How We Date the Past
The age of a fossil is the foundation of everything we know about human evolution. Scientists use at least 14 different dating techniques — each suited to different time ranges, materials, and geological contexts — to build the chronological framework of our past.
Radiometric Methods
Based on the predictable decay of radioactive isotopes.
Radiocarbon (¹⁴C) Dating
Cosmic rays bombarding nitrogen atoms in the upper atmosphere continuously produce carbon-14, a radioactive isotope that mixes into atmospheric CO₂. All living things absorb this ¹⁴C through photosynthesis or diet, maintaining a roughly constant ratio of ¹⁴C to stable ¹²C. The moment an organism dies, it stops taking in new carbon and its ¹⁴C begins to decay back to nitrogen-14. By measuring the remaining ¹⁴C in a sample — typically using accelerator mass spectrometry (AMS), which can work with milligram-sized samples — scientists calculate how many half-lives have elapsed since death. Raw radiocarbon "years" must be calibrated against independent records such as tree-ring chronologies (dendrochronology) and uranium-series-dated corals, because atmospheric ¹⁴C levels have fluctuated over time due to changes in solar activity and Earth's magnetic field. This calibration produces calendar ages. Radiocarbon dating transformed archaeology when Willard Libby developed it in 1949 and remains the most widely used dating method for the last 50,000 years.
- Applicable Range
- 0 – 50 KYA
- Materials Dated
- Bone, charcoal, shell, wood, peat, soil organics
- Strengths
- High precision for recent material; well-calibrated against tree rings and corals.
- Limitations
- Cannot date beyond ~50 KYA; contamination is a major concern; requires calibration curves.
Potassium-Argon (K-Ar) Dating
Potassium is one of the most abundant elements in the Earth's crust, and about 0.012% of natural potassium is the radioactive isotope ⁴⁰K. When volcanic rock crystallizes from molten lava, any argon gas escapes, effectively setting the clock to zero. Over time, ⁴⁰K atoms trapped in the mineral lattice decay to ⁴⁰Ar, which accumulates within the crystal. Scientists extract the argon by melting the sample in a vacuum and measure the ⁴⁰K/⁴⁰Ar ratio using a mass spectrometer. Because the half-life of ⁴⁰K is 1.25 billion years, the method is ideal for dating ancient volcanic deposits but becomes imprecise for very young rocks where little argon has accumulated. K-Ar dating was instrumental in establishing the chronology of early hominin sites in the East African Rift Valley, where volcanic tuff layers conveniently sandwich fossil-bearing sediments. The method dates the volcanic event, not the fossils directly — the fossils are bracketed by dated layers above and below them.
- Applicable Range
- 100 KYA – 4.5 BYA
- Materials Dated
- Volcanic rock (basalt, tuff), mica, feldspar
- Strengths
- Effective for very old samples; crucial for dating the earliest hominin sites in East Africa.
- Limitations
- Less precise than Ar/Ar; cannot date the rocks themselves (only the volcanic minerals); atmospheric argon contamination.
Argon-Argon (⁴⁰Ar/³⁹Ar) Dating
Argon-argon dating overcomes the main weakness of K-Ar by measuring both the parent and daughter isotopes in a single analysis. The sample is first irradiated in a nuclear reactor, which converts a known fraction of ³⁹K to ³⁹Ar. Then the sample is heated in steps — progressively higher temperatures release argon from different mineral domains — and the ⁴⁰Ar/³⁹Ar ratio is measured at each step. This "step-heating" approach reveals whether the sample has remained a closed system: a flat age spectrum (consistent ratios across temperature steps) indicates an undisturbed sample, while a disturbed spectrum warns of argon loss or contamination. The technique is so precise that individual mineral crystals can be dated, and it has been used to calibrate the ages of ash layers across the East African Rift to within a few thousand years even for deposits millions of years old. Ar/Ar dating provided the definitive ages for Olduvai Gorge, the Laetoli footprints, and many other key hominin sites. It is the single most important chronometric tool for the Plio-Pleistocene record of human evolution.
