Bull. Tohoku Univ. Museum, No. 12, pp. 77–89, 2013
© by The Tohoku University Museum

Verifying the Function of Yayoi “Ishibocho” Tools fromTohoku District
Kaoru AKOSHIMA* and Kazuo AOYAMA***Department of Archaeology, Graduate School of Arts and Letters, Tohoku University.
**Faculty of Humanities, Ibaraki University.
要旨：イネ科植物の刈り取りに使用された石器刃部には、コーン・グロスと称される特徴的な摩耗光沢が生じる。粘板岩などの石材におけるコーン・グロスの発達過程と特色を明らかにし、東北地方弥生時代のイネの収穫具である石庖丁の使用痕分析を行なった。福島、宮城、岩手、秋田各県から出土した 14 点の石庖丁の入念な顕微鏡観察により、実際の使用方法が復元された。石庖丁に認められる使用痕光沢の強度と分布を精緻に分析・図化した結果、石器紐孔に通した紐に指を掛け、右手親指でイネの茎を押さえ、穂の部分を摘み取っていく「穂摘み法」であったことが実証された。この方法により、石庖丁以外の様々な石器が収穫具として使用された場合の判定が可能であり、日本列島東北部の初期農耕社会における人間集団の文化的適応プロセスの比較研究に応用できる。

Introduction
From the perspective of the classical Processual
Archaeology, human culture can be investigated as a meansof extra-somatic means of adaptation to the environment(e.g., Binford 1962). The spread of rice agriculture during
the Yayoi period to the northeastern parts of the JapaneseArchipelago entails grave theoretical importance from theperspective. Adoption of rice cultivation included highly
developed technological complexes such as on-site irrigationin environmentally mosaic-like mountainous terrains and notalways broad river basins during the earlier half of the Yayoi
period in northeastern Japan (Tohoku District). There had
been adoption of complex agricultural technology including
construction of rice paddies of small rectangle shape as wellas the annual cycle of organized cultivation techniques. In
addition, the various sets of cultural traits were also adopted
such as ground stone artifacts for agricultural settlements.
These stone artifacts consisted of representative axes andadzes, and are termed as “ground stone tools of Asian
continental derivation”. They constitute an integral part ofhuman activities at the Yayoi settlements in most areasof the Archipelago. The “Ishibocho” tool whose function isinvestigated in the present article is a category of theseground tools.
Across the Tsugaru Strait which lies north of Aomori
Prefecture, human groups in the Island of Hokkaido
remained basically as hunting, gathering, and fishing society
throughout the time periods which correspond to the Yayoi
Age in main islands of Japan (Honshu, Shikoku, Kyushu).

Such H/G/F culture is named as “Epi-Jomon Period” (ZokuJomon jidai). Two contrastive life ways persisted between
Hokkaido and the northern part of Honshu, althoughpossibilities of incipient cultivation remain controversial.
The Tsugaru Strait had not been a barrier against culturaltransmission for most time periods from the Palaeolithic to
the pre-modern period. As the folk knowledge saying goes
until recent era, the Strait is “the salty river” (“shoppee kawa”
in local dialects) in terms of cultural trait complex diffusion.
During the Final Jomon period, the Kamegaoka culture
flourished in both sides of the Strait preceding the Yayoi
Age.
The beginning of rice cultivation in the Tohoku District
dates back to the Early Yayoi period of Japan. The discoveryof rice paddies of the Middle Yayoi period at the Tareyagani
site in 1981 (Aomori Pref. Board of Education 1985), andthose of the Early Yayoi period at the Sunazawa site in 1988
(Murakoshi et al. 1991), both located in Aomori Prefecture,
confirmed the adoption of actual rice cultivation on the
Tsugaru Peninsula which is situated at the northern edge ofthe Honshu Island. During the Middle Yayoi period, stable
agricultural settlements were established in Tohoku District.
Especially, Yayoi villages in the Sendai Plain in Miyagi
Prefecture such as the Nakazaike-minami site (Sendai City
Board of Education 1996) and the Takada B site (Sendai
City Board of Education 2000) testified to developed
agricultural life ways from recent excavations. Abundant
wooden implements were also found.
The diffusion processes of the Yayoi cultural complex in
Japanese archipelago has been a major theme of research

