Fossil Age Research Articles

Age of the oldest known Homo sapiens from eastern Africa

Efforts to date the oldest modern human fossils in eastern Africa, from Omo-Kibish1–3 and Herto4,5 in Ethiopia, have drawn on a variety of chronometric evidence, including 40Ar/39Ar ages of stratigraphically associated tuffs. The ages that are generally reported for these fossils are around 197 thousand years (kyr) for the Kibish Omo I3,6,7, and around 160–155 kyr for the Herto hominins5,8. However, the stratigraphic relationships and tephra correlations that underpin these estimates have been challenged6,8. Here we report geochemical analyses that link the Kamoya’s Hominid Site (KHS) Tuff9, which conclusively overlies the member of the Omo-Kibish Formation that contains Omo I, with a major explosive eruption of Shala volcano in the Main Ethiopian Rift. By dating the proximal deposits of this eruption, we obtain a new minimum age for the Omo fossils of 233 ± 22 kyr. Contrary to previous arguments6,8, we also show that the KHS Tuff does not correlate with another widespread tephra layer, the Waidedo Vitric Tuff, and therefore cannot anchor a minimum age for the Herto fossils. Shifting the age of the oldest known Homo sapiens fossils in eastern Africa to before around 200 thousand years ago is consistent with independent evidence for greater antiquity of the modern human lineage10.

Хронология плейстоценовых находок рода Homo в Сибири: результаты и проблемы (краткий обзор)

This overview article contains a brief critical analysis of the chronology of Late Pleistocene and Early Holocene finds of Homo remains in Siberia. Direct dating of the Homo bones and teeth, as well as the isolation and analysis of the ancient human DNA, has now become firmly established in the practice of paleoanthropological research. About 62% of the Late Pleistocene and Early Holocene Siberian Homo remains have information on ancient DNA and direct dates of the bones and teeth. Particular attention is given to the assessment of the reliability of ages determined by the radiocarbon dating method. Information on the taphonomy (conditions and process of burial and fossilization) of Homo remains in the caves of the Mountain Altai is also of great importance. At present, three species of Pleistocene Homo are known in Siberia: Denisovans, Neanderthals, and anatomically modern humans (Homo sapiens). For the DenisovanNeanderthal hybrid, there is a direct date obtained by the Uranium series method, which shows the age of 67,500 cal BP. The age of other Denisovan fossils cannot be precisely determined due to the significant mixing of layers in Denisova Cave. The timing of the Denisovans in Siberia can be preliminarily determined at 130,000–44,000 cal BP (the upper limit is very approximate). The age of Siberian Neanderthals is greater than 50,000 cal BP; it is difficult to be more precise due to the widespread disturbance of the Altai caves’ stratigraphy by the burrowing activity of animals, primarily cave hyenas. Early Homo sapiens inhabited Siberia from 45,000 cal BP to the Early Holocene. No clear correspondence can be observed between climate changes in the second half of the Late Pleistocene (45,000–12,000 cal BP) and the chronology of Homo sapiens in Siberia. The age of some Homo sapiens fossils (Baigara, Solovyinaya Luka, and Sibiryachikha 6) after direct dating turned out to be much younger than initially expected. The taxonomic status of some Siberian Homo (Tuyana; an individual from the Okladnikov Cave with a date of 28,300 cal BP) has not yet been reliably identified. Obviously, it is necessary to increase the number of direct dates for Siberian hominins.

Distributions of extinction times from fossil ages and tree topologies: the example of mid-Permian synapsid extinctions.

Given a phylogenetic tree that includes only extinct, or a mix of extinct and extant taxa, where at least some fossil data are available, we present a method to compute the distribution of the extinction time of a given set of taxa under the Fossilized-Birth-Death model. Our approach differs from the previous ones in that it takes into account (i) the possibility that the taxa or the clade considered may diversify before going extinct and (ii) the whole phylogenetic tree to estimate extinction times, whilst previous methods do not consider the diversification process and deal with each branch independently. Because of this, our method can estimate extinction times of lineages represented by a single fossil, provided that they belong to a clade that includes other fossil occurrences. We assess and compare our new approach with a standard previous one using simulated data. Results show that our method provides more accurate confidence intervals. This new approach is applied to the study of the extinction time of three Permo-Carboniferous synapsid taxa (Ophiacodontidae, Edaphosauridae, and Sphenacodontidae) that are thought to have disappeared toward the end of the Cisuralian (early Permian), or possibly shortly thereafter. The timing of extinctions of these three taxa and of their component lineages supports the idea that the biological crisis in the late Kungurian/early Roadian consisted of a progressive decline in biodiversity throughout the Kungurian.