- Applicable Range
- 1 KYA – 4.5 BYA
- Materials Dated
- Volcanic minerals (feldspar, biotite, hornblende), tephras, lava flows
- Strengths
- Very precise; single-crystal dating possible; internal consistency checks; workhorse of East African hominin chronology.
- Limitations
- Requires volcanic context; not applicable to sedimentary rocks without volcanic input.
Uranium-Series (U-Th) Dating
When water dissolves limestone and redeposits it as calcite — forming stalactites, stalagmites, and flowstones — it carries dissolved uranium but virtually no thorium, because thorium is insoluble. The freshly precipitated calcite therefore starts with a ²³⁰Th/²³⁴U ratio of zero. As ²³⁴U decays through the uranium series, ²³⁰Th accumulates in the crystal. Measuring the ²³⁰Th/²³⁴U ratio with thermal ionization mass spectrometry (TIMS) or multi-collector ICP-MS gives a precise age. The method reaches secular equilibrium (where decay and ingrowth balance) at roughly 500,000 years, setting its upper limit. U-series dating is particularly valuable for cave sites — which are abundant in South African and European paleoanthropology — because it can date the flowstone layers that cap or underlie fossil-bearing breccias. It was U-series dating of flowstones that helped establish the remarkably young age (236–335 KYA) of Homo naledi in the Rising Star Cave system and revised the chronology of Homo heidelbergensis at Sima de los Huesos.
- Applicable Range
- 0 – 500 KYA
- Materials Dated
- Speleothems (stalactites/stalagmites), flowstones, coral, bone, teeth
- Strengths
- Excellent for cave deposits; fills the gap between radiocarbon and K-Ar; good precision.
- Limitations
- Requires closed-system conditions; direct dating of bone is often unreliable due to uranium uptake.
Uranium-Lead (U-Pb) Dating
U-Pb dating exploits two parallel decay chains: ²³⁸U decays to ²⁰⁶Pb (half-life 4.47 billion years) and ²³⁵U decays to ²⁰⁷Pb (half-life 704 million years). Because these chains are independent, they provide a built-in cross-check: if both yield the same age, the date is said to be "concordant" and is highly reliable. The most commonly dated mineral is zircon (ZrSiO₄), which incorporates uranium into its crystal structure at formation but strongly excludes lead. Any lead found in a zircon must therefore be radiogenic — produced by uranium decay since the crystal formed. For paleoanthropology, U-Pb dating has proven crucial in South Africa, where volcanic tuffs suitable for Ar/Ar dating are rare. Instead, researchers date the calcite flowstones that cap fossil-bearing cave breccias. The technique was central to dating the Australopithecus sediba fossils at Malapa to 1.977 MYA and has been applied to constrain the age of Little Foot at Sterkfontein. Advances in laser ablation ICP-MS now allow U-Pb dates to be obtained from tiny spots on flowstone cross-sections, mapping the growth history of the cave deposit.
- Applicable Range
- 1 MYA – 4.5 BYA
- Materials Dated
- Zircon crystals, flowstones, speleothems
- Strengths
- Highest-precision method for ancient samples; two decay chains allow concordance checking; used for South African cave flowstones.
- Limitations
- Limited material types; complex chemistry; closed-system assumption critical.
Fission Track Dating
Uranium-238 atoms occasionally undergo spontaneous fission — splitting into two smaller nuclei that fly apart at high velocity through the surrounding crystal lattice, leaving narrow trails of damaged structure called fission tracks. These tracks are typically ~10–20 micrometers long and can be revealed by chemically etching a polished mineral surface. The number of tracks per unit area is proportional to both the uranium content and the time elapsed since the crystal last cooled below its "closure temperature" (the temperature below which tracks are preserved). Scientists count tracks under an optical microscope, then determine the uranium concentration by irradiating the sample with thermal neutrons to induce additional fissions from ²³⁵U, creating a second set of tracks for comparison. The ratio of spontaneous to induced tracks gives the age. Fission track dating is particularly useful as an independent check on K-Ar and Ar/Ar ages for volcanic tephra layers, and has been applied to date obsidian artifacts and constrain the thermal histories of sedimentary basins. Its precision is lower than Ar/Ar dating, but its independence from argon systematics makes it a valuable complementary technique.
