Re-dating the oldest known figurative cave art.

The rock-art left behind by prehistoric cultures has the potential to provide us with insights into the lives of these long-vanished peoples. Dating this art is notoriously difficult. In the past few decades the predominant approach has been the analysis of uranium and its decay products within flowstone layers partially covering ancient art. Flowstone is formed by the deposition of calcium carbonate onto surfaces by evaporating water; typically water that has flowed through limestone deposits then run out onto a surface such as a cave wall or cliff face before evaporating. The most obvious examples of this are stalagmites and stalactites, though many caves have an interior surfaces covered by flowstone. Where these flowstone deposits occur in caves with paintings they will often overlay the artwork, which means that if the flowstone can be dated, then a minimum age for the art can be established (as the art cannot be younger than the flowstone that overlays it).

This method has been used to date ancient art in many parts of the world, including Western Europe, Island Southeast Asia, and Russia. Notably, a hand-stencil in Spain has been dated to 64 800 years before the present, which implies that it must have been made by a Neanderthal artist, although the reliability of the data used in this study has been questioned. The oldest date we currently have for figurative cave art comes from Sulawesi, Indonesia, where an image of a Warty Pig, Sus celebensis, at Leang Tedongnge in the Maros-Pangkep karst has been given a minimum age of 45 500 years.

The methods used to date flowstone samples to date have relied upon dissolving a sample to form a solution, something which will tend to homogenise the sample, averaging the age of multiple layers overlaying a piece of art, and therefore producing a younger age estimation for the art than if the oldest of these layers could be isolated. 

In a paper published in the journal Nature on 3 July 2024, a team of scientists led by Adhi Agus Oktaviana of the School of Humanities, Languages and Social Science at Griffith University, the Pusat Riset Arkeometri of the Badan Riset dan Inovasi Nasional, the Griffith Centre for Social and Cultural Research, and the Center for Prehistory and Austronesian Studies, and Renaud Joannes-Boyau of the Geoarchaeology and Archaeometry Research Group at Southern Cross University, present the results of a study which used laser-ablation uranium-series dating to provide more accurate dates for the Leang Tedongnge image, as well as other examples of cave art in the same region. 

The laser-ablation method enables the targeting of an area 44 μm in diameter, within a laboratory environment. This enables far smaller samples to be collected than with previous methods, which typically involved grinding a sample from the rockface with a rotary tool. With the laser ablation method it is possible to take a polished thin section of rock, and target points upon that, which is both cheaper and less destructive than traditional methods, as well as far more accurate, as it enables specifically targeting the layer of rock directly overlaying the pigment.

Map of the study area. (a) The Indonesian island of Sulawesi, showing the location of the southwestern peninsula (area inside rectangle). (b) South Sulawesi, with the limestone karst area of Maros-Pangkep indicated by blue shading. The locations of cave sites with dated Late Pleistocene rock art were as follows: 1, Leang Bulu’ Sipong 4; 2, Leang Karampuang; 3, Leang Tedongnge; 4, Leang Timpuseng. Oktaviana & Joannes-Boyau et al. (2024).

At the Leang Bulu’ Sipong 4 site in the Maros-Pangkep karst, a 4.5 m wide panel on the rear wall of a cave depicts a number of Human, or Therianthrope (Human-Animal hybrid) figures, interacting with Warty Pigs and Anoas (Dwarf Buffalo), Bubalus sp.. The figures are holding some form of objects, possibly spears or ropes. The artwork may depict a hunting scene, or possibly a visual representation of a myth.

Dated rock art panel at Leang Bulu’ Sipong 4. (a) Photostitched panorama of the rock art panel. Ther, Therianthrope. (b) Tracing of the dated rock art panel showing the results of laser-ablation uranium-series dating. (c) Transect view of the rock art sample BSP4.5 after removal from the artwork, highlighting the paint layer and the three integration zones (ROIs) and associated age calculations. (d) Laser-ablation-multicollector inductively coupled plasma mass spectrometry imaging of the BSP4.5 thorium²³²/uranium²³⁸ isotopic activity ratio. Oktaviana & Joannes-Boyau et al. (2024).

