Multi-Analytical Study on Excavated Human Bones in the Burial Environment at Shenna Ruins, Qinghai, China

Abstract

Excavated human bones are important materials for revealing information about ancient human food, the ancient environment and the ancient climate, and the origins of ancient humans. Often, the chemical composition and biological characteristics of bones have changed to varying degrees, which means that they are contaminated and cannot be used for further analysis. Through research on the correlation between human bones excavated from a burial environment and their state of preservation, judging whether the excavated bones are contaminated is a prerequisite for scientific analysis, environmental archeology, and research on ancient human recipes. In this paper, human bones excavated from the Shenna ruins and the contamination of them in the burial environment has been judged using craniofacial measurement characteristics, pH measurement, scanning electron microscopy–energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), Fourier transform red external light spectrum (FTIR), and stable isotope tests (SIT). However, the organic compositions of the remains at Shenna are decomposed to a large degree, and the inorganic structure has been destroyed, which will eventually cause looseness and porosity, and the compositions of inorganic minerals in the human bones have not been changed or contaminated. The results indicate that the burial environment at Shenna accelerated the deterioration of human bones, but it has not affected the typical character of the human bone, and the human bones extracted can still be used for further trace element testing. Moreover, this can help to reduce the effort required to reveal information about ancient human food, as well as the need for further studies of the paleoenvironment and paleoclimate in the Shenna ruins.

1. Introduction

The hard tissues of ancient humans, that is, their bones, are important materials for revealing information about ancient human food [1,2], the ancient environment and the ancient climate, as well as the origin of ancient humans. Through scientific analyses of their chemical composition, we can reveal the recipes used by ancient ancestors, reconstruct their way of life, and explore the ancient environment and human migration activities.

For most of the ancient human hard tissues that have been excavated, bioarcheology is mostly performed via morphological methods [3,4,5], and from the perspective of physical anthropology, through comparisons of the characteristics of human hard tissues, the archeologists can determine racial origins and pathology. Furthermore, after extracting trace elements from the excavated human bones, the archeologists can conduct scientific analyses to reveal the wealth of potential information contained in said bones.

Analyses of excavated ancient human bones are based on the assumption that with the passage of much time after death, the bones still retain their original chemical composition and biological characteristics. Nevertheless, the long time since burial of excavated human bones, the geological environment, soil, temperature, humidity, groundwater, and other factors, [6,7] have caused the isotope ratio and trace elements of the bones to change to varying degrees, and this process is called bone diagenesis [8,9,10]. The chemical compositions and biological characteristics of bones change to varying degrees in the process of diagenesis, which means they become contaminated. Therefore, judging whether excavated ancient human bones are contaminated is a prerequisite for scientific analysis, environmental archeology, and research on ancient human recipes.

The literature states that stable isotopes [11,12,13] are most commonly used as the basis for judging whether a bone is contaminated. However, the process of sample pretreatment and testing is complicated, and requires accurate operation, as well as there being certain requirements regarding sample size. When bones are contaminated, their chemical composition and biological characteristics will also change, as will their crystal structure and crystallinity. Focusing on these characteristics, some scholars have used X-ray diffraction [14], FTIR, laser Raman spectroscopy, as well as other methods [15] to analyze the contamination degree of human remains. In view of the special human cultural heritage represented by bone relics, in the long run, it is necessary to select a faster and more convenient analysis method for the protection of cultural heritage. Therefore, it is necessary to promote the study of the contamination of ancient human bones via X-ray diffraction.

This paper mainly focuses on the two human bones excavated at the Shenna ruins as the research object, using traditional morphological methods to undertake the craniofacial measurement of the excavated human bones, and to identify the degree of pollution of the human bone samples extracted, in order to determine whether they can be used in the scientific analysis of trace elements [16]. We aim to reveal the wealth of hidden information contained in the ancient human bones and provide a scientific basis for reconstructing the recipes of the ancestors buried at the Shenna site, as well as their ethnic information.

