How to Spot a Psychopath

A reader writes:

How the hell did "prune juice" ever come to exist, since a prune is a dried plum and you can't get juice out of dried fruit? Do they mash them up and add water or something?

Isaac

There's a loophole.

Plums grown primarily to be dried are called "prunes", even before they're dried. They can also be eaten fresh, or juiced. Presto, a warrior's drink.

And now, some Bonus Botanical Trivia:

Many people believe nectarines to be a peach/plum hybrid. They're not. They're a smooth-skinned strain of peach, sharing an ancestor with the plum somewhere back in the history of stonefruit, but otherwise unrelated.

Somewhat fewer people believe nashi pears to be an apple/pear hybrid. They're not. They're a natural species, or, at any rate, as "natural" as the apples and pears that humans have been selectively breeding for thousands of years.

(I am greatly amused by Creationist publications that show a magnificent spread of delicious fruit and veg that God in His wisdom has provided for us; the Jehovah's Witnesses have a really nice version of this in one of their numerous happy-pictured books and pamphlets. I always have a hard time finding anything in those pictures that hasn't been gigantically changed from a near-inedible ancestor by human intervention. Possibly the coconut. Good luck opening that with your bare hands, Adam.)

Lemons, on the other hand, are a hybrid, though a pretty ancient one. Genetic analysis (PDF) has shown them to be a hybrid of the bitter orange and the citron.

If you always thought that grapefruit were hybrids too, you'll now be amazed to learn that you were right. The grapefruit only dates back to the 18th century.

Many people are also familiar with the factoid that, technically, the banana is a herb. Banana taxonomy has always been a nuisance, but this bit of pub-trivia information is not actually worth much.

In everyday grocery-shopping terms the banana is obviously a fruit, but in botanical terms it can defensibly be described as a berry, while the botanical "herb" is any non-woody flowering plant, most of which are inedible. (And, by the botanical definition, each individual kernel on an ear of corn is a separate "fruit". Don't get me started on cashews.)

All of these games with definitions and clashes between scientific and everyday terminology are pretty pointless. They make about as much sense as saying that because people who make coins for a living may refer to all of their input metals as "bullion", it is therefore sensible to invest in copper by the ounce.

Another one: In everyday usage, hardwood means wood that is hard. In scientific terms, though, it just means wood from non-flowering flowering [it was inevitable I'd get one of these wrong, wasn't it?] plants, so balsa wood is technically a hardwood.

Finally, and perhaps most interestingly, it turns out that the tomato is technically an amphibian.

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.