When it comes to cuisine, we're all time's fools. We eagerly eat the kind of food that's being cooked in our own day and forget the older dishes. Look in a cookbook from a couple of decades ago and you'll be struck by faded old names--tapioca pudding, chicken croquettes, scalloped tomatoes--as well as flavor combinations, ways of cooking and even ingredients that are no longer common.

Look farther back, and by the time you get to 1,500 BC, you'll find a Babylonian recipe entitled "how to cook tuh'u as agarukku ." We haven't the first idea what tuh'u and agarukku were. We don't even know whether they were animal, vegetable or even (who knows?) mineral.

Usually dishes and ingredients die for no better reason than the whim of fashion. Tasting them can be an intriguing experiment in time travel, even a memorable dining experience.

Often, though, we can see why something disappeared. Some ingredients are just plain less useful than others, such as the "other peppers"--long pepper, grain of paradise, cubeb--that were popular during the Middle Ages. They were doomed when chile peppers reached Europe, because chiles were hotter, could be grown anywhere and had a greater range of uses (for instance, as a vegetable).

In fact, chiles have mostly replaced those antique peppers even on their African and Indonesian home ground. You may be able to find them in herbalist shops, and a dash of cubeb or grain of paradise could still add a piquant effect in cookery. But most of us would probably wonder how a sort of black pepper with a faint turpentine flavor ever got called grain of paradise.

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Some ingredients have not been replaced by anything in particular--we've just decided they're inconvenient. The medlar ( Mespilus germanica ) was esteemed from the days of the ancient Greeks all the way through the Middle Ages, but for its honey-like sweet-tart flavor to develop, the fruit has to be frostbitten when still on the tree and then lie around on a bed of straw to soften until it's just about rotted. That's why you've probably never tasted a medlar.

A lot of one-time food plants are just weeds today, because people have figured they weren't worth the trouble of gathering and cooking. The names of vegetables which have dropped from sight, such as good-king-henry, horse parsley and skirret--to say nothing of once-common kitchen herbs like dittany, southernwood, vervain and hyssop--would fill a book. But there are still those who harvest dandelions and lamb's-quarters and purslane. One day we might decide our ancestors were being rash when they stopped using hyssop.

Whole flavors can fall out of fashion. To judge from medieval cookbooks, people once positively relished bitterness, rather than avoiding it the way we do (unless we can add sweetening, as with coffee, tea and chocolate). That wasn't a primitive habit--it was really almost over-sophisticated, because avoiding bitter things is the natural thing to do. The very reason our tongues can taste bitter flavors at all is for our safety's sake, because so many poisonous things are bitter. The palate has to be taught to value the bracing effect of a bitter ingredient.

So how did medieval people get in the habit of using bitter flavorings? It might have come about because many medicinal plants are bitter. (Even today, a lot of us have a feeling that medicine has to be bitter to be "good for you.") Also, all spices are more or less bitter, and in the Middle Ages it was fashionable to put as much spice on your food as you could afford. The result was that the most expensive dishes were also the most bitter, so perhaps bitterness came to seem classy.

At any rate, bitter herbs like rue and tansy reached their peak of popularity in the Middle Ages. Rue is still around, mostly as an ornamental plant with attractive leaves and flowers. Its bitter flavor is a shock if you've only smelled it, because its attractive scent is something like fresh plums. Tansy is a little harder to appreciate, being almost as bitter as rue but nowhere near as attractive in the aroma department. The fact that tansy is very slightly poisonous has also done its popularity no good.

For thousands of years, the marrow in shank bones was the most desirable part of meat. Some medieval cookbooks give recipes for imitation marrow if you couldn't afford enough meat to serve real marrow to all your guests. Even in the early part of this century, marrow on toast was considered an exquisite appetizer.