The imigary at Leang Bulu’ Sipong 4 is covered by four distinct speleothems (flowstone deposits), which have previously been dated to minimum ages of 35 100 years, 43 900 years, 40 900 years, and 41 000 years. The new data obtained by Oktaviana & Joannes-Boyau et al. revises these dates to minimums of 27 600 years, 39 600 years, 39 500 years, and 48 000 years. Most of these ages are similar or older to the previously obtained ages, though one younger date was obtained, possibly because Oktaviana & Joannes-Boyau et al. were careful to avoid areas showing clear signs of post-depositional alteration. 

Since the speleothems overlie the rock art, the oldest speleothem must still be younger than the art, giving a minimum age. The art was previously dated to a minimum of 43 900 years old, but Oktaviana & Joannes-Boyau et al.'s data raises that minimum age to 48 000 years, an increase of over 4000 years, older than the previous oldest dated art at Leang Tedongnge.

At the Leang Karampuang site, again in the Maros-Pangkep karst, a ceiling panel depicts three Human or Therianthrope figures interacting with an Animal, probably another Warty Pig, although the preservation here is poor due to surface exfoliation (flakes breaking off the surface of the limestone), and extensive overlying coralloid growths (small nodes of calcite, aragonite or gypsum that form on surfaces in caves). The image executed in red, and comprises the large, Pig-like Animal, 92 x 38 cm, in side view, with an infill pattern of stripes or lines, consistent with depictions of Pigs and other Animals elsewhere in South Sulawesi. There are other Pig depictions within the Leang Karampuang cave, although it is uncertain if they are the same age as the dated example. The Pig is surrounded by three Humanoid figures. The largest of these is 42 v 27 cm and lacks legs; it has both arms extended and appears to have a rod-shaped object in its left hand.  The second figure measures 28 x 25 cm and is located directly in front of the Pig, with its head in front of the Pig's snout. The final figure, measuring 35 x 5 cm, is upside-down relative to the other figures, with its legs splayed out away from the Pig and one hand reaching towards the Pig's head. A possible fourth figure may have once been present between the first and third figures. There are also at least three hand stencils on the same panel, two which appear to be contemporary with the Pig, plus one darker one which is partially overlain by the Pig, and presumably, therefore, pre-dates it.

Oktaviana & Joannes-Boyau et al. collected samples from four coralloid growths, one overlying each of the figures, plus one from the Pig. The oldest date came from the coralloid overlying the second figure, with a minimum age of 51 200 years. The minimum dates from the first and third figures were 18 700 years and 44 000 years respectively, while the coralloid growth from the Pig yielded a minimum age of 31 900 years. Thus, if the figures and Pig do represent a single piece of artwork, as seems likely, then the whole scene can be assumed to have a minimum age of 51 200 years, making it the oldest known piece of figurative art in the world. 

Dated rock art panel at Leang Karampuang. (a) Photostitched panorama of the rock art panel. (b) Tracing of the rock art panel showing the results of laser-ablation uranium-series dating. (c) Tracing of the painted scene showing the Human-like figures (H1, H2 and H3) interacting with the pig. (d) Transect view of the coralloid speleothem, sample LK1, removed from the rock art panel, showing the paint layer and the three integration zones (ROIs), as well as the associated age calculations. (e) Laser-ablation-multicollector inductively coupled plasma mass spectrometry imaging of the LK1 thorium²³²/uranium²³⁸ isotopic activity ratio. Oktaviana & Joannes-Boyau et al. (2024).

Oktaviana & Joannes-Boyau et al.'s method shows that the Leang Bulu’ Sipong 4 art is over 4000 years older than the previously determined age, with a minimum age of 48 000 years, while the Leang Karampuang art is at least 51 200 years old. These dates significantly increase the maximum known age of figurative art. The oldest known art dates from the Middle Stone Age of southern Africa, between 75 000 and 100 000 years ago, but this comprises geometric marks carved into ochre nodules. Figurative art is presumed to have arisen within Africa, and from there to have been carried around the world by migrating Humans, but there is currently no evidence for this, and it cannot be excluded that this form of expression arose in another region and then spread back to Africa.

The South Sulawesi art also challenges to long-standing preconceptions about cave art, which have come about largely from studies based upon the extensive European rock-art record. These are that Humans and/or Human-like figures did not appear in rock art until the very end of the Pleistocene, and the other is that narrative compositions were absent from early rock art. 

