Diversity in Human Growth. Growth in African Pygmies – GrowinAP

The data collected are of two types; dental and anthropometric data were obtained from the study of individuals on site (Equatorial Africa) while genetic and endocrinology data are analysed in laboratory from samples taken from the field. The results for pygmies are compared with those from other populations.

Partial results allow us already to identify the possible hypotheses to explain the growth of pygmies and their particular phenotype. In addition, we observed that these results can already identify individuals whose growth deviates from the normal curve. Our initial results on the genetics show that two candidate genes (GHR and IGF1) may be involved in the genetic determination of the low stature of the pygmies.

Data collection in the field progress normally. The discovery of new localities with records or birth allows the extension of these studies to other populations. The development of hormonal analysis is finished and they can begin immediately. Characterization of somatic growth and the identification of genetic and hormonal underlying allow broad understanding of the growth of pygmies.

Becker et al. 2012. The role of GHR and IGF1 genes in the genetic determination of African pygmies’ short stature. European J. Hum. Gen. doi:10.1038/ejhg.2012.223.
Romero, Ramirez Rozzi et al. 2013. Modularity and shape variation of upper P4-M1 teeth in modern humans. Am. J. Phys. Anthropol. suppl. 56.
Froment, Ramirez Rozzi, Maget. Film documentaire ‘Pygmées Baka, le grand virage’ ; produit par CNRS images et IRD Images. 2013. A voir sur
vimeo.com/58753395
mot clé : ouf

It is assumed that all human populations shared a similar pattern of growth. However, considerable variation in growth has been recorded specially in hunter-gatherer populations. It is unfortunate that data for such populations are rare or low-quality. African Pygmies represent one of the most interesting and less acculturated groups among forager populations. The knowledge of growth in Pygmies is crucial to understand physiological variation in modern humans. Many research projects over the past decades have tried to characterize growth in Pygmies in order to explain the reduced adult stature. However, results are contradictories and since no underlying molecular defect has been identified, all suggestions remain inconclusive. Therefore, a definitive understanding of growth processes responsible remains elusive. The principal aim of our project GrowinAP is to characterise growth in Baka Pygmies. All previous works on Pygmies have focused on only one aspect of growth disregarding evidence from other fields. We will conduct multidisciplinary data collection and analysis in order to quantify growth (somatic and dental data) as well as to understand its genetic and endocrinological basis. Excepted two works based on individuals from birth to 5 yrs old, growth in Pygmies has never been documented; it is evident that the lack of chronological data limits any conclusion about growth. In contrast to all previous works, date of birth is available for us. Indeed, from 1988, European nuns established in Bosquet near Lomié (Cameroon) have compiled an accurrate record of births in Pygmy Baka communities for the last twenty years. These records enable us to age each individual from birth to 20 years old. Somatic, dental, genetic, and endocrinological analysis will be carried out in transversal and semi-longitudinal data from individuals of known age. Therefore, our project GrowinAP is the first work on growth in Pygmies to be carried out in individuals whose age is known. The aims of our GrowinAP project are 1. to characterize growth in Baka Pygmies, 2. to describe growth in Nzime, neighbor non-Pygmy group living in similar environment condition and in close economic relation with Baka Pygmies, 3. to detect natural/cultural union preferences which hold stature balanced, 4. to determine particularities of growth in Baka from the comparison with Nzime, 5. to suggest a model of growth in order to explain the short stature in Pygmies. In short, somatic and dental status will be known for each aged Baka Pygmy and non-Pygmies neighbors. The transversal data will be complemented with longitudinal data obtained by following somatic and dental changes over eight years (four years already done and four years of the ANR project). Data supplied by endocrinological and genetic analysis will reveal molecular mechanism of growth for each age class in both group and specify changes at a given period of growth. The implementation of this project will result in data indexed on known chronological ages and will allow 1 to identify genetic bases of Pygmies’ growth, 2 to establish the plasmatic endocrinological variations according to the age, 3 to follow somatic changes coupled with endocrinological characteristics during growth, 4 to caracterise dental growth in relationship with somatic development, 5 to suggest life history variables in Pygmies. Our data will enable us to obtain curves of growth and to establish growth patterns in Pygmies for the first time. Our results will open the way to approach adaptive processes in African Pygmies. The characterization of growth in Baka will give an idea of the growth variation making possible to establish the limits of physiological variation in modern humans. It will allow to gain a better understanding of palaeo-anthropological data and to widen our understanding of hominid evolution.