HAL Id: mnhn-01643208
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Submitted on 22 Nov 2017
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Backed pieces and their significance in the Later Stone Age of the Horn of Africa
Alice Leplongeon, Clément Ménard
To cite this version:
Alice Leplongeon, Clément Ménard. Backed pieces and their significance in the Later Stone Age of the Horn of Africa. ESHE. 7th annual meeting of the European Society for the study of Human Evolution, Sep 2017, Leiden, Netherlands. ESHE, 6, pp.114, 2017, Proceedings of the European Society for the study of Human Evolution. �mnhn-01643208�
and their variability in
the Later Stone Age of
the Horn of Africa
Alice Leplongeon(1,2) & Clément Ménard (2,3)
1 McDonald Institute for Archaeological Research, University of Cambridge 2 UMR CNRS 7194, Muséum national d'histoire naturelle, Paris 3 UMR CNRS 5608, Université Toulouse-Jean Jaurès alice.leplongeon@gmail.com; menard.clement@gmail.com; goo.gl/tSbmux
Why our study?
• The emergence of backed pieces is associated with major Late Pleistocene technological innovations and behavioural changes.
• Backed pieces are often linked to hafting and composite tool technologies as well as the development of projectiles.
• Backed pieces frequently occur in large numbers in most Later Stone Age (LSA) assemblages and therefore allow for inter-site comparisons.
In the Horn of Africa, the study of the emergence and development of backed pieces is hampered by the use of varied definitions and equivocal terms (microliths, crescents, segments, curved backed blades, etc.). This paper aims to facilitate inter-site
comparisons by proposing a set of attributes to describe and analyse the variability of backed pieces in an objective and reproducible way.
Definition of backed pieces
Any product with at least one edge, or part of it, modified by abrupt to semi-abrupt continuous retouch roughly parallel to the longest morphological axis of the blank.
Location of the archaeological assemblages analysed (red dots) and main MIS 3-1 sites with backed pieces (white dots).
Materials and methods
A critical review of the occurrences of backed pieces during MIS 3-1 indicates:
• the absence of any robust evidence before 14 ka cal BP.
• backed pieces become significant only during the Middle and Late Holocene.
We analysed all complete backed pieces from eight archaeological assemblages belonging to sites recently excavated and securely dated that cover the last 15 ky.
For each of the 191 artifacts identified we recorded 31 variables and took standardised photographs. Our analysis includes but is not limited to multivariate analyses (performed with R using FactoMineR) and geometric morphometrics (using Momocs).
Left: Superimposition of scaled outlines of 127 complete backed pieces analysed. Backed edges towards the left.
Right: Principal component analysis (PCA) conducted on elliptic Fourier descriptions of complete backed pieces shapes using the first 10 harmonics. Backed edges towards the bottom.
Multiple correspondence analysis (MCA) performed on 121 backed pieces (limited to completely retouched edges), with 15 active variables and two supplementary variables (archaeological assemblage and raw material).
Results and perspectives
Our analysis enables us to describe chronological trends and regional variations without relying on any pre-existing typology.
• No significant miniaturisation through time
• Increase of frequencies of symmetrical and more convex pieces
• Local patterns of shape variation
Acknowledgements
We thank the Ethiopian Authority for Research and Conservation of Cultural Heritage for permission to access the collections.
Many thanks to the PIs of the sites studied (François Bon & Asamerew Dessie, David Pleurdeau & Zelalem Assefa, Xavier Gutherz).
This project has received funding from the French National Research Agency (ANR-14-CE31-0023 ‘Big Dry’),
a H2020 Marie Sklodowska-Curie grant (no 655459 ‘PleistTechnoVar’), the Fyssen Foundation and a joint research project (PRC) French National Scientific Research Centre (CNRS) - Ministry of Science & Technology of the State of Israel (MOST).
Many thanks to Emily Hallinan for her help with the English editing of the text.
>Backe pieces
10°
5°
15°
35° 40° 45° 50°
Bulbula River sites DW2s2
B1s1 Upper B1s1 Lower DW2s3
Mochena Borago SU 3010
Spit 7
Goda Buticha Unit IIC Unit I Late Glacial
14.8 - 11.7 ka Early Holocene
11.7-8.2 ka Mid Holocene
8.2-4.2 ka Late Holocene 4.2-... ka
B1s1 GB IIC GB I
MB 3010 MB 7
PC1
PC2
60.3%
19%
Eigenvalues
−1.5 −1.0 −0.5 0 0.5 1.0
−1 0 1
2 .
^^^ ^ ^^ ^
^^^^^^ ^^^^^^^ ^
^ ^
^ ^ ^^^^^^^^^^^ ^^^^^^^^ ^^^^^^^^^ ^ ^^^^^^^^^^^^ ^^^^ ^^^^^^^^^ ^
^ ^ ^^^^^^ ^^^ ^^ ^ ^^^^^^^^^^^ ^^^^ ^^^ ^^ ^^^ ^^^^^^^^^ ^
WIDTH: 0-5mm W2s3
Convex
opposed edge
CHALCEDONY
B 1 Upper
Asymmetric No point
B1s1 Lower
GB I Very convex
back
No bulb No butt Pointed Symmetrical
GB IIC MB 7 MB 3010CHERT
OBSIDIAN
Main modalities of qualitative variables Supplementary modalities: raw material Supplementary modalities: assemblage
Retouched opposed edge
5-10mm
Bulb present
MCA factor map
B1s1 Upper B1s1 Lower GB IIC
MB 7 MB 3010
GB 1
Present
Straight Convex
Very convex
Presence of bulb of percussion Convexity of the backed edge Assemblage
DW2s3
Transversal symmetry
Asymmetrical Symmetrical
Absent a
b
a/b = convexity index
.
butt/bulb Y/N Transversal symmetry
Y/N
retouch type
retouch angle
1 cm
