<< . .

. 23
( : 35)



. . >>

ally of a single taxon at a time (Lyman 1994c). Paleozoologists with taphonomic inter-
ests have an advantage over other scientists who study the past such as paleobotanists;
the former have a model of what a complete animal carcass consisted of skeletally. If
it was a mammal, then it had one skull, left and right mandibles, (most likely) thir-
teen left and thirteen right ribs, thirteen thoracic vertebrae, left and right humeri,
and so on. A paleobotanist has no such model of, say, an apple tree; the questions
How many leaves? How many apples? How many seeds? cannot be answered with any
con¬dence for want of a model of a standard apple tree with N1 leaves, N2 apples, and
N3 seeds. The model of a complete animal is where a paleozoological taphonomist
starts. Measuring how a collection of bones and teeth of a taxon differ from a col-
lection of complete skeletons of that taxon is the ¬rst step toward answering the
ultimate taphonomic question: How and why are these bones and teeth here and in
the condition that they are whereas other bones and teeth are missing or in different
condition (Lyman 1994c)?
Increasing demand to answer more taphonomically detailed questions in order to
build strongly warranted explanations of the paleozoological record in the 1960s and
1970s brought about a growth in the number of quantitative units used to measure
aspects of the record (Lyman 1994a). Perhaps not surprisingly, then, the ¬rst explicit
use of MNE is found in a seminal, explicitly taphonomic study. Voorhies (1969)
sought to understand the taphonomy of an early Pliocene paleontological site in
skeletal completeness, skeletal parts, and fragmentation 217


the state of Nebraska. He did not use the term MNE but listed what he termed the
number of individual skeletal elements represented for twenty-six different skeletal
elements of an extinct form of antelope the remains of which made up the bulk of
the collection he studied. Voorhies (1969:1718) described the quantitative unit as the
minimum number of elements (bones) represented by all identi¬able fragments of
the element in the collection, and distinguished it from the [minimum] number of
individual animals represented by nonserial paired [skeletal] elements.
Voorhies designed the MNE quantitative unit because he was concerned with why
some skeletal parts were very frequent in the collection whereas others were of mid-
level abundance and still others were rare. Observed MNE frequencies of skeletal
parts diverged from the model of a set of complete skeletons, and Voorhies wanted
to know why that divergence existed. He began by trying to determine if a pattern
in skeletal-part frequencies existed, and to do that required that he use an MNE-
type quantitative unit. He sought an answer to a question concerning taphonomy,
in particular a question concerning skeletal-part abundances. He found that skeletal
elements that were of light weight relative to their volume tended to be winnowed
out of a deposit by ¬‚owing water whereas bones that were heavy relative to their
volume lagged behind (were not removed by ¬‚owing water). His research resulted in
the designation of what came to be known as Voorhiess Groups distinctive groups
of particular skeletal elements that are variously winnowed, moved, or left behind
by the action of ¬‚owing water (e.g., Behrensmeyer 1975; Lyman 1994c; Wolff 1973).
About a decade after Voorhies (1969) used the MNE quantitative unit, zooar-
chaeologists seem to have independently invented the same unit. The question they
asked was ultimately the same one asked by Voorhies: Why were some skeletal parts
abundant and other parts rare in a collection? Binford (1978, 1981, 1984; Binford
and Bertram 1977) was interested in how hominids differentially dismembered and
transported portions of prey carcasses, and wanted to identify the effects of natural
attrition such as carnivore gnawing on frequencies of skeletal parts. Thus, Binford,
like Voorhies, started with the model of a complete carcass or skeleton (or multiple
complete carcasses or skeletons), and sought to explain why collections of prehis-
toric bones had, say, more thoracic vertebra than ribs, or more distal humeri than
proximal humeri. Binford initially de¬ned the quantitative unit he designed as the
minimum number of individual animals represented by each anatomical part and
referred to them as MNI values (Binford and Bertram 1977:79). Binford (1984:50)
made it clear that his MNI values were not the same as the traditional MNI values of
Stock (1929), White (1953a), and Chaplin (1971 ), when he stated that I have decided
to reduce the ambiguity of language by no longer referring to anatomical frequency
counts as MNIs.
quantitative paleozoology
218