2. Overview of the Shenna Ruins

The Shenna ruin is located in the north of Xiaoqiao Village, Chengbei District, Xining City, Qinghai Province, as shown in Figure 1. In 2006, the State Council declared it as part of the sixth batch of national key cultural relic protection units. The ruin is located on a secondary terrace at the intersection of Huangshui and its tributary Beichuan River. The terrace is narrow from east to west and long from north to south. It is a long strip that is low in the south and high in the north, covering an area of about 100,000 square meters. Its archeological value is firstly represented by the fact that it was a hub within the corridor of cultural exchange between the Hexi Corridor and the Western Regions 4000 years ago, and communication via this route during the Qijia cultural period was the main avenue for the spread of Eastern and Western culture in that period. Secondly, the Qijia culture that dominated where the Shenna ruin is located represented an era of transformation and revolution, with a small representation of the cultures of Majiayao, Banshan, and Kayue; therefore, it is a representative settlement in this era of transformation and revolution. In 1992 and 2016, the Qinghai Provincial Institute of Cultural Relics and Archeology conducted archeological explorations and the excavation of 2000 square meters; the excavated area was 2 m thick, within which were discovered 171 houses, 358 ash pits, and 19 tombs. It was determined to be the site of a Qiang settlement from about 3500 years ago, and a wealth of relics were found here. Therefore, the archeological research into the Shenna ruins is of high value for understanding and researching the cultural exchanges undertaken between the East and the West during the transition from the Neolithic to the Bronze Age, as well as the lifestyles and ethnography of the ancestors in the Northwest.

3. Samples and Pretreatment

As

Table 1. Samples and multi-analytical methods.

Method	Sample	Status	Treatment	Purpose
craniofacial measurement	Human remains	skeleton	Clean surface attachments	biological characteristics
pH	Soil	powder	Grind the soil to a standard powder	Judge whether the burial environment is suitable for the preservation of remains by testing the pH of the soil
SEM	Human remains and pig bones [17,18]	fragments	Cut to standard size according to test sample requirements	Judge the preservation condition of excavated human bones by comparing the microscopic morphology of fresh pig bones and human remains
EDS	Human remains and soil	fragments	Cut to standard size according to test sample requirements	Judge whether the soil is filled in the microscopic morphology of the excavated human bones
FTIR	Human remains and pig bones	powder	Ashing	By comparing the positions and intensities of functional group peaks in the IR spectra, the decomposition degree of organic components and the preservation status of human remains were evaluated
XRD	Human remains	powder	Ashing	The contamination of bones can be judged by the change of inorganic mineral composition before and after ashing
Isotope	Human remains	ossein	Acid bath Alkali bath Dried in vacuum before ashing	The bone collagen in the remains can be judged by IRMS

shows, the human bones excavated at the Shenna ruins, and the contamination of them by the burial environment, was judged using craniofacial measurements, pH measurements, scanning electron microscopy–energy dispersive spectrometer (SEM-EDS) tests, X-ray diffraction (XRD), and the Fourier transform red external light spectrum (FTIR).

3.1. Bone Samples

In order to not damage archeological information during extraction, the remain fragments were selected that least affected the original appearance of the cultural relics. The fragments and soil samples were taken from the bottom of, and around, the burial pits at the Shenna ruins. In addition, pig bones purchased at the market were used as a comparison sample; the excess meat and skin on the pig bones were removed and rinsed with ultrapure water for later use. After exhumation, the bones were stored and sealed in plastic bags at 4 °C prior to analysis.

3.2. Pretreatment of the Samples

The remains were soaked in ultra-pure water and repeatedly cleaned ultrasonically until the soaking solution was colorless. Then, we soaked them in 5% acetic acid solution and continued ultrasonic cleaning for 10 min; we discarded the waste liquid and continued to soak in 5% acetic acid solution for at least 15 h. Finally, we rinsed the fragments with ultrapure water, ashed them at 725 °C for 8 h, cooled and dried them, and ground then into powder.

After the meat, cortex, and bone marrow were removed from the pig bones [14,19], the ultrasonic cleaning was continued to remove impurities. After soaking for several hours in ultrapure water, the samples were dried at 80 °C for at least 10 h. One part of the pretreated pig bone was ground into powder for use, and the other part was calcined at 725 °C for 8 h, cooled and dried, and then ground into powder for use. After exhumation, the bones were stored and sealed in plastic bags at 4 °C prior to analysis.

4. Experimental Methods

4.1. Analysis of Craniofacial Morphology of Excavated Skulls

The gender identification of the excavated human bones, as well as the observation and measurement of craniofacial morphological characteristics [20,21], made use of the standards and methods of Shao Xiangqing and Zhu Hong. The germline purity testing of skull measurement traits was performed via the comparison of skull length, skull width, and skull index standard deviation: the standard differences in skull length, skull width, and skull index in the skull group at the Shenna ruins was calculated, and the Pearson K and Morant GW were calculated to compare the standard deviation in skull length, skull width, and skull index in 2 groups of the same species.

