1. Question one: Do flake attributes differ in morphospace size?
When do similarities in flake attributes reflect common cultural ancestry?
Jonathan Paige, Charles Perreault
Convergence is a potential problem in tracing cultural interactions in the Pleistocene
Question two: Are attributes with smaller morphospaces more prone to convergence?
Morphospace
Attribute A
Wider space
Large coefficient of variation
Greater potential for variation
Methods
Gathered flake data from two groups:
Compared (KS-test) external platform angle (E), platform thickness (P) and length/width ratio (L) distributions between assemblages (315 comparisons).
Similarities between Hohokam and outgroups counted as cases of convergence.
Similarities within Hohokam, and differences between Hohokam and outgroup counted as successes.
Archaeologists use similarities in flake attributes to infer cultural interaction, and migration (Tostevin 2012). However, flake similarities could be due to causes other than cultural interaction, or common cultural ancestry.
How many possible forms a flake may take, or its morphospace (McGhee 2006), is constrained by the physics of fracture mechanics (Magnani et al. 2014, Moore 2011).
Restricted morphospaces should be more prone to convergence: similar forms being made by chance by two groups without a cultural connection.
Ingroups: Hohokam assemblages dating between A.D. recovered from Tonto Basin, Central Arizona. (N =620 flakes).
Possible forms
Outgroups: 13 experimental assemblages, and 5 old world Pleistocene assemblages (N=3,485 flakes).
Attribute B
Restricted space
Small coefficient of variation
Convergence is likely
Impossible forms
Question one: Do flake attributes differ in morphospace size?
Methods
Collected summary data on flakes (N=42,502) from 15 experimental and 51 archaeological assemblages.
Assemblages span MP-UP Eurasia, Lomekwian-MSA Africa, late Holocene North America.
Collected mean external platform angle (E), platform depth (P), and length:width ratios (L).
Calculated coefficient of variation (CV) in each attribute as a proxy for relative size of morphospaces.
Platform Thickness
External platform angle
Length: ratio Width
Results
Convergence more likely for external platform angle than other attributes
Success in both identifying similarities among Hohokam, and differences between Hohokam and outgroup ranges between ~50% and ~70%.
Results
Attributes vary in size of morphospace (CV)
Discussion
Acknowledgements:
Thanks to the researchers who published data used in this study, Derek Miltimore for the flake photo, Dr. Arleyn Simon, The Center for Archaeology and Society, and The Roosevelt Platform Mound Study for their help and access to the Tonto Basin assemblage.
Attributes that have limited morphospaces should be more prone to convergence than other attributes.
Outlining the morphospace for lithic technology is one way of exploring which attributes may be more or less useful for cultural reconstructions.
Future studies will assess the scales at which different attributes retain cultural information.
External platform angle (E) has the smallest CV, the most restricted morphospace, and should be most prone to convergence.
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