A Moment of Science

When You Eat An Egg Are You Eating A Baby Chick?

Were the eggs we buy in the supermarket once embryos?

eggs in a carton

Photo: Pietro Izzo (flickr)

The incredible (edible?) egg or a baby chicken in waiting?

Don Hirose and a friend had an interesting argument. Don’s friend was sure that when you eat an egg you’re eating a baby chick, but Don didn’t think so.

They made a bet and came to A Moment of Science to have it settled. Before we tell you who has to pay up, let’s examine the two situations we’re dealing with.

How Does The Process Develop?

The first, and less common scenario, is eggs that are bought from small farmers–the ones called free-range eggs.

These often are fertilized eggs, and can develop into baby chicks. But usually the development process is halted before this happens. When the egg first forms it’s only one cell, and is fertilized as it moves down the oviduct to be laid.

During the first twenty-four hours after fertilization the single egg cell divides a few times, forming a little mass of cells. At this point it’s technically an embryo (though it doesn’t look like a baby chick), but the cells still have not separated into the ones that make eyes, feet, feathers, etc.

Suspended Animation

After the egg is laid the embryo stays in a kind of suspended animation until the hen sits on it to incubate it. If the egg is not incubated within a few weeks the embryo will die. This is how things work with a fertilized egg, the kind one might get directly from a small farmer.

The second scenario involves the eggs we buy at the local supermarket, which come from what are called “egg factories.” The egg factories rely on a peculiarity of chickens: they lay eggs whether or not they’re fertilized. The egg factories do not have roosters in residence to fertilize the eggs, and these eggs will not develop into baby chicks.

Who Wins The Argument?

So, the eggs that most of us eat do not have embryos, and even the egg cells in the “free-range” eggs probably have not developed enough to be at the stage where one would be eating a baby chick.

So, Mr. Hirose wins the bet, and maybe he’ll want to buy an omelet with his winnings.

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