deletions | additions       diff --git a/materials_and_methods.tex b/materials_and_methods.tex  index 28f5e39..98fa913 100644  --- a/materials_and_methods.tex  +++ b/materials_and_methods.tex 
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To represent variables influencing Neanderthals distribution at the continental scale we have selected a palaeoclimatic simulation performed with the NCAR Community Climate System Model \cite{Otto2006}. This coupled ocean-atmosphere-land-sea-ice general circulation model was also coupled with an ice-sheet simulation to simulate the start of the Eemian (~130 ka BP). The results of this palaeoclimatic model fit very well with the available climatic proxies for the given period \cite{Otto2006}. This simulation is available at www.worldclim.com as a set of maps downscaled to 1km resolution representing 19 bioclimatic variables.   To represent factors influencing Neanderthals distribution  at the local scale, we processed the digital elevation model provided by www.worldclim.com (SRTM model aggregated to 1km resolution, \cite{Farr_2007}) to derive the topographical slope slope, topographic wetness index,  and a measure of topographical complexity (elevation, aspect topographic diversity (see appendix for further details).  We assessed colinearity among the 22 environmental factors (19 bioclim variables  and 3  topographic wetness variables) using a two step approach. Firstly, we computed the correlation matrix among variables, and defined 0.5 pearson correlation  index values scaled as threshold to retain or reject variables. Secondly we applied a variance inflation factor analysis (HH library, R software, )  to [1, 100]) select the final set of variables.  Description of the climatic and topographical layers  Collinearity analysis  \textbf{Species distribution modeling}