When does adolecence begin

Adolescence begins in biology and ends in society. The definitions we accept to describe the onset of adolescence revolve around puberty, biological changes of the body. Therefore I consider adolescence to begin in biology. Adolescence ends in society. Entrance into adulthood marks the end of adolescence. The definitions of who is considered an adult are defined by society and therefore I contest that adolescence ends in society.
The onset of adolescence is marked by a sudden increase in the production of many hormones in the body. The hypothalamus, the part of the brain that controls the pituitary, sends signals the increase hormone production. Growth hormone produced in the anterior pituitary is increased in production, targeting the soft tissue and bones making them grow rapidly. Gonadotropic or follicle stimulating hormone, also produced in the anterior pituitary, is increased and is responsible for the growth of hair on the body and face. The gonads, ovaries and testes, increase production of estrogen and testosterone respectively, which are responsible for the growth of secondary sex characteristics, such as breasts in females and masculine features in males. The production of these hormones causes many of the changes we characterize as the start of adolescence, to occur. The question remains, what causes the hypothalamus to signal these increases in the hormonal production? Much research has been done on this subject, however it has been inconclusive to an accepted reason. This is largely due to the fact that so far we cannot experiment physically on the brain to see what causes the signals to be sent from the hypothalamus to the pituitary. Most of the research is studies of different individuals and groups of similar individuals as to when they began adolescence and the genetic and environmental factors of the groups. Some research has shown the factors that control the onset, to be genetic. They argue that timing of the onset is by inherited factors within the chromosomes of the individual. The anatomy of chromosomes is well known, however the physiology is limited to describing how genes on the chromosomes code for the proteins that are the makeup of hormones. It is not understood what causes a certain gene to be expressed. Until these factors can be shown the theory of genetic control over the onset of puberty cannot be proven as fact. Some patterns have been shown within a group of individuals that are exposed to similar environmental conditions such as nutrition and health, and enter puberty at differing times, that points to a correlation between social interaction and the timing of onset. For example family environment. A stress created by family or other factors can slow the onset of maturation. However, this correlation can be explained by experiments that have proven that stress can affect the secretion levels of hormones. This further proves that the factors controlling the onset of puberty are biological. Another argument to biological control over the onset of maturation is history. Throughout history the timing of puberty has remained similar given similar environmental conditions.
Adolescence ends when adulthood begins. All societies define what is considered an adult. Some define it different than others but the characteristics are largely of social nature not of biological facts. Some societies have discontinuous transitions from adolescence to adulthood, meaning the change in status is sudden and marked. For example ceremonies to mark the entrance of an individual to adulthood. But the timing of the transition is still decided on by society. Other societies have a continuous transition from adolescence to adulthood which is largely defined by social status. Some events that mark transition are graduation from schooling, entrance into work-force, marriage and parenthood. The timing of these events has changed throughout history a great deal. Far more than can be explained by biological changes in generations. Also what defines an adult has changed over time. These changes are made by society. The physical aspects of an individual are the best biological definition of adulthood. A “grown up” is a factor considered that places someone in adulthood, but this is just one factor and the idea of what an adult looks like is determined by society. In fact, the idea of the physical aspects of an adult is has changed over time. The age a person