Three of the oldest dated rock art panels in the world come from South Sulawesi, Leang Karampuang, at least 51 200 years old, Leang Bulu’ Sipong, at least 48 000 years old, and Leang Tedongnge, at least 45 500 years old, all include figures, and all appear to involve interactions between the figures and one-another and/or Animals which imply a narrative context. Another piece of cave art, at Leang Timpuseng, dated to at least 35 300 years before the present, depicts a Pig standing in a painted line, presumably representing a ground surface. This depiction of composed scenes presumably had some communicative function, allowing the telling of a story through a narrative interpretation of the art, probably in conjunction with oral storytelling. Thus, this cave-art can also be interpreted as evidence of the emergence of a consistent form of mythology, many thousands of years before any such evidence appears in Europe.

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The Earth approaches aphelion.

The Earth will reach its aphelion, the furthest point in its orbit from the Sun, a distance of 1.017 AU (1.017 times the average distance between the Earth and the Sun) or 152 099 968 km, at 5.06 am GMT on Friday 5 July 2023. The Earth's orbit is slightly eccentric and slightly variable, leading to the distance between the Earth and the Sun varying by about 3.4% over time, reaching aphelion early in July each year and perihelion (the closest point on its orbit to the Sun) early in January. The exact distance at aphelion and perihelion each year varies, with this year's aphelion being slightly closer to the Sun than last year (2023), when the Earth reached 152 290 632 km from the Sun on 5 July, but slightly further from the Sun last year, when it will only reacha distance of 152 087 774 km.

The difference between the Earth's perihelion (closest point to the Sun) and aphelion (furthest point from the Sun). Time and Date.

This is counter intuitive to inhabitants of the Earth's Northern Hemisphere, who often assume that the Earth is closest to the Sun in midsummer, when in fact it is at its furthest away. This is because the tilt of the Earth plays a far greater role in our seasons than the distance from the Sun, and the Northern Hemisphere has just passed its Summer Solstice, i.e. the point at which the North Pole was pointing as close to the Sun as it ever gets, so that the Northern Hemisphere is currently getting much more sunlight than the Southern. The Earth's surface receives about 7% less sunlight at aphelion to at perihelion, but this is far less than the seasonal variation caused by the tilt of the Earth (23% in each hemisphere).

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Using bone histology to understand the lifestyle of the Triasic Diapsid Ozimek volans.

The outcrops of Late Triassic rock in the village of Krasiejow in western Poland have been the subject of palaeontological investigations since the 1990s, yielding a large number of important Tetrapod fossils, including the Temnospondyls Metoposaurus krasiejowensi and Cyclotosaurus intermedius, the Phytosaur Paleorhinus cf. arenaceus, and the Dinosauroform Silesaurus opolensis. One notable Krasiejow Vertebrate is the Diapsid Ozimek volans, which has been interpreted as a potential gliding Animal on the basis of its very long and graceful forelimb and hind-limb bones. 

Ozimek volans was originally interpreted as a Sharovipterygid, grouping it with the Middle-Late Triassic Sharovipteryx mirabilis from Kyrgyzstan, also thought to have been as a glider, but more recently has been considered to be a member of the Tanystropheidae, a group of early Archosauromorphs often exhibiting long necks and tails, at least some of which may have been aquatic.

No close relative of Ozimek volans has a similar limb arrangement; a similar pattern is seen in Sharovipteryx mirabilis, but this can be ruled out as a close relative on the basis of other parts of its anatomy, suggesting the similarity is the result of similar ecological adaptations, rather than common ancestry. Interestingly, Sharovipteryx mirabilis has a preserved membrane reaching the end of its hind limbs, leading weight to the idea that this species was adapted to gliding, and therefore that the similar morphological adaptations seen in Ozimek volans could also be adaptations to aerial behaviour. 

In Birds and Pterosaurs, flight was achieved not just by the elongation of the limbs, but by numerous adaptations to reduce the weight of the skeleton. The most notable of these is the appearance of pneumatic bones, in which the dense marrow filling of the bone is replaced with a hollow, air-filled cavity. This is known in living Birds, and has been demonstrated in Mesozoic Birds, as well as closely related Theropod groups, and Sauropods, although it is only inferred in Pterosaurs, on the basis of the large size these Animals achieved. Both Birds and Pterosaurs have extremely thin bone walls, made of dense fibrolamellar bone tissue, which is very strong and better able to withstand the stresses of flight.

