The manufacture of geometric engravings is generally interpreted as indicative of modern cognition and behaviour1. Key questions in the debate on the origin of such behaviour are whether this innovation is restricted to Homo sapiens, and whether it has a uniquely African origin1. Here we report on a fossil freshwater shell assemblage from the Hauptknochenschicht (‘main bone layer’) of Trinil (Java, Indonesia), the type locality of Homo erectus discovered by Eugène Dubois in 1891 (refs 2 and 3). In the Dubois collection (in the Naturalis museum, Leiden, The Netherlands) we found evidence for freshwater shellfish consumption by hominins, one unambiguous shell tool, and a shell with a geometric engraving. We dated sediment contained in the shells with 40Ar/39Ar and luminescence dating methods, obtaining a maximum age of 0.54 ± 0.10 million years and a minimum age of 0.43 ± 0.05 million years. This implies that the Trinil Hauptknochenschicht is younger than previously estimated. Together, our data indicate that the engraving was made by Homo erectus, and that it is considerably older than the oldest geometric engravings described so far4, 5. Although it is at present not possible to assess the function or meaning of the engraved shell, this discovery suggests that engraving abstract patterns was in the realm of Asian Homo erectus cognition and neuromotor control.
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Extended data figures and tables
Extended Data Figures
- Extended Data Figure 1: The Pseudodon shells from Trinil. (584 KB)
(See Supplementary Information sections 1-2 and 4). a, Map of Central Java with major hominin sites and volcanic uplands. b, Stratigraphy of Trinil. A = Marine breccia (“Marine Breccie”). B = Mudstone (“Thonstein”). C = Conglomerate (“Conglomerat”). D = Trinil Hauptknochenschicht (“Lapilli Schicht”) containing H. erectus fossils. E = Soft sandstone (“Weicher Sandstein”). F = unnamed level. G = soil. c–j, Scans of thin sections of fossil Pseudodon infilled shell DUB 9717-b (c–f) and of infill DUB 9735 (g–j). The numbers refer to the numbered descriptions in Supplementary Information section 2. Images c, d, g and h are made by reflective scanning; images e, f, i, j are made by transmissive scanning. Scale bar, 4 cm. k, Pseudodon shell length–height data. Black dots show the fossil Pseudodon vondembuschianus trinilensis assemblage from Trinil. Coloured dots show recent Pseudodon vondembuschianus assemblages collected on Java in the 1930s.
- Extended Data Figure 2: XRF analysis. (283 KB)
(See Supplementary Information section 3 and Supplementary Table 2.) a, Fossil Femur I from Trinil undergoing XRF analysis. Dorsomedially, just below mid-shaft is a small white circle representing the filled hole where K. P. Oakley drilled a bone sample. b, Scatter plot of CaO versus P2O5. All values measured with hand-held XRF on hominin and non-hominin bones are included. The line represents the CaO/P2O5 ratio in fresh bone. c, CaO/P2O5 ratios of hominin bones from Trinil. The values were measured with hand-held XRF at four to seven locations on the bones. ‘Calotte’ indicates the skull cap named Trinil 2. d, Scatterplot of sulphur (S) versus Fe2O3 content of fossil bones. Data points represent all measurements performed on hominin fossils from Trinil, plus non-hominin fossil fauna from Trinil and Kedung Brubus. In pyrite, the Fe2O3/S ratio is 1.126. The arrows highlight the measurement locations on Femur II where elevated contents of S and Fe2O3 were measured, which explains the two high CaO/P2O5 values (4 and 4.5) in c. e, Scatterplot of Ba versus Y (calcium-corrected) content of fossil bones. Data points represent all measurements done on hominin fossils from Trinil, plus non-hominin fauna from Trinil and Kedung Brubus. f, Detail of the Ba–Y scatterplot in e.