- Applicable Range
- 100 KYA – 2 BYA
- Materials Dated
- Zircon, apatite, volcanic glass, mica
- Strengths
- Independent of other radiometric methods; useful cross-check; applicable to tephras.
- Limitations
- Tracks can anneal (heal) at high temperatures, resetting the clock; relatively low precision.
Trapped-Charge Methods
Measure the accumulation of electrons trapped by natural radiation in mineral crystals.
Electron Spin Resonance (ESR)
Natural radiation from uranium, thorium, and potassium in the surrounding sediment, plus cosmic rays, continuously bombards buried materials. In crystalline substances like tooth enamel (hydroxyapatite), this radiation dislodges electrons from their normal atomic positions and traps them in defects in the crystal lattice. The number of trapped electrons grows over time at a rate determined by the local radiation dose rate. ESR spectroscopy detects these trapped electrons by placing the sample in a strong magnetic field and exposing it to microwave radiation — trapped electrons absorb microwaves at characteristic frequencies, producing a measurable signal whose intensity is proportional to the total radiation dose received. Dividing this "equivalent dose" by the annual dose rate gives the age. Unlike thermoluminescence, ESR is non-destructive — the sample can be measured repeatedly without resetting the signal. This makes it ideal for dating precious hominin tooth enamel, which is abundant at archaeological sites. ESR dating was instrumental in determining the ages of key Homo naledi specimens and Neanderthal teeth across Europe and the Middle East. The main complication is estimating the uranium uptake history of the tooth, which requires modeling whether uranium entered the enamel shortly after burial (early uptake) or gradually over time (linear uptake), producing two bracketing age estimates.
- Applicable Range
- 1 KYA – 5 MYA
- Materials Dated
- Tooth enamel, quartz, shells, corals, stalagmites
- Strengths
- Non-destructive; applicable to tooth enamel (common in hominin sites); bridges the gap between U-series and K-Ar.
- Limitations
- Requires estimation of environmental radiation dose history; results depend on uranium uptake model (early vs. linear).
Optically Stimulated Luminescence (OSL)
Like ESR, OSL relies on the accumulation of electrons trapped in crystal defects by natural radiation. The critical difference is the resetting mechanism: while ESR signals require high heat to erase, OSL signals in quartz and feldspar are reset by just a few seconds of exposure to sunlight. This means OSL dates the last time a sediment grain saw daylight — the moment it was buried. In the laboratory, the sample is collected under light-safe conditions (opaque tubes hammered into sediment sections) and measured in a darkroom. When stimulated by a carefully controlled light source (typically blue or green LEDs for quartz, infrared for feldspar), the trapped electrons are released and recombine at luminescence centers, emitting photons that are counted by a sensitive photomultiplier. The total light output is proportional to the radiation dose accumulated since burial. This equivalent dose, divided by the annual dose rate (measured using gamma spectrometry of the surrounding sediment), gives the burial age. OSL has been transformative for dating sites without volcanic context, including the coastal cave sites of South Africa where Middle Stone Age occupations at Blombos Cave and Pinnacle Point were dated. Single-grain OSL analysis can date individual quartz grains, identifying those that were incompletely reset before burial and improving accuracy.
- Applicable Range
- 0 – 350 KYA
- Materials Dated
- Quartz and feldspar grains in sediment, fired ceramics, heated stones
- Strengths
- Dates the last time sediment was exposed to sunlight — ideal for burial events; works where no volcanic context exists.
