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Journal of Archaeological Science 49 (2014) 518e523

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Journal of Archaeological Science

journal homepage: http: / /www.elsevier .com/locate/ jas

Smaller fragment size facilitates energy-efficient bone greaseproduction

Anneke Janzen a, *, Rachel E.B. Reid b, Anthony Vasquez a, 1, Diane Gifford-Gonzalez a

a Department of Anthropology, University of California, Santa Cruz, CA 95064, USAb Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064, USA

a r t i c l e i n f o

Article history:Received 2 December 2013Received in revised form2 June 2014Accepted 4 June 2014Available online xxx

Keywords:ZooarchaeologyExperimental archaeologyBone greaseNutritionWorkload

* Corresponding author. Department of AnthropoSciences 1, 1156 High Street, University of CaliforniaTel.: þ1 559 917 4737.

E-mail addresses: annekejanzen@gmail.com, ajanz1 3517 56th Street, Sacramento, CA 95820, USA.

http://dx.doi.org/10.1016/j.jas.2014.06.0040305-4403/© 2014 Elsevier Ltd. All rights reserved.

a b s t r a c t

Conventional zooarchaeological wisdom holds that reduction of bone into small fragments, modally 2e5 cm in maximum dimension, facilitates the extraction of bone grease. However, experiments byChurch and Lyman showed no statistically significant differences in amounts of grease extracted from1 cm, 2 cm, and 4 cm bone fragments. Our research assessed whether other factors, including water andfuel inputs, could influence the degree of bone comminution for grease extraction. Experimental greaseextraction from 15 cattle (Bos taurus) femora, reduced to similar maximum dimensions as in the Churchand Lyman study, supports their finding that grease yield does not significantly increase in fragments<4 cm. However, our research shows that smaller fragment sizes require less water, and hence less fuel,to produce the same grease yields. These results suggest a tradeoff between the work it takes to producevery small modal bone fragment size and broader-scale fuel, water, and human energy budgets.

© 2014 Elsevier Ltd. All rights reserved.

1. Introduction

Zooarchaeologists have long assumed that the extremely smallfragment sizes typical of bone grease production facilitates theextraction of grease from the bone (Vehik, 1977). However, Churchand Lyman's (2003) experimental study showed no statisticallysignificant differences in the amounts of grease produced bysimmering long bone fragments of 5 cm, 4 cm, 2 cm or 1 cm inmodal maximum dimension. They further established that allfragments under 5 cm release 80% of their total grease contentwithin the first five hours of simmering, and therefore little reasonexists for boiling bones over longer periods. The question thusarises: if no gain in grease extraction is produced by comminutionof bones and bone pieces below about 5 cm maximum dimension,why did people consistently reduce elements to the fragment sizesobserved archaeologically and ethnographically? This labor-intensive activity requires substantial time and effort on the partof the processors. Church and Lyman (2003) speculated that further

logy, Faculty Services, Social, Santa Cruz, CA 95064, USA.

en1@ucsc.edu (A. Janzen).

comminution might facilitate the recovery of other nutrients otherthan lipids e which their experiment did not monitor.

An alternative explanation, which this article explores, stepsback and views bone grease extraction in a broader perspective,specifically attending to its fuel and water requirements. Reasoningfrom first principles, we know that a greater volume of water willrequire more time to heat to a boil. The equation Q ¼ mcDT de-scribes the amount of heat required to raise the temperature of asubstance by 1 �C, where Q is the heat added, m is the mass of thesubstance, c is the substance's specific heat (4.168 J/g�C for water),and DT is the change in temperature. To boil this down to plainEnglish, the smaller the fragments of bone, the less water is neededto cover them, and therefore, the smaller amount of fuel needed tobring the water to a boil. Smaller fragments also have a highersurface area to volume ratio, which facilitates quicker greaseremoval.

