Level 3, Lesson 2: Advanced Archaeological Chronology and Bayesian Dating Models

Complete Archaeology Learning Program

LEVEL 3 · LESSON 2 · ADVANCED ARCHAEOLOGICAL CHRONOLOGY

Advanced Archaeological Chronology and Bayesian Dating Models

Radiocarbon Calibration, Stratigraphic Sequences, Bayesian Probability, Chronological Uncertainty, and Scientific Interpretation

Introduction

Establishing when ancient events occurred is one of the most important tasks in archaeology.

Archaeologists must determine not only the age of an object, but also the timing of activities such as settlement construction, occupation, burning, abandonment, burial, and environmental change.

Scientific dating techniques provide measurements associated with particular physical events. Archaeological context provides information about how those dated events relate to human activities.

A radiocarbon date from a charcoal fragment, for example, may help establish the age of a deposit. But the measurement does not automatically reveal when a building was constructed or when a settlement was abandoned.

Advanced chronological research combines scientific measurements with stratigraphy, historical information, and statistical models.

Bayesian chronological modeling provides a formal method for combining dating evidence with independently justified archaeological relationships.

It can improve chronological estimates, but it cannot correct poor excavation records, unsuitable samples, or unsupported assumptions.

Learning objectives

After completing this lesson, students should be able to:

1. Distinguish calendar dates, radiocarbon ages, and dated archaeological events.

2. Explain radiocarbon calibration and calibration-curve uncertainty.

3. Understand Bayesian probability, prior information, likelihoods, and posterior distributions.

4. Construct chronological models using stratigraphic sequences.

5. Interpret modeled boundaries, phases, and outliers.

6. Evaluate radiocarbon, OSL, TL, and other chronological evidence together.

7. Understand chronological uncertainty and model sensitivity.

8. Examine chronological research questions from Pakistan and Afghanistan.

9. Complete four non-destructive exercises.

10. Pass a 10-question examination.

2.1 Why advanced chronology is necessary

A single archaeological site may contain dozens or hundreds of chronological observations.

These may include:

• Radiocarbon measurements from charcoal, seeds, bone, or other suitable carbon-bearing material.

• Luminescence ages from sediments or fired objects.

• Tree-ring dates from preserved timber.

• Stratigraphic relationships.

• Dated inscriptions or historical documents.

• Coins and other chronologically diagnostic artifacts.

• Evidence of construction, repair, reuse, and abandonment.

Each observation may date a different event.

Example: Dating a building

Imagine a building containing:

Evidence	What it may date
Charcoal beneath a foundation	Burning or formation of an earlier deposit
Wood incorporated into a wall	Growth or death of the wood, not necessarily wall construction
Short-lived seed sealed in a construction deposit	Potentially close to deposition if association is secure
Charcoal from an occupation floor	Burning or deposition during occupation, subject to residuality
Coin in a later floor deposit	A possible terminus post quem for that deposit
Sediment covering collapsed walls	Deposition after collapse, if stratigraphic relationships are secure

A chronological model should respect the actual events represented by the evidence.

2.2 Relative chronology and absolute dating

Relative chronology establishes the order of events without necessarily assigning calendar dates.

Chronometric dating uses scientific measurements to estimate the age of specified events.

The term absolute dating is common, but it can be misleading because most scientific ages have uncertainty.

Figure 2.1 — Relative sequence

Hypothetical undisturbed sequence. The ordering is relative; no calendar dates have been established by the diagram alone.

Terminus post quem and terminus ante quem

A terminus post quem (TPQ) is the earliest possible date after which an event or deposit could have occurred.

A terminus ante quem (TAQ) is the latest possible date before which an event must have occurred.

For example, a coin minted in 200 CE and securely deposited in a floor foundation provides a TPQ for the deposition: the foundation cannot have been deposited before that coin existed.

The foundation may nevertheless have been constructed many years after 200 CE.

2.3 Radiocarbon dating: Scientific foundation

Radiocarbon dating uses the radioactive isotope carbon-14.

Living organisms exchange carbon with their environment. Following the end of carbon exchange, radiocarbon decreases through radioactive decay.

The fundamental decay relationship is:

N(t)=N_(0)e^(-λ t)

where:

• N(t) is the remaining number of radioactive atoms.

• N_(0) is the initial number.

• λ is the decay constant.

• t is elapsed time.

The physical half-life of carbon-14 is approximately 5,730 years.

t_(1/2)=(ln 2) / (λ)

Radiocarbon age versus calendar age

A conventional radiocarbon age is expressed in radiocarbon years BP, where BP means before 1950 CE.