4.2. Identification and Characterization

4.2.1. pH Measurement

The pH values of the soil were measured according to the regulations set out in the national standard “Determination of soil pH NY/T 1377-2007”: the distilled water was heated and boiled for 10 min and sealed with plastic wrap for later use. In total, 10.0 g ± 0.1 g of soil was added to 25 mL boiling water, sealed and stirred for 5 min, and left to stand for 1–3 h. Finally, after the supernatant was filtered with a Buchner funnel, the pH of each solution was tested using a pH meter (Sartorius PB-10, Sartorius Scientific Instruments Co., Ltd., Beijing, China).

4.2.2. Scanning Electronic Microscopy (SEM-EDS)

The micromorphologies of the surfaces of untreated and treated samples, as well as the char residues, were observed using a Hitachi SU3500 scanning electron micro-scope (SEM, Hitachi, Tokyo, Japan) with a conductive gold coating at a voltage of 10 KV. Equipped energy dispersive spectrometry (EDS) was used to analyze the elements.

4.2.3. X-ray Diffraction (XRD)

The samples of human bone and site soil were investigated by X-ray diffractiometry (Smart Lab (9), Nippon Science Corporation, Tokyo, Japan). The X-ray emission was assessed as the Cu K-alpha line operating at 40 kV and 30 mA. The scan ranged from 5 to 80, with a step interval of 0.05.

4.2.4. Fourier Transform Red External Light Spectrum (FTIR)

The Fourier transform red external light spectrum (FTIR) can be used to reflect the compositions and structural characteristics of materials. In this paper, FTIR technology was used to study the infrared spectral characteristics of bones to determine composition and structure [22,23], using an infrared spectrometer (PE-Frontier, PE company, Waltham, MA, USA) in the wavelength range of 400~4000 cm⁻¹.

The untreated samples were tested by SEM-EDS, while XRD and FTIR were used to analyze and compare the compositions before and after ashing.

4.2.5. Stable Isotope Test

Cleaning: We used a wire brush or Dremel tool for physical cleaning to remove surface contamination (dirt, stains, surface debris, oil stains that may be generated during previous treatment, etc.).

Acid bath: We then dissolved the sample in 0.2 mol/L hydrochloric acid (HCl) and soaked it at 21 °C for 12–24 h. We scraped off the outermost layer of the bone surface again in the acid bath (size permitting), because the outermost layer may have contained soil or fine root materials buried under the bone’s surface.

Alkali bath: We applied 1%–2% alkaline solution (NaOH solution with mass fraction 50%) until the solution was clear (indicating the effective removal of secondary organic matter, such as humic acid). After rinsing to neutrality, we performed a final pickling to remove any adsorbed carbon dioxide. During the entire process, all roots, organic debris, and minerals were removed. The purified collagen was rinsed to neutrality, dissected, and microscopically checked for cleanliness and uniformity.

Test: The cleaned colloidal collagen extract was dried in a vacuum before burning and was then analyzed by IRMS (Thermo Fisher Delta V Advantage, 50–40,000 mV) to derive the molar ratio of C and N (%C and %N) values of the extracted collagen and in this way determine whether they were within the expected range. The clean colloidal collagen extract was dried in a vacuum before burning. Then, the C and N molar ratio (%C and %N) values of the extracted collagen were analyzed by IRMS.

5. Result and Discussion

5.1. Observation Results of Skull Morphology

As shown in Figure 2, a protection shed covered the important foundations of the first excavated ruins and played an important role in protecting cultural relics. This was key to protecting areas, creating a semi-enclosed “indoor” environment. The internal humidity at the ruins is relatively high in the summer and the ventilation facilities are simple, with only the top window available for ventilation; the ventilation facilities thus cannot effectively improve the humidity conditions at the ruins. Therefore, the burial environment within a temporary protective greenhouse is characterized by high humidity and heat in the summer and dryness in the autumn and winter. The soluble salt in the soil moves with the water to cause salt precipitation, crispy powder, and other kinds of damage, which meant that the skull and facial bones of RG1 were incomplete, and only part of the left facial bone could be seen. The skull bone was relatively intact, as was the mandible. The facial bone on the right side of RG2 was mutilated; the skull was relatively intact, as was the mandible. However, all this does not affect the traditional skull morphology testing process, and traditional physical measurements can still be used to make archeological judgments.

The measurement data and non-measured characteristics of the skull at the Shenna ruins (

Table 2. The main index of the skull.