- Limitations
- Requires that grains were fully reset (bleached) before burial; sensitive to local radiation environment.
Thermoluminescence (TL)
Thermoluminescence was the first trapped-charge dating method developed, predating OSL by several decades. The principle is the same — natural radiation traps electrons in crystal defects — but in TL, the trapped electrons are released by progressively heating the sample rather than exposing it to light. As the sample is heated in a controlled oven, trapped electrons escape at characteristic temperatures and emit light. The total light output across a "glow curve" (luminescence intensity vs. temperature) is proportional to the accumulated radiation dose. TL dates the last significant heating event: for burnt flint, this is the moment the tool was heated by ancient humans (deliberately or in a campfire); for ceramics, the moment of firing. The method was used to provide some of the first absolute dates for Middle Paleolithic Levallois tools and Mousterian hearths in Europe and the Levant. At Tabun and Qafzeh caves in Israel, TL dating of burned flints helped establish that anatomically modern humans were present in the Middle East by ~100 KYA, tens of thousands of years before they replaced Neanderthals in Europe. TL has been largely superseded by OSL for sediment dating, but remains valuable for fired materials where the heating event is the archaeological question of interest.
- Applicable Range
- 0 – 500 KYA
- Materials Dated
- Burnt flint, ceramics, heated sediments, lava flows
- Strengths
- Dates the last heating event — useful for fire hearths and burned tools; applicable to Levallois sites.
- Limitations
- Requires the material to have been sufficiently heated to reset the signal; radiation dose estimation is complex.
Other Absolute Methods
Independent chronometric techniques not based on radioactive decay or trapped charge.
Cosmogenic Nuclide Dating
High-energy cosmic rays from deep space continuously bombard Earth's surface. When these particles strike atoms in exposed rock — particularly silicon and oxygen in quartz — they produce rare radioactive isotopes called cosmogenic nuclides, principally beryllium-10 (¹⁰Be, half-life 1.39 MY) and aluminium-26 (²⁶Al, half-life 717 KY). The concentration of these isotopes in a rock surface increases at a known rate with time, so measuring them reveals how long the surface has been exposed. But the method has a powerful second application for paleoanthropology: burial dating. When sediments containing quartz pebbles are washed into a deep cave, cosmic ray bombardment ceases, and the existing ²⁶Al and ¹⁰Be begin to decay at their different rates. Because ²⁶Al decays about twice as fast as ¹⁰Be, the ²⁶Al/¹⁰Be ratio drops predictably over time, providing a burial age. This approach has been transformative for South African cave sites where volcanic dating materials are absent. Cosmogenic nuclide burial dating revised the age of the Sterkfontein Member 4 Australopithecus africanus fossils, constrained the age of Little Foot (StW 573), and dated the Australopithecus sediba remains at Malapa. The measurements require accelerator mass spectrometry (AMS) and careful accounting for the complex history of sediment exposure and burial.
- Applicable Range
- 100 KYA – 5 MYA
- Materials Dated
- Quartz-bearing rock surfaces, cave sediments
- Strengths
- Dates burial of sediments in caves; independent of volcanic context; effective for South African cave sites (Sterkfontein, Malapa).
- Limitations
- Complex exposure/burial history complicates interpretation; relatively large uncertainties; requires quartz-rich sediment.
Amino Acid Racemization (AAR)
All living organisms build their proteins exclusively from "left-handed" (L-form) amino acids. After death, these L-amino acids begin to spontaneously convert to their mirror-image "right-handed" (D-form) counterparts — a process called racemization. The D/L ratio starts at zero in a living organism and increases toward 1.0 (equal amounts of both forms) over time, at a rate that depends primarily on temperature and the specific amino acid being measured. To determine an age, scientists extract amino acids from a sample using high-performance liquid chromatography (HPLC), measure the D/L ratios for several amino acids (commonly aspartic acid and glutamic acid, which racemize relatively quickly), and calculate the time required to produce the observed ratio. The main challenge is that racemization rates are strongly temperature-dependent: a sample buried in tropical sediments racemizes much faster than one in a cold cave. Without knowing the full temperature history of the burial environment, AAR provides only a relative age or a rough estimate. However, when calibrated against independently dated samples from the same site, AAR becomes a useful tool. It has been applied to ostrich eggshell fragments (which have a particularly well-behaved closed-system chemistry) at African Middle Stone Age sites and to marine shell deposits across the Mediterranean coast.