78

Kaoru AKOSHIMA and Kazuo AOYAMA(e.g., Akazawa 1982 in English). For Tohoku District,
Suto has continued research on the theme and a majorachievement was published (Suto 1998). The regionalvariations of Yayoi period settlements in Tohoku District
represent differential adaptive processes, and thus complex
combinations of subsistence and cultural traits need to beinvestigated. During the Early Yayoi period, the typologicalsimilarity of the Ongagawa style potteries from a numberof Tohoku sites (e.g., Suto 2000) exhibits a fine contrast
with diversified subsistence and settlement strategies
developed during the same period, including tendency for
combined economy in some colder and/or mountainous
areas of Tohoku. Takase (2004) synthesized researcheson the transition from Jomon to Yayoi with special attention
to social structure. In relational researches of economical
aspects and typological aspects of artifacts, the study of tool
function is essentially important. Reliable identification oftools which were actually utilized for agricultural purposes
would shed light on the problem. Use wear studies would
play an important role in this line of research.
The present paper focuses on the function of Ishibocho
tools on the basis of high power microwear analysis. The
name Ishibocho literally means “stone kitchen knife”. It isa historical name for Japanese archaeology, but from theviewpoint of actual function, it is rather misleading. The typewas evidently used as rice reaping tools for annual harvest
at paddies. Tools of the same category are widely found incontinental China, Taiwan, and Korean Peninsula, during
the Neolithic and the Bronze Age. The origin of Japanese
Ishibocho was investigated in relation to Asian continent.
However, the actual method of its use has not necessarily
been fully investigated globally. The article verifies detailed
method of use on the basis of distribution and intensity
patterns of microwear traces on both faces of Ishibocho
artifacts.
Experimental replication of the tools clarifies thedevelopmental processes of a distinctive type of microwear
polishes called “corn gloss”. The result will also contributeto differentiation of artifacts which were actually utilized
as harvest tools from tools of various other functions.
Throughout the Japanese Archipelago, various other typesof stone tools were used for harvest. It is important to
identify harvest tools and it is quite feasible to do so, basedon the hard evidence described here.

The sample and the method
The phenomenon of “sickle gloss”, or “corn gloss” wasrecognized early in the history of stone tool function (Curwen
1930, 1935). The line of research was further synthesized tounderstand the strong polish on the edge of Neolithic sickle
blades (retouched small blades) which were inserted to thehaft for the purpose of harvest, and general characteristicsof the “corn gloss” was described (Witthoft 1967). The corn
gloss is so strong that it is often observable with the naked
eye or with magnifying glasses. Keeley further integrated thecorn gloss phenomena with elucidation of microwear polishin general. The polish was classified as a strong variety
of “plant polishes” (Keeley 1980). According to Keeley, it
exhibits the following characteristics (after Witthoft 1967,
and Semenov 1964), (1) very smooth texture and highlyreflective surface, (2) “fluid” appearances, (3) “embedded”
striations, and (4) “comet shaped” pits.
Tohoku University Microwear Research Team (TUMRT)
directed by the late Professor Chosuke Serizawa (Akoshima2008) conducted a series of experiments in 1978 to 1980 toconfirm the variation of microwear polish which was reported
in Keeley (1977). Our team conducted a systematic programof replicative experiments for shale (siliceous hard shale),chert, and obsidian. It was confirmed that microwear polishes
produced on these Japanese materials were almost identicalwith those on European flint (Kajiwara and Akoshima 1981).
However, it was pointed out that the correlation between thepolish types and the worked materials was not necessarily
exclusive to one another, but the correlation was probabilistic(Serizawa, Kajiwara, Akoshima, 1982, Akoshima 1989). The
classification scheme of Tohoku University team has since
been widely adopted among Japanese researchers of highmagnification use-wear analysis (e.g., Aoyama 1999, 2009,
Harada 2005, Midoshima 2005, Yamada 2007, Takahashi2007). The “corn gloss” is a part of “Type A” polish of
Tohoku Univ. classification scheme (Akoshima 1996 forEnglish explanation). The term “corn gloss” is used here forconvenience to denote the polish type which was observedon the sample of Ishibocho.
The type A polish is not difficult to identify, comparedto other types of polish. Their characteristics are very
distinctive. The polish is produced as the result of surface
texture alteration. It is the transformation of rock surface
itself. It is neither an additive phenomenon of silica gel, norremnant residues on the rock surface. The polish is thepermanent change of stone surface structure, and thus it is
not erasable by washing or cleaning.
The above mentioned characteristics of the corn gloss are
ideal for identification of harvest tools of rice crop. Actually,
crude flake tools were also used for rice harvest and they
were identified on the basis of patterns of corn gloss (e.g.,
Harada 2003, Midoshima 2005). Reconstruction of the use
method of Ishibocho tools was carried out by the same
methodology as the case of flake tools in the Palaeolithic
period.
A total of 14 Ishibocho tools from Tohoku District wereselected for the present analysis. On the rice reaping
knives, Suto conducted a detailed and meticulous study ofVerifying the Function of Yayoi “Ishibocho” Tools from Tohoku District