Petrogenesis and tectonic setting of Late Devonian high-Mg andesites in the Beishan orogen, NW China

AbstractHigh-Mg andesites (HMAs) are crucial for the reconstruction of plate tectonics, continental margin formation and lithospheric evolution. In this study, we present new fossil age, whole-rock geochemical and Sr–Nd isotope data on the newly discovered Dundunshan Group HMAs in the Dundunshan area of the Beishan orogen (central-southern Central Asian Orogenic Belt). The Dundunshan HMA samples are characterized by high MgO (6.47–7.02 wt%) contents and high Mg# values (67.27–68.77), with SiO2 (58.57–62.13 wt%), Al2O3 (14.49–16.07 wt%) and CaO (5.05–6.24 wt%) resembling typical HMAs. The Dundunshan HMA samples are calc-alkaline and strongly enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs), with slightly negative Eu anomaly and high-field-strength element (HFSE) depletions. Their (87Sr/86Sr)i ratios (0.7041–0.7057) and ϵNd(t) (3.73–5.59) indicate that the Dundunshan HMAs were mainly formed by the interactions between subducted oceanic sediment-derived melts and mantle peridotites. Fossil evidence and published radiometric age data constrain the formation of the Dundunshan HMAs to early Late Devonian time. Sedimentological features of the Middle Devonian Sangejing Formation and regional tectonic correlation suggest that the Hongliuhe–Niujuanzi–Xichangjing Ocean in the Dundunshan area was likely closed during late Middle Devonian time, and that the Dundunshan HMAs were formed in a post-collision extensional setting.

Sustainable hydrogen society – Vision, findings and development of a hydrogen economy using the example of Austria

Based on technical, environmental, economic and social facts and recent findings, the feasibility of the transition from our current fossil age to the new green age is analyzed in detail at both global and local level. To avert the threats of health problems, environmental pollution and climate change to our quality and standard of life, a twofold radical paradigm shift is outlined: Green Energy Revolution means the complete change from fossil-based to green primary energy sources such as sun, wind, water, environmental heat, and biomass; Green Hydrogen Society means the complete change from fossil-based final energy to green electricity and green hydrogen in all areas of mobility, industries, households and energy services. Renewable energies offer a green future and are in combination with electrochemical machines such as electrolysers, batteries and fuel cells able to achieve higher efficiencies and zero emissions.

Catarrhine Evolution in China

Cattrthrines (humans and nonhuman primates) in Asia experienced similar migrating routes from Africa to East Asia but with different time frames during the Miocene and Early Pliocene. They dispersed and radiated in East and Southeast Asia during the Pliocene and Pleistocene so that one’s experiences of evolutionary development and biodiversity changes can mutually be interpreted for the others. Thus, it is necessary to jointly explore the issues in mainland China, the major part of East Asia. Their regional fossil diversity profiles during Pliocene, Pleistocene, and Early Holocene and extant distribution patterns of the primates are analyzed in this study. The results indicate that primate diversity reached the climax before the Early Holocene, which has unfortunately been shrunken gradually in the following Holocene, especially during the most recent Chinese history, so that many taxa are on the edger of extinction. That fossil age in Eastern and Central China is older than in Western China clarifies that, instead of from Africa, the modern human (Homo sapiens) evolved directly from H. erectus in the regions.

On the origin of Caimaninae: insights from new fossils of Tsoabichi greenriverensis and a review of the evidence

ABSTRACT An incomplete fossil record and unstable phylogenies of extinct taxa hamper reconstructing the early evolution of Caimaninae. We describe previously unpublished articulated fossils of a key species, Tsoabichi greenriverensis from the early Eocene Green River Formation of North America, exhibiting further character evidence for the caimanine affinities of this taxon. Parsimony analysis of modified morphological taxon-character datasets coupled with a critical review of character evolution and published phylogenies reveals that fossil evidence for Palaeogene crown group and Late Cretaceous total-group representatives is unreliable due to uncertain character evolution in early Alligatoridae. The earliest unambiguous fossil age for total and crown-group Caimaninae are 63.5 Ma and 18.06 Ma, respectively. These calibration points follow best practices and are vital for better constrained estimates of time calibrated analyses. Phylogeny continues to imply two separate Caimaninae dispersals between North and South America, but instead of a northward back-dispersal, we find two Palaeogene dispersals to South America an equally likely hypothesis. Miocene taxa of Central America previously assigned to the stem lineage ancestral to South American Caimaninae are reinterpreted as part of a Neogene northward expansion of the crown group.