- Applicable Range
- 1 KYA – 5 MYA
- Materials Dated
- Bone, shell, teeth, ostrich eggshell
- Strengths
- Inexpensive; widely applicable to organic materials; useful for relative age estimates in the absence of other methods.
- Limitations
- Temperature-dependent rate makes absolute dates uncertain without independent calibration; contamination sensitive.
Relative Methods
Establish the order of events rather than numerical ages.
Biostratigraphy
Biostratigraphy is one of the oldest dating methods in geology, rooted in the observation that fossil species change in a predictable sequence through time. Certain animals — called index fossils — evolved rapidly, were geographically widespread, and are easily identifiable, making them diagnostic of specific time intervals. In African paleoanthropology, the most important index fossils are bovids (antelopes), suids (pigs), elephantids, and rodents. By identifying the assemblage of animal fossils found alongside hominin remains, scientists can correlate a site to a known biochronological framework. For example, the presence of the suid Metridiochoerus andrewsi narrows a South African deposit to approximately 2.0–1.5 MYA, while the bovid Pelorovis oldowayensis suggests an age younger than ~1.7 MYA. Biostratigraphy has been indispensable for dating the South African cave sites (Sterkfontein, Swartkrans, Kromdraai, Makapansgat) where volcanic tuffs suitable for radiometric dating are absent. The method provides relative, not absolute, dates — the faunal "biozones" are themselves calibrated against radiometrically dated sequences in East Africa. Resolution varies from tens of thousands to hundreds of thousands of years, depending on how well the faunal sequence is established for the region in question.
- Applicable Range
- Any age (relative only)
- Materials Dated
- Fossil assemblages (bovids, suids, rodents)
- Strengths
- Works where no radiometric context exists; essential for South African cave sites where volcanic materials are rare.
- Limitations
- Provides relative, not absolute, dates; resolution depends on quality of faunal database; diachronous faunal change across regions.
Paleomagnetism (Magnetostratigraphy)
Earth's magnetic field periodically reverses polarity — the north and south magnetic poles swap positions. These reversals are recorded in rocks and sediments: when lava cools or fine-grained sediment settles, magnetic mineral grains (primarily magnetite) align with the ambient magnetic field and become locked in place, preserving a record of the field direction at that moment. By taking oriented samples through a sedimentary or volcanic sequence and measuring their magnetic polarity in the laboratory (using a cryogenic magnetometer in a magnetically shielded room), scientists construct a polarity stratigraphy — a sequence of normal and reversed intervals. This local sequence is then matched to the global Geomagnetic Polarity Timescale (GPTS), which has been calibrated against radiometrically dated volcanic rocks worldwide. The most important reversal for human evolution is the Brunhes-Matuyama boundary at ~780 KYA: any site with normal polarity sediments below reversed ones must straddle this age. The Matuyama-Gauss boundary at ~2.6 MYA and the Olduvai subchron (1.95–1.78 MYA, named after Olduvai Gorge) are equally important markers. Paleomagnetism was used to establish the chronology at Dmanisi, Georgia, and to bracket the age of the Drimolen hominin site in South Africa. The method cannot provide precise ages on its own — it identifies which polarity interval a sample falls within — but combined with other methods, it provides a powerful framework for correlation across continents.
