Neanderthals versus Modern Humans: Evidence for Resource Competition from Isotopic Modelling

doi:10.4061/2011/689315

Virginie Fabre, Silvana Condemi, Anna Degioanni and Estelle Herrscher

During later MOIS3, in Europe two populations were present, autochthonous Neanderthals and modern humans. Ecological competition between these two populations has often been evoked but never demonstrated. Our aim is to establish whether resource competition occurred. In this paper, in order to examine the possibility of ecological competition between these two populations, 599 isotopic data were subjected to rigorous statistical treatment and analysis through mixing models. The aim of this paper was to compare dietary strategies of Neanderthals and modern humans over time. Our conclusions suggest that Neanderthals and modern humans shared dietary habits in the particular environmental context of MOIS3 characterised in Europe by climatic deterioration. In this environmental context, the resource competition between Neanderthals and modern humans may have accelerated the disappearance of the Neanderthal population.

Adam and Eve

Mme Degioanni made a good point today. She asked us if there was an incompatibility with the fact that the mitochondrial ‘Eve’ is dated at around 200ky and that a similar study based on the Y-chromosome study (‘Adam’) cites a last common ancestor at around 90ky. Eve never met Adam! Nobody in the class could give an answer, but when she explained the reason it seemed so obvious.

These studies are based on today's modern populations, so any haplotypes that went extinct are not represented.  Had they used a sample from say 100 or 1000 years ago, the picture could be quite different, potentially pushing the LCA estimate back. 

That's the nature of the beast with classic mtDNA analyses. This is why recent breakthroughs in using fossil DNA is so exciting. Seeing snapshots in the past will help correct the bias inherent in using a sample from today's existing haplotypes.

Test Tajima (Tajima's D)

Test de neutralité sélective basé sur la diversité moléculaire des échantillons.  Si marqueurs sont neutres, la difference est 0.  Si D ≠ 0, there is selection.  

D < 0, excès de variant rares

D > 0, déficit de variant rares

Bamshad et al.

STRUCTURE software

Pritchard et al 2000

• On assume qu'un certain nombre K de groupes sont présents. 
• On assume que chaque groupe est caractérisé par un groupe de fréquences d'alleles à chaque locus.

Degioanni is very skeptical of this software that is very à la mode these days. Results are too dependant on a researchers choice of groups.

Qu'est-ce que c'est qu'une population ?

"C'est un joker." - Mme Degioanni
On parle souvent de:

• Proximité géographique 
• Même langue 
• Partage réligion, culture, ethnie (moins de probabilité de mariages intergroupe)