79

incident light attachment was used for the present analysis.
Cleaning of specimens was done according to the following
processes without using any brushes. 1) Hand wash withsoap and ordinary water. 2) Application of ultrasonic cleaningof 150 W for 5 minutes, suspending the sample in the watertub. 3) Hand wash again with soap water. 4) Application ofultrasonic cleaning for 2 to 3 minutes. 5) Wipe with alcoholic
cotton (Ethanol) during each observation session. This is toprevent finger grease from sticking on the surface which isoften misleading as “pseudo-microwear polishes”. Surface
treatment such as vacuum coating was not necessary.
Observation was conducted at the magnification of 100
X. Polishes always extend to a certain area of specimen.
Especially in the case of “corn gloss” on Ishibocho, thepolished surface appears in wider areas, compared to sucha case as scraping bone where the polish is localized tothe contact edge. Observation was carried out with an X –Y movable stage of the microscope to cover the entire areaof the sample with movements of several millimeters. Whenthe corn gloss polish was found, the magnification of 200 X
was used for observation of detailed texture of the surface.
Both density of polish patches for the unit area and size
and texture of these patches were combined to produce the
distribution maps of each Ishibocho, according to the criteria
described below.

Tohoku District Ishibocho (Suto 2004). The samples whichwere microwear analyzed here were actually a part of his
research objectives. It was highly labor intensive to observe
the entire surface of the large specimens. The sample hereis made up of 14 specimens as follows. (They are listed fromsouth to north in Tohoku District).
The Tenjinsawa site, Soma City, Fukushima Prefecture, 2
specimens.
The Nishinoda site, Natori City, Miyagi Prefecture, 1
specimen.
The Shimonouchiura site, Sendai City, Miyagi Prefecture, 2
specimens.
The Nabeta locality, Tomizawa site, Sendai City, Miyagi
Prefecture, 1 specimen.
The Izumizakimae locality, Tomizawa site, Sendai City, 1
specimen.
The Minamikoizumi site, Sendai City, Miyagi Prefecture, 4specimens.
The Shikama burial mounds site, Shikama Town, Miyagi
Prefecture, 1 specimen.
The Shimizushita site, Oshu City (Isawa Ku), Iwate
Prefecture, 1 specimen.
The Yotsugoya site, Kosaka Town, Akita Prefecture, 1
specimen.
For the locational information and description of thesesites, please refer to Suto (2004). For the characteristics
of Ishibocho tools in Tohoku District, and description andillustration of the samples above, also see Suto (2004). On
production processes of Ishibocho, Arai (2003) analyzed
cases at Takada B and Tenjinsawa sites.
A metallurgical microscope that is Olympus BHM type with

Characteristics of corn gloss on slate
Characteristics of corn gloss polish on slate rock arebasically identical with other rock types as flint or shale.
Once it is developed to the stage of “weak” described below,

6

4

1

2

None
無
Slight微弱
Weak
弱Medium
中

5
0

5cm

3

Figure 1. Distribution of corn gloss on Ishibocho (reaping knife) from Nishinoda, Miyagi Pref.
(Numbers correspond to figure 2 microphotographs).

Kaoru AKOSHIMA and Kazuo AOYAMA80(1) Nishinoda site, “slight”(2) Nishinoda site, “weak”(3) Nishinoda site, transition from “weak” to “medium” (4) Nishinoda site, “medium”(5) Nishinoda site, “medium”(6) Nishinoda site, “medium”(7) Minamikoizumi site, “huge corn gloss patches”(8) Minamikoizumi site, “huge corn gloss patches”

Figure 2. Corn gloss on reaping knives (The scale bar is 200 microns. 400 microns in case of (3)).

Verifying the Function of Yayoi “Ishibocho” Tools from Tohoku District
it is not difficult to differentiate between corn gloss and othertypes of polish. It is also possible to differentiate it from othermicro-traces from manufacture, especially from grinding
polishes, based on experimental results. An interesting
example is a reaping knife discovered at the Iwanoiri site,
Marumori Town, Miyagi Prefecture (Figure 5, no.3 in Suto
(2004)). It is an unfinished Ishibocho as is known from halfpierced depressions, but entire surface was fully shaped andground. Two depressions were intended as string holes but
not finished. Microwear observation of the specimen only
exhibit grinding wears, but no corn gloss was found.
A notable difference between corn gloss polishes on slate
type rocks from which many Ishibocho tools were made andthose on other CCS rocks (crypto-crystalline silica) such as
flint, chert, and siliceous shale, is the development of patch
like polish structure in case of slate type sedimentary rocks.
Let us take an example of reaping knife from the Nishinodasite (Figure 1). There are portions of different degrees ofcorn gloss development on a single specimen and theirdisposition is shown on the illustration. There are placesfrom very incipient developmental stages to highly affectedareas. The change of surface texture is gradual, and thedegree of development is classified into “none”, “slight”,“weak”, “medium”, and “heavy”. They are shown in figure2(1) to 2(6) for the reaping knife from Nishinoda. Figure 2(7)and 2(8) are huge corn gloss patches on a reaping knife
from the Minamikoizumi site, Sendai.
Appearance of unused surface is quite similar to other
CCS rocks. Polishes from grinding during manufacture areoften observed, but its granular rock structure looks almost
identical with shale and chert. Corn gloss polishes first
appear as tiny shiny points in the granular structure. Small
shining points of less than 10 microns in diameter begin toappear with a sharp contrast to surrounding areas. Then, theshiny points grow into small patch like features. At the sametime, the density of polished points and patches per unit
area increases.
Development of gloss features brings a notable situation
where various shiny points and patches coexist in the same
portion, observable under magnifications. Polish patchesof different sizes from minute to large coexist in the same
area to be seen. In the case of chert and shale, “corn gloss”
polishes begin to develop with appearances very similar to“wood polish”. They begin to develop from the very edgeof working blade and also from higher elevated portions of
granular structure. Then they extend into surrounding areas
gradually and the corn gloss finally covers overall affectedarea (cf. Kajiwara and Akoshima 1981, figure 1 (2) (3)). In
the case of slate type sedimentary rocks, the process is not
uniform gradual developments of polished portion, but ii is acollective formation of demarked patches of variable sizes.
A factor leading to non-uniform development of polished81