- Applicable Range
- Any age (calibrated via absolute methods)
- Materials Dated
- Fine-grained sediments, lava flows, baked clays
- Strengths
- Independent of material type; provides a global correlation framework; excellent for bracketing sites between reversals.
- Limitations
- Requires undisturbed sedimentary or volcanic sequence; cannot distinguish between same-polarity intervals without additional context.
Tephrochronology
Volcanic eruptions inject vast quantities of fine ash (tephra) into the atmosphere, where it disperses over wide areas and settles as thin, geologically instantaneous layers in sedimentary sequences. Each eruption produces tephra with a unique geochemical fingerprint — a distinctive ratio of major and trace elements (SiO₂, FeO, CaO, TiO₂, rare earth elements) that depends on the specific magma chemistry. By analyzing the chemical composition of tephra layers using electron microprobe analysis (EMPA) or laser ablation ICP-MS, scientists can "fingerprint" an ash layer and correlate it to tephras of the same composition found at other sites hundreds or even thousands of kilometers away. If the tephra layer has been radiometrically dated (typically by Ar/Ar dating of feldspar crystals within it), every site containing that same tephra inherits the same age. In the East African Rift, where numerous volcanoes have produced distinctive tephras throughout the Plio-Pleistocene, tephrochronology provides the backbone of the chronological framework. The Kibish Formation tuffs that bracket the oldest Homo sapiens fossils at Omo, the Toba super-eruption tephra (~74 KYA, found from India to eastern Africa), and the numerous tuffs of the Turkana Basin are all examples. Tephrochronology essentially transforms every recognizable ash layer into a time-stamped geological marker that links sites across entire continents and even between marine, lacustrine, and terrestrial records.
- Applicable Range
- Any age (calibrated via radiometric dating of the tephra)
- Materials Dated
- Volcanic ash (tephra) layers in sediment, ice cores, marine cores
- Strengths
- Provides instantaneous time markers across large regions; excellent for correlating sites across East Africa.
- Limitations
- Requires preservation of tephra; chemical fingerprinting can be complex; not all eruptions have been characterized.
Method Applicability by Time Range
Each method covers a different span of geological time. This chart shows the applicable range of each technique on a logarithmic scale.
Dating Records in Our Database
46 dated samples across 10 methods.
| Method | Date (MYA) | Uncertainty | Material | Site | Specimen | Lab | Notes |
|---|---|---|---|---|---|---|---|
| radiocarbon C14 | 0.0500 | +0.0050 / −0.0050 | Charcoal (Neanderthal layers) | Shanidar Cave | Old Man of Shanidar (Shanidar 1) | — | Shanidar MP/UP chronology (site-specific calibrations). |
| radiocarbon C14 | 0.0500 | +0.0100 / −0.0100 | Charcoal / bone (molecular age) | Denisova Cave | — | — | Denisova Cave stratigraphic chronology (multiple labs). |
| radiocarbon C14 | 0.0400 | +0.0050 / −0.0050 | Charcoal (Aurignacian contexts) | Hohle Fels | — | — | Hohle Fels Upper Palaeolithic ages. |