Detrital zircon provenance of Permian to Triassic Gondwana sequences, Zealandia and eastern Australia

ABSTRACT Permian Parapara Group and Triassic Topfer Formation are small clastic sedimentary outliers that rest on Cambrian to Devonian basement terranes in the Western Province of South Island, New Zealand. New detrital zircon U-Pb age datasets from three Parapara sandstones, one Topfer sandstone and four age-equivalent eastern Australian sandstones reveal age and provenance information about former Gondwana intracontinental basins. Youngest significant zircon age populations of 264 ± 6 and 261 ± 2 Ma in two Parapara Group sandstones and 215 ± 2 Ma in the Topfer sandstone match fossil ages and indicate broadly syn-depositional igneous activity. The provenance of the igneous detritus was probably the nearby Median Batholith and/or its volcanic equivalents. Zircons in a third Parapara sandstone are predominantly Cambrian and Precambrian in age and represent a separate petrofacies with a local Western Province basement terrane provenance. Intra-basin provenance switching between Gondwana margin arc and older basement sources is thus documented in Gondwana basin sequences in Zealandia, as well as those in Australia and Antarctica.

Fossils improve phylogenetic analyses of morphological characters.

Fossils provide our only direct window into evolutionary events in the distant past. Incorporating them into phylogenetic hypotheses of living clades can help time-calibrate divergences, as well as elucidate macroevolutionary dynamics. However, the effect fossils have on phylogenetic reconstruction from morphology remains controversial. The consequences of explicitly incorporating the stratigraphic ages of fossils using tip-dated inference are also unclear. Here, we use simulations to evaluate the performance of inference methods across different levels of fossil sampling and missing data. Our results show that fossil taxa improve phylogenetic analysis of morphological datasets, even when highly fragmentary. Irrespective of inference method, fossils improve the accuracy of phylogenies and increase the number of resolved nodes. They also induce the collapse of ancient and highly uncertain relationships that tend to be incorrectly resolved when sampling only extant taxa. Furthermore, tip-dated analyses under the fossilized birth–death process outperform undated methods of inference, demonstrating that the stratigraphic ages of fossils contain vital phylogenetic information. Fossils help to extract true phylogenetic signals from morphology, an effect that is mediated by both their distinctive morphology and their temporal information, and their incorporation in total-evidence phylogenetics is necessary to faithfully reconstruct evolutionary history.

On the Supposed Presence of Miocene Tayassuidae and Dromomerycinae (Mammalia, Cetartiodactyla) in South America

The earliest record of North American mammals in South America is significant for constraining the timing of intercontinental faunal interchange. At present, the oldest securely dated remains of a North American terrestrial mammal in South America pertain to a late Miocene procyonid; a few other North American mammal groups are present in late Miocene and early Pliocene outcrops in South America, but most are not recorded until the late Pliocene or Pleistocene, after the complete emergence of the Panamanian Isthmus. This long-established pattern has recently been called into question by reports of a proboscidean, two tayassuids, and a dromomerycine cervoid in supposed late Miocene deposits of Peruvian Amazon. In this contribution, we analyze the taxonomic identities and stratigraphic provenances of the tayassuid and dromomerycine fossils in detail. We conclude that these specimens are not distinguishable from modern tayassuids (Tayassu pecari and Dicotyles tajacu) and cervids, and that previous taxonomic identifications are based on misinterpretation of characters or inadequate specimens. In addition, there is insufficient evidence to support a late Miocene age for these terrestrial cetartiodactyl fossils; the stratigraphic provenance of the specimens is highly dubious, and the fossils are likely Quaternary in age.

