Concise description of the PhD project

The project includes extensive measurements on postcranial elements of Ursus spelaeus, U.

deningeri and U. etruscus of different sites, primarily of collections in Germany, but also of

other European countries. For the time being measurements have been chosen mainly for long

bones and metapodial bones of adult individuals (16 different objects) on the basis of

DUERST (1926) and VON DEN DRIESCH (1976). Matrices of data-sets were developed for

each object, in which the data of definitely identified remains was entered. The amount of

measurements per object vary between 8 and 24 variables each, 244 endpoints altogether,

with a maximum of 40 repetitions per object and site. The data is statistically analysed with

the computer-programs SAS, SPSS and Excel. During the current main statistical analysis the

number of endpoints (amount of measurements) is to be minimized, if possible, so in future

less time will be needed for measuring.

Although it is not the main matter of concern in this project, data of recent European brown

bears and polar bears has also been raised. Even though it is not yet enough for decent

statistical analysis and interpretation, this data has been included in the following example.

All data will be expanded in future.

The purpose of this briefly described project is to help interpreting the relationship between

the fossil ursids mentioned above. The intention is to show the variability of the examined

species and the differences between them, based on selected postcranial material. Especially

the distinction between Ursus spelaeus and U. deningeri by further definite distinctive marks

on postcranial elements, and to grasp these marks statistically, is the aim of this project.

Statistical Analysis

First, endpoints have to be found, which show approximate homogeneous measurements

within each group of species. Afterwards, from these endpoints the ones have to be selected,

which allow a best classification between the species. To select the correct statistical test for

this kind of data, first of all it is necessary to find out whether the data is approximately

gaussian distributed or not. For this purpose a list was calculated with summary statistics like

minimum, maximum, mean, median and standard deviation with help of a SAS (Statistical

Analysis System) procedure. In addition, for each endpoint data boxplots were raised,

measurements split by species. These descriptive statistical methods showed in the pre-

examination that some of the data is approximately gaussian distributed, others is not. This

result allows the usage of Kruskal-Wallis-Test and other suitable multiple tests for these

independent sample surveys. To look for significant differences between the investigated

groups (sites split by species), for each of the 244 endpoints (measurements) the Kruskal-

Wallis-Test was used for each of the data-sets. All these tests in the pre-examination showed

that within the group of Ursus spelaeus proportions stay more or less equal, despite their high

variability in size. These calculations were the preparation for the main examination, where

the aim is to show that the data-sets within one group (e.g. Ursus spelaeus or Ursus

deningeri) are homogeneous and in some of the measurements or proportions significantly

different between the investigated groups. Concluding, it appeared to be necessary to choose

statistical procedures in the main examination, which are able to handle small sample sizes.

The next step, based on the above described, was taken in the main examination by Pivottables

and diagrams, which give a first impression of the data. One example for statistical

approach is presented in the following (fig. 1 - fig. 4), where two correlated measurements are

applied to each other.

In the figures 3 and 4 the proximal breadth (Bp) of tibiae is on the one hand applied to the

breadth of the medial part of its joint (BJpm) and on the other hand to the lateral part of its

joint (BJpl). (See abbreviations on the last page.) These figures show that the clustering data

of Ursus deningeri is around the sparse data of Ursus arctos, the data of Ursus spelaeus lies

slightly ahead of that. This implies that in these endpoints there might be a distinctive mark

between the main fossil groups, which needs to be proved by additional statistical tests. Also,

it will be necessary to raise more data, in order to avoid problems with small sample sizes.

For the time being finding further differences between Ursus deningeri and U. spelaeus,

which become statistically apparent, like the one described in figure 3 and 4, is the main

emphasis during the current analysis. Especially differences in proportions of the two main

groups are looked for, which are probably most meaningful. On the one hand this is contrived

by capturing usual indices, on the other hand with extensive multivariate analysis. Indices as

well as variable-sets, which prove to be especially characteristic in the analysis of

discriminance, shall be used for identification of the species. Figure 5 and 6 show two

examples for the analysis of discriminance.

Sticking to the example of measurements on the proximal joint of tibiae, Wilcoxons nonparametrical

test (npar1way procedure) is looking for pair-differences in the case of

dependent samples and can be used for associated random samples (see tab. 1, fig. 7).

Table 1 shows that out of 153 objects, which is the whole data-set of tibiae so far, only 60 are

associated samples in the variables BJpm and BJpl. Of these 60 associated samples in 44

cases BJpm is smaller than BJpl. In the remaining 16 cases measurements of BJpm are larger

than BJpl. In none of the 60 cases both measurements have the same size. Figure 7, diagrams

1 and 2 show this effect graphically.

In diagrams 1 and 2 in almost all cases BJpl is much larger than BJpm in Ursus arctos, U.

deningeri and U. maritimus, in contrast to data of Ursus spelaeus. On closer examination it is

ascertainable that the rarer relationship ‘BJpm larger than BJpl’ is unequally distributed

among this species of different sites. Of 37 associated samples of U. spelaeus there are 14

samples with the relationship ‘BJpm larger than BJpl’, which means the biggest share out of

the above mentioned 16. The question is which group is especially affected. On even closer

examination, this remarkable relationship cannot be assigned to a particular gender, although

there is a hint that it might have to do with the body size. Up to 10 out of the 16 tibiae with

this relationship probably used to belong to male individuals, judged by the greatest length of

the bone, the shaping of muscle impression and the robustness of the bones. This needs to be

tested again in a later examination with even larger data-sets.

Outlook

This article was compiled at the beginning of the main statistical analysis. By the time of the

International Symposium there will be more information presented.

For the final examination the basis of all data-sets will be extended and the choice of variables

used in the statistical analysis will be improved. Especially further data-sets of Ursus

etruscus, but also of U. deningeri, are needed most for the final solid statistical analysis.

 

Abbreviations

Bp = proximal breadth

Dp = proximal depth

BJp = breadth of complete proximal joint

BJpm = breadth of proximal joint, medial part

BJpl = breadth of proximal joint, lateral part

Spec = species

U = Ursus n. sp.

Ua = U. arctos

Ud = U. deningeri

Um = U. maritimus

Us = U. spelaeus

 

References

DUERST, J.U. (1926): Vergleichende Untersuchungsmethoden am Skelett bei Säugern. - In:

ABDERHALDEN: Handbuch der biol. Arbeitsmethoden, Abt. 7: Methoden der

vergleichenden morphologischen Forschung, Heft 2: 125-530, Berlin, Wien.

VON DEN DRIESCH, A. (1976): A guide to the measurement of animal bones from

archaeological sites. - Peabody Museum Bulletin 1: 1-137 (Peabody Museum of

Archaeology and Ethnology Harvard University).

Dipl. Geol. Kerstin Athen

Marschnerstr. 45

D – 30167 Hannover

Tel.: 0049/ 511/ 1690 -620

KAthen@t-online.de

 

8th International Cave Bear Symposium, Kirchheim/Teck, 21.09.2002

© KAthen

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