Follicles that are more oval in shape cause curlier hair to grow. Very tightly coiled hair is due to the nearly flat, ribbon-like structure of their follicles. This hair texture is very common in people of African ancestry. Not only is African hair often coiled, it also has a unique texture.
Black hair is literally different than all other hair.
While other races can have straight, wavy, or curly strands, most black people have varying degrees of tightly curled strands. (Check out this article's chart for a more in-depth explanation.) It may come in spirals, coils, loops, zig zags, or other curves.
Compared to silkier hair African-American hair contains more lipids, or fats, but the lipids are less bonded which is why the hair loves oils so much. Along with that, the follicle size is much thicker and it has a flattened elliptical cross section causing it to be curlier than other hair types.
Afro-textured hair, or kinky hair, is a human hair texture originating from sub-Saharan Africa. Each strand of this hair type grows in a tiny, angle-like helix shape.
Studies suggest that Afro hair evolved so that our ancestors could thrive under the blazing African sun. You may therefore even describe it as 'nappy' by design. Delving into African history shows that, much like today, hair is very much seen as a woman's crowning glory; so inherently associated with beauty.
Caucasians have the highest hair density among the ethnicities studied. Black people have the lowest. Asian people have hair density that falls somewhere in between.
Most people of East Asian descent have thick, straight hair. This corresponds with a SNP (rs3827760) in the EDAR gene which is involved in hair follicle development. The ancestral allele of this SNP is the A-allele. The G-allele is the newly derived allele that leads to the thick, straight hair.
Less than 20% of people have naturally curly hair. The percentage gets even smaller when you consider the scores of guys out there who don't embrace their curls.
Caucasian hair can be smooth, wavy or curly.
Curly hair is not certain to a race or ethnicity, it appears all over the world in many forms. White, brown, black and everything inbetween! There is also a scale on which curly hair is classified (2a-4c).
Many Asians have naturally straight hair, but there is a significant group of us who do have naturally curly or wavy hair! However, because it's the norm to see straight and sleek hair, curly haired boys and girls tend to think that their hair is some kind of unruly straight hair that isn't behaving.
Black hair is known to be the most common in the countries of Asia and Africa. Though this characteristic can also be seen in people of Southern Europe and France, it is less common. People of Celtic heritage in Ireland with such traits are sometimes known as the "Black Irish".
So, why is Afro-textured hair so fragile? With its tight curls and twists, is more prone to breakage for several reasons. Its shape increases tangling and makes combing harder. The shape also creates internal stresses when the hair is unbent, untwisted or stretched that lead to fracturing.
Fros don't absorb as much moisture as our caucasian cousins' hair, added to this the structure of our hair (curls and kinks, and increased density) means that nutrients often don't travel along the length of our strands as well as we'd like.
Most African American babies are born with thick, coarse, curly or wavy hair that requires special care. Because of its texture and curl pattern, the hair tends to be dry and prone to breakage – so treat it gently!
Curly hair is considered a “dominant” gene trait. Straight hair is considered “recessive.” To put that in simple terms, that means that if one parent gives you a curly-haired gene and the other parent gives you a straight-haired gene, you'll be born with curly hair.
In fact, more people prefer curly hair to straight hair. Though beauty is seen differently by everyone, one thing is for sure; curly hair is getting a lot of love lately. In fact, in a survey conducted by StyleCaster, a surprising 58% of guys thought curly hair was sexier than other hair textures.
They suggest that either environmental or sexual selective pressure began acting on hair after humans began dispersing out of Africa, helping shape the wide range of human hair types present today. The limited evidence points to temperature as a factor. Curly hair may help keep the head cool in warm climates.
Hair morphology is one of the more conspicuous features of human variation and is particularly diverse among people of European ancestry, for which around 45% of individuals have straight hair, 40% have wavy hair, and 15% have curly hair.
Hair type 1A is super-straight. It doesn't even hold a curl! 1A is the rarest hair type. It is usually found on people of Asian descent.
Thick (Coarse)
Thick or coarse hair texture is the strongest hair texture and typically feels coarse or thick to the touch. Coarse hair contains all three hair layers – the cortex, cuticle and medulla.
So for hair type, CC gives curly, Cs gives wavy and ss gives straight hair. Back to your specific situation. As you can probably tell, the couple you describe could only have wavy haired kids. That is because the curly headed parents, CC, can only contribute a C gene and the straight haired parent, only an s gene.
There are plenty of blue-eyed Asians. This probably happens when the traditional blue-eyed allele comes into a family from a (possibly very distant) European ancestor. Blue eyes then resurface in a child generations later if they inherit the allele from both parents.
Asian hair is also the straightest hair of any ethnic group. According to HealthGuidance, African American hair texture varies. Some people have thicker, coarser hair whereas others have finer hair. Many have a mixture of fine and coarse hair.
Middle Eastern, South Asian, South American, and Native American. These varying races have something in common– thick hair.