Fig 1.
Outline of the proposed algorithm for predicting the demographic characteristics of a population represented by a skeletal sample using age-at-death ratios.
Fig 2.
Regression fits between the D5+/D20+ ratio and (a) the growth rate, (b) the crude birth rate, and (c) the total fertility rate. Generalized additive regression models (solid lines) are based on 500 simulated reference skeletal samples (circles) with 50 adult skeletons (D20+ = 50) randomly drawn from populations with a life expectancy between 18 and 25 years and annual growth rate between −3 and 3%.
Table 1.
Characteristics of univariate regression fit between three age-at-death ratios and three demographic variables based on skeletal samples with three different numbers of adults (D20+).
Fig 3.
Relationship between the size of skeletal sample (measured as number of adults, D20+) and 95% prediction error of (a) the growth rate, (b) the crude birth rate, and (c) the total fertility rate. Prediction errors (half of the 95% prediction interval) are calculated from regression models using the D5+/D20+ ratio as predictor and based on 500 simulated skeletal samples randomly drawn from populations with a life expectancy at birth between 18 and 25 years and annual growth rate between −3 and 3%. Predictions are made for the D5+/D20+ ratio of 1.26.
Fig 4.
Comparison of annual growth rate (%) predicted using D5+/D20+ ratio and Bocquet-Appel’s [12] P index in 63 Mesolithic and Neolithic skeletal samples (circles) [12, pp. 640–641].
(a) Scatterplot comparing two growth rate estimates; the identity line is dashed; (b) Bland and Altmann plot showing the mean difference and limits of agreement between the two methods of estimation.
Fig 5.
Comparison of crude birth rate (CBR, live births per 1,000 population) predicted using the D5+/D20+ ratio and Bocquet-Appel’s [12] P index in 63 Mesolithic and Neolithic skeletal samples (circles) [12, pp. 640–641].
(a) Scatterplot comparing two CBR estimates; the identity line is dashed; (b) Bland and Altmann plot showing mean difference and limits of agreement between the two methods of estimation.
Fig 6.
Relationship between the growth rate and the D5+/D20+ ratio (solid lines) in the sets of large-sized reference populations (circles) with the life expectancies at birth of (a) 18–25, (b) 18–38, and (c) 42–74 years. Mortality patterns of reference populations are based on the Coale and Demeny West model life tables with annual growth rate between −3 and 3%. The dotted lines depict the predicted growth rates in a population with the D5+/D20+ ratio of 1.2.
Fig 7.
Relationship between the growth rate and the D5+/D20+ ratio (solid lines) in (a) large-sized reference populations (circles) and small-sized reference skeletal samples (circles) with (b) 50, and (c) 10 adult individuals. Mortality patterns of reference populations are based on the Coale and Demeny West model life tables with a life expectancy at birth between 18 and 25 years and annual growth rate between −3 and 3%. The dotted lines depict the estimated growth rates in the population or sample with the D5+/D20+ ratio of 1.6.
Fig 8.
Comparison of regression fits of annual growth rate (%) as a function of the D5+/D20+ ratio (solid line) and P index (dashed line).
The P index values have been converted to D5+/D20+ ratio values to allow the comparison in the same plot. Rectangles show the range of age-at-death ratio and growth rate observed in Bocquet-Appel’s [12] reference populations (dark gray) and in the set of reference skeletal samples used in our study (light gray).