Cultural attraction in pottery practice: Group-specific shape transformations by potters from three communities

Abstract Pottery is a quintessential indicator of human cultural dynamics. Cultural alignment of behavioral repertoires and artifacts has been considered to rest upon two distinct dynamics: selective transmission of information and culture-specific biased transformation. In a cross-cultural field experiment, we tested whether community-specific morphological features of ceramic vessels would arise when the same unfamiliar shapes were reproduced by professional potters from three different communities who threw vessels using wheels. We analyzed the details of the underlying morphogenesis development of vessels in wheel throwing. When expert potters from three different communities of practice were instructed to faithfully reproduce common unfamiliar model shapes that were not parts of the daily repertoires, the morphometric variation in the final shape was not random; rather, different potters produced vessels with more morphometric variation among than within communities, indicating the presence of community-specific deviations of morphological features of vessels. Furthermore, this was found both in the final shape and in the underlying process of morphogenesis; there was more variation in the morphogenetic path among than within communities. These results suggest that the morphological features of ceramic vessels produced by potters reliably and nonrandomly diverge among different communities. The present study provides empirical evidence that collective alignment of morphological features of ceramic vessels can arise from the community-specific habits of fashioning clay.


Figures S1 to S22
Tables S1 to S2 Figures and Tables Figure S1.Morphological development as a function of time for the last of the five trials of producing Cylinder using 0.75 kg of clay thrown by each of the 21 potters.(A) Prajapati potters, (B) French potters, and (C) Multani Kumhar potters.Successive outlines on the timelines represent the vessel form after each fashioning gesture of the potter, from the initial pre-formed shape (t = 0) up to the final vessel shape.The size scale (height) is indicated on the y-axis.Table S2.Results (F, df, and P-values) for the factor Stage of the betadisper homogeneity of multivariate variance tests of the Euclidean distance from the group centroid in the full dimensional space of sizecorrected Fourier coefficients, at the initial pre-formed stage, the middle stage, and the final stage, for each model vessel type thrown by the French (9 potters), Prajapati (6 potters), and Multani Kumhar potters (6 potters).For each vessel type, within-potter effects are based on five trials.

Figure S2 .
Figure S2.Morphological development as a function of time for the last of the five trials of producing Cylinder using 2.25 kg of clay thrown by each of the 21 potters.(A) Prajapati potters, (B) French potters, and (C) Multani Kumhar potters.Successive outlines on the timelines represent the vessel form after each fashioning gesture of the potter, from the initial pre-formed shape (t = 0) up to the final vessel shape.The size scale (height) is indicated on the y-axis.

Figure S3 .
Figure S3.Morphological development as a function of time for the last of the five trials of producing Bowl using 0.75 kg of clay thrown by each of the 21 potters.(A) Prajapati potters, (B) French potters, and (C) Multani Kumhar potters.Successive outlines on the timelines represent the vessel form after each fashioning gesture of the potter, from the initial pre-formed shape (t = 0) up to the final vessel shape.The size scale (height) is indicated on the y-axis.

Figure S4 .
Figure S4.Morphological development as a function of time for the last of the five trials of producing Bowl using 2.25 kg of clay thrown by each of the 21 potters.(A) Prajapati potters, (B) French potters, and (C) Multani Kumhar potters.Successive outlines on the timelines represent the vessel form after each fashioning gesture of the potter, from the initial pre-formed shape (t = 0) up to the final vessel shape.The size scale (height) is indicated on the y-axis.

Figure S5 .
Figure S5.Morphological development as a function of time for the last of the five trials of producing Sphere using 0.75 kg of clay thrown by each of the 21 potters.(A) Prajapati potters, (B) French potters, and (C) Multani Kumhar potters.Successive outlines on the timelines represent the vessel form after each fashioning gesture of the potter, from the initial pre-formed shape (t = 0) up to the final vessel shape.The size scale (height) is indicated on the y-axis.

Figure S6 .
Figure S6.Morphological development as a function of time for the last of the five trials of producing Sphere using 2.25 kg of clay thrown by each of the 21 potters.(A) Prajapati potters, (B) French potters, and (C) Multani Kumhar potters.Successive outlines on the timelines represent the vessel form after each fashioning gesture of the potter, from the initial pre-formed shape (t = 0) up to the final vessel shape.The size scale (height) is indicated on the y-axis.

Figure S7 .
Figure S7.Morphological development as a function of time for the last of the five trials of producing Vase using 0.75 kg of clay thrown by each of the 21 potters.(A) Prajapati potters, (B) French potters, and (C) Multani Kumhar potters.Successive outlines on the timelines represent the vessel form after each fashioning gesture of the potter, from the initial pre-formed shape (t = 0) up to the final vessel shape.The size scale (height) is indicated on the y-axis.

