Supplementary data 1
The Strasbourg medical school juvenile human series ordered by individual ages. The skulls
were prepared by anatomists between 1872 and 1918. Half of the specimens were born in
Strasbourg, 34% in Alsace or bordering regions and the rest came from Germany. Calendar
ages are known with a precision of one month, one week or sometimes one day. Dental ages
are scored as such : A : unerupted deciduous teeth, B : deciduous incisors in eruption or
occlusal level, C : dm1 in eruption, D : dm1 in occlusal level and dm2 in eruption, E : dm1
and dm2 in occlusal level, F : M1 in eruption, G : M1 in occlusal level. Fontanelle is scored as
open (o) or closed (c). Tympanic plate is scored as non fused (nf) or fused (f). Endocranial
volume were obtained by direct measurement. The specimens are assigned to classes of 10
percent of the average adult brain size.The subarcuate fossa could be measured on 44 of the
best preserved specimens taken at random in each age class. The method of measurement is
defined in figure 1.
Supplementary data 2
The Augier Paris medical school juvenile human series. The series is composed by
individuals mostly collected during the second half of the XIXth century in Paris. The cranial
bones were separated by the preparation. Fontanelle is scored as open (o) or closed (c).
Supplementary data 3
The Spitalfields juvenile human series. Fontanelle is scored as open (o) or closed (c).
The material studied come from the crypt of Christ Church, Spitalfields, London, a series
coffin-buried between 1729–1852. The Huguenot origin of the sample explained why 41.6%
have French sounding names. The weaning diet was often nutritionally deficient and some
developmental retardations are noticed.
Supplementary data 4
The chimpanzees series ordered by dental stages. The Tervuren series was collected in
Central Africa without precise record of the origin and the Museum National d'Histoire
Naturelle chimpanzees series is composed by: 7 formalined chimps of known age (3 full term
fetuses,1 stillborn, 1 of 3 days, 1 of 19 days and 1 of 43 days), 11 dried skulls (3 of known
calendar age: 8 months,13 months and 18 months). Available information on the origin of the
specimens is: 10 came from the zoological park in Vincennes, Paris (one of them arrived dead
from Africa); 4 came from the zoo of Jardin des Plantes, Paris; 1 from the "Jardin
d’acclimatation du Bois de Boulogne", Paris. In the table, species are indicated as labeled in
the collections. Dental ages are scored as such : N/J1: unerupted deciduous teeth (ca 3
months), J1 : first deciduous eruption to complete deciduous dentition (ca 4 years), J2 :
eruption of the first permanent molar (ca 8 years). Fontanelle is scored as open (o) or closed
(c). Tympanic plate is scored as non fused (nf) or fused (f). To complete the data from
Zuckerman 27 and Schultz 28, endocranial volumes could be measured on some N/J1 and J1
by direct measurement or medical imaging. The specimens are assigned to classes of 10
percent of the average adult brain size. The subarcuate fossa was measured on the 17
specimens representative of the earliest stages of individual development (full term fetuses
and N/J1). Afterward the fossa is closed. The method of measurement is defined in figure 1.
Supplementary data 5
Bayesian posterior probabilities of occurrence of the Mojokerto phenotype in the human
Strasbourg series and Bayesian posterior probabilities of occurrence of the Mojokerto
phenotype in the Pan troglodytes series (two Excel sheets).
Let Ci be the i th age class, X a feature (attribut) (for example « fontanelle ») and j one of the
states of this feature (« o » for « opened », « c » for « closed »). Then the posterior
probability that an individual belongs to the class Ci, given that its attribut X is in state j, is
given by Bayes’ theorem:
where π(Ci) is the prior probability that an individual from the sample belongs to class age Ci.
Using the reference sample to define the prior probabilities for the different age classes is not
appropriate as the distribution in this sample does not result from a sampling procedure
reflecting any structure of age of a real population. It just results from the availability of
individuals in the reference collection.
As there is an absence of any information concerning the natural mortality distribution of
Homo erectus infants we have assumed a uniform prior probability of age at death for the
classes between 0 and 8 years. Although this model does not likely correspond to a natural
age distribution at death, it appears to us the most conservative and cautious as it does not
make any prior assumption on the age of the specimen we want to estimate.
Then for the calculation on attributes alone (fontanelle, subarcuate fossa or endocranial
volume), if one assumed that all the prior values were equally likely, the formula can be
simplified:
For the calculation of the posterior probability of the second attribute (subarcuate fossa), the
posterior probabilities obtained for the first attribute (fontanelle) were taken as prior
probabilities. The order in which attributes are taken into consideration does not change the
final posterior probabilities.
In order to test non uniform profiles for the age at death, we have also used the mortality
profiles of modern hunter-gathers (Howell, 1979) and of wild chimpanzees (Hill et al., 2001)
to determine prior probabilities on the age distribution. When assessing the maturation of the
bregmatic area (closing fontanelle) and the subarcuate fossa (SF=[20-25[), the use of these
profiles still result in age estimates under 1.5 year with even higher probabilities on younger
ages than in the uniform model.
References:
Hill K., Boesch C., Goodall J., Pusey A., Williams J., Wrangham R., 2001. Mortality rates
among wild chimpanzees. Journal of Human Evolution, 40, 5 : 437-450.
Howell N., 1979. Demography of the Dobe !Kung. New York, Academic Press
Supplementary figure 1
Coronal cuts 2-3 mm behind bregma in the Strasbourg series. In the Strasbourg series, the
fontanelle closure occurs between a minimal age of 20 months and a maximum age of 33
months. For this window of calendar age we have 23 individuals . However out of these 23
individuals only 2 individuals display a fontanelle less than 10 mm in one of its dimensions.
And out of 113 individuals of the collections displaying a fontanelle only 4 have a fontanelle
less than 10 mm in one of its dimensions. The figure provides pictures of the 10 individuals
belonging to this range of age with a closing or a just closed fontanelle and of one 3 year old
individual. It shows the pattern of suture closing and the individual variation observed in the
sample. The individuals with thicker bone all display a diploe extending not far from the edge
of the existing bone.
Supplementary figure 2
Pan paniscus 84036M7 (Tervuren). Dental age : N/J1. Superior view