We hypothesized that the volume of water, and its essentialrelation to the energy required to heat it to boiling temperatures,influence the size of bone fragments when extracting grease. To testthis hypothesis, wemonitored the volume of water (ml) required tocover bone fragments and thus to capture grease freed from bonefragments, total fuel consumption during grease extraction, the rateof temperature (�C) increase, and the total amount of greaseextracted (ml/kg) from fifteen cattle femora reduced to threedifferent fragment size classes.

A. Janzen et al. / Journal of Archaeological Science 49 (2014) 518e523 519

2. Background

Mammalian bone grease is composed primarily of fatty acids,including essential fatty acids (EFA), which humans cannot physi-ologically synthesize andmust obtain from food. Bone grease levelsvary seasonally according to the condition of an animal and,especially in the case of females, through its reproductive cycles.Brink (1997:260) reports that bone grease can comprise up to one-third of the weight of a portion of a bone. Thus, animals in peakcondition offer a substantial amount of storable fat to those willingto extract it.

Archaeological, ethnoarchaeological, and experimental studiesfrom Europe and North America have shown that bone greaseproduction usually correlates with percussion-mediated reductionof skeletal elements into very small fragments. Archaeologically,“signatures” of bone grease extraction are dense concentrations ofminimally identifiable bone scraps, of 1e5 cm in maximum di-mensions (Outram, 2001). Leechman (1951) first noted the abun-dance of smashed bone in archaeological sites in the northernUnited States Plains as well as southern Ontario and linked this toextraction of bone grease, based upon ethnographic observations.Brink (1997), Church and Lyman (2003), and Outram (2001) offercomprehensive bibliographic overviews of the process and its by-products.

Bamforth (2011) cites evidence for the widespread extraction ofwithin-bone nutrients in late prehistoric Great Plains archaeolog-ical sites (e.g. Brooks and Flynn, 1988; Lintz, 1991; Logan, 1998;Reeves, 1978; Savage, 1995; Scheiber, 2007; Vehik, 1977). Such ac-tivities are also indicated by stable isotope analysis of residues inceramics (in addition to the abundance of typical smashed bonefragments) from the Rush Site in Texas, Quigg (1997).

Bonnichsen and Will (1980) and Binford (1978) describedethnographic cases of rendering grease. Bones fromwhich marrowand meat had been removed were broken into smaller fragmentsand simmered in a container until fat floated to the top of thewater.Congealed fat was skimmed off the top of the cooled liquid andstored for use in meals featuring lean meat. Binford (1978) reportedNunamiut women using snow to more quickly cool such water andto congeal the grease, facilitating its efficient removal for storage.

Both Outram's (2001) Lupo and Schmitt's (1997) experimentalresearch indicates that the cost of grease rendering by boiling ishigh, relative to the amount of grease collected. Evidence for greaserendering has been identified as early as the Upper Paleolithic, andis often indicative of resource intensification (Manne, 2014; Munroand Bar-Oz, 2005). Bone grease extraction usually dropped out ofculinary processing techniques in societies that took up dairying,probably reflecting milk fats' less labor- and fuel-intensive natureas a source of storable animal lipids. The early Neolithic site ofÇatalh€oyük in Turkey, with domestic caprines but no domesticcattle, displays evidence of bone grease manufacture from bones ofdomesticates (Russell and Martin, 2005). Later Turkish Neolithicsites with domestic bovines lack evidence of grease production,instead showing isotopic evidence for dairying in the fabric ofceramic vessels (Evershed et al., 2008). Outram's (2003) compari-son of Norse archaeofaunas from Iceland and Greenland revealedthat bone grease extraction may appear again in dairying societiesunder severe, climate-induced stress. Icelanders produced no bonegrease debris, whereas Greenlanders in the failing Norse colonythere did.

Our experiment focuses on how the reduction of bones tosmaller fragments could conserve four critical and finite “re-sources:” water, fuel, processors' time, and processors' effort. Forpeoples residing in a fixed locale, fuel can be a major limiting factor(Binford, 1978; Charmes, 2006). Water, if not a limiting resource initself, imposes opportunity costs and a literal, energetic burden on

its bearers during its procurement. Thus, considerations of work-load, as well as fuel and water efficiency, may drive decisions byknowledgeable actors regarding the degree of effort to invest incomminuting bone elements.