- Extended Data Figure 3: Holes in shells. (524 KB)
(See Supplementary Information sections 5–7.) a, Fossil Pseudodon shell DUB9718-a (detail in b); c, DUB5234-aR (detail in d); e, DUB9714-bR (detail in f). Scale bar, 1 cm. g, Recent Lobatus gigas (“Strombus”) shell with a hole at the location of the columellar muscle attachment, made by pre-Hispanic modern humans (photograph provided by C. L. Hofman). Scale bar, 1 cm. h, Detailed view of g. i, Similar hole in another Lobatus gigas specimen (photograph provided by A. Antczak). Scale bar, 1 cm. j, Experimentally drilling a hole in a living Potamida littoralis specimen, using a fossil shark tooth. k, Hole drilled, damaging the adductor muscle. l, The shell starts to gape. m, The valves can be easily opened. n, Example of undamaged fossil teeth of the shark species Glyphis sp. from Trinil. o, Glyphis teeth with side damage, on the serrated edge. p, Glyphis sp. teeth with tip damage. q, Glyphis sp. teeth with tip and side damage. Scale bar, in q, 1 cm, also applies to n–p. r, Fossil teeth of the shark species Carcharius taurus from Trinil. Scale bar, 1cm. s, Detail of a fossil Carcharius taurus tooth.
- Extended Data Figure 4: Shell modification on Pseudodon shell DUB5234-dL. (793 KB)
(See Supplementary Information section 8.) a, Interior of the shell valve. b, Ventral margin with contiguous flake scars. c, Shallow striations parallel to the retouched edge. d, Micropits made by pecking with a sharp agent. e–g, Magnifications of the retouched edge, showing step fractures associated with rounding and smoothing of the edge. h, Traces of damage by roots or fungi inside and across the striations. Scale bars: 1 cm in a and b and f, 1.25 mm in c, 1.5 mm in d, 0.5 mm in e and h, and 1 mm in g.
- Extended Data Figure 5: Engraved pattern on Pseudodon shell DUB1006-fL. (519 KB)
(See Supplementary Information section 9.) a, Tracing of the engraved lines, with numbers indicating the sequence of engraving. b, White rectangles refer to the locations of the images shown in the panels of Extended Data Figs 5 and 6, featuring portions of grooves and intersections. The white dots indicate the location of the areas where three-dimensional roughness parameters were measured (Supplementary Table 4). Scale bar, 1 cm. c, Composite of four SEM images made of a portion of groove number 3–4; numbered locations of the grooves on the shell are shown in panels a and b. d, Intersection number 2. e, Portion of groove number 6–7. f, Portion of groove number 1–2. g, Infinite Focus image of a portion of groove number 3–4; see b for location on the shell (same as the location of c). Scale bar, 1 mm.
- Extended Data Figure 6: Comparison of engraving on DUB1006-fL with experimental engravings. (605 KB)
(See Supplementary Information section 9.) a, Portion of groove in DUB1006-fL (see Extended Data Fig. 5b for location on the shell). b, Experimental groove made with shark tooth tip. c, Experimental groove made with flint point. d, Experimental groove made with steel scalpel. e–h, Higher magnification (200× instead of 60×) of Extended Data Fig. 5a–d. i, Infinite Focus image of groove in DUB1006-fL (see Extended Data Fig. 5b for location on the shell). j, Infinite Focus image of experimental groove made with shark tooth tip. k, Infinite Focus image of experimental groove made with flint point. l, Infinite Focus image of experimental groove made with steel scalpel. m, Infinite Focus image of groove number 6–7 in DUB1006-fL (see Extended Data Fig. 5b for location on the shell). Scale bar, 1 mm.
- Extended Data Figure 7: 40Ar/39Ar analysis. (305 KB)
(See Supplementary Information section 10.) a, b, Pseudodon shells DUB9721-bR (Trinil-2) and DUB9714-bR (Trinil-3) with detrital infilling used for 40Ar/39Ar analysis. The other side of hominin-modified valve DUB9714-bR is featured in Extended Data Fig. 3e. Scale bar, 1 cm. c, 40Ar/39Ar analysis results on multiple-grain hornblende obtained from three samples. They constitute three populations (age groups) of ‘young’, ‘middle’ and ‘old’ age respectively. Note that three individual analyses (indicated in italics) belong to both the ‘young’ and ‘middle’ populations on statistical grounds.
- Extended Data Figure 8: 40Ar/39Ar results. (330 KB)
(See Supplementary Information section 10.) a, Total population of hornblende data, showing probability density curve, individual analyses with 1σ analytical uncertainties, and percentage enrichment in radiogenic 40Ar and estimates of the K/Ca ratios calculated from 39Ar/37Ar ratios. b, Three populations (age groups) as identified in the Trinil sample. Note that three individual analyses belong both to the ‘young’ (blue) and ‘middle’ (green) populations on statistical grounds. The error bars represent the 1σ analytical uncertainties. c, Inverse isochron representation of all three data sets showing overlap of the respective non-radiogenic intercepts with atmospheric 40Ar/36Ar ratios, and the isochron regression of the three subsets in blue (young), green (middle) and red (old) populations. The outliers are in grey. The 1σ error ellipses are in most cases smaller than the symbol size. MSWD, mean squared weighted deviate.
