What if you had no teeth?

Crunch! You bite into an apple. Your teeth do the work.

What if you had no teeth? How would you eat your lunch?

Take a bite of an apple and listen to the crunch. Your front teeth slice off a piece, and your back teeth mash it into mush you can swallow. You probably never think about it, but your teeth work every time you eat.

So what if you had no teeth at all? Could you still eat an apple? A carrot? A sandwich? In this lab we follow three clues: what life would be like with soft food only, how our baby teeth and adult teeth grow, and how birds eat without any teeth at all.

Chewing, or mastication, starts with the teeth: Britannica describes incisors that cut and molars that crush and grind food into pieces we can swallow. Teeth also help us speak and give the face its shape, according to the American Dental Association.

This thought experiment removes the teeth and asks what changes. It follows three threads: eating with soft food only, the development of our two sets of teeth, and how toothless animals, from birds with gizzards to the giant anteater, solve the problem another way. Facts come from the ADA, Britannica and the Smithsonian's National Zoo; the toothless human is a reasoned scenario.

Your front teeth are flat and sharp. They cut and bite.

Your back teeth are wide and bumpy. They mash and grind your food!

Your teeth aren't all the same. Each kind has a job, Britannica explains. Incisors, the flat front teeth, have a sharp chisel edge for biting and cutting. Canines, next to them, are pointed for cutting and tearing.

Farther back, premolars can both cut and grind, and molars, at the very back, have bumpy tops called cusps for crushing and grinding. Together they turn a big bite into small, soft pieces. The American Dental Association adds that teeth also help you speak and smile.

Britannica describes the human dentition as specialized: incisors, with a wide, thin, chisel-shaped edge, for plucking, cutting, tearing and holding; canines, often pointed and peglike, for cutting and tearing; premolars, with two cusps, for cutting and grinding; and molars, typically with four or five cusps, used exclusively for crushing and grinding.

Each tooth has three layers. The outer enamel, wholly inorganic, is the hardest tissue in the body; beneath it lies dentine, and at the center the pulp. Teeth also shape speech and the face, the ADA notes, which is why their loss would affect more than eating.

Now pretend you have no teeth. You can't bite an apple!

You might eat soup, yogurt and mashed bananas instead.

Without teeth, you couldn't bite off a piece of apple or grind up a carrot. You might eat mostly soft food: soups, yogurt, mashed potatoes, ripe bananas. You could still cut food into tiny pieces with a knife or mash it with a fork, letting tools do your teeth's job.

Talking might change too, because the American Dental Association says teeth help us speak. Try saying 'teeth' or 'fifty' and notice where your tongue and lips touch your teeth. These ideas about a toothless life are reasoned, not tested.

Without dentition, food would need to be reduced before it reached the mouth: cooked until soft, mashed, blended or finely cut. Each of these replaces the mechanical work of incisors and molars with tools or processing. Some foods, such as raw, fibrous vegetables, might become much harder to eat.

Speech might also be affected, since the ADA notes that teeth help us speak; exactly which sounds would change is something to test with the hands-on activity, not a measured result here. Facial shape, which teeth help support, might change as well. These consequences are reasoned extensions of the facts, not results of a study.

Babies are born with no teeth showing. Their first teeth come in when they are about six months old.

Later, baby teeth fall out and grown-up teeth grow in.

Here's something surprising: a baby is born with 20 baby teeth already in its jaws, hidden under the gums. The American Dental Association says they start to come in at about 6 months old. So for the first months of life, everyone eats with no teeth showing!

During childhood, baby teeth fall out one by one, and bigger permanent teeth take their place. By about age 21, all 32 permanent teeth have usually come in. That's 12 more than you started with: the extra ones are molars at the back.

The ADA states that people usually have 20 primary teeth at birth, which begin to erupt at about 6 months and are shed at various times through childhood; by age 21, all 32 permanent teeth have usually erupted.

Britannica details the arrangement. The primary set has, in each jaw, four incisors, two canines and four molars. In the permanent set, premolars replace the primary molars, and 12 permanent molars erupt behind the primary teeth without replacing any of them, giving four incisors, two canines, four premolars and six molars in each jaw. Infants, notably, manage the first months entirely without erupted teeth.

Birds have no teeth! A chicken swallows its food whole.

A strong part of its tummy, called a gizzard, squishes and grinds the food.

Birds don't have any teeth. So how does a chicken eat hard seeds? It swallows them, and they travel to its gizzard, a special part of the stomach with thick, strong muscle walls. Britannica explains that the gizzard can hold small stones that help grind up seeds, doing the job our teeth do.

The giant anteater has no teeth either. The Smithsonian's National Zoo says it slurps up ants and termites with a sticky, 2-foot-long tongue that can flick in and out up to 150 times a minute.

Britannica defines the gizzard, in many birds, as the hind part of the stomach modified for grinding: located between the crop and the intestine, with a thick muscular wall, it may contain small stones (gastroliths) that break down seeds and other food mechanically, making it comparable to the teeth of other animals. Earthworms and some other animals have gizzardlike structures too.

The giant anteater, per the Smithsonian's National Zoo, has no teeth and feeds almost entirely on ants and termites, using a 2-foot tongue coated in sticky saliva that flicks up to 150 times per minute. Toothless animals show that chewing can be replaced, but only by a body built for it.