Items		RG1		RG2
		Index	Type	Index	Type
Cranial index		75.5	Mid-cranial	70.4	Long skull
Cranial height index		74.1	Ortho-cranial	77.2	Tall skull
Cranial width and height index		98.1	Narrow skull	109.6	Narrow skull
Forehead width		66.3	Mid-forehead	69.8	Generous
Foramen magnum index		90.4	Generous	-	-
Upper index		-	-	-	-
Orbital IndexⅠ	Left	83.8	Mid-orbit	-	-
	Right	-	-	82.6	Mid-orbit
Orbital IndexⅡ	Left	85.5	Mid-orbit	-	-
	Right	-	-	89.9	High orbit
Nose index		47.4	Mid-nose	-
Palatal index		85.4	Broad palate	-
Facial protrusion index		-	-	93.8 Orthognathic

and

Table 3. Non-measured characteristics of the skull at Shenna ruins.

Observation Items		RG1	RG2
Cranial shape		Oval	Oval
Eyebrow protrusion		Medium	Weak
Eyebrow bow range		<1/2	<1/2
Forehead		Medium	Medium
Cranial suture	Bregma section	Deep wave	Zigzag wave
	Top section	Deep wave	Zigzag wave
	Top hole section	Microwave	Deep wave
	Back section	Microwave	Zigzag wave
Mastoid		Small	Medium
Carina		Slightly obvious	Slightly obvious
Orbital		Square	-
Pear-shaped hole		Pear-shaped	Heart-shaped
Lower edge of pear-shaped hole		Anterior nasal fossa-shaped	Sharp
Nasal spines		Grade I	-
Canine fossa		Weak	Weak
Nasal depression		Shallow	Shallow
Wing area		Top butterfly-shaped	Top butterfly-shaped
Nasal bridge		-	Concave
Nasal bone		-	Type I
Top hole		No	All left and right
Sagittal crest		Weak	Medium
Forehead seam		No	No
Palatine		U type	V type
Palate pillow		Crest-shaped	-
Chin type		Pointed shape	Round shape
Mandibular angle		Eversion	Eversion
Mental hole position		P2 position	P2M1 position
Mandibular pillow		Small	-
Lower jaw of rocking chair		Obviously rocking chair	Slightly rocking chair

) show that the skull shape was mainly oval and elliptical, the eyebrow arch was underdeveloped, the orbital shape was square and rectangular, the nasal spines were not obvious, the canine fossa was weak, the nasal root was shallow, the pear-shaped hole was eccentric, and the pear-shaped lower edge of the hole was sharp. The remaining two lower jaws were rocking chair-type. The skulls were long, moderately high, and obviously narrow. The forehead width types were mainly wide-headed and medium forehead. The orbit was mainly of the middle orbit type and the low orbit type. The nose was moderate in width, with a mostly middle nose shape. The phylogenetic type seems to belong to the Mongolian race and have certain characteristics of the East Asian race.

As shown in Figure 3, most of the measurement data and corresponding indicators suggest the Mongolian race, but the skull width seen here is smaller than that in the common variation range; the skull width and height indices are too large, and RG1 and RG2’s width and height indices are greater than the variation range. The final judgment is that the skulls belong to the Mongolian race and have certain characteristics of the East Asian race. The craniofacial characteristics of the residents of the Shenna site are consistent with the lifestyles of the time in which they lived.

5.2. The pH Values of the Burial Environment

Studying the correlation between the characteristics of the excavated human bones and their preservation state and judging whether the excavated ancient human bones are contaminated is a prerequisite of scientific analysis and environmental archeology.

Table 4. The pH values of the burial environment at the ruins.

Sampling Location	pH			Average Value
RG2	8.16	8.10	8.14	8.13
Around RG2	7.87	7.91	7.87	7.88
Southwest RG2	8.15	8.14	8.14	8.14

shows that the pH values of the remains and of the burial environment ranged from 7.8 to 8.2, indicating that the bones at the Shenna ruins have been maintained in an alkaline environment for a long time. These conditions cannot easily preserve organic components, which has aggravated the corrosion of the remains. The pH value of the burial environment at the Shenna ruins is mostly neutral or alkaline, which is mainly a result of the fact that most of the soil contains Ca²⁺, which is consistent with the location of the Shenna ruins in the northwest of our country and its unique soil properties.

