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Quantifying Archaeology
This book introduces archaeologists to the most important quantitative methods, from the initial description of archaeological data to techniques of multivariate analysis.These are presented in the context of familiar problems in archaeological practice, an approach designed to illustrate their relevance and to overcome the fear of mathematics.
eBook
Climate effects on archaic human habitats and species successions
It has long been believed that climate shifts during the last 2 million years had a pivotal role in the evolution of our genus
Homo
1
–
3
. However, given the limited number of representative palaeo-climate datasets from regions of anthropological interest, it has remained challenging to quantify this linkage. Here, we use an unprecedented transient Pleistocene coupled general circulation model simulation in combination with an extensive compilation of fossil and archaeological records to study the spatiotemporal habitat suitability for five hominin species over the past 2 million years. We show that astronomically forced changes in temperature, rainfall and terrestrial net primary production had a major impact on the observed distributions of these species. During the Early Pleistocene, hominins settled primarily in environments with weak orbital-scale climate variability. This behaviour changed substantially after the mid-Pleistocene transition, when archaic humans became global wanderers who adapted to a wide range of spatial climatic gradients. Analysis of the simulated hominin habitat overlap from approximately 300–400 thousand years ago further suggests that antiphased climate disruptions in southern Africa and Eurasia contributed to the evolutionary transformation of
Homo heidelbergensis
populations into
Homo sapiens
and Neanderthals, respectively. Our robust numerical simulations of climate-induced habitat changes provide a framework to test hypotheses on our human origin.
A new model simulation of climate change during the past 2 million years indicates that the appearances and disappearances of hominin species correlate with long-term climatic anomalies.
Journal Article
Pressure flaking to serrate bifacial points for the hunt during the MIS5 at Sibudu Cave (South Africa)
Projectile technology is considered to appear early in the southern African Middle Stone Age (MSA) and the rich and high resolution MSA sequence of Sibudu Cave in KwaZulu-Natal has provided many new insights about the use and hafting of various projectile forms. We present the results of a functional and technological analysis on a series of unpublished serrated bifacial points recently recovered from the basal deposits of Sibudu Cave. These serrated tools, which only find equivalents in the neighbouring site of Umhlatuzana, precede the Still Bay techno-complex and are older than 77 ka BP. Independent residue and use-wear analyses were performed in a phased procedure involving two separate analysts, which allowed the engagement between two separate lines of functional evidence. Thanks to the excellent preservation at Sibudu Cave, a wide range of animal, plant and mineral residues were observed in direct relation with diagnostic wear patterns. The combination of technological, wear and residue evidence allowed us to confirm that the serration was manufactured with bone compressors and that the serrated points were mounted with a composite adhesive as the tips of projectiles used in hunting activities. The suite of technological and functional data pushes back the evidence for the use of pressure flaking during the MSA and highlights the diversity of the technical innovations adopted by southern African MSA populations. We suggest the serrated points from the stratigraphic units Adam to Darya of Sibudu illustrate one important technological adaptation of the southern African MSA and provide another example of the variability of MSA bifacial technologies.
Journal Article
The weighted sitting closer to friends than enemies problem in the line
The weighted
Sitting Closer to Friends than Enemies
(SCFE) problem is to find an injection of the vertex set of a given weighted graph into a given metric space so that, for every pair of incident edges with different weight, the end vertices of the heavier edge are closer than the end vertices of the lighter edge. The
Seriation
problem is to find a simultaneous reordering of the rows and columns of a symmetric matrix such that the entries are monotone nondecreasing in rows and columns when moving towards the diagonal. If such a reordering exists, it is called a
Robinson
ordering. In this work, we establish a connection between the SCFE problem and the Seriation problem. We show that if the
extended adjacency matrix
of a given weighted graph
G
has no Robinson ordering then
G
has no injection in
R
that solves the SCFE problem. On the other hand, if the extended adjacency matrix of
G
has a Robinson ordering, we construct a polyhedron that is not empty if and only if there is an injection of the vertex set of
G
in
R
that solves the SCFE problem. As a consequence of these results, we conclude that deciding the existence of (and constructing) such an injection in
R
for a given
complete
weighted graph can be done in polynomial time. On the other hand, we show that deciding if an
incomplete
weighted graph has such an injection in
R
is NP-Complete.
Journal Article
Uncertainty of Line-of-sight Velocity Measurements of Faint Stars from Low- and Medium-resolution Optical Spectra
Massively multiplexed spectrographs will soon gather large statistical samples of stellar spectra. The accurate estimation of uncertainties on derived parameters, such as the line-of-sight velocity v los, especially for spectra with low signal-to-noise ratios (S/Ns), is paramount. We generated an ensemble of simulated optical spectra of stars as if they were observed with low- and medium-resolution fiber-fed instruments on an 8 m class telescope, similar to the Subaru Prime Focus Spectrograph, and determined v los by fitting stellar templates to the simulated spectra. We compared the empirical errors of the derived parameters—calculated from an ensemble of simulations—to the asymptotic errors determined from the Fisher matrix, as well as from Monte Carlo sampling of the posterior probability. We confirm that the uncertainty of v los scales with the inverse square root of the S/N, but also show how this scaling breaks down at low S/N and analyze the error and bias caused by template mismatch. We outline a computationally optimized algorithm to fit multiexposure data and provide a mathematical model of stellar spectrum fitting that maximizes the so called significance, which allows for calculating the error from the Fisher matrix analytically. We also introduce the effective line count, and provide a scaling relation to estimate the errors of v los measurements based on stellar type. Our analysis covers a range of stellar types with parameters that are typical of the Galactic outer disk and halo, together with analogs of stars in M31 and in satellite dwarf spheroidal galaxies around the Milky Way.
