Reconstructing contact and a potential interbreeding geographical zone between Neanderthals and anatomically modern humans

Abstract

While the interbreeding of Homo neanderthalensis (hereafter Neanderthal) and Anatomically modern human (AMH) has been proven, owing to the shortage of fossils and absence of appropriate DNA, the timing and geography of their interbreeding are not clearly known. In this study, we applied ecological niche modelling (maximum entropy approach) and GIS to reconstruct the palaeodistribution of Neanderthals and AMHs in Southwest Asia and Southeast Europe and identify their contact and potential interbreeding zone during marine isotope stage 5 (MIS 5), when the second wave of interbreeding occurred. We used climatic variables characterizing the environmental conditions of MIS 5 ca. 120 to 80 kyr (averaged value) along with the topography and coordinates of Neanderthal and modern human archaeological sites to characterize the palaeodistribution of each species. Overlapping the models revealed that the Zagros Mountains were a contact and potential interbreeding zone for the two human species. We believe that the Zagros Mountains acted as a corridor connecting the Palearctic/Afrotropical realms, facilitating northwards dispersal of AMHs and southwards dispersal of Neanderthals during MIS 5. Our analyses are comparable with archaeological and genetic evidence collected during recent decades.

Keywords: Anatomically modern humans; Ecological niche; Neanderthals; Palaeoenvironment; Zagros Mountains.

Figure 1

Habitat suitability models of the two Homo species and their potential contact and interbreeding zones in Southwest Asia and Southeast Europe. This figure was generated in QGIS 3.14.1 (www.qgis.org). The figures of the Neanderthal (left) and modern human (right) are adapted from www.demorgen.be.

Figure 2

Response curves showing how the presence of Neanderthals (a) and AMHs (b) is related to the environmental variables (Bio5: maximum temperature of the warmest month, Bio6: minimum temperature of the coldest month, Bio12: annual precipitation and Bio18: precipitation of the warmest quarter) (https://biodiversityinformatics.amnh.org/open_source/maxent/).

Figure 3

Precipitation changes from 140 to 40 kyr at 10,000 intervals.

Figure 4

Distribution of key archaeological sites dating between MIS 5 to 3 across southwest Asia and southeast Europe. Map data acquired from http://www.roceeh.org and created in www.qgis.org.