Lemon : A Hybrid of Bitter Orange And A Citron. Life never gave us lemons, we invented them all by ourselves.
There is molecular evidence that most cultivated citrus species arose by hybridization of a small number of ancestral types, the citron, pomelo, mandarin and to a lesser extent, papedas and kumquat. Hybrids of citrons with other citrus are commercially more prominent, notably lemons and many limes.

Life never gave us lemons, we invented them all by ourselves. All modern citrus was derived from four naturally occurring species, citron is one of them.
There is molecular evidence that most cultivated citrus species arose by hybridization of a small number of ancestral types, the citron, pomelo, mandarin and to a lesser extent, papedas and kumquat. Hybrids of citrons with other citrus are commercially more prominent, notably lemons and many limes.
Kumquats are great little fruit that most people I’ve met have never tried. They are the size and shape of grapes, but with skin like an orange (but much thinner).
They also look like too much work: why peel this tiny thing when the reward is so small?
The trick is that you eat them skin and all — they’re delicious!
Most of the produce we eat has been modified for centuries through the basic genetic techniques learned by Mendel on his pea plants. Carrots didn’t start out orange, potatoes and cauliflower didn’t used to be white, corn used to be a freaking rainbow and also less edible, and in general a lot of the variety we enjoy today are man-made crossbreeds. Nature didn’t come up with 100 types of tomato on it’s own.
The origin of the lemon is unknown, though lemons are thought to have first grown in Assam (a region in northeast India), northern Burma or China. A genomic study of the lemon indicated it was a hybrid between bitter orange (sour orange) and citron.
Citron (pas citron en français)
The most common citrus hybrids that are sometimes treated as a species by themselves –
• Lemon
• Limes
• Orange
• Grapefruit
To create the lemon, the bitter orange was cross bred with the citron. In most languages of Europe, citron is the word for lemon, deriving from the Latin word citrus. This can cause some confusion, since the citron and the lemon are two different fruits. Fortunately for English speakers, we use different words for them and thus have an easier time keeping them straight in our heads.
The citron looks a lot like the lemons that are so popular today. The citron’s skin isn’t as smooth as the lemon’s, but the color is about the same. The fruit looks different, but tastes about the same. The main advantage a lemon has over a citron is that citrons don’t yield much juice; lemons do. The citron is used a lot in traditional Chinese medicine, but as a foodstuff, it’s a lot less versatile than the lemon is.