5.3. Microstructure and Composition

Figure 4a,c,e shows the sectional micromorphology of the remains, and Figure 4b,d,f show the sectional micromorphology of modern pig bones. Figure 4b,d,f show that the structure of pig bones consists of soft and flexible bone marrow, oil, and other organic matter closely intertwined with dense hard bone, which all interact with each other, yielding good mechanical properties such as pressure resistance and flexural resistance. However, the remains shown in Figure 4a are full of holes of different sizes [24], and there is almost no organic matter. Only loose trabeculae just about maintain the structure of the bone relics. It was also found that some of the holes in the remains shown in Figure 4c were filled with soil from the environment in which they were found, and it is assumed that the holes in the remains were formed via the decomposition that will have taken place over thousands of years. A close-up of Figure 4e shows that the walls of the pores are full of very small pores, which loosened the bones and caused decayed. We can thus infer that the mechanical strength of the remains decreased due to the influence of various factors; for example, organic matter typically suffers significant degradation, via water migration and other mechanisms, and the groundwater and soil provide suitable filling materials that further the erosion of bone, accelerating the process of becoming brittle, and directly causing the remains to appear crisp and undergo the pulverization phenomenon.

Energy dispersive spectrometry (EDS) analysis has been performed on the soil samples and buried human remains, and the test results are shown in Figure 5, revealing the types and percentages of elements contained in the soil samples. The top three elements present at the greatest abundance are oxygen, silicon, and calcium, with mass fractions of 44.69%, 16.50%, and 12.52%, respectively. It can be preliminarily inferred from the element types and contents that the main components of the soil at the Shenna ruins are quartz (SiO₂) and calcium carbonate (CaCO₃). As Figure 5 shows, the main contents in the bones are oxygen, calcium, and phosphorus, present at 38.77%, 38.59%, and 12.43%, respectively. In addition, the relative molar ratio of Ca/P may be as high as 2.4, which is inconsistent with the Ca/P ratio of uncontaminated bones seen in the literature. The content of calcium is much higher, and it is speculated that the much higher content of calcium may be the result of the high content of calcium carbonate in the soil of the Shenna ruins.

The remains are mainly composed of biogenic hydroxyapatite. Hydroxyapatite is generally present in fresh bone in a weak crystalline state. After burial, some amorphous hydroxyapatite will adopt a crystalline structure through diagenesis, resulting in increased crystallinity. The structure and composition of apatite will change during burial and diagenesis. XRD analysis can provide a basis for determining whether the bones are contaminated, and whether they can be used for further element analysis, as shown in Figure 6c, which shows the XRD spectrum peaks of the soil. The corresponding PDF card information shows that the soil is mainly composed of quartz SiO₂ and limestone CaCO₃, which is consistent with the element composition and content data yielded by EDS analysis, and this also explains the alkaline pH of the soil. The content of CaCO₃ in the soil also proves that the presence of Ca in the EDS test results for the surface of the remains is too high. The data on the remains before and after ashing (shown in the PDF card), and Figure 6a, show the characteristic peaks of calcium hydroxyphosphate (Ca₁₀(PO₄)₆(OH)₂), while in pig bones before and after ashing, the characteristic peak is (Ca₁₀(PO₄)₅CO₃(OH)), and this is due to the frequent occurrence of the CO₃²⁻ to PO₄³⁻ ion substitution phenomenon in organisms. The crystal structure of hydroxyapatite will not be destroyed by this substitution, and it is not affected by chemical pollution, so we can infer that it is normal substitution.

In the comparison of the X-ray diffraction (XRD) data of the remains and the pig bone samples before and after ashing, we can see that the half high width value of the XRD characteristic peaks is smaller than that of the unashed sample. The diffraction peaks of the sample after chemical treatment become stronger and sharper, indicating that ashing [25] will not only burn off organic components, but will also improve the crystallinity of hydroxyapatite, as changes in the phase and microstructure of hydroxyapatite can cause significant changes, and ashing can eliminate this effect. The diffraction peaks of pig bones are noticeably broader before ashing; that is, the crystallinity is poor, but the diffraction peaks after the ashing treatment are obviously changed. After the remains were ashed, the intensity and sharpness of the XRD diffraction peaks were significantly improved. This also proves that the samples in this paper were not contaminated and can still be used for meaningful scientific research. At the same time, the characteristic peaks of hydroxyapatite in the XRD spectrum show strong and sharp signals. It can thus be further concluded that although being buried for thousands of years has a certain stimulating effect on the decomposition of organic matter in bone samples, the influence of this process on the composition of inorganic substances is relatively weak.