Bunn (1982) is the ¬rst paleozoologist I know of to use the term MNE. Bunn
(1982:35) de¬ned the unit as the minimum number of elements, but he did not de¬ne
element. He, like Binford (1978, 1981 ; Binford and Bertram 1977) before him, used
MNE to signify not only anatomically complete skeletal elements (e.g., femora),
but anatomically incomplete skeletal parts (e.g., the distal half of humeri) and also
portions of a skeleton made up of multiple discrete skeletal elements (e.g., thoracic
portion of vertebral column). This makes MNE even more of a derived unit than
traditional MNI values. Both MNE and MNI might be determined with or without
consideration of age, sex, and size differences among specimens (is a particular frag-
ment of a proximal left humerus from a small female, 2-year-old deer, distinguished
from another fragment of a proximal left humerus from a large male, 5-year-old deer
that does not anatomically overlap the ¬rst?). But whereas an individual animal is a
natural, inherently bounded unit (its boundaries are its skin), a femur is a skeletal
element that is naturally bounded (it is discrete), but a distal femur is not naturally
bounded and a thoracic section of the vertebral column is not necessarily discrete.
These sorts of considerations in¬‚uence MNE values, and there are even more fun-
damental issues to contend with when it comes to deciding if femora outnumber
humeri and the like. There are other as yet unmentioned phases to the history of
MNE, but discussion of them is better served if they come up later. The next issue
that must be dealt with is how MNE values are determined.



D E TE R M I N A T I O N O F M N E V A L U E S


Despite a relatively simple de¬nition of MNE as the minimum number of skeletal
elements necessary to account for the specimens under study, this quantitative unit
has seen more discussion and debate over how it is to be determined during the past
20 years or so than any one might have imagined. This is because MNE and two
quantitative units based on it (not including MNI) became extremely important to
answering taphonomic questions about skeletal-part abundances beginning in the
1970s (e.g., Andrews 1990; Binford 1981, 1984; Dodson and Wexlar 1979; Hoffman
1988; Klein 1989; Korth 1979; Kusmer 1990; Lyman 1984, 1985, 1994b, 1994c; Marean
and Spencer 1991 ; Shipman and Walker 1980; Turner 1989).
Many researchers suggested ways to determine MNE. For example, Klein and
Cruz-Uribe (1984:108) proposed that each specimen be recorded as a fraction using
common and intuitively obvious fractions (e.g., 0.25, 0.33, 0.5, 0.67) and not attempt-
ing great precision. The fractions were used to record how much of a category of
skeletal part (typically a proximal or distal half of a long bone) each specimen rep-
skeletal completeness, skeletal parts, and fragmentation 219


Table 6.1. MNE values for six major limb bones
of ungulates from the FLK Zinjanthropus site

Bunn (1986); Bunn
Skeletal element and Kroll (1988) Potts (1988)
Humerus 20 19
Radius 22 18
Metacarpal 16 14
Femur 22 8
Tibia 31 12
Metatarsal 16 16



resented; all recorded fractions were summed to estimate the MNE for a category of
skeletal part. Thus, if the category is proximal half of the femur, the analyst records
a specimen representing the proximal half of a femur as 1.0, a specimen representing
one half of a proximal femur is recorded as 0.5, and a specimen representing one
third of a proximal femur as 0.33. Adding those fractions produces an MNE of 1.83,
or an MNE of two proximal femora halves. This procedure does not, however, take
account of anatomical overlap. For example, what if the three specimens of proximal
femur all include the greater trochanter? If they do, the MNE is not two, but three.
Marean and Spencer (1991:649650) suggested measuring the percent of the com-
plete circumference represented by long-bone diaphysis specimens. Summing the
percentages recorded for each portion of the diaphysis measured say, proximal dia-
physis, middiaphysis, and distal diaphysis would provide an estimate of the MNE
of particular shaft portions. Again, the weakness is that anatomically overlapping
skeletal parts are ignored, potentially resulting in under estimates of MNE. Bunn
and Kroll (1986, 1988) described three ways to derive MNE values from a collection
of mammalian long bones. The analyst may determine (1) the minimum number
of anatomically complete limb skeletal elements necessary to account for only the
specimens with one or both articular ends, (2) the minimum number of complete
limb skeletal elements necessary to account for only the specimens of limb diaphyses
(without an articular end), and (3) the minimum number of complete limb skele-
tal elements necessary to account for both the specimens with one or both articular
ends and the diaphysis specimens lacking articular ends. These are labeled MNEends,
MNE shafts, and MNEcomp, respectively.
Underscoring that the quantitative unit is derived, if the method of determining
MNE varies, different MNE tallies are produced. Table 6.1 presents MNE values
for the six major limb bones of ungulates represented in the Plio-Pleistocene FLK
quantitative paleozoology
220