A radiocarbon result such as:

3500 ± 30 ^(14)C BP

is not equivalent to a calendar date obtained by subtracting 3,500 years from 1950.

Conventional radiocarbon ages are calculated under defined conventions, including the historical Libby half-life, isotopic fractionation corrections, and reporting standards.

Calendar interpretation requires calibration.

2.4 Radiocarbon calibration

Atmospheric radiocarbon concentrations have varied over time.

Consequently, the relationship between radiocarbon age and calendar age is not a straight line.

Calibration uses independently dated reference material to translate radiocarbon measurements into probability distributions of calendar ages.

The internationally developed IntCal20 covers approximately 0–55,000 calibrated years BP. Its recent portion relies heavily on precisely dated tree-ring records, while older portions integrate several types of geological and environmental archives.

Cambridge Core

Figure 2.2 — Why calibration produces uncertainty

Conceptual calibration curve, not IntCal20 numerical data. Irregularities and plateaus in the real curve can produce broad or multiple calendar-age ranges.

Calibration plateaus

When a calibration curve is relatively flat, several calendar years may correspond to very similar radiocarbon ages.

This reduces chronological precision even when the laboratory measurement is precise.

A radiocarbon result with a small laboratory error does not necessarily produce a narrow calibrated date range.

Calibration intervals

Results are commonly summarized using probability ranges containing approximately:

• 68.3% probability.

• 95.4% probability.

These may consist of more than one disconnected calendar interval.

A reported 95.4% range should not be described as the single most likely year.

Appropriate calibration curves

Sample type	Common calibration approach
Terrestrial material from the Northern Hemisphere	IntCal20, where appropriate
Terrestrial material from the Southern Hemisphere	SHCal20, where appropriate
Marine organisms	Marine20 with appropriate regional reservoir treatment
Mixed marine–terrestrial diets	Model the relevant mixture and reservoir uncertainties

The correct choice depends on the carbon source, environmental context, and assumptions about reservoir effects.

2.5 Bayesian probability: The foundation

Bayesian statistics provides a formal method for updating the probability of a hypothesis when new evidence becomes available.

Bayes' theorem is:

P(H | D)=(P(D | H)P(H)) / (P(D))

where:

• H is a hypothesis.

• D is observed data.

• P(H) is the prior probability.

• P(D | H) is the likelihood.

• P(H | D) is the posterior probability.

• P(D) is the normalizing probability of the evidence.

Archaeological meaning

Prior information: Independently supported knowledge, such as stratigraphic ordering.

Likelihood: How compatible a proposed calendar age is with the dating measurement and calibration curve.

Posterior distribution: The resulting probability distribution after combining prior information and measurement evidence.

Example

Two samples come from securely recorded layers.

The lower layer is older than the upper layer.

This stratigraphic relationship is independent chronological information that can be included in a Bayesian model.

The model evaluates possible calendar dates consistent with both the dating measurements and the stratigraphic ordering.

Figure 2.3 — Bayesian chronological reasoning

Bayesian modeling does not mean choosing dates that fit a preferred historical narrative. Priors must be justified independently of the results they are intended to explain.

2.6 Likelihood functions and chronological constraints

For a simplified normally distributed laboratory measurement r with uncertainty σ, a calendar date t can be assigned a likelihood proportional to:

L(t) ∝ exp [-((r-C(t))^(2)) / (2(σ^(2)+σ_(C)(t)^(2)))]

Here C(t) is the expected radiocarbon age from the calibration curve, and σ_(C)(t) represents its uncertainty.

This expression illustrates the basic principle; professional calibration software accounts for additional details and dependencies.

The posterior distribution is obtained by combining the likelihood with the prior model and normalizing over the permitted chronological possibilities.

Chronological ordering constraints

Suppose events A, B, and C occurred in that order.

A model can impose:

t_(A)<t_(B)<t_(C)

when t increases forward in calendar time.

When using BP ages, older events have larger numerical ages, so the inequality direction reverses.

Mixing BP, BCE, and CE without an explicit convention is a common source of chronological mistakes.

2.7 Bayesian phases, sequences, and boundaries

Chronological models often distinguish three concepts.

Sequence: Events whose order is known or constrained.

Phase: A collection of events belonging to a period of activity, without requiring an exact order among them.

Boundary: A modeled transition such as the beginning or end of a phase.

Figure 2.4 — Model structure

Illustrative phase model. The three samples are not assumed to have a known order within the phase.