surface is probably the structure of granular components of
the rock itself. Observation at high magnifications from 200
X to 400 X reveals differential appearances among patches
and non-affected granules. Adjustment of focusing dials of
the microscope also reveals that relatively elevated parts
produce gloss patches in higher density.
In summary, the phenomenon of corn gloss development
in case of slate type sedimentary rocks is defined asincrease of the number of polish patches per unit area andenlargement of the size of polish patches. On the contrary, it
is not a phenomenon of increasing brightness of each patchor the degree of smoothness of patch surfaces. Once thepatches are formed, even if they are tiny, their texture is verysmooth, their surface shape is flat, their surrounding edges
are rounded, their brightness that is light contrast is strong,and patches are clearly demarked from their background.
Their brightness is similar between large and small patches.
It is not that more developed patches are brighter thanothers.
Distributions of corn gloss polishes over both faces of thereaping knife exhibit very informative patterns. The specimen
from Nishinoda (Figure 1) represents a typical pattern ofwear disposition brought from the method of use. The lithic
raw material is composed of high density darker color partsand low density lighter color parts. The latter consists ofsandy rock type. The stone constitutes thin laminar structure
and the reaping knife was manufactured with its length in
the direction of the laminar structure. The difference of stonequality is reflected in the degree of development of corn
gloss polishes as is seen in the distribution map. The lighter
color parts exhibit relatively heavier development of corn
gloss. It is evident from the case that the variation of rocktypes generally affects the speed of polish development.
Figure 2(3) is a microphotograph of the border part of two
different laminar units. It is interesting that two different
stages of polish development are seen in the same photo.
When the tool is placed with its convex blade edge
down, areas of stronger polish extend toward the left partof the body of reaping knife. The polish distribution is not
symmetrical between the left and the right. There is notmuch difference between either face of the implement. Thatis, the corn gloss is developed similarly on both surfaces of
the tool and the left part of the body exhibit stronger polishon either face. This means that the implement was used in“turn around” method repeatedly. The polish is extraordinary
weak around the two string holes on either face. The edgeof the convex blade shows weaker polish relative to thebody part. The units of grinding finish well accord with thedifference of polish strength along the blade edge on either
face. These distribution patterns are rather typical for mostIshibocho tools, as we will see below.