Zinjanthropus collection. MNE values were calculated by two researchers who used
different methods. Bunn (1991 ) used all specimens diaphysis fragments as well as
epiphyses whereas Potts (1988) focused mostly on articular ends. Given what we
have seen in preceding chapters and the consistently strong relationship between
NISP and MNI, and between sample size (however measured) and a variable of
interest, it should come as no surprise that if Bunn included more long-bone dia-
physis specimens in his derivation than did Potts, then Bunns MNE values would be
greater than Pottss.
MNE is de¬ned in precisely the same way that MNI is de¬ned but at the scale of
a partial skeleton (what I have been referring to as a skeletal part or portion) rather
than at the scale of a complete skeleton (Lyman 1994b). To reiterate using different
wording, MNE is de¬ned as the minimum number of skeletal elements necessary
to account for an assemblage of specimens of a particular skeletal element or part
(discrete item) or portion (multiple discrete items, such as all thoracic vertebrae in a
vertebral column) (Lyman 1994b:289). The de¬nition is operationalized by examining
specimens of each kind of skeletal element or part, say, left femora or distal right
humeri, for anatomical overlap (e.g., Bunn 1986; Morlan 1994). If three specimens
of left femora comprise the collection (assuming all are of the same taxon), then the
possible MNE represented by those specimens ranges from 1 to 3. If two specimens
represent the complete distal end and one represents the proximal end, then the
MNE of left femora is two. Just as when two left scapula and one right scapula are
said to represent a minimum of two individuals (MNI = 2), anatomically overlapping
skeletal specimens must represent unique individuals, whether these are individual
organisms or individual skeletal elements.
The techniques used to determine MNE have, in the past 15 years, become hotly
contested issues in paleozoology. Bunn (1991 ) and Potts (1988) used different methods
to determine MNE values; the difference was whether or not diaphysis fragments
were included in the tallies or only articular ends of long bones. That difference
alone spawned a huge debate, in the literature, on whether a tally of skeletal-part
frequencies was valid if diaphysis fragments were not included (e.g., Bartram and
Marean 1999; Marean and Frey 1997; Pickering et al. 2003; Stiner 2002). A recent effort
to bring all concerned parties together did not resolve the debate, though concessions
were made (e.g., Cleghorn and Marean 2004; Marean et al. 2004; Stiner 2004). The
debate originated in part with assumptions by some commentators regarding how
other researchers were thought to count skeletal-part frequencies. In particular, those
who advocate tallying diaphysis fragments have assumed that many have not counted
diaphysis fragments but instead tallied only taxonomically diagnostic articular ends
of long bones. This assumption is suspect given that ribs and many vertebrae are not
taxonomically diagnostic, yet these specimens were tallied by those who allegedly did
skeletal completeness, skeletal parts, and fragmentation 221


not tally nontaxonomically diagnostic long-bone diaphysis fragments. Whatever the
case, the important point is this: We must be explicit about how we count, whether
we count NISP, MNE, MNI, or any other measure. Many paleozoologists still do
not distinguish skeletal specimens, elements, parts, fragments, and the like, despite
numerous suggestions over the past several decades that they be distinguished via
explicit de¬nitions (e.g., Casteel and Grayson 1977; Grayson 1984; Lyman 1994a,
1994b).
Assuming that all specimens in a collection, whether of articular ends or diaphysis
fragments, are included in MNE (and NISP) tallies, we are left with the question of
how to tally those specimens in order to derive an MNE value. The practical aspects of
operationalizing the de¬nition of MNE as based on anatomically overlapping speci-
mens became technologically more sophisticated when Marean et al. (2001 ) applied
GIS image software to the problem. They had found verbal descriptions and individ-
ual drawings of specimens that were anatomically incomplete skeletal elements to
be cumbersome to manipulate when determining MNE values. For them, computer
software provided a solution. Each specimen is outlined on a template of the skele-
tal element it represents; the template has previously been loaded into the software
program. The software allows the analyst to digitally overlay outlines of multiple
specimens. The maximum number of overlaps detected by the software indicates
the MNE. The key step to the process, whether using hard-copy drafting paper or
computer software, is drawing the specimens accurately. Marean et al. (2001 ) do not
address this most critical step. Efforts by a student in my zooarchaeology class to
replicate drawings of the same set of fragments of known (experimental) deriva-
tion found that the general shape of the fragment could be reproduced fairly con-
sistently, but its size and location varied from iteration to iteration. Thus, some
fragments that did not overlap in reality were sometimes drawn in such a way as
to overlap in the database, and other fragments that did overlap in reality were
sometimes drawn so as to not overlap. Errors increased in frequency and magnitude
(degree of overlap, or lack thereof) as specimens displayed fewer and fewer anatom-
ical landmarks. Tallies of MNE produced using the software varied from the actual
number of elements by anywhere from 0 to more than 50 percent greater than the
actual number across several trials.
The errors described in the preceding paragraph may be the result of inexperience,
but the student who performed them earns her living applying GIS to archaeological
problems, so degree of experience does not seem to be a signi¬cant factor. Additional
trials by others using specimens of known derivation (e.g., experimentally generated
from anatomically complete skeletal elements) might prove revealing, but I hazard
the guess that the smaller the fragments one tries to draw the more errors in tallying
MNE will result. Whether this is found to be true may be academic. This is so
quantitative paleozoology
222