Journal Article
Food Reconstruction Using Isotopic Transferred Signals (FRUITS): A Bayesian Model for Diet Reconstruction
Human and animal diet reconstruction studies that rely on tissue chemical signatures aim at providing estimates on the relative intake of potential food groups. However, several sources of uncertainty need to be considered when handling data. Bayesian mixing models provide a natural platform to handle diverse sources of uncertainty while allowing the user to contribute with prior expert information. The Bayesian mixing model FRUITS (Food Reconstruction Using Isotopic Transferred Signals) was developed for use in diet reconstruction studies. FRUITS incorporates the capability to account for dietary routing, that is, the contribution of different food fractions (e.g. macronutrients) towards a dietary proxy signal measured in the consumer. FRUITS also provides relatively straightforward means for the introduction of prior information on the relative dietary contributions of food groups or food fractions. This type of prior may originate, for instance, from physiological or metabolic studies. FRUITS performance was tested using simulated data and data from a published controlled animal feeding experiment. The feeding experiment data was selected to exemplify the application of the novel capabilities incorporated into FRUITS but also to illustrate some of the aspects that need to be considered when handling data within diet reconstruction studies. FRUITS accurately predicted dietary intakes, and more precise estimates were obtained for dietary scenarios in which expert prior information was included. FRUITS represents a useful tool to achieve accurate and precise food intake estimates in diet reconstruction studies within different scientific fields (e.g. ecology, forensics, archaeology, and dietary physiology).
Journal Article
Ambiguous landscapes: A framework for assessing robustness and uncertainties in archaeological point pattern analysis
Landscape research in archaeology has greatly benefited from the increasing application of computational methods over the last decades. Spatial statistical methods such as point pattern analysis have been particularly revolutionary. Archaeologists have used point pattern analysis to explore spatial arrangements and relations between ‘points’ (e.g., locations of artefacts or archaeological sites). However, the results obtained from these techniques can be greatly affected by the uncertainty coming from the fragmentary nature of archaeological data, their irregular distribution in the landscape, and the working methods used to study them. Furthermore, the quantification of uncertainty in spatial data coming from non-systematic surveys has never been fully addressed. To overcome this challenge, archaeologists have increasingly relied on applying advanced methods from statistics, data science, and geography. While the application of advanced methods from formal sciences will provide robustness to models based on uncertain datasets, as with uncertainty, robustness must be assessed in relation to the case study, the regional context, and the methods used. These issues are of great importance when the models from advanced methods are directly used to create narratives about past landscapes. In this paper, we gather previous research on uncertainty quantification in archaeology and formalize its best practices into a framework to assess robustness and uncertainty in spatial statistical models, particularly focusing on one commonly used in the discipline, i.e., the Pair Correlation Function. This framework allows us to understand better how incomplete data affect a model, quantify the model uncertainties, and assess the robustness of the results achieved with spatial point processes.
Journal Article
Archaeology of random recursive dags and Cooper-Frieze random networks
We study the problem of finding the root vertex in large growing networks. We prove that it is possible to construct confidence sets of size independent of the number of vertices in the network that contain the root vertex with high probability in various models of random networks. The models include uniform random recursive dags and uniform Cooper-Frieze random graphs.
Journal Article
NLTE Analysis of Y i and Y ii in the Atmospheres of FGK Stars
The nonlocal thermodynamical equilibrium (NLTE) line formation of Y i and Y ii is considered in 1D LTE model atmospheres of FGK-type stars. The model atom was constructed with the most up-to-date atomic data, including quantum cross sections and rate coefficients for transitions in inelastic collisions of Y i and Y ii with hydrogen atoms. For seven reference stars, we obtained an agreement between NLTE abundances inferred from the two ionization stages, while the difference in LTE abundance (Y i and Y ii) can reach up to −0.31 dex. In the atmospheres of FGK-type stars, for both Y i and Y ii lines, the NLTE abundance corrections are positive. In solar metallicity stars, the NLTE abundance corrections for Y ii lines do not exceed 0.12 dex, while in atmospheres of metal-poor stars, they do not exceed 0.21 dex. For Y i lines, the NLTE abundance corrections can reach up to ∼0.5 dex. We determined the yttrium NLTE abundances for a sample of 65 F and G dwarfs and subgiants in the −2.62 ≤ [Fe/H] ≤ +0.24 metallicity range, using high-resolution spectra. For stars with [Fe/H] ≤ −1.5, [Y/Fe] versus [Fe/H] diagram reveals a positive trend with an average value of [Y/Fe] ≃ 0. For metal-poor stars, among Sr, Y, and Zr, the arrangement [Sr/Fe] < [Y/Fe] < [Zr/Fe] remains consistent. The current study is useful for Galactic chemical evolution research. The model atom will be applied for NLTE yttrium abundance determination in very metal-poor stars studied with LAMOST and Subaru.
Journal Article