A modeled boundary is not necessarily a directly dated event

A start boundary may be inferred from a group of dated samples.

Its estimate depends on the sampling strategy, model assumptions, and how closely the dated material represents the true beginning of activity.

If the earliest occupation was not sampled, the estimated boundary may be misleading.

Duration estimates

A model may estimate the duration of an occupation phase:

D=t_(end)-t_(start)

when dates are expressed on a forward-running calendar axis.

The uncertainty of the duration must be calculated from the joint posterior distribution. It should not be inferred simply by subtracting two separately reported interval endpoints.

2.8 Bayesian outliers and problematic samples

Not every radiocarbon measurement accurately dates the archaeological event of interest.

Possible problems include old wood, residual material, intrusive deposits, contamination, reservoir effects, and incorrect context assignments.

Old-wood effect

Charcoal from the inner portion of a long-lived tree can be centuries older than the event in which the wood was burned.

Residuality

Older material may be redeposited into a younger archaeological layer.

Intrusion

Younger material may enter an older deposit through roots, burrowing animals, later pits, or other disturbance.

Outlier modeling

Some Bayesian approaches allow a date to have a specified probability of being an outlier.

This helps investigate whether a measurement is inconsistent with the main model.

However, an outlier model is not a license to discard inconvenient evidence.

A scientifically defensible report should document the original measurements, the reason for concern, model settings, and sensitivity to alternative assumptions.

2.9 Model diagnostics and sensitivity testing

A Bayesian model should be evaluated, not merely run.

Important questions include:

• Are the stratigraphic constraints supported by field records?

• Are the dated samples appropriate for the events being modeled?

• Are the calibration curve and reservoir assumptions suitable?

• Do the dates fit the model reasonably?

• Are the posterior estimates strongly influenced by a few samples?

• Do conclusions change when uncertain assumptions are modified?

A narrower posterior distribution is not automatically a more accurate chronology.

A model may produce artificially precise results if its prior constraints are too restrictive.

Sensitivity testing

Researchers can compare alternative models:

Model	Assumption
Model A	All dated samples belong to one occupation phase
Model B	Samples belong to two sequential phases
Model C	One potentially residual charcoal sample is modeled as an outlier
Model D	An uncertain stratigraphic relationship is removed

Differences between results help reveal how much the conclusions depend on the assumptions.

2.10 Pakistan case study — Mehrgarh and a major chronological reassessment

Mehrgarh is central to research on early farming and settlement development in northwestern South Asia.

For many years, the early aceramic Neolithic occupation was commonly associated with dates extending back to approximately the eighth millennium BCE, although published chronological schemes have varied.

A peer-reviewed study published in Scientific Reports in 2025 reassessed this chronology using radiocarbon measurements from tooth enamel associated with 23 Neolithic burials and Bayesian modeling.

The researchers estimated that the aceramic Neolithic cemetery began between approximately 5200 and 4900 BCE and lasted roughly two to five centuries, substantially later than some earlier proposed chronologies.

Scientific Reports

Why this case matters

This is an important example of how new measurements and explicit chronological modeling can challenge long-established archaeological interpretations.

The study does not mean that every archaeological phase, burial, or occupation deposit at Mehrgarh has now been independently dated to the same narrow interval.

Its conclusions concern the sampled material, archaeological associations, and the chronological model used.

Scientific questions for students

1. What event does the dated tooth enamel most directly represent?

2. How securely does that event relate to the burial?

3. What stratigraphic and archaeological assumptions were used?

4. How were the calibration and modeling procedures implemented?

5. How sensitive are the proposed phase boundaries to sample selection?

The first question is especially important. Human tooth enamel formation precedes death, sometimes by many years. Radiocarbon dating of enamel therefore does not directly measure the moment of burial.

Comparison of chronological interpretations

Figure 2.5 — Mehrgarh chronology: Historical proposals and new evidence

Earlier interpretations placed the beginning of aceramic Neolithic activity substantially earlier than the new cemetery model.

The 2025 study proposes a younger beginning for the sampled cemetery, with important implications for regional interpretations of early farming.

The compared estimates do not necessarily date identical archaeological events. The newer cemetery estimate should not be substituted uncritically for the entire site's occupational chronology.

The earlier chronology summarized in UNESCO's tentative-list description also differs from some older eighth-millennium BCE claims, illustrating why researchers must cite the exact source and phase definition used.

UNESCO World Heritage Centre

2.11 Pakistan case study — Indus civilization chronology

Harappa and Mohenjo-daro illustrate the complexity of dating long-lived urban settlements.

