The stereotype of Swedes outside their country usually depicts them with very light blonde hair and blue eyes. However, dirty blonde hair is closer to what the average Swede looks like.
Dirty blonde hair doesn’t only come from Sweden, but it is one of the most common hair colors in the country. There isn’t much data on dirty blondes, but most people in Sweden have light hair. Light hair colors appeared in Northern Europe as a result of a genetic mutation related to light skin.
Although it’s safe to assume that most Swedes have some degree of light hair, dirty blonde isn’t exclusive to the country. This article will explain the origin of dirty blonde hair and why it’s so prevalent in countries in Northern Europe.
Also see Why Does Sweden Have So Many Islands? to learn more.
Where Does Dirty Blonde Hair Come From?
Dirty blonde hair, together with most light hair colors, comes from Northern Europe. The people of this area evolved a light-colored skin better adapted to low-light environments, and this mutation is related to the appearance of light hair.
This is not to say that dirty blonde hair is exclusive to Northern Europe. Science suggests that blonde hair evolved independently in different parts of the world. This is why it’s common to find people with blonde hair in certain parts of Asia, such as Mongolia and parts of Northern China.
There isn’t a single explanation for the appearance of blonde hair. However, studies have shown that light hair is a consequence of a mutation of a gene sequence called KIT ligand (KITLG). Fittingly, this mutation is present in about one-third of people from Northern Europe. 
There isn’t a single way to explain this mutation. The most well-accepted theory states that blonde hair is a by-product of a different mutation: light skin.
The first human groups that spread out of Africa and into Northern Europe had to deal with very different light conditions, which might have been an obstacle to getting enough vitamin D.
Vitamin D is a crucial nutrient for human health that is present in very few foods. However, the skin produces vitamin D when exposed to sunlight, which is how humans get most of it in nature.
The climate in Northern Europe has little sunlight, and this new environment might have favored mutations that allowed better absorption of vitamin D. Light skin tones are more able to synthesize vitamin D, while darker skin tones block more of the sun’s UV rays. 
There are other factors that might have induced light-skinned mutations, such as a switch to a diet that was low in vitamin D and the transition to agricultural practices.
There is a myth that says that blonde people share a common ancestor, but this is not true. The mutation appeared several times across history and can’t be traced back to a single person.
Scientists used to believe that light skin, together with light hair, started developing around 40,000 years ago, but recent findings push that date to as recently as 7,000 years ago.
This is different from blue eyes—another common trait in Northern European countries. Blue eyed-people do share a common ancestor. 
Also see Why Do Swedish Bands Sing in English? to learn more.
What Color Is Swedish Blonde Hair?
The most common Swedish blonde hair is dirty blonde. Dirty blonde is a medium blonde hair color with darker brown tones. Between 50% and 80% of people in Sweden have light-colored hair.
There seem to be different meanings ascribed to “dirty blonde” hair. The term is sometimes used interchangeably with “platinum blonde, which is a very pale hue of blonde, almost resembling silver. This is one of the less common uses of the term, and it’s also one of the rarest types of blonde hair there are. Only a very small percentage of Swedes have platinum blonde hair.
More commonly, dirty blonde hair refers to a darker hue of blonde. Dirty blonde is ashier than stronger blonde colors and has brown tones.
Hair color can change as a person grows, which is why dirty blonde hair darkens over time. In Sweden and other parts of Europe, it’s very common for babies and children to have intense, very light blonde hair. However, as they grow older, it becomes ashier and darker.
Sweden is one of the countries with the largest concentrations of light hair in the world. Across a great part of its territory, over 80% of people have light hair.  The figure drops to 50% – 80% through the rest of the country, which is still extremely high when compared to the rest of Europe.
Interestingly, light hair has its epicenter in a small zone that includes parts of Sweden, Norway, and Denmark. The farther away from this center, the lower the percentage of light-haired people.
Also see What Do Swedes Think of Norwegians? to learn more.
Do All Swedes Have Blonde Hair?
Despite the stereotype, it’s common for Swedes to have dark hair colors.
It’s important to note that the figure mentioned above doesn’t only refer to strong blonde hair. It includes a wide range of blondeness, going all the way to darker, almost brown hues. In fact, dirty blonde, the most common hair color in Sweden, has brown streaks and is darker than other blonde hair colors.
Another factor contributing to so many Swedes being blonde is hair dying. It’s very common for Swedish women to dye their hair. They usually choose a natural-looking color, which, in their case, is some shade of blonde.
However, many Swedish women dye their hair with a very light-colored blonde, whether because their natural color has darkened with age or because it was naturally dark. This practice may contribute to the impression that all Swedes have blonde hair.
Not all Swedes have blonde hair. Between 50% and 80% of Swedes have light hair, including darker hues such as dirty blonde. It’s very common for Swedes to have dark hair. Many Swedes, especially women, dye their hair, which contributes to the impression that all Swedes are blonde.
Most Swedes have dirty blonde hair, which is a medium type of blonde with brown tones. However, this hair color isn’t exclusive to Sweden.
Also see Why Does Swedish Sound So Unusual? to learn more.