Figure S8 .
Figure S8.Development of the morphology of Cylinder (0.75 kg) in shape space.Right panels: Development of vessel morphology is represented as trajectories through 3D shape space, from the initial pre-formed shape (open circles) to the final shape (open squares), for vessels thrown by six Prajapati potters (B), by six Multani Kumhar potters (D) and by nine French potters (F).Individual potters are color-coded.For each potter mean initial shape (pre-form) is depicted on the right side.Left panels: Zoom on final vessel shapes (open squares) thrown by Prajapati potters (A), by Multani Kumhar potters (C), and by French potters (E).For each potter, the mean final form is depicted on the right side.

Figure S9 .
Figure S9.Development of the morphology of Cylinder (2.25 kg) in shape space.Right panels: Development of vessel morphology is represented as trajectories through 3D shape space, from the initial pre-formed shape (open circles) to the final shape (open squares), for vessels thrown by six Prajapati potters (B), by six Multani Kumhar potters (D) and by nine French potters (F).Individual potters are color-coded.For each potter mean initial shape (pre-form) is depicted on the right side.Left panels: Zoom on final vessel shapes (open squares) thrown by Prajapati potters (A), by Multani Kumhar potters (C), and by French potters (E).For each potter, the mean final form is depicted on the right side.

Figure S10 .
Figure S10.Development of the morphology of Bowl (0.75 kg) in shape space.Right panels: Development of vessel morphology is represented as trajectories through 3D shape space, from the initial pre-formed shape (open circles) to the final shape (open squares), for vessels thrown by six Prajapati potters (B), by six Multani Kumhar potters (D) and by nine French potters (F).Individual potters are color-coded.For each potter mean initial shape (pre-form) is depicted on the right side.Left panels: Zoom on final vessel shapes (open squares) thrown by Prajapati potters (A), by Multani Kumhar potters (C), and by French potters (E).For each potter, the mean final form is depicted on the right side.

Figure S11 .
Figure S11.Development of the morphology of Bowl (2.25 kg) in shape space.Right panels: Development of vessel morphology is represented as trajectories through 3D shape space, from the initial pre-formed shape (open circles) to the final shape (open squares), for vessels thrown by six Prajapati potters (B), by six Multani Kumhar potters (D) and by nine French potters (F).Individual potters are color-coded.For each potter mean initial shape (pre-form) is depicted on the right side.Left panels: Zoom on final vessel shapes (open squares) thrown by Prajapati potters (A), by Multani Kumhar potters (C), and by French potters (E).For each potter, the mean final form is depicted on the right side.

Figure S12 .
Figure S12.Development of the morphology of Sphere (0.75 kg) in shape space.Right panels: Development of vessel morphology is represented as trajectories through 3D shape space, from the initial pre-formed shape (open circles) to the final shape (open squares), for vessels thrown by six Prajapati potters (B), by six Multani Kumhar potters (D) and by nine French potters (F).Individual potters are color-coded.For each potter mean initial shape (pre-form) is depicted on the right side.Left panels: Zoom on final vessel shapes (open squares) thrown by Prajapati potters (A), by Multani Kumhar potters (C), and by French potters (E).For each potter, the mean final form is depicted on the right side.

Figure S13 .
Figure S13.Development of the morphology of Sphere (2.25 kg) in shape space.Right panels: Development of vessel morphology is represented as trajectories through 3D shape space, from the initial pre-formed shape (open circles) to the final shape (open squares), for vessels thrown by six Prajapati potters (B), by six Multani Kumhar potters (D) and by nine French potters (F).Individual potters are color-coded.For each potter mean initial shape (pre-form) is depicted on the right side.Left panels: Zoom on final vessel shapes (open squares) thrown by Prajapati potters (A), by Multani Kumhar potters (C), and by French potters (E).For each potter, the mean final form is depicted on the right side.

Figure S14 .
Figure S14.Development of the morphology of Vase (0.75kg) in shape space.Right panels: Development of vessel morphology is represented as trajectories through 3D shape space, from the initial pre-formed shape (open circles) to the final shape (open squares), for vessels thrown by six Prajapati potters (B), by six Multani Kumhar potters (D) and by nine French potters (F).Individual potters are color-coded.For each potter mean initial shape (pre-form) is depicted on the right side.Left panels: Zoom on final vessel shapes (open squares) thrown by Prajapati potters (A), by Multani Kumhar potters (C), and by French potters (E).For each potter, the mean final form is depicted on the right side.

Figure S15 .
Figure S15.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Cylinder (0.75 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).

Figure S16 .
Figure S16.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Cylinder (2.25 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).

Figure S17 .
Figure S17.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Bowl (0.75 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).

Figure S18 .
Figure S18.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Bowl (2.25 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).

Figure S19 .
Figure S19.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Sphere (0.75 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).

Figure S20 .
Figure S20.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Sphere (2.25 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).

Figure S21 .
Figure S21.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Vase (0.75 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).

Figure S22 .
Figure S22.Raw data (points) and fitted generalized additive model (lines) for 3D shape space trajectory data of Vase (2.25 kg).Black points indicate individual trial observations in the training data (trials 1, 3, and 5), and gray points are observations in held-out trials used for model validation (trials 2 and 4) from the three communities of practice.Each line indicates predicted PC values as a function of time for each participant based on model SI (inter-community variation with similar smoothness plus random effects for individual-level intercepts and temporal variation).