Archaeological layers may contain evidence of construction, rebuilding, flooding, occupation, craft production, and abandonment.

A chronological study might ask whether two neighborhoods were occupied simultaneously or whether particular construction phases followed one another.

Appropriate approach

Use securely recorded short-lived samples where available, establish stratigraphic relationships, compare material-culture phases, and test alternative chronological models.

Avoid assuming that every artifact associated with a cultural phase was manufactured in exactly the same year.

The terms Early Harappan, Mature Harappan, and Late Harappan refer to broad archaeological periods and regional developments, not single events with perfectly sharp boundaries everywhere.

2.12 Afghanistan case study — Balkh River palaeochannels

A study published in the Journal of Archaeological Science investigated former channels of the Balkh River in northern Afghanistan.

Fouache and colleagues combined geomorphological mapping, archaeological observations, and luminescence dating to examine relationships between changing river courses and human occupation since the Bronze Age.

ScienceDirect

Chronological significance

A dated alluvial deposit may help constrain when sediment accumulated.

But it does not necessarily date the beginning or end of an entire river channel's activity.

A Bayesian chronological investigation could combine multiple sediment ages with stratigraphic relationships and archaeological constraints, provided the dating processes and error structures are modeled appropriately.

Important: The published Balkh study is an example of integrated geoarchaeological chronology. The hypothetical Bayesian models described in this lesson are teaching proposals, not claims that the authors used those particular models.

2.13 Afghanistan case study — Bamiyan and archaeological phase dating

Bamiyan Valley contains complex archaeological remains representing different activities and periods.

Chronological research may involve the dating of organic material associated with wall paintings, archaeological deposits, architectural phases, and other contexts.

A responsible model would distinguish the age of a pigment binder, the preparation of a plaster layer, the painting event, later repairs, and eventual abandonment.

These events may not be contemporary.

Geographic orientation

Regional orientation map © OpenStreetMap contributors. Case-study maps: Mehrgarh · Harappa · Balkh · Bamiyan

Mehrgarh

Harappa

Mohenjo-daro

Balkh

Bamiyan Valley

Use two fingers to move the map

Use ctrl + scroll to zoom the map

All groups

Map markers indicate general study locations and do not identify sensitive deposits or excavation areas.

2.14 Practical exercise A — Radiocarbon decay worked example

This exercise calculates the fraction of carbon-14 remaining after a specified elapsed time using the physical half-life of 5,730 years.

It is a demonstration of radioactive decay, not a radiocarbon calibration program.

Interactive Carbon-14 Decay

Elapsed time

5,730 years

Estimated carbon-14 remaining

50.00%

Elapsed half-lives: 1.00

Idealized physical decay model. Conventional radiocarbon-age calculation and calendar calibration involve additional conventions and corrections.

2.15 Practical exercise B — Bayesian probability worked example

Consider two hypothetical chronological hypotheses.

H1: An occupation event occurred during an earlier period.

H2: The event occurred during a later period.

You can change the prior probability of H1 and the likelihood of the observed evidence under each hypothesis.

The worked example applies Bayes' theorem for two mutually exclusive, exhaustive hypotheses.

Interactive Bayesian Reasoning

Prior probability of H1

50%

Likelihood of evidence if H1 is true

80%

Likelihood of evidence if H2 is true

20%

Posterior H1

80.0%

Posterior H2

20.0%

These are hypothetical probabilities for teaching Bayes' theorem. They are not derived from radiocarbon measurements or archaeological calibration curves.

2.16 Practical exercise C — Build a stratigraphic sequence

Three hypothetical events are recorded:

• A: Construction of an early wall.

• B: Occupation deposit accumulated against the wall.

• C: Later rebuilding cuts through the occupation deposit.

Stratigraphic Reasoning

1. Which event is earliest?

Construction A

Occupation B

Rebuilding C

2. Which event is latest?

Construction A

Occupation B

Rebuilding C

3. If charcoal in B is residual, what does it imply?

The charcoal must date rebuilding C

Its radiocarbon age may be older than deposition B

It proves that the wall was constructed at the same time as B

2.17 Practical exercise D — Chronological model documentation

Use this form to prepare a non-invasive research plan based on published data.

Chronological Model Planning Form

Project title

What event is being dated?

Deposition of short-lived plant remains in documented occupation layers

Independent prior information

Stratigraphic order of the published contexts

Possible limitations and outliers

Possible residuality, uncertain associations, calibration plateaus and incomplete sampling

2.18 MCQ examination

10 questions · 10 marks · Select your answers, then check the expandable answer key.