| K Ar | 1.7900 | +0.0500 / −0.0500 | Basalt below OH 5 | Olduvai Gorge | Zinj / Nutcracker Man (OH 5) | — | OH 5 approximate stratigraphic age (literature range). |
| K Ar | 0.4000 | +0.0500 / −0.0500 | Volcanic sediment associated with calvaria | Ceprano | Ceprano calvaria (Ceprano 1) | Various (revised from original ~800 kya) | |
| Ar Ar | 3.6600 | +0.0300 / −0.0300 | Laetolil Beds tephra | Laetoli | — | — | Footprint surface bracketing ~3.66 Ma. |
| Ar Ar | 3.2000 | +0.0200 / −0.0200 | Tuffs at Hadar (Kada Hadar Member) | Hadar | — | — | Lucy horizon age cluster ~3.18–3.2 Ma (recalibrated over decades). |
| Ar Ar | 2.5000 | +0.0500 / −0.0500 | Tuffs West Turkana | West Turkana | — | — | Black Skull / Nachukui Formation ages. |
| Ar Ar | 1.8000 | +0.0200 / −0.0200 | Tuff I Bed I (crystal separates) | Olduvai Gorge | — | — | Classic Ar/Ar chronology for Olduvai Bed I hominins/tools. |
| Ar Ar | 1.8000 | +0.0500 / −0.0500 | Trinil section | Border Cave | — | — | Java Homo erectus classic age brackets. |
| Ar Ar | 1.7700 | +0.0200 / −0.0200 | Basalt beneath hominin layers | Dmanisi | Dmanisi edentulous (D3444) | — | Dmanisi hominins ~1.77–1.85 Ma (stratigraphic summaries). |
| Ar Ar | 1.6600 | +0.0300 / −0.0300 | Sangiran tuffs | Callao Cave | — | — | Sangiran H. erectus chronology. |
| Ar Ar | 1.5600 | +0.0200 / −0.0200 | KBS Tuff (context) | Koobi Fora | Turkana Boy / Nariokotome Boy (KNM-WT 15000) | — | Turkana Boy ~1.56 Ma (Turkana radioisotope framework). |
| Ar Ar | 1.2000 | +0.0500 / −0.0500 | Atapuerca section tephras | Atapuerca | — | — | Gran Dolina TD6 context (regional chronologies). |
| Ar Ar | 0.7900 | +0.0500 / −0.0500 | Basalt chronology (Levant) | Gesher Benot Ya'aqov | — | — | GBY ~780 ka occupation (classic range). |
| Ar Ar | 0.6000 | +0.0500 / −0.0500 | Bodo volcanic context | Herto | — | — | Bodo cranium Middle Pleistocene East Africa. |
| Ar Ar | 0.3200 | +0.0300 / −0.0300 | Tephra correlations | Olorgesailie | — | — | Olorgesailie Acheulean chronology (southern Kenya). |
| Ar Ar | 0.1960 | +0.0050 / −0.0050 | KHS tephra Omo Kibish | Omo Kibish | Omo Kibish I (Omo 1) | — | Omo I KHS ~196 ka (radioisotope frameworks). |
| Ar Ar | 0.1600 | +0.0020 / −0.0020 | Dacitic tuff underlying hominin-bearing horizon | Herto | Herto adult 1 (BOU-VP-16/1) | Berkeley Geochronology Center | |
| Ar Ar | 0.0600 | +0.0100 / −0.0100 | Jaramillo ash near Liang Bua | Liang Bua | Hobbit / Flo (LB1) | — | LB1 bracketing (Flores chronology). |
| U series | 0.4300 | +0.0200 / −0.0200 | Speleothems / flowstone (Sima) | Atapuerca | Miguelon / Sima de los Huesos (Cranium 5) | — | Sima de los Huesos minimum ages (U-series frameworks). |
| U series | 0.4000 | +0.0500 / −0.0500 | Zhoukoudian speleothems / stratigraphy | Zhoukoudian | Peking Man representative (Zhoukoudian III) | — | Locality 1 chronology (complex). |
| U series | 0.3150 | +0.0300 / −0.0300 | Flowstone Irhoud | Jebel Irhoud | — | — | Jebel Irhoud H. sapiens ~315 ka (multi-method). |
| U series | 0.3000 | +0.0300 / −0.0300 | Speleothem / peat (context) | Schoningen | — | — | Schöningen spears ~300 ka (site summaries). |
