Quantifying Archaeology

369 Pages·1988·19.1 MB·English

by  Stephen Shennan (Auth.)

Quantifying
ARCHAEOLOGY
STEPHEN SHENNAN
EDINBURGH
UNIVERSITY PRESS
ACADEMIC PRESS, INC.
Harcourt Brace Jovanovich, Publishers
© Stephen Shennan 1988
Published in Great Britain by
Edinburgh University Press
22 George Square, Edinburgh
Printed in Great Britain by
J. W. Arrowsmith Ltd, Bristol
British Library
Cataloguing in Publication Data
Shennan, Stephen
Quantifying archaeology
1. Mathematical statistics
2. Archaeology—statistical methods
I. Title
519.5Ό2493 QA276
ISBN 0 85224 460 6 cloth
0 85224 473 8 paper
Published in the
United States of America by
Academic Press, Inc.
Harcourt Brace Jovanovich, Publishers
San Diego, California
ISBN 0-12-639860-7
Preface
As chapter one of this book makes clear, quantitative methods
have become increasingly important in archaeology in recent years,
and indeed considerable progress has been made in terms of the
degree of sophistication of the analyses and of the matching be-
tween archaeological data and appropriate mathematical methods.
The specialists in any sub-field of a discipline, particularly when
that sub-field involves mathematics, are always going to be working
at a level which non-specialists cannot match, but it is important for
the general health of the discipline as a whole that its practitioners
should have some awareness of the sub-field and its wider implica-
tions. Archaeology now has a small group of impressively com-
petent mathematical specialists but the bulk of the people practising
the discipline do not even understand what they are talking about,
never mind its implications. This is a dangerous state of affairs
because it leads on the one hand to the outright dismissal of
methods which may be useful, and on the other to an excessive
gullibility with regard to claims backed by mathematical arguments
and analyses. If you can't actually evaluate the arguments, what
choice is there? This situation contrasts with what I believe is a
much more healthy situation in geography, where the body of
mathematical and statistical specialists is at the apex of a broadly
based pyramid of practitioners with basic mathematical and statisti-
cal knowledge.
The difference lies in the educational process in the two discip-
lines. Quantitative methods were quickly integrated into the educa-
tion of geographers as a result of the quantitative geography revolu-
tion of the 1950s and 1960s. Comparable developments in archae-
ology were never incorporated into the education of archaeologists
to anything like the same extent, for reasons which, I suspect, have
more to do with the sociology of the discipline, especially within the
universities, than with anything else. Correspondingly, textbooks
on mathematics and statistics in geography have proliferated, while
vu
viii Preface
it would be true to say that archaeology has had nothing compar-
able.
This book aims to fill that gap. It fits between Mathematics in
Archaeology (Orton 1980) on the one hand, and Mathematics and
Computers in Archaeology ( Doran and Hodson 1975 ) on the other.
Orton's book is a very clear, indeed excellent, account of how
quantitative methods can be of assistance to archaeologists, but in
no sense is it a textbook. Doran and Hudson's book is basically
more advanced than this one. Its brief coverage of elementary
methods, while in many ways a model of elegant conciseness, is too
compressed for people who don't know the material already.
This book arises from a course in quantitative methods of data
analysis which I have given over a number of years in the Depart-
ment of Archaeology, University of Southampton. As time has
gone on the course has changed considerably from the earliest
version, in response to student feedback and developments in the
field. (Statistics itself is a fast changing discipline, a fact which
outsiders tend not to appreciate.) Indeed, some discussion and
explanation is appropriate at this point, concerning what the book
contains and what it doesn't.
First, it is about data analysis in archaeology and is thus oriented
more towards studies of objects, excavations and archaeological
data from surveys than towards more laboratory based studies,
such as soil properties, chemical analyses, etc. ; in general such
studies have their own mathematical and quantitative tradition,
derived from the discipline where the techniques originate.
This orientation has undoubtedly influenced the selection of
material to present here. And indeed my next point concerning the
book's content is precisely that it is not comprehensive, in the sense
of covering all the quantitative techniques which have been used or
could be useful to archaeologists. To do that would have taken a
book far longer than this one. The intention has been to give an
impression of the kinds of things which can be done at different
levels ; how the archaeological topic becomes translated into statis-
tical terms, and the problems associated with this ; and to provide a
technical grounding in some of the most important techniques. In a
textbook such as this it is natural that the latter should take up most
of the space.
The aim of the first part is to show students how to carry out some
of the most basic techniques for themselves ; the aim of the second
part is to give an intuitive understanding of some of the more
complex methods, based on a geometric approach and archaeo-
Preface ix
logical examples, as a basis for understanding the literature. Famili-
arity with the material presented here in the context of archaeologi-
cal examples will make it much easier for those who want to use
other techniques not covered here to understand statistical litera-
ture written for other audiences, such as geographers and socio-
logists.
At the basic statistics level the most obvious omission is the Mest,
and more generally a lack of discussion of distributional theory,
except rather briefly in chapters 8 and 14. This was not done
without considerable thought. In fact, such material was covered
extensively in the early versions of the course from which this book
originates. It was dropped because the amount of complex technical
detail which had to be covered at a fairly early point in the proceed-
ings was proving to be a major obstacle both to understanding the
quantitative methods themselves and to seeing any relevance of
them to archaeology. Not including them proved to be a lot more
satisfactory: the gain far outweighed the loss.