because MNE is typically strongly correlated with NISP (Grayson and Frey 2004). This
should not be surprising at all given that we know NISP and MNI are often strongly
correlated, and we know that MNI is based on MNE. The relationship between
MNE and NISP is examined in a subsequent section on fragmentation. Several other
issues need to be dealt with ¬rst.



MNE Is Ordinal Scale at Best

Given the de¬nition of MNE as the number of skeletal parts or portions necessary to
account for the specimens under study, it should be clear that MNE is but MNI at a
less skeletally inclusive scale. Both are derived measures. Quite simply (and sadly) this
means that all of the problems that attend MNI must also attend MNE. Furthermore,
at best MNE can be only ordinal scale. To ensure these problems are appreciated,
lets quickly review the major bene¬t and the major problem with MNI, but in terms
of MNE.
MNI was designed to control for specimen interdependence when measuring tax-
onomic abundances. Thus, if two or more specimens came from the same individual,
NISP would tally that individual twice but MNI would tally that individual only once.
The same bene¬t attends MNE at the level of skeletal part or portion. Determination
of MNE ensures that each skeletal part (or portion) that contributed to a collection
will not be tallied, say, twice if represented by two specimens. This takes care of the
treacherous problem of differential fragmentation that causes some paleozoologists
to use MNI rather than NISP when measuring taxonomic abundances, and it takes
care of the same problem at the level of skeletal part or portion when tallying abun-
dances of ribs, cervical vertebrae, and tibiae. If humeri are broken into three pieces
(on average) but femora are broken into six pieces (on average), the NISP of humeri
will be half the value of the NISP of femora simply because of differential fragmen-
tation and the attendant specimen interdependence. MNE values circumvent these
problems. Varying degrees of interdependence of specimens representing a skeletal
part or portion such as proximal (half of the) humerus, left half of the rib cage,
or thoracic section of the vertebral column could in¬‚uence relative NISP values of
skeletal parts and portions. MNE might seem, therefore, to be a better unit than NISP
for quantifying the abundances of skeletal parts and portions because it controls for
specimen interdependence.
But, alas, MNE, like MNI, is subject to two serious problems. First, MNE is just that
it is a minimum. Therefore, one cannot statistically compare two minimum values
that might differentially range to some maximum value. Second, MNE is in¬‚uenced
skeletal completeness, skeletal parts, and fragmentation 223


Table 6.2. Fictional data showing how the distribution of specimens of two
skeletal elements across different aggregates can in¬‚uence MNE. Assuming
no anatomical overlap of specimens, if stratigraphic boundaries are
ignored, seven right and six left humeri, and fourteen right and nine left
femora are tallied. If stratigraphic boundaries are used to de¬ne
aggregates, nine right and eight left humeri, and fourteen right and ten left
femora are tallied. R, right, L, left; P, proximal, D, distal

Humerus Femur
Stratum 1 6 R P; 2 L P; 3 R D; 3 L D 4 R P; 1 L P; 4 L D
Stratum 2 1 R P; 4 L P; 1 R D; 1 L D 4 R P; 1 L P; 3 R D; 1 L D
Stratum 3 2 R D; 1 L D 6 R P; 5 L P; 4 R D; 4 L D




by sample size, aggregation, and de¬nition (are sex, age, size taken into account).
Different aggregates of specimens will often produce different MNE values, especially
as sample sizes grow larger. If a collection is treated as one aggregate, the MNE of
tibiae may be ¬ve, but if that collection is divided into three aggregates the MNE
of tibia will likely increase because the parts that are redundant may be proximal
ends in one aggregate, diaphyses in another, and distal ends in the third aggregate.
Consider the data in Table 6.2, which is based on Table 2.13 where the in¬‚uence
of aggregation on MNI is illustrated. To produce Table 6.2 from Table 2.13, Taxon
1 in the latter was converted to humerus and Taxon 2 to femur, and humerus in
Table 2.13 was converted to proximal in Table 6.2 and femur to distal. Assuming that
there is no anatomical overlap of the skeletal parts in Table 6.2, the ¬ctional data
there show that exactly the same sorts of in¬‚uence of aggregation can occur at the
scale of skeletal element, part, or portion (MNE), as occur at the scale of individual
animal (MNI). If stratigraphically de¬ned aggregates are ignored and specimens are
treated as one aggregate, there are seven right and six left humeri ( = 13 humeri) and
there are fourteen right and nine left femora ( = 23 femora) listed in Table 6.2.
If the remains in each stratum in Table 6.2 are treated as comprising distinct
aggregates, then the total number of humeri increases to nine right and eight left ( = 17
humeri) and the total number of femora increases to fourteen right and ten left ( = 24
femora). Note that if the remains are treated as one aggregate, the ratio of humeri to
femora is 13:23 (or 0.565), but if the remains are treated as three separate aggregates,
the ratio of total humeri to total femora is 17:24 (or 0.708). Just as with altering the
aggregates of most common (redundant) skeletal specimens alters the resulting MNI,
quantitative paleozoology
224