Phylogeny and time scale of diversification in the fossil-rich sunfishes and black basses (Teleostei: Percomorpha: Centrarchidae)

Species of the North American freshwater fish lineage Centrarchidae are apex predators in their habitats and are among the world’s most popular sport fishes. Centrarchids boast a rich fossil record that extends from the latest Eocene to the Pleistocene. To investigate the phylogeny and timing of diversification of Centrarchidae, we deploy a dataset of DNA sequences of 16 nuclear genes sampled from nearly all of the recognized and undescribed species. We also utilize previously published morphological datasets to assess the phylogenetic placement of one of the oldest known centrarchid fossils, †Plioplarchus whitei. A Bayesian multispecies coalescent species tree analysis provides insight on relationships that evaded resolution in earlier studies, such as the relationships of Acantharchus pomotis, the resolution of a clade consisting of species previously synonymized under the Spotted Bass, Micropterus punctulatus, and a clade of recently described species previously considered populations of the Redeye Bass, Micropterus coosae. This new molecular phylogeny and the inclusion of †P. whitei and other centrarchid fossils in the tip-dated fossilized birth–death analysis results in a new hypothesis of the timing of diversification in Centrarchidae that contextualizes the ages of centrarchid fossils to the timing of speciation among the extant species. In addition to providing new temporal perspectives on the diversification of freshwater fishes in North America, this study may close of the chapter of centrarchid phylogeny inferred using Sanger-sequenced genes, as the use of genomic-scale datasets becomes mainstream in the phylogenetics of fishes.

The Clicking Elateroidea from Chinese Mesozoic Deposits (Insecta, Coleoptera).

Simple SummaryFossil click beetles from the family Elateridae are frequent in Mesozoic deposits, especially in Russia and China. In order to understand their relationship to extant species, we need to search for evolutionary important characters that unite these dinosaur-era beetles with extant forms. We show that about one third of the identifiable click-beetles described from Mesozoic Chinese deposits are in fact members of other related families. Our results strengthen the view that these beetle groups are significantly older than often assumed, being present in the Early Jurassic. This is an important result as it indicates that molecular studies based on modern species do not replace paleontology—both are needed, even in the future.Recent molecular studies have suggested that the clicking beetle families Elateridae, Eucnemidae, Throscidae, and Cerophytidae evolved in the Jurassic and diversified in the Cretaceous. These studies paid little attention to fossils, using them only as dating tools. The identification of Elateridae fossils is challenging, as external synapomorphies are not known for this family. Elateridae can be identified only as something not belonging to the other related families, all of which have diagnostic synapomorphies. Most subfamilies and tribes of Elateridae do possess definite diagnostic characters, however, making their identification feasible. We checked the 28 Elateridae described from Chinese Mesozoic deposits. Twelve were Elateridae, seven were Eucnemidae, and one was a Throscidae. Three species could be Eucnemidae, but showed aberrant characters. Five species could not be placed and may not belong to Elateroidea at all. On the basis of these results we suggest that all previously described Elateridae fossils should be re-checked. They should be searched for synapomorphies defining Eucnemidae, Throscidae, and Cerophytidae. If such characters are not present, a click beetle type of fossil can be placed in Elateroidae incertae sedis. The Mesozoic Chinese Elateridae fossils all belong to clades that do not exist today, whereas the Mesozoic Eucnemidae subfamilies are extant ones. This may be the source of the disagreement between Elateridae fossil age and datings based on molecular studies. One new combination was made: Desmatus ponomarenkoi (Chang, Kiretjshuk & Ren, 2009) NEW COMBINATION (= Paradesmatus ponomarenkoi Chang, Kirejtshuk & Ren, 2009).

In situ wood fossil from Gorontalo, Indonesia

Gorontalo, one of the provinces in Indonesia, has not been widely known for its potential of wood fossil. The anatomical structures observation and the age estimation were conducted on two specimens of wood fossils buried in Tohupo Village, Bongomeme District, Gorontalo. The anatomical features of wood fossils were observed through thin slices of the cross, radial, and tangential sections using a Carl Zeiss-Axio Imager-A1m microscope. The description of anatomical features referred to the IAWA (International Association of Wood Anatomists) list of microscopic features for hardwood identification. The age estimation of the wood fossils was based on Geological Map (scale 1: 100.000) of the Tilamuta sheet, Sulawesi. Based on anatomical structures observation, the species of wood fossils were identified as Hopenium sp. (merawan/hopea) and Shoreoxylon sp. (balau). The estimated age of wood fossils was 3.6 to 1.8 million years before the present (BP) (between the late Pliocene and Early Plistocene periods).