Notably, neither the presence or absence of pneumatic bone nor fibrolamellar bone tissue can be used as absolute determiners of flying behaviour. Fibrolamellar bone tissue is found in a number of Archosaur groups which show no other adaptations to flying, but absent in both small Birds and Bats, while Bats also lack pneumatic bone, something found in the (clearly non-areal) Sauropods. Thus, to establish the flying capacity of an extinct Animal it is necessary to look at its whole morphology, including skeletal and muscular adaptations and the possible presence of flight membranes and/or feathers.

Gliding is a form of flight in which the Animal has active control of aerodynamic forces, but is unable to gain altitude by muscular activity. Such behaviour can be hard to determine in an Animal simply from its morphology, as it is achieved in different ways in a very wide range of organisms, with no single set of adaptations common to all. Indeed, many gliding organisms are morphologically little different to their closest non-gliding relatives, achieving flight purely through behavioural changes. Examination of living gliding Mammals suggests that long humeri and femora improve the aspect ratio of gliding Animals, and that this becomes more important as the Animal becomes larger. Little is currently known about the bone histology of gliding Mammals, although some Flying Squirrels have a light-weight humerus and more circular diaphysis in cross-section compared to non-gliding taxa, which helps to resist torsional loads and provide resistance to multidirectional bending.

Ozimek volans has been noted to have had very thin bone walls, an adaptation associated with weight-reduction and flight, but its histology has not, to date, been examined, limiting our understanding of the living Animal's growth and life history.

In a paper published in the journal Palaontology on 26 June 2024, Dorota Konietzko-Meier of the Institute of Organismic Biology at the University of Bonn, Elżbieta Teschner, also of the Institute of Organismic Biology at the University of Bonn, and of the Institute of Biology at the University of Opole, Agnieszka Tańczuk of the Department of Zoology and Nature Protection at the Maria Curie-Skłodowska University in Lublin, and Martin Sander, again of the Institute of Organismic Biology at the University of Bonn, present the results of a study of the bone histology of Ozimek volans, and the implications of this for the life history and behaviour of the living Animal. 

Most of the material from which Ozimek volans was described is held in the collection of the Institute of Paleobiology of the Polish Academy of Sciences in Warsaw, though two blocks containing bones assigned to the species are held in the collection of the Institute of Biology at Opole University, and it is material from one of these blocks which is used in Konietzko-Meier et al.'s study. The block contains a cluster of bones interpreted as a partial skeleton, including articulated cervical vertebrae, possible coracoids and a pes, as well as a humerus and a femur, although Konietzko-Meier et al. note that the humerus is only 46% of the size of the largest known humerus, and therefore have been presumed to have come from a juvenile, while the femur is the largest known femur assigned to the species, and at least twice as long as the humerus, making it unlikely that they were from the same Animal.

Konietzko-Meier et al. took three thin sections, each about 40μm thick, from the midshaft of the humerus, one transverse, one longitudinal and one oblique tangential, and two from the femur, the bone here being too thin for an oblique section to be taken. These were then examined under both light and scanning electron microscopes at the University of Bonn.

Simplified phylogeny and long bones of Ozimek volans from the Late Triassic of Krasiejów (Poland). (A) Simplified phylogeny showing the position of Ozimek volans among Archosauromorpha, the black silhouette on the right represent the skeletal restoration of Ozimek, with the flight membrane stretched between the elongated forelimbs and hindlimbs. (B) Left humerus UOPB 1148a in medial view. (C) Right femur UOPB 1148b in anterior view. The white lines mark the cutting planes: 1, transverse section; 2, longitudinal section; 3, oblique tangential section. Scale bars represent 10 cm (A) and 10 mm (B) and (C). Konietzko-Meier et al. (2024).

The humerus has a thickness of 3.4 mm at the site where it was sampled, with a cortex (outer layer of bone) thickness of 0.5 mm. This cortex is made up of two layers, the periosteal portion, which is laid down on the exterior as the bone grows, and a compact endosteal layer, formed from the inner surface outwards as a secondary structure, by reworking of the original bone. The outer periosteal is more heavily mineralized, and made up of fibrous lamellae with simple vascular canals, with several lines of arrested growth (marks left in growing bone by slowed growth at one time of year, typically winter in a temperate climate). The fibres which make up this layer are not arranged at random, but have a longitudinal orientation. No sign of pneumosteum can be seen anywhere on the bone.

