Abstract

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Conclusions

1. CT RESOLUTIONS < 100 m ARE REQUIRED

2. ONE CT SLICE PER TOOTH OR SKELETAL ELEMENT MAY BE SUFFICIENT TO ASSESS DATING POTENTIAL

3. CT DATA OF ENTIRE SPECIMENS PROVIDE A DIGITAL ARCHIVE FOR OSTEOMETRIC ANALYSES

4. SAMPLING LOCATIONS ARE READILY MAPPED

5. CD DATA PERMIT STEREOLITHOGRAPHY OF BONES AND TEETH USED FOR 14C

6. SEVERE LEACHING AFFECTED ALL BONES AND TEETH

7. NON-COLLAGENOUS COMPOSITIONS PREVAIL

2. ENAMEL IS THE BEST CHOICE FOR 14C & 13C

3. ENAMEL GEOCHEMISTRY STUDIES ARE NEEDED

4. DIRECT 14C DATING OF HUMAN FOSSILS WILL EVALUATE THEIR PURPORTED ASSOCIATION WITH EXTINCT FAUNA

FOSSIL HUMAN REMAINS FROM SITES IN FLORIDA CONTAINING EXTINCT, LATE PLEISTOCENE MEGAFAUNA:

ASSESSING 14C DATING FEASIBILITY BY USING HIGH RESOLUTION CT SCANNING AND GEOCHEMICAL ANALYSES

Barbara A. Purdy1 bpurdy@ufl.edu, Thomas W. Stafford, Jr.2 thomasw@geology.wisc.edu & John Krigbaum1 krigbaum@ufl.edu1Department of Anthropology, University of Florida, Gainesville, FL 32611 2Department of Geology & Geophysics, University of Wisconsin, Madison, WI 53706

Computerized tomography (CT) and amino acid analyses (AAA) were used to assess the 14C dating potential of human fossils. The Devil’s Den and Vero Beach sites in Florida yielded human skeletal remains and several genera of extinct, late Pleistocene fauna. The rarity and fragmentary nature of the human remains required non-destructive (CT) and minimally destructive (AAA) testing to assess dating potential. High-resolution (70 m) CT was used on Devil Den’s human remains to identify greatest-density bone (highest dating potential). High-resolution CT imaging provides: 1) internal morphological data not available by medical CT, 2) digital images suitable for morphology and osteometrics, and 3) archived data for eventual stereolithographic reproductions of bones or teeth. AAA on 10 mg of bone determined the preservation quality and amount of collagen present.

Acknowledgments

Although thousands of diagnostic Clovis artifacts have been discovered in North America, only extremely fragmentary skeletal remains of two humans (Anzick Montana juvenile; Arlington Springs, CA female) have been dated to 11,000 RC yr. BP. Consequently, any possible Clovis-era remains require direct analysis to determine their geologic age. Two Florida sites with human fossils potentially dating as late Pleistocene are Vero Beach (8IR9), Indian River County, FL and Devil’s Den, Levy County, FL (8LV84). Both sites yielded fossil human bones purportedly associated with extinct, late Pleistocene mammal fossils; specimens are curated at the Florida Museum of Natural History (FLMNH), University of Florida, Gainesville, Florida. The Vero Beach fossils at FLMNH comprise two indurated blocks of clastic carbonate and mollusk fragments, in which are encased cranial bones and teeth of at least two individuals, respectively. These fossils are attributed to 1915-1916 canal excavations described by E.H. Sellards in 1916. He published the discovery of a single human’s femora, tibiae, fibulae and foot bones from brown sands (stratum no. 2) that also yielded Pleistocene fauna. Sellards observed that “Elephas columbi and Equus leidyi and other extinct species were found at an equal or higher level in the beds on either side of the human remains.” (Sellards, 1916:132).