Try to find it at a restaurant now, though. About the only time Americans eat marrow these days is when they have osso buco, if it's correctly served with a tiny spoon for scooping the marrow out of the bones. Some modern diners can't even see what the fuss was about. How medieval people would gape to hear them complain that marrow is bland and odd-tasting, though undoubtedly rich.

We don't eat as much game as our ancestors because most of us live in cities, where game is hard to get, but venison, buffalo and their like seem to be making a comeback among foodies. On the other hand, if anybody serves raccoon, opossum or muskrat today, it's usually as a flamboyant gesture, and if we ever recover the taste for the relative of the grasshopper called the locust, a recognized food in biblical days, it won't be soon.

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In earlier times, people often aged meat even longer than we do, partly for flavor but also because enzymes in the meat tenderize it, which was important when there were no dentists or false teeth. But there was always a race between tenderness and downright putrefaction. Right into this century, many Englishmen insisted that pheasant should be hung until it turned green and the flesh started to fall off the bones. (So much for the story that medieval recipes called for a lot of spice to cover up the smell of rotting meat--many people liked that aroma.)

Fish notoriously develops a "fishy" smell, which we dislike (or think we do--there's nothing fishier than a sardine). But all the modern peoples of Southeast Asia make a sauce by letting fish spend a couple of weeks ripening in brine (as did the ancient Romans). For many years, Americans considered the mere mention of fish sauce amusing, but now that we've been exposed to Thai food, we're getting used to the mysterious, brassy richness it can add to a dish's aroma. Still, we might not be ready to use it in desserts, the way the ancient Romans did.

The list of condiments that have fallen out of favor is just about endless. In some 18th-Century English cookbooks, every other recipe seems to call for products like Harvey's sauce and walnut ketchup (made from pickled unripe walnuts, not a drop of tomato in it), most of which tasted a little like Worcestershire sauce.

One condiment we can be glad has disappeared is murri , which was popular everywhere in the Near East, and as far west as Spain, in the Middle Ages. It was based on barley dough that had been left to rot in a box for 40 days. The rotten dough was mixed with water, salt and spices and then rotted for another 40 days on rooftops in the height of summer. The main thing wrong with it was not its aroma, which probably resembled a ripe salami, but the fact that it must have been highly carcinogenic.

In a 14th-Century English book known as " Diversa Cibaria," 16 of the first 23 recipes call for something called almond milk, which is made by soaking ground almonds in water. Nearly all 16 combine almond milk, sugar and meat. Add ginger, white wine and pomegranate seeds to this basic recipe and you had blanc desire ; add fried almonds and saffron instead and it was anesere . Viaunde despyne was flavored with pistachios and cloves, spinette with hawthorn flowers and ginger, and so on.

Part of the reason for the popularity of almond milk in the Middle Ages was that almonds were an expensive, show-offy imported ingredient; part was the fact that it wasn't an animal product so you didn't have to give it up for Lent. But as transportation improved and almonds became cheap, and as Lenten observances became less strict, almond milk lost its culinary importance. It's just as tasty as it ever was, though.

Of all the lost flavors of the past, the easiest for us to experience today are the ones that call for ingredients that are still attainable. It's no problem to recreate a forgotten use of spices, such as the combination of saffron with sweet and sour flavors that was as much a part of medieval cookery as chiles and cumin are of Mexican cookery today. In the 17th and 18th centuries, sweet spices such as cinnamon, clove and coriander (the last usually with lemon) were common flavorings for ice cream, and they're still very good ones.

It's also easy when the lost flavor is a matter of an ingredient that we cook but our forebears ate raw, or vice versa. Lettuce and cucumbers were often cooked in the past.

One day, people will look through our cookbooks and wonder what sun-dried tomatoes, carpaccio and tiramisu were. Just like us, they'll have to try the antique recipes out--no doubt reluctantly; the names will be as puzzling and frumpy-sounding to them as viaunde despyne is to us--before they'll really be able to decide whether these 20th-Century foods were as boring or bizarre as they'll sound. It would be nice to think they'll do us the courtesy.