Under ideal circumstances, a break in the skin would stimulate the skin’s own repair processes to seal up the wound and restore normal skin. Clotting factors in the blood would stop the bleeding by forming a scab. The second deepest layer of the skin (the dermis) would produce new cells called fibroblasts. Those fibroblasts would produce collagen and other proteins to seal up the wound and produce a seamless layer of new skin. In some cases, evidence of the wound skin completely disappears in about a week, leaving no scar at all.
For the skin to heal without leaving a scar, healing processes have to occur at exactly the right time in precisely the right degree. However, the body puts a premium on fast healing rather than accurate healing.1 Prehistoric man had a better chance at survival if a wound healed quickly than if it had healed perfectly. The skin had to close quickly to prevent excessive blood loss and infection. When the skin heals quickly, the skin that covers the wound is structurally different from normal skin. The wound heals, but the scar tissue that remains is usually permanent.