82

Kaoru AKOSHIMA and Kazuo AOYAMA

Developmental stages of corn gloss and striations
Developmental process of corn gloss is a continuous
phenomenon, but here the degree of polish strength isclassified into five stages, namely “none”, “slight”, “weak”,“medium”, and “heavy”, based on the following criteria.
“None”; the stage where no polish is detected under themagnification of 100 X.
“Slight”; the stage where the polish begins to form as tiny
points in low density. The diameter of each polish patch
generally does not exceed 10 microns. When they areobserved under the magnification of 200 X to 400 X, theircharacteristic features as corn gloss barely begin to appear.
In case of stone implements which exhibit only this stage ofdevelopment, it is not always reliable to identify the polish as
being corn gloss.
“Weak”; the stage where corn gloss patches exhibit sporadic
distribution. When a frame of 1000 microns X 70 microns
is set on the surface of the tool, several pieces of corn
gloss patches of about 20 microns or larger in diameter aredetected within the frame. The frame is measured using thescale in the eyepiece lens of the microscope. The size ofthe corn gloss patches does not reach 50 microns in length
even for larger patches. However, the characteristic features
as corn gloss polish are observable at the magnification of
100 X.
“Medium”; the stage where corn gloss patches exhibitgrouped emergence. Within the same frame as above, 10
to 20 pieces of corn gloss patches of about 20 microns orlarger in length are detected. Larger patches in this stage
reach the size of 50 to 100 microns in length. Sometimes
they exceed 100 microns in diameter.
“Heavy”; the stage where the corn gloss polish covers allover the observation area. This phenomenon is observed in
the case of siliceous shale experiments. However, there was
no implement of this stage in the present analysis. The mostnotable example of strong corn gloss for Ishibocho is shownin figure 2(7) (8). It is from the Minamikoizumi site. The hugepatches reach the size of several hundred microns. They
share the common characteristics as corn gloss in othersamples in the paper. The stone raw material is not slate,but semischist .
Striations with corn gloss phenomena of Ishibocho needspecial cautionary attention, because their manufacture
processes include broad application of grinding techniques.
In the present analysis, only those striations whichaccompany with the surface of the corn gloss patches
are denoted as use-wear striations. They are fused withsmoothed flat surface of the patches themselves. Theyshow a distinctive appearance as if the surface looked likeswept with a brush, so to speak. The striations are extremely
thin, shallow and parallel. They are observable only at highmagnification of 400 X in most cases. This type of striation isconsidered to form as a part of surface structure of polishedarea. They generally indicate the direction of motion of theworking edge of the tool. The same sort of striae is also seen
on CCS rocks and they were called as “filled-in striations”(Keeley 1980, p.60). In the case of slate, striations areeven more tiny and subtle. In the present specimens, only alimited number of reaping knives retain the traces. Existence
and directional tendency could be recorded, but quantitativeevaluation such as density was not possible. Those
striations in the background area of polish patches were
not included in the analysis, because they may have been
the results of manufacture processes. Striations which areon top of polish patches but are not integrated with surface
texture were not recorded as use-wear striae. Examples
are shown in figure 2(7) on the right side corn gloss patch,running oblique together. They are “damage like grooves”.

Results
The results of microwear observation confirmed the so far
supposed use method of this category of artifacts. Figure
4 shows microphotographs for intensity degree “medium”
portions. They were taken at 200 X magnification. All theuse-wear polishes detected in the analysis were type Aof Tohoku University classification scheme (Kajiwara andAkoshima 1981). The areas around the string holes werealso observed but no other types of polish were found.
The Tenjinsawa site (Figure 3 (1) (3))
Both implements show polish distributions mainly on
the lower parts of the tool body. Both have stronger polishareas in the left half of the body. In the case of (1), there aredifferences in intensity of polish, according to the laminarstructure of the stone material. Brighter color areas of sandyrock stripe structure exhibit relatively stronger polish. At theleft part of face B (bottom), polish patches are found on theedge part. On specimen (3), there are differences between
both faces, namely, face B shows stronger polish patterns.
The Shimonouchiura site (Figure 3 (2) (4))
Two faces of the implements show almost the same
degree of polish intensity. This is the same pattern for two
Ishibocho which were placed in a pit as grave goods. In
the case of (2), the stripe pattern of “medium” and “weak”
portions corresponds to the rock material lamination pattern.
Both implements exhibit stronger corn gloss in the lower partof the body at the area adjacent to the edge. The edge parts
themselves do not retain strong gloss on the other hand.
The area surrounding the string holes show almost no polishpatches. Detailed microphotographs are shown in Suto andAkoshima (1984). These two Ishibocho were repeatedlyused probably for many years with edge re-grinding
maintenance, before they were offered into the grave.

Verifying the Function of Yayoi “Ishibocho” Tools from Tohoku District(1) Tenjinsawa, Fukushima Pref.

83(2) Shimonouchiura, Miyagi Pref.

1(4) Shimonouchiura, Miyagi Pref.
2(3) Tenjinsawa, Fukushima Pref.

(6) Shikama, Miyagi Pref.
(5) Shimizushita, Iwate Pref.

(8) Nabeta, Miyagi Pref. 5(7) Yotsugoya, Akita Pref.

4

7

3

8

Figure 3. Distribution of corn gloss on reaping knives (Numbers correspond to figure 4 microphotographs).

Kaoru AKOSHIMA and Kazuo AOYAMA84(1) Tenjinsawa, Fukushima Pref.

(2) Tenjinsawa, Fukushima Pref.

(3) Shimizushita, Iwate Pref.

(4) Shimizushita, Iwate Pref.

(5) Shikama, Miyagi Pref.

(6) Shikama, Miyagi Pref. (Edge part of a fragment)(7) Nabeta, Miyagi Pref.

(8) Nabeta, Miyagi Pref.

0

200μ

Figure 4. Corn gloss on reaping knives (Intensity is “medium” for all 8 microphotoraphs).

Verifying the Function of Yayoi “Ishibocho” Tools from Tohoku District

(1)

(3)

(2)

(5)
7
8

(4)

Figure 5. Distribution of corn gloss on reaping knives((1), (2), (3), (4); Minamikoizumi, Miyagi Pref., numbers in(2) correspond to fig. 2 microphotographs. (5); Izumizakimae, Miyagi Pref.).

