Maslow's hierarchy of needs
Abraham Maslow formulated a hierarchy of human needs. His theory contends that as the basic needs are met humans desire higher needs.
Physiological Needs The body aims to achieve homeostasis (an equilibrium of different factors (water content of the blood, salt content, sugar content, protein content, fat content, calcium content, oxygen content, constant hydrogen-ion level /acid-base level, constant blood temperature). If all of a human's needs are unmet then the physiological need takes the highest priority. Given hunger for love and food, a human is more likely to find a solution for the latter first. As a result all other desires and capacities are pushed on to the back burner.
Safety Needs When the physiological needs are met then the human turns towards safety needs. Safety attains the highest priority over all other desires. A functioning society tends to provide this to its members. Examples in the recent past/present of where this has failed include Somalia and Afghanistan. In Kosovo, while food was available, the absence of security for the Kosovars resulted in a large population being displaced in search of security.
Love Needs If safety and physiological needs are met then the human being gravitates towards achieving fulfilment of love needs. A note worth making here is that sex is not equivalent to love. Love can and is often expressed sexually. Sexuality can at points be considered solely for its physiological basis.
Esteem Needs
Self actualization