The rarity of potential Late Pleistocene human remains necessitates using non- to minimally destructive methods to assess 14C dating potential. Conventional CT scans of Vero Beach blocks were used to identify human bones within sediment blocks and plan amino acid analyses and 14C dating. High resolution scans of Devil Den’s human remains were used to:

1) Locate dense bone where collagen preservation is most likely.2) Observe tooth morphology beneath enamel.3) Obtain high resolution digital images of single teeth or entire specimens for

osteometric analysis and the production of stereolithographic plastic models. Conventional, medical-resolution (~1 mm) CT scans were done at the McKnight Brain Institute, University of Florida; high resolution (50-100 m) CT scans were made at the Center for Quantitative Imaging, Penn State University. Scanning generated DICOM or TIFF files respectively. These digital data are a permanent archive of both single-slice data of discrete anatomical elements or virtual reconstruction “models” based on the total-scan of an entire specimen. AAA sampling of Devil’s Den remains was conducted on 10 mg of bone powder removed from 1/16” diameter holes in the densest regions as determined by CT. Collagen per milligram of bone (nanomoles per milligram) and the spectrum of each of 18 amino acids were measured relative to modern bone. The AAA data established if the specimen contained collagen for dating, if protein was collagenous or non-collagenous and how many milligrams of bone would be required for 14C dating.

CT scans of in situ human mandible, teeth (arrow), and skull fragments. Note associated shell.

VERO BEACH SITE (2005)

Devil’s Den Sinkhole (2005)

B

B/

B

B/

cochlea

A A/

A A/

Devil’s Den Juvenile Mandible

Un-erupted Tooth: CTX-Section

Devil’s Den Temporal Bone with Petrosal

Stratigraphically ex situ bones of Megalonyx jeffersoni and Mammut americanum were attributed to the human fossil horizon. Later excavations (April 1916) uncovered in situ bird bone and proboscidean ivory with “… markings which apparently were made by tools.” (Sellards, 1916: 134) and in situ extinct fauna including Equus spp., Smilodon, and Tapirus. Sellards concluded the human bones were stratigraphically coeval with the Pleistocene fauna. Other scientists examining the site in 1916 were divided between accepting or rejecting the hypothesized Homo sapiens-extinct fauna association (McCardy, 1917). As Vero Beach faunal remains became scattered among several museums, physical anthropological studies assumed the human remains’ contemporaneity with the extinct fauna (see Stewart, 1946) and geochronological studies were never done. The impetus for re-examining the Vero Beach collection are the capabilities of AMS 14C and an imminent engineering project that will expose the locality’s stratigraphy near the original discovery site. Direct AMS 14C dating of human skeletal material and re-exposure of the sediments will definitively test the fossils’ purported late Pleistocene age. Devil’s Den is an extant, approximately 10 m diameter sinkhole that is a tourist diving locale. The site has yielded several extinct or extralocal taxa (including Mammut, Megalonyx, Canis dirus, Smilodon, Equus, Platygonus compressus and Synaptomys australis (Martin and Webb, 1974)).

A minimum of six human individuals were collected in the 1950’s and 1960’s from the sink hole and are curated at FLMNH. Although the human remains were “found associated” with extinct fauna, the sinkhole’s depositional history precludes using fossil associations for assigning ages. The incremental accumulation of animals over millennia, absence of physical stratigraphy, and collection of specimens by non-scientists require direct 14C dating to test the humans’ “association” with extinct, late Pleistocene species.

Literature CitedMacCurdy, George (1917) The Problem of Man’s Antiquity at Vero, Florida. American Anthropologist, 1917: 252-261. Martin, Robert A. and S. David Webb (1974) Late Pleistocene Mammals from the Devil's Den Fauna, Levy County. In Pleistocene Mammals of Florida, edited by S. David Webb, pp. 114-145 University Press of Florida. Sellards, E. H. (1916) Human remains and associated fossils from the Pleistocene of Florida. Annual Report of the Florida Geological Survey 8:123–160.Stewart, T. D. (1946) A reexamination of the fossil human skeletal remains from Melbourne, Florida, with further data the Vero skull. Smithsonian Misc. Collections 106(10):1-28.

TransverseCT Section

Partial Maxilla(Photograph)

High Resolution (70 µm) Total-Specimen CT Scans (Center Quant. Imaging)DEVIL’S DEN

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Amino Acid Analyses of Devil’s Den Human Bones

Methods

© Stafford/Purdy/Krigbaum 2005

Background

• Ms. Donna Ruhl and the Human Osteology Advisory Committee (FLMNH) facilitated loans of specimens for analysis and provided curation data on collections. • Drs. Tim Ryan and Avrami Grader, Center for Quantitative Imaging, Penn State University performed CT scans and analyses on the Devil’s Den specimens.• Dr. Frank Bova, McKnight Institute, University of Florida provided the CT images for the Vero Beach blocks.• Funding of this research was from the Florida Wetlands Project, University of Florida.