Using the most fundamental reduction model it could
be expected that cores exhibiting high rotations [Rn]
should be on average smaller than those with fewer
rotations. Analysis has already shown this not to be the
case, with the R2 quartzite cores retaining a
(see table 4.13). A comparison of all rotated cores (Rl/2) with the unrotated (R o ) also shows there to be no significant difference in the mass of both populations which is again not consistent with the model (MW-U z=.6 p = .25 ) .
While the statistical evidence shows the mass distributions of rotated and unrotated cores to be generally comparable as discarded cores, this does not provide any insight into the original populations from which the samples derived. It appears that the rotated and unrotated cores can not derive from a single population and retain comparable reduction trajectories. Either the blank populations are different or the trajectories are dissimilar, possibly a combination of both .
It is argued that this anomaly as well as the meaning of the Mode I material can be seen as reflecting the presence of persistent yet substantially different behavioural m odes,related principally to variation in the disposition to reduce cores. This variable disposition may be manifest not only in the degree of reduction but also in the reduction trajectory and choice of material. It is argued that Ro cores represent a low disposition to reduce the core, which will be evident in relatively low concern for the control of core geometry and little concern with utilizing cores beyond the initial onset of platform overstabilization. This is consistent with the Ro sample, which despite retaining a high percentage of
overstabilized platforms, also retain potentially reducible shapes.
The disposition to extended core reduction is
manifest in core rotation where core overstability occurs
as successive overstabi1ized platforms are abandoned and
new ones initiated. Figure 4.11 illustrates the various
behavioural correlates which can be associated with the
dispositions as they have been described. First, there is
the conventional reduction model which derives all cores
from a single population with a single reduction
trajectory. As already noted this results in a
hierarchical set of expected mass relationships (ie.,
Ro>Rl>R2) which the data do not support. The second
shows the expected relationship between the cores given the operation of two distinct reduction trajectories and the third the relation expected from the presence of two
separate blank populations. Axiomatically, two and three
produce a separation in the unrotated and rotated cores,
the size of which is dependent on the difference between
the trajectories and the original blank population.
Again, this does not clearly fit these data which exhibit
no clear distributional separation - the Ro cores occupy a central position between R2 and R1.
The fourth model which varies both population size
and trajectory produces a picture which more closely fits
the actual distribution except for the reversed
relationship between the R1 and R2 cores. The reversal in
the real distributions suggests that the disposition to greater core reduction modifies the expected relationship
by reducing larger cores more than smaller examples. The strength of the disposition could, therefore, be modified by the size of the core itself. To incorporate this into these models requires a more behaviourally realistic set of assumptions.
The fundamental weakness of these basic models lies in their assumption of a single point population and single trajectory slopes, ie., the limitation of using means and the assumption of normal distributions. While it is not certain how realistic it would be to model the original blank population as normally distributed it is less realistic to envisage trajectories as essentially normal. This can be illustrated by reference to figure 4.12 which shows what might be expected to represent the actual reduction trajectories of a given core in terms of mass and platform angle. The A slope shows the expected trajectory of a core with poor trajectory control, the B that of a core exhibiting increased control. The degree of control is defined by the mean slope of the trajectory and the dispersion about the slope; poor control resulting in low slope and high variability and good control in high slope and low variability. In both, the threshold conditions would tend to flatten the trajectories as they approached and became less variable. The variability in trajectories which may change slope through the process ensures that there can be no certainty as to the exact point at which a core will strike the threshold, although in principle a range of points could be determined. These outcomes can be assigned probabilities and the
m a s s F i g u r e 4 . 1 2 : R e d u c t i o n t r a j e c t o r i e s - (A) p o o r l y c o n t r o l l e d t r a j e c t o r y ; (B) w e l l c o n t r o l l e d t r a j e c t o r y . co CO CC E p I--- I I Pa I I I j F i g u r e 4. 1 3 : H y p o t h e t i c a l p r o b a b i l i t y p r o f i l e f o r r e d u c t i o n t r a g e c t o r y o u t c o m e s .
distribution of both these sources of variability forms a probability profile (shown in figure 4.13).
As the profiles exemplify the varying degree of knapping control they may be normally distributed as a result random error about a trajectory or skewed in direct
relation to the reduction disposition. On normallyy
distributed blank populations the effect of a highly skewed reduction profile is to pull the mean of the
discard population in the direction of the skew, and the
discard distribution also becomes more platykertic and
extended. In populations which are already skewed towards
smaller blanks the effect is similar while in populations skewed in favour of heavier blanks the discard population approaches a normal distribution.
The model argues that under average reduction
conditions cores approaching platform threshold
conditions will show higher mass variability than the
original population. This variability also increases as
the degree of reduction increases. The probability of
cores retaining high mass as a result of poor reduction
trajectories is dependent on the strength of the
disposition to reduce them beyond the initial threshold
conditions (ie., to rotate the core [Ro>Rl]).
A second problem with the conventional models of reduction shown in figure 4.11-1 is its assumption that the disposition to reduce cores is independent of core
size. A more realistic suggestion is that under
where there is a range of material on-hand, the knapper will attempt to maximize the extent of reduction episodes
by progressively selecting for larger cores to work. This
may be observable in the closeness of the Ro and R1
quartzite core means which results, it is suggested, from
the heavier of the Ro cores being selected for further reduction, producing the comparable size ranges in both
groups. Where the disposition is increased only the
heaviest of the R1 cores are in turn subjected to a second
rotation. If the process were continued the difference
between the mean values of Ro>Rl>R2>Rn cores would
increase as the heaviest remaining cores were further reduced.
Using this model there is no necessity to assume that the increased reduction of cores is associated with
either a change in the distribution of the blank
population or alteration in the trajectory profiles as was
originally suggested. This is consistent with the
distribution of the Ro quartzite sample which retains a small number of cores substantially heavier than the
llOgms class, the limit of the main Mode II distribution,
which may form the basis of the R1 and R2 populations.