Late Silurian to early Devonian development of the Chingiz accretion arc, West Junggar: insights into accretion arc evolution in the Central Asia Orogenic Belt

ABSTRACT Early Palaeozoic evolution of the Kazakhstan orocline in the Central Asian Orogenic Belt (CAOB) is key to reconstructing the Palaeozoic tectonic framework in Central Asia. This study presents field mapping, geochemistry, and geochronological data from the Wulasitai area of northern West Junggar to constrain the subduction polarity and major tectonic events in the Chingiz arc of the Kazakhstan orocline during the Early Palaeozoic. The mapping area outcrops imbricated coherent turbidite slices and mélanges that consist of chert, limestone, silt, sandstone, and conglomerate blocks in mudstone matrix, representing an OPS (Ocean Plate Stratigraphy) mélange in an accretionary complex. Existing fossil ages from these blocks range from the Ordovician to Silurian, while our new detrital zircon U-Pb samples from the turbiditic matrix yield maximum depositional ages (MDTs) from 428 ± 2 Ma to 450 ± 1 Ma. Detrital zircon ages of ~510 to 430 Ma in the mélange suggest the Chingiz arc to the south of the study area as a major sediment source, providing an indirect constraint on the polarity of subduction. We suggest that the northern part of the Chingiz arc may be underlain by southward subduction, with the accretionary complex located on the Wulasitai area of the northern West Junggar. The Wulasitai mélange is overlain depostionally by volcanic rocks carrying depleted HFSE and enriched LILE, LREE. The andesite and tuff are dated to 415 ± 5 Ma, 414 ± 3 Ma, and 402 ± 6 Ma, which we interpret as reflecting the development of the volcanic arc onto the previous subduction complex. This model implies the generation of the arc (accretion arc) as the slab rolling back and trench retreating, which may play an important role in the evolutionary history of CAOB.

Phylogenomics, biogeography, and evolution of the blue‐ or white‐fruited dogwoods (Cornus)—Insights into morphological and ecological niche divergence following intercontinental geographic isolation

AbstractThe eastern Asian (EA)–eastern North American (ENA) floristic disjunction represents a major pattern of phytogeography of the Northern Hemisphere. Despite 20 years of studies dedicated to identification of taxa that display this disjunct pattern, its origin and evolution remain an open question, especially regarding post‐isolation evolution. The blue‐ or white‐fruited dogwoods (BW) are the most species‐rich among the four major clades of Cornus L., consisting of ~35 species divided into three subgenera (subg. Yinquania, subg. Mesomora, and subg. Kraniopsis). The BW group provides an excellent example of the EA–ENA floristic disjunction for biogeographic study due to its diversity distribution centered in eastern Asia and eastern North America, yet its species relationships and delineation have remained poorly understood. In this study, we combined genome‐wide markers from RAD‐seq, morphology, fossils, and climate data to understand species relationships, biogeographic history, and ecological niche and morphological evolution. Our phylogenomic analyses with RAxML and MrBayes recovered a strongly supported and well‐resolved phylogeny of the BW group with three intercontinental disjunct clades in EA and ENA or Eurasia and North America, of which two are newly identified within subg. Kraniopsis. These analyses also recovered a potential new species but failed to resolve relationships within the C. hemsleyi–C. schindleri complex. In an effort to develop an approach to reduce computation time, analysis of different nodal age settings in treePL suggests setting a node's minimum age constraint to the lower bound of a fossil's age range to obtain similar ages to that of BEAST. Divergence time analyses with BEAST and treePL dated the BW stem back to the very Late Cretaceous and the divergence of the three subgenera in the Paleogene. By integrating fossil ages and morphology, a total evidence‐based dating approach was used in conjunction with time‐slice probabilities of dispersal under a DEC model to resolve ancestral ranges of each disjunct in the Miocene: Eurasia and ENA (disjunct 1), EA and western North America (disjunct 2), and EA (disjunct 3). The dated biogeographic history supports dispersal via the North Atlantic Land Bridge in the late Paleogene in disjunct 1 and dispersal via the Bering Land Bridge in the Miocene for disjuncts 2 and 3. Character mapping with a stochastic model in phytools and comparison of ecological niche, morphospace, and rate of evolution indicated differential divergence patterns in morphology, ecological niche, and molecules between disjunct sisters. Although morphological stasis was observed in most of the characters, evolutionary changes in growth habit and some features of leaf, flower, and fruit morphology occurred in one or both sister clades. A significant differentiation of ecological habitats in temperature, precipitation, and elevation between disjunct sisters was observed, suggesting a role of niche divergence in morphological evolution post‐isolation. The patterns of evolutionary rate between morphology and molecules varied among disjunct clades and were not always congruent between morphology and molecules, suggesting cases of non‐neutral morphological evolution driven by ecological selection. Our phylogenetic evidence and comparisons of evolutionary rate among disjunct lineages lend new insights into the formation of the diversity anomaly between EA and ENA, with particular support of an early diversification in EA. These findings, in conjunction with previous studies, again suggest that the EA–ENA disjunct floras are an assembly of lineages descended from the Mesophytic Forests that evolved from the early Paleogene “boreotropical flora” through varied evolutionary pathways across lineages.