3. Material and methods

Although our basic operations e bone fragmentation,simmering, fat skimminge replicate ethnographically documentedcases of bone grease extraction, we stress that we in no way soughtto imitate “traditional” methods in our research design. Ourexperimental goals were to closely calibrate bone grease yieldsagainst: (1) fragment size; (2) elapsed time to end of grease pro-duction; (3) the amount of water used; (4) amount of fuelconsumed. We therefore used techniques that best suited thesegoals.

We obtained fifteen fresh, whole young adult cattle (Bos taurus)femora from local butchers in Corralitos, Santa Cruz County, Cali-fornia. Cattle were raised on pastures and grass-fed. We manuallyremoved all connective tissues, fat and marrow from the bonesusing scalpels. Such elements weremuch larger than the Odocoileusvirginianus elements in the Church and Lyman study. We chose tosaw the femora to produce the desired modal fragments sizes, aftertwo trials of smashing elements with hammerstones and anvils andwith a sledgehammer produced irregularly sized fragments. Theuniformity of the sawed pieces in no way compromises and in factenhances experimental control. Fragments were stored in a freezeruntil the night before each trial, when they were removed andpassively thawed.

Experimental femora were sawed into fragments with 4 cm,2 cm, or 1 cm maximum dimensions using a Barranca Diamondmodel PF10 10" power feed rock saw. These fragment size cate-gories coincide with those of Church and Lyman's 2003 Lots 3, 4,and 5 categories. We restricted our trials to 4 cm, 2 cm, and 1 cmmaximum dimension fragments, excluding Church and Lyman'sLots 1 and 2 (smashed bone fragments � 5 cm and bones cut intoepiphysis and diaphysis sections). We did so because our primaryaimwas to explore the influence of the smaller size ranges onwaterand fuel use.

All trials were carried out in a fume hood in the ZooarchaeologyLaboratory at the University of California, Santa Cruz. Bone frag-ments were weighed to the nearest tenth of a gram on a digitalbalance, and then placed in a 12 L uncovered stainless steel potwiththe measured water and brought to a low boil over a natural gasBunsen burner attached to a gas flow meter (Fig. 1). Gas flow ratesduring the experiment were set at full (2.5 m3/h) or half-full (1.25/m3/h). We converted the fuel flow to an estimate of energyconsumed, using the scale of 1m3 of natural gas¼ 38.14megajoules(MJ) (Hofstrand, 2008).

We separated the sawed bone samples into three differentexperimental groups for boiling and grease extraction usingdifferent techniques. Each group consisted of femora sawed intodifferent fragment sizes (1, 2, and 4 cmmaximum dimensions), andeach experimental trial contained fragments from a single wholefemur. In the first experimental group (Lot 1: Trials 1e5, 13e15),measured volumes of water were added to cover the top of thebone fragments up to 1 cm depth. As anticipated, the volume ofwater added varied according to bone fragment size. The measuredvolume of water (ml) added and the starting temperature (�C) wererecorded. The bones were simmered over an ignited natural gasBunsen burner set to maximum (2.5 m3/h) gas flow. Trials 13 and15, intended to be conducted with full gas flow, were not. Under-graduate interns accidentally had set the gas to half flow, and themistake went unnoticed because the fume hood sash was loweredto a point lower than the level originally specified by UCSC

Fig. 1. Experimental set-up in fume hood. Gas flow-meter is on the left.

A. Janzen et al. / Journal of Archaeological Science 49 (2014) 518e523520

Environmental Health and Safety inspectors, thus preventingincoming air from diverting the flame from the Bunsen burneraway from the pot- directingmore heat towards the pot. As a result,the water increased in temperature at a rate very similar to that inprevious trials at the full gas flow rate. Thus, despite the decrease infuel flow, each set came to boiling temperatures within 30e45 min,even slightly sooner than most of the other Lot 1 trials (Fig. 2; 3).We are including Trials 13 and 15 in our discussion of the amount ofgrease extracted among the different experimental lots becausethis error actually revealed some valuable insights into fuel econ-omy dealt with in the Discussion.