Another obvious omission is spatial analysis. Hodder and Orton
(1976) still provide a good introduction for archaeologists here,
backed up by the many geographical texts. In this light it was felt
that the desirability of including something rather more elementary
than Hodder and Orton on spatial analysis was outweighed by the
significant increase in size of this book which it would have in-
volved.
The introductory intention of the book precludes examination of
the more advanced techniques now being used in archaeological
research, such as those based on computer simulation, but there is
a brief discussion of these in the final chapter. One or two sections
of the book, however, are more advanced than the rest and many
people will want to skip them on the first time through. This is
especially the case with the last section of chapter 7 and, to a lesser
extent, parts of chapter 10 and 11. They are included to show what
detailed data analysis can involve and how it may be done. They are
examples, as are others in this book, of the realisation of a sceptical
approach to data and data patterning. Indeed, if I have one hope
for this book, it is not that readers will retain a memory of the
details of the statistical techniques it covers, but that they will have
acquired an informed, sceptical and questioning attitude to the
quantitative analyses of themselves and others. In this way things
can only improve.
Over the years, in teaching quantitative methods and preparing
this book I have incurred a number of debts which must be acknow-
x Preface
ledged. First, and most important, I have to thank the students who
have taken my courses, especially Todd Whitelaw, Hans-Peter
Wotzka and Nick Winder. Their critical questioning has meant that
I could never get away with anything and I've benefited enormously
as a result ! I'm also grateful to Professor Colin Renfrew for his
early encouragement and support for the teaching of quantitative
methods at Southampton, and to Archie Turnbull of Edinburgh
University Press for encouraging me in the writing of this book and
offering many constructively critical comments on an earlier draft.
Finally, I owe a special debt of gratitude to Dr Nick Fieller, Depart-
ment of Probability and Statistics, University of Sheffield, for his
invaluable assistance in reading the manuscript with an expert eye ;
and to Professor R.Barry Lewis, Department of Anthropology,
University of Illinois at Urbana-Champaign, who made many help-
fully blunt comments and suggestions. Neither they nor anyone else
except myself is responsible for the inadequacies that remain.
One
Introduction
The aim of this text is to make students familiar with some of
the basic quantitative methods currently used in archaeology. Of
course, these techniques are not specific to archaeology, being used
in a great variety of fields, but experience has shown that archae-
ology students do not gain a great deal from attending statistics
classes for sociologists or biologists because, although the statistical
theory and methods are the same, the examples used are alien. To
the student of archaeology such examples are boring and often
incomprehensible. To most people quantitative methods tend to be
sufficiently forbidding to need no handicaps of this kind. Teaching
in such an alien framework is particularly unfortunate because
many non-mathematically inclined people find that they can best
get an initial grasp of a topic not by learning about the theory
behind it, but by following through a worked example. For these
reasons a specifically archaeological introductory text seemed
worthwhile.
It is hoped that by the end of the book students will themselves
be able to use the simple techniques described, will have some feel
for the way archaeological questions can be translated into quanti-
tative terms, and will have a basis for talking to statisticians, in their
own terms, if problems are more complex. This last point is of some
importance. If you turn to a statistician for help and neither of you
knows what the other is talking about, you will probably end up
with the wrong answer to the wrong question.
The text assumes very little in the way of prior knowledge. Only
the most basic mathematical operations of addition, subtraction,
multiplication and division, together with roots, powers and loga-
rithms are needed. Calculus and matrix algebra are not required.
WHY QUANTITATIVE METHODS?
This question must be considered before we go further. In fact, it is
possible to divide it into two rather different questions : why should
1
2 Quantifying Archaeology
students concern themselves with quantitative methods in archae-
ology, and why should archaeology, as such, concern itself with
quantitative methods.
One answer to the first of these questions is that the archaeologi-
cal literature is increasingly given over to papers whose arguments
depend on the application of such methods. A knowledge of them
is therefore essential if their arguments are to be understood and
evaluated. This is certainly true, but it does not answer the second
and larger question. The most cynical view would be that archae-
ology has become involved with quantitative methods purely as a
result of disciplinary fashion. The last thirty years have seen the
biological sciences, geography and many of the social sciences
become increasingly quantitative ; it is now a matter of prestige for
a discipline to appear to be 'scientific', an endeavour in which
quantitative methods have a key role. Archaeology has simply
followed this trend, adopting the 'archaeologists in white coats'
image, and in the process has carried out a successful piece of
disciplinary imperialism, expanding its influence, its manpower and
the resources allocated to it generally. In due course, such an
argument might go, such approaches will become less fashionable,
indeed perhaps are already becoming so, and will gradually fade
from significance. I think it would be foolish to try to deny al-
together this aspect of the 'quantitative revolution' as it has been
called in geography, but such arguments from the sociology of
science are certainly only part of the story.
One key factor has been the rise of the computer. As we are well
aware, computers now have a great variety of roles in archaeology.
