Demography: Principles Governing Human Populations

• Demography - Refers to the study of human populations – their size, composition and distribution across space – and the process through which populations change.
• Principal determinants of population growth:

  • fertility,

  • mortality, and

  • migration.
• Principal determinants of population growth:

  • fertility,

  • mortality, and

  • migration.
• The human female is generally fertile from early teens to about mid-forties.
• The human male generally remains fertile throughout adulthood, though sperm count and quality diminish from middle-age onward.
• Women ovulate at about the fourteenth day of their cycle, this obviously being the most fertile time for females.
• In areas where natural disasters or politico-military concerns lead to entire populations being displaced the initial population structure will be unchanged, though post-migration the population will have altered to reflect those who have survived the process, typically showing increases in older children and younger adults. 
• Explanations for rates of natural mortality have generally fallen into two classes: intrinsic or extrinsic.
• Intrinsic explanations are based on long-standing correlations reported between life span and individual metabolic rate.
• Extrinsic explanations of mortality are based on the observation that organisms in natural environments typically die as a result of disease, predation or accident, well before they reach their maximum possible life span.