85

86

Kaoru AKOSHIMA and Kazuo AOYAMAThe Nabeta locality of Tomizawa site (Figure 3 (8))
The implement does not show stronger polish generally,
but the distributional pattern of corn gloss is recognized. The
tendency of relatively strong polish area in the left half ofthe lower portion of tool body applies. The back side and its
edge area of tool in the left half also show considerable corn
gloss. The thin line below the left string hole is a linear areaof peculiar rock material.
The Izumizakimae locality of Tomizawa site (Figure 5 (5))
This is a broken reaping knife, and it is not possible tocompare between the left and the right part. However, thetendency of stronger corn gloss in the lower portion of thetool body is recognized. Relatively weak polishes along theworking edge on face A (top) and the fact that it demarked
the ridge of grinding finish line indicate the maintenancebehavior of edge re-grinding. Detailed microphotographs areshown in Akoshima and Suto (1984).
The Minamikoizumi site (Figure 5 (1) (2) (3) (4))
Implement (1) shows stronger polish on face B (bottom),and it is more eminent in the left half of the lower portionof tool body. The back part also exhibit considerable corn
gloss. The area around the string holes shows very little
polish.
Implement (2) is made of semischist rock type. The corn
gloss is extraordinary strong on face B. A wide area iscovered with “medium” and partially even stronger polishes.
It is noteworthy that there are groups of “huge corn gloss
patches” as are seen in figure 1 (7) (8). The areas along theedge also retain developed polish parts on both faces of thespecimen.
Implement (3) exhibits polished areas along the back sideof the right half of tool body. However, the polish is stronger
in the left half of the body. Along the edge of the right half,corn gloss is weaker on either face.
Implement (4) also shows the pattern of concentrating
onto the left half of the tool body, but there are polishedareas along the back side as well. The area along the edge
exhibits polishes in the left half of the tool. The string holesof this Ishibocho are made asymmetrical to the tool shape.
They are not in the central part, but the development of corn
gloss is similar between two faces.
The Shikama burial mound site (Figure 3 (6))
Portions of developed polish distribute irregularly. The
tendency to the left half of body and weakness along theedge is recognized. Stronger polished areas exist in thelower portion of central part of the tool body on face B. The“none” polish area in the left half of the body on face B is apeculiar step flaked part of the rock material.
The Shimizushita site (Figure 3 (5))
The corn gloss polish is eminent in the lower portionof the central part of the body. The degree of polishdevelopment over both faces very well corresponds to thestripe laminar structure of the raw material rock and theunits of grinding finish ridges. Some parts of this implement
are not observable due to a certain substance sticking to thesurface.
The Yotsugoya site (Figure 3 (7))
This is a broken Ishibocho, and it is one of rare cases
discovered in Akita Prefecture. Some corn gloss polishes
are found in the left half of the tool body. They are of “slight”
and “weak” stages of development.

Discussion
Consistent patterns of corn gloss distribution are observedon all the Ishibocho implements of the Yayoi period fromTohoku District. The microwear patterns indicate actual
method of use in rice crop harvest activities. There iscertain variability in the intensity of polishes, some variableappearances from raw material quality, and differences
between two faces of the tool. However, the distributional
pattern of corn gloss exhibits a strong tendency, fromrepeated use in the same manner, toward a generaluse-method of this type of curated technology (Binford
1979). The actual behavior of harvest is un-ambiguously
reconstructed.
General patterns of use-wear on Ishibocho aresummarized as follows.
(1) The corn gloss polish does not necessarily develop ina uniform pace and manner from the edge portion to thewider surface of the implement. The formation and resultant
distribution of the corn gloss are influenced by at least threefactors. They are the quality of lithic raw materials, or raw
material characteristics of the particular portion in case oflaminar rock structure, the degree of contact and intensitywith the worked materials that were exclusively rice crops,and disappearance of corn gloss as the result of re-grindingof convex edge parts for rejuvenation of the sharp workingedge.
(2) In case of rock types with laminar sedimentary structure,generally whitish portions of sand stone quality exhibit
relatively stronger corn gloss development, relative to darkcolor portions.
(3) Two faces of Ishibocho do not show much differencein the degree of corn gloss development. Both faces are
similarly affected with corn gloss phenomenon generally. In
the meantime, the distribution patterns of polish on either
face are consistent in that the left half of either face is more
affected compared to the right half. There is no “ventral” or“dorsal” face for Ishibocho which is a ground finished stone
tool, and the implement was repeatedly used by the “turnover” method.
(4) When the implement is placed with its convex edge
part down and its back up, the left half of the body exhibits