In the last decade they have become increasingly widely used as
data management tools for such tasks as the recording of excavation
data and the building up of regional data banks of archaeological
information, the former development in particular greatly en-
hanced by the advent of microcomputers ( Richards and Ryan 1985,
Gaines 1981 ). The use of computers in archaeological model-build-
ing has also become important: computer programs have been
written to simulate processes as diverse as the collapse of Maya
civilisation ( Hosier et al. 1977 ) and tool manufacture and discard in
Australian aboriginal subsistence-settlement systems ( Aldenderfer
1981); numerous examples are to be found in books edited by
Hodder (1978), Renfrew and Cooke (1979) and Sabloff (1981).
Here I want to consider only their use as tools for carrying out
data analysis, which is in fact the purpose for which computers were
first introduced into archaeology, and indeed into many other sub-
Introduction 3
jects. Prior to the development and first application of computers in
the 1950s and early 1960s uses of mathematics and statistics were
largely restricted to the 'hard sciences'. This was at least partly
because the solutions to many problems of interest could be ob-
tained by means of elegant methods of mathematical analysis which
did not require enormous numbers of calculations. Similarly, the
statistical techniques which for the same reason were practically
possible, proved very useful in many scientific, technological and
industrial applications, but less so with the more intractable data of
geography, archaeology or the social sciences. Only with the de-
velopment of a means of carrying out enormous numbers of calcula-
tions at very high speeds did it become possible to apply methods
appropriate to the kind of problems which the data from such
disciplines presented.
It might be said that such an exciting new toy as the computer was
eventually bound to be tried by archaeologists, and that the involve-
ment of archaeology in quantitative methods simply stems from an
attempt by archaeologists who like such toys to find a use for them.
This cannot altogether be excluded.
However, it still does not take us to the heart of the matter, which
lies not in fashion, nor in the availability of computers, but in the
fact that quantitative reasoning is central to archaeology, and that a
better grasp of this fact might well improve our work as archae-
ologists. Clive Orton's book Mathematics in Archaeology (1980)
provides an excellent demonstration of why this is the case, by
taking some of the standard questions which archaeologists ask,
such as 'What is it?', 'How old is it?', 'Where does it come from?'
and 'What was it for?', and showing how a quantitative approach
can help to provide the answers. It follows, therefore, that quantita-
tive methods should be seen, not as a distinct scientific specialism
within archaeology, like pollen analysis, for example, or the various
techniques of artefact characterisation, but as part of every archae-
ologist's mental tool-kit. Statistical, mathematical and computer
specialists may often be required to cope with particular problems,
but archaeologists must have sufficient quantitative awareness to
recognise when problems arise which can be helpfully tackled in a
quantitative fashion. No one else can do this for them.
Given that this is the case, it remains to be specified exactly
where the mathematics and the archaeology come together. Part of
the answer is in the simple description of the archaeological record :
numbers of potsherds of different types, sizes of pits, and so on.
Such quantitative information is an essential part of all modern
4 Quantifying Archaeology
archaeological reports, and simple quantitative description is the
first topic we will consider.
Much more important than this, however, is the link described by
Orton (1980). The archaeologist makes his inferences about the
past on the basis of patterning and relationships in the archaeologi-
cal record. Mathematics is an abstract system of relationships. The
possibility then exists that mathematics may help us to recognise
patterning in the archaeological record and to specify its nature.
The area where mathematics meets the messier parts of the real
world is usually statistics. It is precisely this fact that makes statistics
in many ways a tricky subject, because mathematical and factual
considerations are both involved, and because the relationships
which we look at are almost never perfect ones.
Orton shows very clearly that all interpretation of the archaeo-
logical record is concerned with identifying patterning and is cap-
able of benefiting from a quantitative approach. It is nevertheless a
historical fact that the main impetus for the introduction of quanti-
tative methods of archaeological data analysis came from the North
American 'New Archaeology' tradition of the 1960s, and as a result
of this 'New Archaeology' and the use of quantitative methods
became inextricably associated in the general archaeological con-
sciousness, both being labelled as 'anti-humanistic' (Hawkes 1968).
Doran and Hodson (1975) were at pains to point out, correctly,
that^there was no necessary connection between the two, and that
quantitative approaches could be used to tackle traditional archaeo-
logical problems. However, it is still the 'New Archaeology' tradi-
tion, now known, twenty-five years on, as the 'processual' school,
that has made the greatest use of such techniques and it is worth
asking why quantitative analysis has been, and remains, one of its
distinguishing features, despite the fact that some applications of
such methods have since been shown to be classic examples of
misuse and misinterpretation (Thomas 1978).
I believe there are several reasons for this. First, least praise-
worthy and probably least important: quantitative methods are
regarded as 'scientific' and the New Archaeology specifically set out
to adopt a scientific approach to the subject, making the use of
quantitative methods ideologically necessary. Second, New Archae-
ology emphasised explicitness and objectivity, both of which are
considerably aided by the rigour of quantitative analysis, which has
a vital role to play in removing at least some potential sources
of self-deception. Third, it advocated a hypothetico-deductive
approach to the study of the past, in which hypotheses are gener-