Here's a more detailed breakdown:
* Genetics are the biggest factor: Genes determine the shape of your hair follicles. Follicles that are round tend to produce straight hair, while oval or asymmetrical follicles produce wavy or curly hair. You inherit these genes from your parents, so if they have wavy or curly hair, you're more likely to have it too. However, it's not always a direct inheritance, as gene expression can be complex.
* Hormones: Hormonal changes can also influence hair texture. Sometimes, a baby is born with a certain hair type, but it changes later in life (often during puberty or pregnancy) due to hormonal shifts.
* Ethnicity: Certain ethnicities are more likely to have genes associated with wavy or curly hair.
* It can change over time: Some babies are born with straight hair that later develops into waves or curls, and vice versa. It's not uncommon for a baby's hair to change significantly during the first few years of life.
In summary: While genetics are the most significant determinant, it's not always a simple case of "if your parents have wavy hair, you will too." Hormones and other factors can play a role, and hair texture can even change over time. So, you can be born with the genetic predisposition for wavy hair, but it might not fully manifest until later in life, or you might be born with straight hair that later becomes wavy.