Level 3 — Lesson 2 Examination

1. What is the principal purpose of Bayesian chronological modeling?

A. To replace all archaeological evidence with mathematics

B. To combine dating measurements with independently justified chronological information

C. To guarantee exact calendar dates

D. To remove all uncertainty from scientific measurements

2. What does BP mean in conventional radiocarbon dating?

A. Before 1950 CE

B. Before the present calendar year

C. Before pottery

D. Before the first excavation

3. Why must conventional radiocarbon ages be calibrated?

A. All radiocarbon samples are contaminated

B. Carbon-14 has no half-life

C. Atmospheric radiocarbon concentrations have varied over time

D. Radiocarbon dating only works on pottery

4. Which statement correctly describes a Bayesian prior?

A. It is always a historical guess

B. It is the final result of the model

C. It is the laboratory instrument error

D. It represents information or assumptions incorporated before evaluating the modeled evidence

5. What is a calibration plateau?

A. A flat archaeological mound

B. A portion of the calibration curve where similar radiocarbon ages correspond to a broad range of calendar ages

C. A type of pottery

D. A statistical method that removes uncertainty

6. What does the old-wood effect mean?

A. The dated wood may be older than the archaeological event in which it was used or deposited

B. Old wood cannot be radiocarbon dated

C. Wood always gives a younger date than its context

D. The wood was necessarily imported

7. What does a modeled start boundary estimate?

A. The exact date of every artifact

B. The date of the oldest geological bedrock

C. The beginning of a defined phase under the model assumptions

D. The publication date of the excavation report

8. Which Pakistan site was the subject of a 2025 radiocarbon and Bayesian reassessment of its early Neolithic cemetery?

A. Taxila

B. Harappa

C. Mohenjo-daro

D. Mehrgarh

9. What does OSL dating commonly estimate in suitable sediments?

A. The date of a written inscription

B. Time since mineral grains were last sufficiently exposed to light before burial

C. The date a modern laboratory received a sample

D. The time when the nearest city was founded

10. What is good practice when a Bayesian chronological model produces unexpectedly narrow date ranges?

A. Examine prior assumptions, sample associations, diagnostics, and model sensitivity

B. Assume the dates must be correct

C. Remove all contradictory measurements without explanation

D. Ignore the archaeological stratigraphy

2.19 Advanced research assignment

Prepare a 1,800–2,500-word research proposal titled:

Bayesian Chronological Modeling of Archaeological Occupation and Environmental Change in Pakistan or Afghanistan

Choose one of three themes: the revised Neolithic chronology of Mehrgarh, the occupational development of an Indus civilization settlement, or the relationship between Balkh River palaeochannels and archaeological settlement.

Your proposal must include a literature review, a clearly defined archaeological event, sample-selection criteria, appropriate dating methods, proposed stratigraphic constraints, calibration procedures, outlier considerations, model comparisons, and limitations.

Include a stratigraphic diagram, a proposed Bayesian model structure, a table identifying what each sample dates, and at least eight scholarly references.

Do not invent calibrated ages or present hypothetical model outputs as published results.

Assessment rubric

Criterion	Marks
Research question and archaeological context	15
Scientific understanding of dating methods	15
Sample-event relationships and stratigraphy	20
Bayesian model design and assumptions	20
Uncertainty, diagnostics and sensitivity testing	15
Scientific presentation and references	15
Total	100

2.20 Scholarly references and further reading

1. Reimer, P. J., et al. (2020). The IntCal20 Northern Hemisphere Radiocarbon Age Calibration Curve (0–55 cal kBP). Radiocarbon, 62(4), 725–757.

   Cambridge Core

2. Heaton, T. J., et al. (2020). The IntCal20 Approach to Radiocarbon Calibration Curve Construction. Radiocarbon.

   Cambridge Core

3. Heaton, T. J., et al. (2020). Marine20—The Marine Radiocarbon Age Calibration Curve. Radiocarbon.

   Cambridge Core

4. Bronk Ramsey, C. (2009). Bayesian Analysis of Radiocarbon Dates. Radiocarbon, 51(1), 337–360. DOI: 10.1017/S0033822200033865.

5. Bayliss, A. (2009). Rolling Out Revolution: Using Radiocarbon Dating in Archaeology. Radiocarbon, 51(1), 123–147.

6. New Radiocarbon Dates of Human Tooth Enamel Reveal a Late Appearance of Farming Life in the Indus Valley. Scientific Reports (2025).

