Presentation Title

Comparing Cranial Morphology of Homo georgicus and Modern Humans

Faculty Mentor

Scott Suarez

Start Date

23-11-2019 8:00 AM

End Date

23-11-2019 8:45 AM

Location

35

Session

poster 1

Type of Presentation

Poster

Subject Area

behavioral_social_sciences

Abstract

Because of the sparseness of the human ancestral fossil record, it is challenging to establish evolutionary relationships among early human ancestors. The discovery of five surprisingly complete skulls (collectively classified as Homo georgicus) at the Dmanisi paleontological site in Georgia has provided an opportunity to clarify relationships among human ancestors close to 1.8 million years ago. Variation in anatomical traits among these five skulls, however, has caused controversy about their phylogenetic position relative to other previously known species such as Homo habilis, and Homo erectus/ergaster. The difficulty in the categorization of the Dmanisi skulls is in part due to the use of qualitative, rather than quantitative data for comparison. Here, I use linear algebra to analyze relationships among standard anatomical landmarks (e.g. bregma, lambda, and opisthion) to quantify and standardize characteristics such as degree of prognathism, foramen magnum position, forehead angle, and cranial width index. I use these quantified measurements to compare two of the Dmanisi skulls (D2700 and D4500) to Australopithecus afarensis (n=1), Homo sapiens (n=4), and Pan troglodytes (n=2) to determine overall similarity in characteristics, and assess phylogenetic position based on these comparisons. D2700 (Dmanisi 3) was more similar in prognathism and position of the foramen magnum to Homo sapiens than to more primitive taxa, while D4500 was more similar to A. afarensis and P. troglodytes. These data highlight the diversity in prognathism and position of the foramen magnum among the single population of Homo georgicus, indicating either a highly varied population or multiple migrations into Dmanisi from different ancestral lines or times. The quantified methods of measurement developed here can be used to facilitate statistical comparisons among early human ancestors, ultimately leading to a more clear understanding of the relationships among early human ancestors.

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Nov 23rd, 8:00 AM Nov 23rd, 8:45 AM

Comparing Cranial Morphology of Homo georgicus and Modern Humans

35

Because of the sparseness of the human ancestral fossil record, it is challenging to establish evolutionary relationships among early human ancestors. The discovery of five surprisingly complete skulls (collectively classified as Homo georgicus) at the Dmanisi paleontological site in Georgia has provided an opportunity to clarify relationships among human ancestors close to 1.8 million years ago. Variation in anatomical traits among these five skulls, however, has caused controversy about their phylogenetic position relative to other previously known species such as Homo habilis, and Homo erectus/ergaster. The difficulty in the categorization of the Dmanisi skulls is in part due to the use of qualitative, rather than quantitative data for comparison. Here, I use linear algebra to analyze relationships among standard anatomical landmarks (e.g. bregma, lambda, and opisthion) to quantify and standardize characteristics such as degree of prognathism, foramen magnum position, forehead angle, and cranial width index. I use these quantified measurements to compare two of the Dmanisi skulls (D2700 and D4500) to Australopithecus afarensis (n=1), Homo sapiens (n=4), and Pan troglodytes (n=2) to determine overall similarity in characteristics, and assess phylogenetic position based on these comparisons. D2700 (Dmanisi 3) was more similar in prognathism and position of the foramen magnum to Homo sapiens than to more primitive taxa, while D4500 was more similar to A. afarensis and P. troglodytes. These data highlight the diversity in prognathism and position of the foramen magnum among the single population of Homo georgicus, indicating either a highly varied population or multiple migrations into Dmanisi from different ancestral lines or times. The quantified methods of measurement developed here can be used to facilitate statistical comparisons among early human ancestors, ultimately leading to a more clear understanding of the relationships among early human ancestors.