Experimental Lot 2 trials (Trials 6, 7, and 11) were also simmeredover a Bunsen burner set to maximum (2.5 m3/h) gas flow, but thevolume of water added was standardized to 4.0 L in each trial.

Finally, in Lot 3 trials (Trials 8e10 and 12), 4.0 L of water wasadded to bones with the Bunsen burner intentionally turned to halfflow (1.25/m3/h).

In each trial, water temperature and fuel consumption wasrecorded every fifteen minutes for the first two hours of theexperiment. Thereafter, water temperature measurements wererecorded every half hour until six hours had elapsed, or the waterhad completely boiled off, in which case, we ended the trial,recording the time elapsed.

In each trial, we replicated two grease extraction processesdescribed in ethnographic accounts. First, grease was skimmedfrom the top of the heated water with bone fragments still in thepot when a sufficient amount had accumulated during simmering,and second, grease extraction at the conclusion of each trial wasfacilitated by adding 1 L of cold water to the pot, which helped tobring the remaining grease to the water surface above the level ofthe bones, and the fat to congeal. After some trial and error withvarious grease recovery tools during the first two trials, we skim-med grease from the water surface with a shallow ladle.

For Lot 1, grease was skimmed from the surface of the waterand measured every hour. Based upon the rates of yield in the Lot1 sampling, grease from Lots 2 and 3 was skimmed just twice: atfive hours' and again at six hours' elapsed time. The volume ofgrease extracted was measured in a calibrated beaker and recor-ded (ml).

4. Results

In agreement with Church and Lyman's (2003) findings, weobserved no statistically significant difference in total grease yields

among fragment size groups (Fig. 4; ANOVA: F(2,10) ¼ 0.29;p ¼ 0.76). Within Lot 1 trials, differences in fragment size did notsignificantly differ from one another in grease yield (ANOVA:F(2,3) ¼ 0.46; p ¼ 0.67).

We did, however, observe striking differences among experi-mental trials in the amounts of grease extracted in relation to theamounts of fuel and water consumed (Table 1). The volume ofwater required to cover the variously sized fragments in Lot 1ranged from 1475 ml for the two cm fragments to 4500 ml for the4 cm fragments. The trials that required the lowest volume of waterto cover came to a boil fastest (Figs. 2, 3). A significant differenceexists between Lot 1 and Lots 2 and 3 in terms of volume of waterrequired and grease yield (Student's t-test: p ¼ 0.019). The lowervolumes of water required for Lot 1 trials correlate with a propor-tionately higher grease yield, as Lot 1 trials came to a boil muchmore quickly, facilitating rapid grease removal (Fig. 5).

Irrespective of fragment size, Lot 1 trials consistently had thelowest ratios of water to grease yield and fuel to grease yield; thatis, trials in Lot 1 required the least water and the least fuel to extracta unit (ml/kg) of grease (Table 1, Fig. 5). This was, on average,1.04 m3 (39.7 MJ) of fuel consumption and 34.7 ml water to everyml/kg grease on average. The Lot 1 Trials inadvertently set to halfgas flow were especially fuel-efficient, exhibiting even lower ratesof fuel consumption (see Discussion). Trial 13 in particular usedonly 13.4 MJ for every ml/kg grease. Lot 1's reduced volumes ofwater boiled off in as little as 150 min.

The proportionate grease yields for Trials 1 and 2 in Lot 1 are notavailable because the bone specimens were not weighed before thestart of the trials.