| U series | 0.3000 | +0.0500 / −0.0500 | U-series on bone (context) | Lazaret Cave | Broken Hill / Rhodesian Man (Kabwe 1) | — | Kabwe direct dating attempts (contested). |
| U series | 0.2360 | +0.0300 / −0.0300 | Flowstone ages (Dinaledi) | Rising Star Cave | Neo / H. naledi holotype (DH1) | — | Young end of naledi age distribution. |
| U series | 0.1300 | +0.0100 / −0.0100 | Bovid tooth enamel from same stratum | Nesher Ramla | Nesher Ramla parietal (NR-1) | Griffith University / CENIEH | |
| U Pb | 2.8000 | +0.0500 / −0.0500 | Flowstone (Taung) | Middle Awash | Taung Child (Taung 1) | — | Taung Child age debates; U-Pb flowstone models. |
| U Pb | 2.6700 | +0.1500 / −0.1500 | Flowstone (Little Foot) | Sterkfontein | Little Foot (Stw 573) | — | StW 573 flowstone bracketing (published ranges). |
| U Pb | 1.9770 | +0.0030 / −0.0030 | Flowstone Malapa | Lomekwi | — | — | Au. sediba U-Pb flowstone ages ~1.977 Ma (Dirks et al.). |
| ESR | 1.8000 | +0.2000 / −0.2000 | Tooth enamel (Swartkrans) | Swartkrans | — | — | Swartkrans Member chronologies. |
| ESR | 0.4000 | +0.0500 / −0.0500 | Tooth enamel | Terra Amata | — | — | Petralona cave chronologies (debated). |
| ESR | 0.4000 | +0.0500 / −0.0500 | Tooth enamel | Qesem Cave | — | — | Qesem Cave ages ~400 ka (range in literature). |
| ESR | 0.3350 | +0.0500 / −0.0500 | Tooth enamel (H. naledi) | Rising Star Cave | — | — | Dirks et al. 2017: H. naledi ages 236–335 ka. |
| ESR | 0.2600 | +0.0400 / −0.0400 | Enamel (Florisbad) | Bouri Formation | — | — | Late Middle Stone Age hominin contexts (illustrative). |
| ESR | 0.2590 | +0.0350 / −0.0350 | Bovid tooth enamel from associated deposit | Florisbad | Florisbad Man (Florisbad cranium) | Various | |
| OSL | 1.0700 | +0.1000 / −0.1000 | Cave sediments (Wonderwerk) | Wonderwerk Cave | — | — | Early fire evidence layers (site publications). |
| OSL | 0.1640 | +0.0200 / −0.0200 | Coastal sediments | Pinnacle Point | — | — | Pinnacle Point 5–164 ka MSA occupations. |
| OSL | 0.1150 | +0.0150 / −0.0150 | Coastal sediments | Klasies River Caves | — | — | Klasies River MSA ages (site publications). |
| OSL | 0.0770 | +0.0070 / −0.0070 | Sediments (MSA) | Blombos Cave | — | — | Blombos Still Bay / MSA chronologies. |
| paleomagnetism | 1.8000 | +0.1000 / −0.1000 | Section (Drimolen) | Gona | — | — | South African cave breccia magnetostratigraphy (site-dependent). |
| paleomagnetism | 1.7800 | +0.0500 / −0.0500 | Section through Dmanisi | Dmanisi | — | — | Magnetostratigraphic alignment to global polarity timescale. |
| biostratigraphy | 2.0000 | +0.2000 / −0.2000 | Faunal assemblage | Kromdraai | — | — | Kromdraai relative dating via biozones (illustrative). |
| biostratigraphy | 0.3000 | +0.1500 / −0.1500 | Associated dredged fauna (Stegodon, Rhinoceros) | Penghu Channel | Penghu mandible (Penghu 1) | — | |
| cosmogenic nuclide | 3.6700 | +0.1600 / −0.1600 | Quartz pebbles from cave infill surrounding skeleton | Sterkfontein Member 2 | Little Foot (StW 573) | Purdue PRIME Lab | |
| cosmogenic nuclide | 2.8000 | +0.3000 / −0.3000 | Member 4 breccia (surface exposure models) | Sterkfontein | — | — | Sterkfontein Member 4 age debates; multiple methods. |