Two yolks in one egg--what's up with that?

Today at breakfast I found that my boiled egg had two yolks.
Several eggs from the same dozen have been the same way. From a nutritional standpoint, I’m really more interested
in the whites, so it seems like I’m getting less albumin when there are two yolks. And, to be honest, it’s kind of
creepy to find two yolks.

Why does it happen?

My WAG - baby chicken is getting started, caught right at the point where the nucleus has divided but the rest of the cell hasn’t yet.

The yolk is the the nutrition for the baby chicken, not the embryo itself, I believe. (So if it’s nutrients you want you’re better off eating the yolk, not the white.)

Anyway, I’ve heard that double-yolked eggs are commonly produced by young hens, but I don’t know what the process is. There used to be a chicken ranch near us that sold cases of double-yolked eggs as a specialty product.

Here are some other threads on the same (and/or related) topics:

Double yolks in eggs - 19 replies

double yolks - 12 replies

Franken-eggs - 17 replies

Ever hear of non-identical twins? That’s when two sperm fertilize two eggs (yolks, if you will).

Doesn’t happen all that often, but certainly isn’t an incredible rarity.

Don’t knock it. It happens often and in many areas, finding a double yolked egg is considered good luck.

yolks are not the eggs (ova). The egg is a single cell & it certainly is not as big as a yolk. The yolk is just a foodstore for the developing embryo (when one exists). Even if there isn’t an embryo (the small red-brown bit), there will be an ovum, it will just be too small to see without a microscope.

& re the other threads - if it is to be be fertilised at all, they would have to be fertilised before the egg was laid, because the egg is sealed sufficiently to keep bacteria out to protect the developing chick (but allow CO2 out & O2 in, brilliant design), so there is no way it will get fertilised after laying - not like fish eggs!

Fi.

…but I remember seeing a diagram at some point that showed
that the embryo starts as a speck on the surface of the
yolk. So I wondered, could two yolks sustain two embryoes?

Anyone know if “twins” have ever been reported in chickens?

or on the other hand could the whole two-yolk phenomenon occur only in unfertilized eggs?