Theoretically, as the human jaw receded into the face, the womans body compensated with round breasts.Ashley Montague (1965) proposed that breasts came about as an  adaptation for infant feeding for a different reason as early human ancestors adopted bipedalism and the loss of body hair. Human upright stance meant  infants must be carried at the hip or shoulder instead of on the back as in the apes. This gives the infant less opportunity to find the nipple or the  purchase to cling on to the mothers body hair. The mobility of the nipple on a large breast  in most human females gives the infant more ability to find grasp it and feed.Other suggestions include simply that permanent breasts attracted mates, that "pendulous" breasts gave infants something to cling to, or that permanent breasts shared the function of a camels hump, to store fat as an energy reserve. Anatomy
In women, the breasts overlie the pectoralis major muscles and extend on average from the level of the second rib to the level of the sixth rib in the front of the rib cage; thus, the breasts cover much of the chest area and the chest walls. At the front of the chest, the breast tissue can extend from the clavicle (collarbone) to the middle of the sternum (breastbone).
The most common symptom that led to the incidental discovery of RIS is headache. Other common reasons are trauma, psychiatric disorders, and endocrinological disorders. Management
Currently, routine clinical follow-up and MRI neuroimaging surveillance is the standard by which patients are observed. While treatment of MS disease modifying therapies have been given to some individuals with RIS, the majority opt for active surveillance and the appearance of clinical symptoms before commencing treatment, as treatment is considered controversial. Prognosis
In a 5 year study, clinical events, which refers to the first symptoms of exacerbations, clinical attacks, flare ups, or severe symptoms, indicative of MS, appeared in 34% of individuals. Of those who developed symptoms, 9.6% fulfilled criteria for primary progressive multiple sclerosis (PPMS). Epidemiology
Due to the incidental nature of RIS, exact figures on prevalence is unknown, though it has been suggested that RIS is the most common type of asymptomatic MS. The prevalence may be higher in relatives of patients with MS. One study, at a university hospital that is located in a high region of MS disease incidence, put the disease prevalence at approximately 1 in 2000. An earlier study in 1961 of 15,644 autopsies found 12 cases (0.08%) of unexpected MS findings without a previous history of MS symptoms. The mean age of first indication of RIS from 451 patients is 37.2 years. RIS in children
Though rare, some children that have had MRI scans for reasons unrelated to MS have shown signs of RIS. The most common reason for an initial MRI in these children was a headache.