In the infrared spectrum [26,27,28,29,30], 3576 cm⁻¹ is the absorption vibration peak of -OH [31], which appears in all curves, and the peak deformation of curves B and D sharpen after high-temperature ashing. The symmetric and asymmetric stretching vibration peaks of C-H in methylene are 2853 cm⁻¹ and 2924 cm⁻¹ [32]; 1746 cm⁻¹ is the stretching vibration absorption peak of ester carbonyl C=O [33], and 1662 cm⁻¹ is the stretching vibration peak of amide I [26]. This is because the p-π conjugation of the unshared electron pair on the nitrogen atom and carbonyl group is larger than the electron absorption induction effect of the nitrogen atom. The vibration peak of amide II at 1543 cm⁻¹ [31] is caused by the in-plane deformation vibration of NH₂, indicating the presence of grease, bone marrow, protein, and other substances in the pig bone, but these do not appear in curves B and D. This is because the organic components in the bone were burned at high temperatures in the process of ashing, so the infrared spectrometer did not capture the signal. However, the relatively weak vibration peaks of amides I and II appear in curve A, indicating that the remains still retained a small amount of organic matter, after thousands of years of burial. The vibration peak of CO₃²⁻ was found near 1455 cm⁻¹, which appeared in both curves A and B. However, only the characteristic peak of Ca₁₀(PO₄)₆(OH)₂ was detected in the XRD patterns of the remains before and after ashing. This may be because the characteristic peak of PO₄³⁻ was too strong, and it masked the vibration peak of CO₃²⁻. The peak at 873 cm⁻¹ was attributed to HPO₄²⁻, as is consistent with findings in the literature that fresh bone contains a small amount of CaHPO₄·2H₂O. All curves show strong and sharp characteristic peaks at 1037 cm⁻¹, 564 cm⁻¹, and 604 cm⁻¹, representing the existence of PO₄³⁻. This indicates that the organic components of the remains are largely decomposed due to various factors, even in the underground environment, which eventually gives rise to the loose and porous structure of the remains and the deterioration of their mechanical properties. However, the compositions of inorganic minerals were not changed or contaminated, and the human bones extracted could still be used for further trace element testing.

5.4. Stable Isotope Test

Regardless of whether the archeological bone samples are contaminated by environmental influences, the most important indicator is generally believed to be the content and molar ratio of C and N isotopes [34,35] in the collagen extracted from the remains, and there are strict standards for the assessment of this. The value of C:N (as shown in

Table 5. Samples’ C and N contents and stable isotope ratios.

Sample	Ingredient	%C	%N	C:N
RG1	Ossein	40.78	15.11	3.1
RG2	Ossein	41.55	15.42	3.1

) should be in the range of 2.9–3.6; values outside this range are considered to represent a contaminated sample, but this standard has since been refined to 3.29 +/− 0.27 by van Klinken based on experimental data. Regarding the contents of C and N isotopes, it is generally considered that the C content should be about 35%, and the N content should be 11%–16%; nether should be too high, exceeding the C and N contents in fresh samples (43% and 16%), as this is considered contamination.

It is obvious from the data in Table 5 that the samples in this study contain C and N elements, and the contents and ratios of C and N isotopes in RG1 and RG2 are 40.78%, 15.11%, 3.1 and 41.55%, and 15.42% and 3.1, respectively, all of which fall within the normal range, which indicates that although the bone collagen in the remains has undergone much degradation, it has not been contaminated, and still maintains the original biological, physical and chemical properties. This means that further recipe analyses and in-depth testing can be performed.

6. Conclusions

Most excavated relics are closely related to their surrounding burial environment. Since excavated human bones are important materials for revealing information about ancient human food, the ancient environment and the ancient climate, as well as the origins of ancient humans, contamination resulting from the burial environment means the chemical compositions change to varying degrees as a result of diagenesis. This paper takes the human bones excavated at the Shenna ruins as the research object, and the contamination of the burial environment was judged using multi-analytical methods. The results indicate that the burial environment at Shenna did accelerate the deterioration of human bones, but it has not affected the typical human bone character, and the human bones extracted can still be used for further trace element testing. The results show that the bone collagen in the remains has undergone much degradation, but it has not been contaminated, and still maintains its original biological, physical, and chemical properties, meaning that further recipe analyses and other in-depth testing can be undertaken. Moreover, the multi-analytical study of the contamination of excavated human bones could help reduce the wasting of energy via unnecessary further studies on ancient human food at the Shenna ruins.