Verifying the Function of Yayoi “Ishibocho” Tools from Tohoku District
much stronger polish development, as mentioned above.
This characteristic distribution is the most eminent pattern ofpolish.
(5) The polish is usually strongest on the lower part of theimplement body. The edge part itself is rather weak. The
corn gloss is often very faint along some portions of theworking edge. In such cases, the contrast between the edge
and the lower part of the body is sharp. The lines between
grinding finish units in manufacture are often the border ofpolish strength. Thus, it is evident that the edge parts were
frequently re-ground, leading to disappearance of corn gloss
polish. The re-grinding behavior is well represented in one
fragment of the edge part of Ishibocho from the Shikama
tumulus (burial mound) site. A microphotograph is shown infigure 4(6). The broken edge still retains intense corn gloss

87

polish.
(6) The back part side that is the opposite side of the edge
often exhibits well developed polishes. However in thosecases, the lower portions of the body in the left half generally
exhibit even stronger polishes than the back part.
(7) The portion around two string holes does not showpolished areas generally. Even in cases where the backside and the upper part of the body close to the back exhibit
polish development, the string holes are surrounded by very
intact areas where polish is faint or sometimes none. Thispattern indicates that the area around two string holes is theplace where direct contacts with rice crops were prevented,
even when the Ishibocho was repeatedly utilized.
(8) Striations are not always evident even on the edge
portion, but when they are existent it is a pattern that they

(1)

(2)

Figure 6. Reconstruction of use method of reaping knife.

Kaoru AKOSHIMA and Kazuo AOYAMA88

run perpendicularly to the edge line. They are minutestriations which are fused with the corn gloss surface texture
on patches.
(9) From above observation results, it is very certain that theimplement was used in a way where the motion was exerted
perpendicular to the edge line, and the left part of the bodywas mainly in contact with the worked materials, with morepressure on one face of the two.
It is concluded with confidence that the actual methodof the use of Ishibocho was like figure 6(1)(2). The method
was picking off the ears with the right hand, the thumb being
placed on the stalk below the ear. Some other fingers werein the ring of string which was tied through two string holes.
The Ishibocho was turned over repeatedly, but the methodof use remained the same, thus resulted in the symmetrical
distribution of corn gloss polish on both sides.
The Ishibocho of the Yayoi period was an integral part ofground stone technology of the Asian continental derivation.
It is a part of complex agricultural technology and also
represents a category of “curated tools” in terms of the“organization of technology”, in the sense of Binford (1983).
Further investigation is necessary to identify other lithic tool
categories which were also used for harvest activities, even
where the typological Ishibocho and other ground tools ofcontinental derivation are lacking in the lithic technology, but
cultivation and harvest was a part of their annual life cycles
in complex mosaic like adoption of new cultural traits relating
to plant food production by human groups in northeasternparts of the Japanese Archipelago.

Acknowledgement
The late Professor emeritus Chosuke Serizawa directed
the Tohoku University Microwear Research Team since 1976
and led us to this area of lithic analysis. Professor emeritus
Dr. Takashi Suto conducted his solid organized research of
Jomon and Yayoi settlements in Department of Archaeology
until 2007. He supervised the present paper study. The
Ishibocho samples analyzed here could not have been
available without his aforementioned research. Membersof the Tohoku University Team contributed to the replicative
experiments. The authors are deeply grateful to them. The
basic work for this paper was conducted in 1980s by theauthors (Suto and Akoshima 1985). The first draft on the
results was long kept in Tohoku Univ. and lost an opportunityof publication. With the current project of storage collection
archives with Prof. Toshio Yanagida of Tohoku University
Museum, the present publication was made possible. We
are also thankful to him.