- Extended Data Figure 9: Luminescence dating. (404 KB)
(See Supplementary Information section 11.) a, Outside of the left valve of Pseudodon DUB1006-fL with engraving. b, Outside of the right valve. c, Inside of the right valve with infill, before sampling for luminescence dating. d, Inside of the right valve with infill, after sampling. e, pIRIR decay curves and dose–response behaviour for two representative individual aliquots of samples DUB1006-f(I) (left) and (II) (right) obtained from the engraved shell. The upper panels of e show the pIRIR signals for the natural dose (Ln), test dose (Tx) and regenerative dose (Lx). Indicated on the graphs are the integration intervals used for analysis. The lower panels of e show sensitivity-corrected dose–response curves showing the saturation behaviour, and the natural signal intercept that is above 2D0 for both aliquots.
- Extended Data Figure 10: The Trinil engraving in broader archaeological context. (369 KB)
(See Supplementary Information section 12.) The upper panel shows dating results from this study compared with previous age estimates, against the background of the marine isotope record. The lower panel shows a selection of engraved objects of Middle and Late Pleistocene age, with the chronological position of each indicated. a, Trinil, b, Quneitra, c, Klasies River Cave 1, d, Blombos Cave (~100 kyr), e, Qafzeh, f, Blombos Cave (~75 kyr), g, Diepkloof. Scale bar, 1 cm.
- Video 1: Animation of shell opening made on the basis of a CT scan of a living Unio mancus turtonii. (19.86 MB, Download)
- It shows how a sharp object perforates the shell at the location of the anterior adductor muscle and hits the muscle (indicated in red). This causes loss of muscle control, and the shell then can be opened.
- Supplementary Information (666 KB)
This file contains Supplementary Text 1-12, which includes additional results and discussion, Supplementary Tables 3 and 4 (see separate files for Supplementary Tables 1,2, 5, 6), and additional references.
- Supplementary Table 1 (164 KB)
This file contains the Shell database: Shell dimensions of fossil Pseudodon vondembuschianus trinilensis from Trinil HK, recent Pseudodon vondembuschianus from Java, and recent Unio crassus from the Seine River (France). For the Pseudodon it is recorded whether valves are single or paired (articulated) and still connected; and whether the valves are closed or partially open; and whether shells were consolidated in the museum by applying glue. The Pseudodon shell area is divided into seven zones (AC3;Fig. 1b), and presence of breakage, etching, dissolution pits, desquamation, abrasion, holes and grooves is recorded for each zone.
- Supplementary Table 2 (705 KB)
This file contains the HH-XRF data of fossil hominins and non-hominin fauna from Trinil: The value for yttrium (Y (Ca-corrected)) is obtained by dividing Y counts by Ca counts, multiplied by six (see Supplementary Information section 3).
- Supplementary Table 5 (36 KB)
This file contains the analytical details of Trinil hornblende, glass shards and feldspars single multi-grain fusion experiments: Location indicates the sample split taken from the three shell infill samples (Trinil-1-3). The reduced and full isotope intensities are given; corrected for baseline, mass discrimination and decay of 37Ar and 39Ar, as well as radiogenic 40Ar contents and K/Ca ratios for individual analyses (see Supplementary Information section 10).
- Supplementary Table 6 (691 KB)
This file contains the characteristics and dose rates of the investigated samples: a Water content estimate is based on the lithology and information on the burial context of the sample. b Grain size fraction used for luminescence measurements. c The internal concentration of potassium was assumed to be 12.5 ± 0.5 %67. Rubidium concentration was assumed to be 400 ± 100 ppm68. d Based on the U, Th and K concentrations from neutron activiation analysis and converted to dose rate using the conversion factors of Guérin et al.69. e Total dose rates include a cosmic dose rate of 0.11 ± 0.03 Gy/ka; the systematic (syst.) error (shared by the samples) and random (rand.) errors are specified. Reference numbers refer to references listed in the SI pdf (see Supplementary Information section 11).