This study compared 19th-20th century dental traits between White and Black Americans to track ancestry markers and temporal shifts. After calculating trait frequencies, I assessed population differences and interpreted patterns using admixture frameworks, revealing key evolutionary trends in modern populations.
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Analysis
Analysis
I analyzed dental morphology data from 1,127 individuals across five 19th-20th century U.S. populations.
Using the ASUDAS scoring system, I calculated trait frequencies for each population group and compared distributions between White and Black Americans.
By looking at the differences in frequency rates between White and Black Americans in the 19th and 20th centuries, I was able to discern a pattern whereby dental morphological traits began to homogenize between Black and White populations.
Specific traits such as the appearance of cusp seven on the mandibular first molar have seen a reduction in the difference between frequency rates observed in White and Black American populations (from a 39% difference in the 19th century to a 31% difference in the 20th century).
The analysis revealed temporal shifts in trait expression, particularly the homogenization of cusp-related traits in 20th-century samples.
Results
Results
The analysis revealed distinct dental trait patterns: 19th-century Black Americans showed markedly higher frequencies of cusp-related traits (83% vs 4% for lingual cusp complexity) compared to White Americans.
These differences narrowed significantly in 20th-century samples, with traits like hypoconulid presence dropping from a 47% to 22% intergroup gap. Urban populations exhibited intermediate frequencies, suggesting greater historical admixture.
Table Displaying the Frequency Rates for Bethel Cemetery and Freedman's Cemetery
Discussion
Discussion
The findings strongly supported both hypotheses: extra-cusp-related traits (metaconule, hypoconulid) showed the greatest ancestral divergence (difference = 52%), while 20th-century samples demonstrated significant frequency homogenization (35% reduced intergroup variation).
This empirically validated Edgar's (2012) admixture models while addressing a literature gap - prior studies focused either on pre-1900 or modern samples, but none tracked continuous morphological change across this transitional period.
By analyzing 1,127 individuals spanning two centuries, this research established: 1) which traits remain stable ancestry markers despite admixture, and 2) quantitative benchmarks for temporal variation in dental trait frequencies, crucial for improving forensic identification accuracy in historically mixed populations.
Current approaches to forensic anthropology can benefit from this research as it strongly supports the use of extra-cusp related traits in the estimation of ancestry in historic American contexts, therefore suggesting they would have the highest degree of success in forensic or 21st century contexts.
It also suggests that the frequency rates for White and Black Americans have began to homogenize as the United States progressed into the 20th century, an interesting observation to note as forensic anthropologists may begin to use outdated data to estimate ancestry as time progresses.
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