Radiolarian age and geochemistry of cherts from the Atbashi accretionary complex, Kyrgyz South Tianshan

Cherts, radiolarites, and radiolarian cherts are one of the most important components of accretionary complexes, and much used in the reconstruction of imbricated sections of ocean plate stratigraphy, and of the palaeogeographic and tectonic settings of ophiolitic mélanges. There has been little research on radiolarian cherts in the Kyrgyz South Tianshan, and the tectonic setting and temporal framework of the South Tianshan ocean are controversial. Here, we report well‐preserved radiolarians in ribbon‐bedded cherts in an ophiolitic mélange of the Atbashi accretionary complex (South Tianshan, Kyrgyzstan), which provide key evidence of ambient Palaeozoic oceanic conditions. The hydrofluoric acid technique was used to extract from the cherty rocks siliceous radiolarian, which yielded an age of late Early Carboniferous. Analyses of major, trace, and rare‐earth elements of four cherts indicate they are biogenic and deposited with little hydrothermal influence in a hemipelagic to continental margin environment. Our fossil ages and geochemical results of the radiolarian cherts from the Atbashi accretionary complex indicate that the South Tianshan ocean was still open in the Late Carboniferous, implying that it was a wide, long‐lived, major ocean that closed by northward subduction.

Core surprise: What's inside a plate boundary?

Despite the fact that 90% of global seismicity occurs at plate boundary faults, our understanding of their internal structure is lacking. It’s not easy to see inside a plate boundary fault – typically composed of a high-strain fault core surrounded by a fractured damage zone – and when we can, it often requires expensive drilling projects that yield limited information on the internal structure of the whole fault. Understanding the internal structure of large faults is crucial, because their chemical and mechanical properties control how and where earthquakes rupture, nucleate and propagate. This in turn limits the size of the earthquake or the amount of radiated seismic energy, and consequently the severity of surface damage. The 1999 magnitude 7.7 earthquake along the Chelungpu plate boundary fault, for example – the second deadliest earthquake in Taiwan’s recorded history – saw significant variations in slip and ground motion at different locations along the fault which resulted in large local variations in casualties and damage. Subsequent field investigations related these variations to changes in the fault’s structure (i.e., clay width, geometry), which in turn controlled how the fault moved.

Ignoring Fossil Age Uncertainty Leads to Inaccurate Topology and Divergence Time Estimates in Time Calibrated Tree Inference

Time calibrated trees are challenging to estimate for many extinct groups of species due to the incompleteness of the rock and fossil records. Additionally, the precise age of a sample is typically not known as it may have occurred at any time during the time interval spanned by the rock layer. Bayesian phylogenetic approaches provide a coherent framework for incorporating multiple sources of evidence and uncertainty. In this study, we simulate datasets with characteristics typical of Palaeozoic marine invertebrates, in terms of character and taxon sampling. We use these datasets to examine the impact of different age handling methods on estimated topologies and divergence times obtained using the fossilized birth-death process. Our results reiterate the importance of modeling fossil age uncertainty, although we find that the relative impact of fossil age uncertainty depends on both fossil taxon sampling and character sampling. Sampling the fossil ages as part of the inference gives topology and divergence time estimates that are as good as those obtained by fixing ages to the truth, whereas fixing fossil ages to incorrect values results in higher error and lower coverage. The relative effect increases with increased fossil and character sampling. Modeling fossil age uncertainty is thus critical, as fixing incorrect fossil ages will negate the benefits of improved fossil and character sampling.

Tip dating with fossil sites and stratigraphic sequences.