Table 6.3. NISP and MNE per skeletal part of deer and wapiti at the Meier site

Skeletal part Deer NISP Deer MNE Wapiti NISP Wapiti MNE
Mandible 192 58 28 9
Atlas 44 22 3 2
Axis 19 17 5 5
Cervical 77 22 20 12
Thoracic 75 53 27 20
Lumbar 104 32 35 18
Rib 221 110 61 35
Innominate 130 43 34 15
Scapula 73 45 12 6
Humerus 150 58 26 11
Radius 164 60 40 15
Ulna 102 60 17 10
Metacarpal 133 87 34 10
Femur 86 29 34 13
Patella 13 11 2 2
Tibia 190 88 30 11
Astragalus 127 118 18 18
Calcaneum 159 121 18 16
Naviculo-cuboid 86 75 9 9
Metatarsal 143 89 48 12
First phalanx 224 148 86 58
Second phalanx 158 109 68 47
Third phalanx 75 75 25 25




changing the aggregates of most common (redundant) skeletal specimens alters the
resulting MNE.
Sample size rendered as NISP also in¬‚uences MNE values, as recently shown by
Grayson and Frey (2004). Consider the deer (Odocoileus sp.) and wapiti (Cervus
elaphus) data from the Meier site (Table 6.3). For deer, the NISP and MNE data
are strongly correlated (Figure 6.1 , r = 0.883, p < 0.0001 ), and the same holds for
the wapiti data (Figure 6.2, r = 0.837, p < 0.0001 ). Grayson and Frey (2004) present
numerous other examples in which the NISP per skeletal part and the MNE of skeletal
parts are correlated. Their results and those for the Meier site deer and wapiti indicate
that MNE values are often strongly in¬‚uenced by sample size measured as NISP. The
larger the NISP value per skeletal part or portion, the larger the MNE value for that
part or portion. MNE is also in¬‚uenced by how it is de¬ned in the sense of whether
figure 6.1. Relationship of NISP and MNE values for deer remains from the Meier site.
Best-¬t regression line (Y = 0.126X0.807 ; r = 0.837) is signi¬cant (p = 0.0001). Data from Table
6.3.




figure 6.2. Relationship of NISP and MNE values for wapiti remains from the Meier
site. Best-¬t regression line (Y = 0.063X0.692 ; r = 0.883) is signi¬cant (p = 0.0001). Data from
Table 6.3.

225
quantitative paleozoology
226




figure 6.3. Frequency distributions of NISP and MNE abundances per skeletal part for
deer remains from the Meier site. Data from Table 6.3.


or not size, ontogeny, and the like are taken into account when seeking to determine
if two or more nonanatomically overlapping specimens come from the same original
skeletal element.
Finally, MNE is at best ordinal scale. This can be shown using the same tech-
nique that was used to show that MNI is often at best ordinal scale (Chapter 2).
The NISP and MNE data from Table 6.3 for the Meier site deer and wapiti are
graphed in Figures 6.3 and 6.4, respectively. Note that the distributions of frequen-
cies are different than those across taxonomic abundances illustrated in Figures
2.132.16. This is likely because in any given skeleton, there is a standard frequency
of skeletal elements such that the frequency distribution is right skewed (like that
observed for taxonomic abundances) but the mode is not to the farthest left but
instead is slightly to the right (unlike that observed for taxonomic abundances)
skeletal completeness, skeletal parts, and fragmentation 227




figure 6.4. Frequency distributions of NISP and MNE abundances per skeletal part for
wapiti remains from the Meier site. Data from Table 6.3.


(Table 6.4, Figure 6.5). Given that most paleozoological samples derive from > 1
individuals the taphonomic starting point (prior to variation in accumulation,
preservation, and recovery) of a paleozoological collection it is unlikely that a more

<< . .

. 23
( : 35)



. . >>