All seven trials in Lots 2 and 3 lasted the full six hours andconcluded with water still remaining in the pot. It took >90 min forLot 2 trials (4.0 L of water, at maximum fuel input) to come to a boil,while Lot 3 trials never reached a boil (4.0 L of water, at half fuelinput; Fig. 2). We should note that even though Lot 3 trials did notboil, they did reach temperatures high enough to facilitate somegrease extraction. Saturated fatty acids, which have higher meltingpoints than unsaturated fatty acids, are concentrated at higherlevels in upper limb bones relative to more distal elements. Stearicand palmitic acid are the most abundant saturated fatty acids inthese elements (Meng et al., 1969). The melting point of stearic acidis 69.9 �C, and 62.9 �C for palmitic acid (Beare-Rogers et al., 2001).While these are well below the boiling point of water, our half-flowexperiments rarely reached temperatures higher than 70 �C, pre-cluding a portion of the grease from melting and exiting the bone.

A.

B.

0

20

40

60

80

100

120

0 30 60 90 120 150 180 210 240 270 300 330 360 390

Time (minutes)

Lot 1 Trials

Trial 5: 1cm, 1850 ml

Trial 13: 1cm, 1500 ml

Trial 4: 2cm, 1750 ml

Trial 14: 2cm, 1475 ml

Trial 1: 4cm, 2750 ml

Trial 2: 4cm, 4500 ml

Trial 3: 4cm, 2500 ml

Trial 15: 4cm, 2100 ml

0

20

40

60

80

100

120

0 30 60 90 120 150 180 210 240 270 300 330 360 390

Time (minutes)

Lots 2 & 3 Trials

Lot 2, Trial 6: 1 cm

Lot 2, Trial 7: 2 cm

Lot 2, Trial 11: 4 cm

Lot 3, Trial 12: 1 cm

Lot 3, Trial 9: 2 cm

Lot 3, Trial 8: 4 cm

Lot 3, Trial 10: 4 cm

Fig. 2. Water temperatures of each trial. A: Lot 1. B: Lots 2 and 3 in degrees Celsius over the course of the experiment. 1 cm trials are indicated by black markers, 2 cm trials areindicated by gray markers, and 4 cm trials are indicated by open markers. Note the considerably steeper curves in A, which show a faster rise in temperature. Note temperature atwhich boiling was observed is roughly 90 �C for many trials. This is likely due to a malfunctioning thermometer, but we wish to include the trials because it cannot be discountedthat the presence of the bone material itself may have altered the boiling point in relation to volume.

A. Janzen et al. / Journal of Archaeological Science 49 (2014) 518e523 521

Irrespective of fragment size, Lot 2 trials used the greatestamount of fuel and required an intermediate amount of water perunit grease: 3.63 m3 (138.4 MJ) of fuel consumption and 75.2 mlwater to every ml/kg grease (Table 1). Lot 2 trials thus had thesecond highest grease yields but also required the greatest amountsof fuel. Trial 6 showed that a large amount of water covering thesmallest bone fragment size was the most energetically expensiveof all. Finally, Lot 3 trials proved to be the least water-efficient,though slightly more fuel-efficient than those in Lot 2 at 2.8 m3

(106.8 MJ) of fuel consumption and 131 ml water to every ml/kggrease. It should be noted that the 1 cm fragment size trials in Lots 2

and 3 have relatively lowgrease yields (ml/kg). Such low yieldsmaybe explained by variations in the nutritional status of the animals.Alternatively, at least in the case of Lot 3, the 1 cm fragment trialtookmuch longer to come to a boil and never reached temperaturesabove 70 �C, and it is possible that much of the grease still remainedin the bone.

5. Discussion

Both experimental (Lupo and Schmitt, 1997) and ethno-archaeological (Binford, 1978) data indicate that the cost of grease

0

0.5

1

1.5

2

2.5

0 1000 2000 3000 4000 5000

Rat

e of

tem

pera

ture

cha

nge

(/m

in)

Volume of water (mL)

Fig. 3. Correlation between water volume and rate of temperature change to boilingpoint. Pearson's r ¼ �0.844. Lot 1 trials are indicated by closed markers and Lot 2 trialsare indicated by open markers. Circles represent 1 cm trials, triangles represent 2 cmtrials, and diamonds represent 4 cm trials. Lot 3 trials are not represented here becausethey never came to a boil, and one never even reached temperatures high enough tomelt all saturated fatty acids. Note Lot 1, 4 cm outlier with a very high rate of tem-perature change is Trial #15, in which the gas setting was inadvertently set to half.

