The Iceman's Last Meal Consisted of Fat, Wild Meat, and Cereals

Abstract

The history of humankind is marked by the constant adoption of new dietary habits affecting human physiology, metabolism, and even the development of nutrition-related disorders. Despite clear archaeological evidence for the shift from hunter-gatherer lifestyle to agriculture in Neolithic Europe [1], very little information exists on the daily dietary habits of our ancestors. By undertaking a complementary -omics approach combined with microscopy, we analyzed the stomach content of the Iceman, a 5,300-year-old European glacier mummy [2, 3]. He seems to have had a remarkably high proportion of fat in his diet, supplemented with fresh or dried wild meat, cereals, and traces of toxic bracken. Our multipronged approach provides unprecedented analytical depth, deciphering the nutritional habit, meal composition, and food-processing methods of this Copper Age individual.

Keywords: European Copper Age mummy; Iceman; ancient DNA; diet; last meal; lipidomics; microscopy; multi-omics study; proteomics; stomach content.

Figure 1

The Iceman’s Gastrointestinal Tract (A) Gastrointestinal (GI) tract preservation and content texture. The radiographic image shows the completely filled stomach (asterisk) and the intestinal loops of the lower GI tract (arrows). Content samples of the stomach (left, asterisk) and of two different sites in the lower GI tract (middle, right) that were re-hydrated in phosphate buffer are shown below the radiographic image. (B) Animal muscle fibers detected in the stomach content using light microscopy. Scale bar, 50 μm. The black box contains a zoomed-in view of one muscle fiber (scale bar, 20 μM). (C) Plant tissue detected in the stomach content using light microscopy. Scale bar, 50 μm. See also Figure S1 for additional plant and animal remains detected in the Iceman intestinal contents.

Figure 2

Metagenomic and Proteomic Analysis (A) GI tract samples included in the metagenomic approach. The blue-bar diagrams below the sample description display the read distribution between the two kingdoms Bacteria and Eukaryota in selected shotgun datasets (for details, please refer to STAR Methods and Data S1). The number of shotgun datasets included in all further metagenomic analyses is provided in brackets. (B) Most abundant taxa detected in the intestinal content shotgun datasets. The circle size corresponds to the number of unambiguously assigned mitochondrial and chloroplast reads per million metagenomic reads. (C) Plant and animal proteins detected in the stomach content. The inner circle displays the number of identified proteins for the taxa Caprinae, Cervinae, and Triticinae. The outer circle highlights the number of unique peptides present for protein identification. The table summarizes details about the proteins detected with the highest unique peptide hits. See also Figures S2, S3, and S4 for a taxonomic overview of the plastid reads, the phylogenetic assignments, damage pattern, and DNA-barcode analysis. Data S1 contains details to the datasets and the plastid mapping statistics. Data S2 provides additional information to the identified peptide hits.

Figure 3

Lipid Analysis of the Iceman’s Stomach Content (A) Triacylglycerol (TAG) distribution in the Iceman’s stomach’s content in comparison to the TAG distribution in ibex muscle and fat tissue and goat dairy products. Displayed is the relative abundance of TAGs based on their chain length. (B) Saturation level of the TAGs in the stomach content and the fresh tissue samples. The Iceman’s stomach TAGs contain a much higher saturated bond content than fresh tissue samples. (C) The dispersion factor (DF) plotted against the average carbon number (M) of each TAG detected in the ancient and modern samples. The DF measures the spread of the TAG distribution. Together with M, DF can be used for discrimination between archaeological artifacts [26]. See also Data S2 for further details to the relative abundance of TAG species and to the mass spectrometry results.

Figure 4

Atomic Force Microscope Images and Raman Spectra of Muscle Fibers from the Iceman’s Stomach Content (A) Fibers obtained from the content of the Iceman’s stomach (I) show structures similar to those of recent fibers (II and VI). The typical Z-line is observed in raw (II) and air-dried lamb muscle fibers (IV). After thermal treatment such as frying or cooking of the meat, the sarcomeres disappear (III). The surface of the fibers becomes blurred, and only faint fibrillary structures can be found. (B) Raman spectra of samples extracted from the Iceman’s stomach content show similarities to untreated (fresh) lamb meat spectra. See Data S2 for details to the modern comparative animal samples.