Divergent mtDNA lineages of goats in an Early Neolithic site, far from the initial domestication areas

Abstract

Goats were among the first farm animals domesticated, approximately 10,500 years ago, contributing to the rise of the "Neolithic revolution." Previous genetic studies have revealed that contemporary domestic goats (Capra hircus) show far weaker intercontinental population structuring than other livestock species, suggesting that goats have been transported more extensively. However, the timing of these extensive movements in goats remains unknown. To address this question, we analyzed mtDNA sequences from 19 ancient goat bones (7,300-6,900 years old) from one of the earliest Neolithic sites in southwestern Europe. Phylogenetic analysis revealed that two highly divergent goat lineages coexisted in each of the two Early Neolithic layers of this site. This finding indicates that high mtDNA diversity was already present >7,000 years ago in European goats, far from their areas of initial domestication in the Near East. These results argue for substantial gene flow among goat populations dating back to the early neolithisation of Europe and for a dual domestication scenario in the Near East, with two independent but essentially contemporary origins (of both A and C domestic lineages) and several more remote and/or later origins.

Fig. 1.

Map shows occidental part of the current geographic distribution of the wild goat, Capra aegagrus (dotted area), as well as the two main waves for the initial advancement of the Neolithic culture into Europe: the Mediterranean route and the Danubian route (4, 8, 9). The location of Baume d’Oullen is indicated by a star. The dates on the map are calibrated radiocarbon date-derived B.P. (cal. B.P.). Solid-line arrows indicate main flow; broken-line arrows indicate possible secondary flows. Dark gray zones indicate the area of the Impressa culture (8,000–7,500 cal. B.P.); light gray zones indicate the area of the Cardial and cultures (between 7,500 and 6,800 cal. B.P.) (4).

Fig. 2.

Neighbor-joining tree shows the ancient haplotypes that cluster in the two divergent lineages A and C. The number on the branch is the percentage of 2,000 bootstrap trees with the same branch structure. The four ancient goat haplotypes from southern France (red branches BO-A1, BO-A2, BO-C1, and BO-C2) are compared with 43 previously published modern goat sequences from local autochthonous breeds. Lineage A sequences are from contemporary goats from France (n = 14), Slovenia (n = 2), and Switzerland (n = 18). Lineage C sequences are from contemporary goats from Slovenia (n = 6) and Switzerland (n = 3). Lineage C has been identified only in the Slovenian goats and the Swiss Toggenburg goats; it has never been found in contemporary goats from France. Trees constructed by using Bayesian analyses give similar results (see Fig. 6).

Fig. 3.

Calibration histograms in cal. B.P. calendar dates for five AMS radiocarbon-dated goat bones from Baume d’Oullen. Each sample label is followed by its AMS lab number, stratigraphic layer, and uncalibrated date (B.P.) with standard deviation. The calibration histograms for each sample show the probability distribution of possible true calendar ages, and the brackets under each histogram delineate the 1- and 2 σ calendar age ranges. All five samples are statistically the same radiocarbon and calendar age. Mitochondrial lineage (A or C) is indicated on the right.