Tip dating, a method of phylogenetic analysis in which fossils are included as terminals and assigned an age, is becoming increasingly widely used in evolutionary studies. Current implementations of tip dating allow fossil ages to be assigned as a point estimate, or incorporate uncertainty through the use of uniform tip age priors. However, the use of tip age priors has the unwanted effect of decoupling the ages of fossils from the same fossil site. Here we introduce a new Markov Chain Monte Carlo (MCMC) proposal, which allows fossils from the same site to have linked ages, while still incorporating uncertainty in the age of the fossil site itself. We also include an extension, allowing fossil sites to be ordered in a stratigraphic column with age bounds applied only to the top and bottom of the sequence. These MCMC proposals are implemented in a new open-source BEAST2 package, palaeo. We test these new proposals on a dataset of early vertebrate fossils, concentrating on the effects on two sites with multiple acanthodian fossil taxa but wide age uncertainty, the Man On The Hill (MOTH) site from northern Canada, and the Turin Hill site from Scotland, both of Lochkovian (Early Devonian) age. The results show an increased precision of age estimates when fossils have linked tip ages compared to when ages are unlinked, and in this example leads to support for a younger age for the MOTH site compared with the Turin Hill site. There is also a minor effect on the tree topology of acanthodians. These new MCMC proposals should be widely applicable to studies that employ tip dating, particularly when the terminals are coded as individual specimens.

Chronological problems in Chinese human fossil sites

Archeologists and chronologists have realized that dating age divergence exists in some human fossil sites. However, this problem has not been systematically elaborated and studied to date. This paper makes statistics and analysis on the dating results of 86 published Chinese human fossil sites and attempts to clarify this problem. We find that the U-series dating method has the largest proportion of application and occupies a prominent position in each dating method, 37 sites use one dating method, and 28 sites utilize more than two (including two) methods. Dating age divergence uses different methods in the same site, of which 17 sites are with large age divergence. We assume that the following are the reasons for the large dating age divergence in the same site: The taphonomy problems and the difference of the dating method itself. In summary, the problem of the dating age divergence in the same site is common. The taphonomy problems of human fossil sites must be discovered and corrected through multiple dating methods. The difference of the dating method itself also needs the combination of multiple dating methods for evaluation and judgment. We suggest the following multiple dating strategies: Early Pleistocene human fossil sites should mainly rely on paleomagnetic dating, and 26Al/10Be burial dating, climatic stratigraphy, and ESR dating methods should be combined to obtain a relatively accurate human fossil age. Middle Pleistocene sites should be based on paleomagnetic dating, climatic stratigraphy, 26Al/10Be burial dating, U series, ESR/U series, TT-OSL, and pIRIR dating methods. Three or more dating methods must be selected for cross-examination. Late Pleistocene site dating must be performed on the basis of U series, 14C, and OSL dating methods. 14C dating and DNA analysis can be cautiously conducted in Late Pleistocene sites. The use of multiple dating methods can avoid accidental errors caused by only one dating method, especially in the cave sites of Middle and Late Pleistocene. The summary of the dating results for 86 Chinese human fossil sites shows that some sites have applied multiple dating methods. After cross-checking, the following sites obtained reliable ages: Yuanmou, Zhoukoudian Localities, Bailong Cave, Dali, Panxian Dadong, Jinniushan, Xujiayao, Tianyuan Cave, Shuidonggou, and Xiaogushan. Certain sites should be further checked by adding dating methods, such as, Yunxian, Hualongdong, Maba, Changyang, Hexian, Ganqian Cave, Xinglong Cave, Luna Cave, Huanglong Cave, Fuyan Cave, Wuguidong Cave, Xianren Cave, Tongzi Cave, Mao-Mao-dong Cave, Chuandong, and Maludong. Twenty-one sites, such as, Meipu Longgu Cave, Jimuyan Cave, Baojiyan Cave, Guoshandong Cave, and Zhuzailong Cave, still have no dating research. We must make a detailed investigation and reinvestigation because the fossil discovery records of these sites may be unclear, or they may have unsuitable dating materials. Obtaining some ages from these sites is significant. The accurate age of human fossil is the basis for establishing the correct theory of human evolution in China. Multiple dating strategies should be adopted for the newly discovered human fossil sites. Such strategies should be used to check and evaluate the age of some important Chinese human fossil sites that have been previously discovered. Doing so can further improve the reliability of the dating results for Chinese human fossil sites.