Fig. 4. Box plot showing amount of grease extracted (in ml of grease per kg of bone)for each class of bone fragment size in centimeters.

A. Janzen et al. / Journal of Archaeological Science 49 (2014) 518e523522

rendering by boiling is high, relative to the finite amount of greasecollected. Nonetheless, the fats are nutritionally significant,particularly during late winter and early spring in temperate andboreal zones, when stored food supplies are dwindling and driedplant foods and lean meat may become a principal source of energy

Table 1Results for all 15 trials. See Results section for discussion of N/A in Lots 1 and 3. *See Ma

Trial# Fragmentsize (cm)

Volume waterat start (ml)

Total waterused (ml)

Gas flow Grease yield(ml/kg)

Fue(m3

Lot 11 4 2750 2750 Full NA 982 4 4500 3760 Full NA 1203 4 2500 2500 Full 66.7 70.4 2 1750 1750 Full 56.0 58.5 1 1850 1812 Full 49.6 50.

13 1 1500 1415 Full 75.78 2714 2 1475 1385 Full 38.08 67.15 4 2100 2030 Full 42.11 41.

Lot 211 4 4000 3445 Full 54.9 1287 2 4000 3445 Full 42.8 1306 1 4000 1875 Full 22.8 125

Lot 38 4 4000 1300 Half 36.3 71.

10 4 4000 3660 Half 38.3 66.9 2 4000 3843 Half 15.6 48.

12 1 4000 2250 Half 15.5 68.

(Speth and Spielmann, 1983). Lipids do provide twice as muchenergy per gram as do carbohydrates and proteins, but theirmixture with low-fat foods even in small amounts assures trans-port of nutrients from other foods consumed across gut walls,warding off various forms of malnutrition as well as the viciouscycle of the energetic demands imposed by high levels of proteindigestion and the consequent raised metabolic rate (Speth andSpielmann, 1983). Moreover, animal fats' provision of EFA, espe-cially vital to pregnant and lactating females and to young childrenwith developing nervous systems, may justify the labor-intensivemanufacture of bone grease as well as rendering and storage ofother fatty animal products.

In sum, results of our study suggest that reducing the size ofbone fragments used in grease extraction facilitates the conserva-tion of fuel and water, as well as the human time and energeticcosts involved in collecting them. Bone fragments in Lot 1, to whichjust enough water was added to cover the fragments to a centi-meter depth, yielded the most grease in absolute terms, as well asin the most favorable ratios of fuel use and water to grease.

The intern error mentioned in Materials and Methods, whichreduced both fuel and airflows to two trials provided us with avaluable insight into the rest of our trials. We followed standard UCSanta Cruz lab safety parameters for the fume hood sash settings, tocomply with Environmental Health and Safety inspectors' specifi-cations. However, such standards were instituted to protect ex-perimenters from backflow of noxious chemical fumes, smoke, etc.with a strong airflow. For our experiment, this airflow was so briskthat the Bunsen burner flame was partly deflected from under thepot containing the specimens and water. In the “erroneous” trialsour interns set the sash to reduce airflow, which permitted more ofthe energy from the flame to transfer to the pot and water. The factthat these trials reached boiling in about the same time, while usingabout half the fuel, suggests that the “official” airflow settingcertainly reduced fuel efficiency. Thus, the intervals and rates offuel consumption at which all other trials came to boil should beseen asmaximum estimates, with Trials 13 and 15 hinting at a lowerrate of fuel consumption required to produce the same results.Stepping back from the experimental situation, we can assume thatgrease producers knew how to maximize fuel inputs by, amongother things, shielding fires from excessive wind. This could beaccomplished either by processing stockpiled bone fragments oncalm days or by rigging a windbreak on windy ones.

