It has been suggested that the adult scarring phenotype has been actively selected during evolution, perhaps as a reminder of previous inappropriate behaviour. It may also have been passively selected as a result of co-selection for other advantageous phenomena, such as speed of healing. Types of scar Surgery is the most common cause of scarring, but there are many other causes and they can result in different types of scar. The most common type of scar is flat and pale. While scars may be red or dark and raised initially, most will become paler and flatter over time.
Stretched scars occur when skin cells around a healing wound are put under tension.
This type of scarring usually only happens after surgery, but can also accompany obesity or weightlifting. Initially, the scar may appear normal but can lengthen and thin over a period of weeks or months. This can occur where the skin is close to a joint and is stretched during movement, or may be due to poor healing through general ill health or malnutrition. Stretch marks are similar to stretched scars and usually develop during pregnancy or adolescence when the skin is stretched too quickly for it to respond naturally. They occur in the dermis and are the result of thinning and loss of elasticity of collagen bundles.