Estimating Life Expectancy in Archaeological Populations

Palaeodemography And Palaeoepidemiology

Joseph R. Krecioch Cave & Necropolis

Session 1 2011

Demography

• “the study of population statistics” (White and Folkens 2005)

(mortality and birth rates; population size, growth, and density; life expectancy, etc)

• Palaeodemography: “vital statistics of past populations” (Brothwell 1981)

Epidemiology

• “concerned with the distribution of disease and death, and with their determinants and consequences in population groups” (Omran 1971)

• Palaeoepidemiology not only attempts to describe disease and mortality in prehistoric populations, but also informs future trends. Depends upon osteoarchaeology and palaeopathology.

Estimating Life Expectancy

• Even in modern populations, LE is fraught with inconsistencies and uncertainties.

• High infant mortality significantly reduces life expectancy, so LE changes according to age

• Famines, wars, epidemics also contribute to misleading LEs

• If LE is ’38’, it doesn’t mean 19 year-olds were ‘middle-aged’

LE in Archaeology

• Age estimation of human remains would ideally provide LE of a population.

• Age estimation has been thought unreliable for ages above 50 or 60 years

• Archaeological sample or site does not imply a once living ‘community’ or population

Methods

• First, determine ages osteologically

• Drop individuals under 20-23yo

• Apply statistics: Bayesian methods

• Newer statistical methods give different LEs

Ageing Skeletal Remains

• Until Old Adult stage, ageing is based upon generation; after Adult stage, bone degeneration gives clues to age.

• Most important for older age estimation is the pubic symphysis and auricular surfaces

(Lovejoy et al 1985; Buckberry and Chamberlain 2002)

Auricular Surface

• Surface Texture• Fine• Coarse• Dense

• Microporosity• Surface pores <1mm

• Macroporosity• Surface pores >1mm

• Apical Changes• lipping

Storey’s comparison of Statistical

methods

Epidemiological Transitions• Post-Neolithic: Agriculture and Sedentarism

– Big drop from Mesolithic to Neolithic– Large increase Neolithic to Copper Age– Smaller increases Copper to Bronze/Iron

• European Industrialization and urbanization– 17th to 18th Centuries: Drastic declines in LE

Transitions in the Balearics

• Pre-Talaiotic– Epipalaeolithic– Chalcolithic

• Talaiotic• Roman• Pre-Arab Transition• Arab…

Further Reading

Gage, Timothy (2005) Are Modern Environments Really Bad for Us?: Revisiting the Demographic and Epidemiologic Transitions. A JP A 48:96-117

Konigsberg ande Frankenberg (2002) Deconstructing Death in Palaeodemography. A JP A 117:297-309

Roksandic and Armstrong (2011), Using the Life History Model to Set the Stage(s) of Growth and Senescence in Bioarchaeology and Paleodemography. AJPA (online Perspective)