Church and Lyman (2003: 1083) end their article by asking,“whether or not the fat in extracted grease is the only resource

terials and Methods section for explanation of Trials 13 and 15 gas and airflow.

l consumed)

Boiling time (min) Fuel:greaseratio

Water:greaseratio

Fuel/minwhile boiling

207 N/A N/A 0.4734.9 270 N/A N/A 0.44786 150 1.06 37.5 0.47077 120 1.05 31.3 0.48928 105 1.02 36.5 0.4838

140 0.36 18.7 *0.19293 135 1.77 36.4 0.49857 180 0.99 48.2 *0.2317

.3 255 2.34 62.8 0.5031

.2 255 3.04 80.5 0.5106

.5 120 5.51 82.3 0.1046

6 0 1.98 35.9 N/A1 0 1.73 95.6 N/A6 0 3.12 247 N/A2 0 4.39 145 N/A

0

10

20

30

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50

60

70

80

0 1000 2000 3000 4000 5000

Gre

ase

Yiel

d (m

l/kg)

Volume of water (mL)

Fig. 5. Correlation between water volume and grease yield. Pearson's r ¼ �0.608. Lot 1trials are indicated by closed markers and Lot 2 trials are indicated by open markers.Lot 3 trials are indicated by gray markers. Figure excludes Trials 1 and 2, in whichinitial bone weight was not recorded.

A. Janzen et al. / Journal of Archaeological Science 49 (2014) 518e523 523

being pursued.” Our study suggests that other resources areimportant, and that the goal being pursuedmay not be restricted towhat is inside the container of bone scraps, that is, to nutritionalpayoffs. Rather, bone fragmentation materially may reflect timeand effort trade-offs by knowledgeable actors, aimed at maxi-mizing grease benefits while minimizing water and fuel costs. Asmany references cited in the introduction testify, bone greasemanufacture, gathering fuel and carrying water are ethnographi-cally documented as being predominantly the work of women. Thedecision to break bone into smaller fragments was thus likely tohave been informed by weighing the costs of gathering firewood,procuring water, and pounding bones against one another. Suchdecisions, often made by women in the midst of their reproductivecareers, would have had to balance a complex set of time, energy,and physiological demands (Charmes, 2006). Even if actors otherthan such women were involved in these tasks and trade-offs, the“resource” to which Church and Lyman allude may have comprisedtime and energetic budgets of the bone grease processors.

6. Conclusions

The results from this experiment unequivocally indicate thatbones come to a boil faster when less water is used, and thatsmaller bone fragments allow the amounts of water and fuel to beminimized, while shortening the boiling time and hence maxi-mizing the amount of grease extracted per unit of the processors'time. These data strongly suggest that the goals of reducing cookingtime and the costs of acquiring water and fuel, rather than a questfor non-lipid nutrients, are likely significant factors in bone frag-mentation decisions. Ethnographic cases implicate women in bonegrease extraction, as well as in gathering water and fuel, suggestingthat bone fragmentation results from tradeoffs in overall energyand time costs by actors engaged in the entire process of this formof nutrient capture. The study further suggests the value for ar-chaeologists of broadening their scope to include the cost-benefittradeoffs of food processing “outside the container,” to better un-derstand strategic decisions that structure the evidence recoveredfrom sites.

Acknowledgments

We wish to thank Anthropology Laboratories Manager RichardBaldwin for providing technical assistance at all stages of thisproject, and Bruce Tanner, Laboratory Specialist in the Department

of Earth and Planetary Sciences, for guidance and assistance withsawing. We thank the butchers at Corralitos Market and SausageCompany for the cattle femora. Spencer Frasher helped withremoval of soft tissue and bone sawing, and Alexis Garcia andRachel Dailey aided in boiling experiments. We thank R. Lee Lymanfor helpful comments and suggestions on a preliminary draft, andare grateful to the anonymous reviewers who offered insightfulfeedback. We wish to acknowledge Benjamin Broyles (CulturalResource Specialist, California Department of Transportation, Sac-ramento), who suggested during his 1998 undergraduate experi-ments in bone grease rendering at UC Santa Cruz that thermalinertia should be considered as a factor in bone grease rendering,which was an impetus to this experimentation.

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