, the hammer shoves the anvil, the anvil shoves the stirrup, and the stirrup pushes on the fluid of the inner ear. Three bones passing a message along.

A reptile has one bone in there. A bird has one. Only mammals have three, all the way from the numbat to the blue whale.

Now the part that should stop you.

Two of them used to be jaw.

In your reptilian ancestors, the hammer and the anvil were bones at the back of the jaw, and their job was to be the hinge the jaw opened on. Load bearing. Chewing. And over tens of millions of years, in a sequence of animals that is one of the best documented transitions in the entire fossil record, that hinge shrank, unhooked, drifted backwards and upwards, and moved into the ear, where it stopped opening the mouth and started carrying sound.

You can watch it happen in the rocks. There are animals in that sequence with both joints at once, an old jaw hinge and a new one working side by side, halfway through the handover. It is not inferred. It is sitting in drawers.

And it still happens in you. A human embryo builds those bones in the jaw region and then migrates them into the ear during development. Every one of us reruns the whole thing in a few weeks, quietly, before we are born.

Which is why every mammal on this list can hear high frequencies that a reptile simply cannot. Three bones give you leverage. Leverage gives you sensitivity. Sensitivity in the dark is why the whole group got anywhere at all, in the long stretch when the animals on the dinosaur list owned the daylight.

You are listening with a jaw hinge. That is the actual membership card.

The animal that breaks every rule

Pull the platypus off the list and everything above starts wobbling.

It lays eggs. Leathery ones, in a burrow. So much for live birth.

It has no nipples. It makes milk and it has nowhere to put it, so it sweats it through patches on its skin and the young lap it out of the fur. So the class named after the breast contains an animal without one.

The males have venom. A spur on each back ankle, connected to a gland, and the venom is not fatal to a person but it is reportedly so painful that morphine does not touch it. No other mammal does this at all.

It has no stomach. The oesophagus runs straight into the intestine. Somewhere back down the line its ancestors had one and the lineage simply threw it away.

And it hunts with electricity. It shuts its eyes, ears and nostrils underwater, completely, and finds prey using electroreceptors in the bill that pick up the tiny electrical fields of a shrimp's muscles twitching. It is not feeling around. It is reading the water.

When the first specimen reached British scientists in 1799 they thought it was a hoax. Somebody had obviously sewn a duck's bill onto a beaver. There are cut marks on the original where a curator went looking for the stitches.

But it has hair. And it has the three bones. And it makes milk, however inelegantly. So it is a mammal, absolutely and without argument, and the echidna on this list is the same story.

Which is the useful lesson about definitions. The platypus is not an exception to the rules. It is the thing that shows you which rules were ever load bearing. Live birth turned out to be optional. Nipples turned out to be optional. The three bones did not.

Where these come from

The animals here come from a list our team put together and checked by hand. Press the button and one is drawn out of it at random.

That is the whole thing, and it runs on your own device.

From a bumblebee to a blue whale

One last thing worth having in your head when you read a batch of these.

The blue whale is on this list. It is the largest animal that has ever lived, and that includes everything on the dinosaur list. Its tongue outweighs an elephant. A child could crawl through its main arteries. It got that big by eating some of the smallest animals in the ocean, in quantities that are difficult to write down.

The bats on this list are at the other end. The smallest mammals alive weigh about two grams, which is less than a coin, and their hearts run at over a thousand beats a minute. They are close to a physical floor. Go much smaller and you cannot eat fast enough to stay warm, because a small body loses heat faster than a tiny mouth can replace it.

That is a range of something like a hundred million to one, in body mass, inside one group of animals, all of them running the same warm blooded chemistry and all of them carrying the same three bones.

And the whale and the bat both use sound to see. Independently. One in the ocean and one in the air, both shouting into the dark and reading what comes back, using an ear built out of a jaw hinge.

Pull twenty names and you are looking at that whole spread. It is the same animal, solved a hundred and seventy nine different ways.

Questions people ask

Are whales and dolphins really mammals?

Completely, and the evidence is in the bones rather than in a textbook rule. They breathe air, they make milk, they are warm, they have the three ear bones, and they have hair, at least as embryos and often as a few bristles on the snout. Better still, they have hips. Small useless leg bones floating in the body wall, connected to nothing, left over from ancestors that walked on land and went back to the sea about fifty million years ago. A whale is a mammal that changed its mind.

What is the difference between a marsupial and the rest?

Timing. A kangaroo, a koala, a quokka and a Tasmanian devil are all on this list, and what they share is giving birth extremely early to something the size of a jellybean, which then crawls, unaided and blind, to a pouch and finishes the job attached to a nipple. The rest of us do that development inside instead. Both work. The pouch version is cheaper if things go wrong, because a mother can drop a joey and try again next season, which is a useful thing to be able to do in a country as unreliable as Australia.

How many kinds are there?

Something over six thousand species, and the number keeps moving as genetics splits things that look identical. It is worth knowing the shape of it though. Roughly two in five mammal species are rodents, and about one in five are bats. So the actual mammal, statistically, is a small brown thing that squeaks. Everything on this list that you can name is the strange minority.

Are humans on this list?

Not as an entry, but the chimpanzee, the bonobo and the gorillas are, and the honest answer is that they are on it for the same reason you would be. Hair, milk, three bones. Whatever you feel about that is between you and the list.

Can I use this for a school project?

That is a lot of why it is here. Pull one nobody has heard of and you already have a better project than the lion, because you will have to find real sources instead of copying the first page. Start with where it lives and what it eats. Those two facts explain most of its body.

References

1. Schiebinger, L. (1993). Why mammals are called mammals: gender politics in eighteenth-century natural history. The American Historical Review, 98(2), 382 to 411. https://doi.org/10.1086/ahr/98.2.382
2. Luo, Z.-X. (2011). Developmental patterns in Mesozoic evolution of mammal ears. Annual Review of Ecology, Evolution, and Systematics, 42, 355 to 380. https://doi.org/10.1146/annurev-ecolsys-032511-142302
3. Linnaeus, C. (1758). Systema Naturae, 10th edition. https://www.biodiversitylibrary.org/item/10277