References
Akazawa, T. 1982, Cultural Change in Prehistoric Japan: Receptivity
to Rice Agriculture in the Japanese Archipelago. Advances inWorld Archaeology, vol.1, pp.151-211.
Akoshima, K. 1989, Use-wear of Stone Tools. Archaeological
Library 56, New Science Co. (in Japanese)
Akoshima, K. 2008, Emergence of High-power Microwear Analysis
in Japan, 1976 to 1983: Prof. Serizawa’s Legacy and Beyond.
Papers on Archaeology, Ethnology, and History in memory ofProfessor Chosuke Serizawa*, pp.189-207. Rokuichi Shobo.
Akoshima, K., and G. C. Frison 1996, Lithic Microwear Studiesof the Mill Iron Site Tools. The Mill Iron Site, edited by G. C.
Frison, pp. 71-86. University of New Mexico Press.
Akoshima, K., and T. Suto 1984, Use-wear on a Rice Reaper
Excavated from Izumizaki-mae Locality, Tomizawa Rice Field
Site. Tomizawa Rice Field Site, pp. 213-216. Sendai City Boardof Education. (in Japanese)
Aomori Prefecture Board of Education 1985, The Tareyanagi Site*.
Aomori Prefecture Buried Cultural Properties Research Report,
no.88. (in Japanese)
Aoyama, K. 1999, Ancient Maya State, Urbanism, Exchange, andCraft Specialization: Chipped Stone Evidence from the Copán
Valley and the La Entrada Region, Honduras. University ofPittsburgh Memoirs in Latin American Archaeology No. 12,
Pittsburgh.
Aoyama, K. 2009, Elite Craft Producers, Artists, and Warriors at
Aguateca: Lithic Analysis. Volume two of Monographs of theAguateca Archaeological Project First Phase. The University of
Utah Press, Salt Lake City, Utah
Arai, I. 2003, The Stone Reaping Knives of the Tohoku Region:
Production Processes and Raw Material Selection. Nihon
Kokogaku, Journal of the Japanese Archaeological Association,
no. 15, pp. 1-10.
Binford, L. R. 1962, Archaeology as Anthropology. American
Antiquity, vol. 28, pp.217-225.
Binford, L. R. 1979, Organization and Formation Processes: Looking
at Curated Technologies. Journal of Anthropological Research,
vol. 35, pp. 255-273.
Binford, L. R. 1983, Working at Archaeology. Academic Press.
Curwen, E. C. 1930, Prehistoric Flint Sickles. Antiquity, vol. 4, pp.
179-186.
Curwen, E. C. 1935, Agriculture and the Flint Sickle in Palestine.
Antiquity, vol. 9, pp. 62-66.
Harada, M. 2003, Use-Wear Analysis of Lithic Farming Implements:
Current Status and Limitations of the Studies on HarvestingTools. Kodai (Journal of the Archaeological Society of Waseda
University), no. 113, pp. 115-138. (in Japanese)
Harada, M. 2005, A Decade of the Society for Lithic Use-wear
Studies*. Newsletter of the Society for Lithic Use-wear Studies,no.5, pp.1-2. (in Japanese)
Kajiwara, H., and K. Akoshima 1981, An Experimental Study ofMicrowear Polish on Shale Artifacts. Kokogaku Zasshi, vol. 67,
no. 1, pp. 1-36. (in Japanese)
Keeley, L. H. 1977, The Functions of Palaeolithic Flint Tools.
Scientific American, vol. 237, no. 5, pp. 108-126.
Keeley, L. H. 1980, Experimental Determination of Stone Tool Uses.
University of Chicago Press.
Midoshima, T. 2005, Sekki Shiyoukon no Kenkyu (A Study of Usewear on Stone Tools*). Doseisha. (in Japanese)
Murakoshi, K., et. al. 1991, Excavation Report of the Sunazawa
Site*. Hirosaki City Board of Education. (in Japanese)

Verifying the Function of Yayoi “Ishibocho” Tools from Tohoku District
Semenov. S. 1964, Prehistoric Technology, translated by M.
Thompson. Cory, Adams and Mackay.
Sendai City Board of Education 1996, The Nakazaike-minami Siteand others*. Sendai City Cultural Properties Research Report,
no.213. (in Japanese)
Sendai City Board of Education 2000, The Takada B Site*.
Sendai City Cultural Properties Research Report, no.242. (inJapanese)
Serizawa, C., H. Kajiwara, K. Akoshima 1982, Experimental
Study of Microwear Traces and Its Potentiality. Kokogaku to
Shizenkagaku, (Archaeology and Natural Sciences*), no. 14,
pp. 67-87. (in Japanese)
Suto, T. 1998, A Study of Culture Change and Social Transformationin Prehistoric Period of Northeast Japan: from Jomon to Yayoi*.
Sanshudo. (in Japanese)
Suto, T. 2000, Tohoku District in the Yayoi Period. The Miyagi
Archaeology, no.2, pp.1-24. (in Japanese)
Suto, T. 2004, Yayoi Period Polished Stone Reaping Knives ofNortheastern Japan: A Marker of Early Agricultural Economy.
Bulletin of the Tohoku University Museum, no. 3, pp. 17-67.
Suto, T., and K. Akoshima 1984, Rice Reapers excavated from the
Shimonouchi-ura Site, SK2 Burial Pit. Sendai City Cultural
Property Research Report*, no. 69, pp. 59-66. (in Japanese)
Suto, T. and K. Akoshima 1985, On Ishibocho in Tohoku
District*. Paper presented at 51st meeting of The JapaneseArchaeological Association, at Nihon University, p.19.
Takase, K. 2004, Sociography of Yayoi Period in the NE Honshu
Island. Rokuichi Shobo. (in Japanese)
Takahashi, A. 2007, Use-wear Analysis of Tanged Scrapers*.
Kokogaku Danso, pp.369-388. Rokuichi Shobo (in Japanese)
Witthoft, J. 1967, Glazed Polish on Flint Tools. American Antiquity,
vol.32, pp.383-388.
Yamada, S. 2007, Chapter 2: The function of Stone Tools. Seminar
Palaeolithic Archaeology*, edited by H. Sato, pp.32-49.
Doseisha. (in Japanese)
Note: English titles with * mark are translated by Akoshima. Titles
without an asterisk are original English titles, or English
translation by its author.

89