   Scientific Reports

7. UNESCO — Archaeological Site of Mehrgarh. Historical excavation sequence and previously proposed chronology.

   UNESCO World Heritage Centre

8. Fouache, E., et al. (2012). Palaeochannels of the Balkh River (Northern Afghanistan) and Human Occupation Since the Bronze Age Period. Journal of Archaeological Science, 39(11), 3415–3427.

   ScienceDirect

9. IntCal Working Group — Calibration Publications. Primary calibration-curve research and supporting literature.

   Publications

10. Buck, C. E., Cavanagh, W. G., and Litton, C. D. (1996). Bayesian Approach to Interpreting Archaeological Data. Wiley.

Lesson 2 conclusion

Advanced archaeological chronology is not simply the process of assigning dates to artifacts.

It requires understanding what an analytical measurement dates, how that event relates to archaeological activity, and which independent constraints can legitimately improve the chronological estimate.

Radiocarbon calibration translates measurements into calendar-age probability distributions. Bayesian models combine those distributions with archaeological information such as stratigraphic ordering and phase membership.

The reassessment of Mehrgarh illustrates the importance of questioning established chronologies when new evidence becomes available.

The essential principle: A chronological model is only as reliable as its samples, archaeological associations, dating measurements, and assumptions.

Examination answer key

1 B · 2 A · 3 C · 4 D · 5 B · 6 A · 7 C · 8 D · 9 B · 10 A

Answers and explanations from the supplied PDF

The explanations and practical guidance below are editorial learning aids from the PDF appendix.

1. B - What is the principal purpose of Bayesian chronological modeling? To combine dating measurements with independently justified chronological information. Related lesson explanation: Bayesian chronological modeling provides a formal method for combining dating evidence with independently justified archaeological relationships.

2. A - What does BP mean in conventional radiocarbon dating? Before 1950 CE. Related lesson explanation: A conventional radiocarbon age is expressed in radiocarbon years BP, where BP means before 1950 CE .

3. C - Why must conventional radiocarbon ages be calibrated? Atmospheric radiocarbon concentrations have varied over time. Related lesson explanation: Conventional radiocarbon ages are calculated under defined conventions, including the historical Libby half-life, isotopic fractionation corrections, and reporting standards.

4. D - Which statement correctly describes a Bayesian prior? It represents information or assumptions incorporated before evaluating the modeled evidence. Related lesson explanation: Understand Bayesian probability, prior information, likelihoods, and posterior distributions.

5. B - What is a calibration plateau? A portion of the calibration curve where similar radiocarbon ages correspond to a broad range of calendar ages. Related lesson explanation: When a calibration curve is relatively flat, several calendar years may correspond to very similar radiocarbon ages.

6. A - What does the old-wood effect mean? The dated wood may be older than the archaeological event in which it was used or deposited. Related lesson explanation: Charcoal from the inner portion of a long-lived tree can be centuries older than the event in which the wood was burned.

7. C - What does a modeled start boundary estimate? The beginning of a defined phase under the model assumptions. Related lesson explanation: Boundary: A modeled transition such as the beginning or end of a phase.

8. D - Which Pakistan site was the subject of a 2025 radiocarbon and Bayesian reassessment of its early Neolithic cemetery? Mehrgarh. Related lesson explanation: A peer-reviewed study published in Scientific Reports in 2025 reassessed this chronology using radiocarbon measurements from tooth enamel associated with 23 Neolithic burials and Bayesian modeling.

9. B - What does OSL dating commonly estimate in suitable sediments? Time since mineral grains were last sufficiently exposed to light before burial. This is the answer supported by the definitions and method limits in the lesson; the alternatives do not meet those conditions.

10. A - What is good practice when a Bayesian chronological model produces unexpectedly narrow date ranges? Examine prior assumptions, sample associations, diagnostics, and model sensitivity. This is the answer supported by the definitions and method limits in the lesson; the alternatives do not meet those conditions.

Practical decisions - editorial answers

1. Which event is earliest? Answer: Construction A. Explanation: Use the documented construction-occupation-rebuilding sequence; residual material may predate its deposit.

2. Which event is latest? Answer: Rebuilding C. Explanation: Use the documented construction-occupation-rebuilding sequence; residual material may predate its deposit.

3. If charcoal in B is residual, what does it imply? Answer: Its radiocarbon age may be older than deposition B. Explanation: Use the documented construction-occupation-rebuilding sequence; residual material may predate its deposit.

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