Microstructure and histology of the humerus UOPB 1148a midshaft of Ozimek volans from the Late Triassic of Krasiejów (Poland). (A)–(C) Overview of the histological framework visible in the transverse section in: (A) normal light; (B) polarized light; (C) with lambda filter. (D) Schema of the distribution of the growth marks visible in the transverse section of the humerus midshaft. (E)–(G) closeup of the posterior part of cortex with clearly visible lamellae and growth marks in: (E) normal light; (F) polarized light; (G) with lambda filter. (H)–(J) Close-up of the anterior fragment of cortex with visible island of coarse compact cancellous bone and growth marks in: (H) normal light; (I) polarized light; (J) with lambda filter. (K) Scanning electron microscope photograph showing the osteocyte lacunae surrounded by a network of canaliculi. (L)–(M) Overview of the histological framework visible in the longitudinal section in: (L) normal light; (M) polarized light; note the vascular canal. (N) Close-up of the fragment of cortex visible in the longitudinal section in polarized light. (O)–(Q) Overview of the histological framework visible in the oblique tangential section in: (O) normal light; (P) polarized light; (Q) with lambda filter. Continuous lines indicate reversal lines; dashed lines mark lines of arrested growth. Abbreviations: A, annulus; CCCB, coarse compact cancellous bone; eA, endosteal annulus; eZ, endosteal zone; PO, primary osteon; SV, simple vascular canal. Scale bars represent: 500 μm (A(–(D), (L), (M), (O)–(Q); 200 μm (N); 100 μm (E)–(J); 20 μm (K). Konietzko-Meier et al. (2024).

The femur is 2.7 mm in width at the point where it was sampled, with a cortex thickness of 0.2 mm. The structure of this bone is less complex, with signs of bone resorption on the inner surface, but no endosteal cortex layer. The periosteal layer is again lamellar and highly mineralized, with several lines of arrested growth. Vascular canals are more tightly backed than in the humerus. 

Microstructure and histology of the femur UOPB 1148b midshaft of Ozimek volans from the Late Triassic of Krasiejów (Poland). (A)–(C) Overview of the histological framework visible in the transverse section in: (A) Normal light; (B) polarized light; (C) with lambda-filter. (D) Close-up of the cortex with visible well-organized lamellae system, image in polarized light. (E)–(F) Close-up of the cortex with preserved fragments of coarse compact cancellous bone in: (E) normal; (F) polarized light. (G)–(I) Close-up of the anterior fragment of cortex with visible growth marks in: (G) normal light; (H) polarized light; (I) with lambda filter; the arrow indicates the second zone. (J)–(L) Overview of the histological framework visible in the longitudinal section in: (J) normal light; (K) polarized light; (L) with lambda filter. Continuous lines indicate reversal lines; dashed lines mark lines of arrested growth. Abbreviations: A, annulus; CCCB, coarse compact cancellous bone; PO, primary osteon; SV, simple vascular canal; Z, zone. Scale bars represent: 500 μm (A)–(C), (J)–(L); 100 μm (E)–(I); 50 μm (D). Konietzko-Meier et al. (2024).

Konietzko-Meier et al. recognise that their sample size is small, but propose thar some simple observations about bone growth in Ozimek volans can be made. Bone growth is typically driven from the periosteal surface, where lamellae of new cortex tissue are laid down. A line of bone reworking called the Haversian substitution front progresses outwards from the medullary (inner) edge of the bone, producing a layer of secondary tissue including Haversian bone. At the same time, a resorption line also works outwards from the inner surface, removing bone tissue, and sometimes overtaking the Haversian substitution front.

This three-front model of bone growth was first observed in Sauropods, but has now been found in a wide range of Tetrapod groups. However, the compact endosteal layer is a tissue not seen in Sauropods (or most other Tetrapods) and may represent a fourth growth front (i.e. lamellar bone/Haversian bone/compact endostreal bone/resorbtion line). Notably, the Hacersian growth front in Ozimek volans appears to be very slow, generally being obliterated by the endostreal growth front and resorption line.

Lamellar bone is common in Tetrapods, particularly non-endothermic ones, although it is also found in many small Mammals. However, the lamellar structure of Ozimek volans is exceptionally well-developed, unlike anything seen in any other fossil group. However, something similar has been observed in living Bats, and is thought to be an adaptation enabling the formation of lone, lightweight, and strong bones needed for flight in a group which has not evolved pneumatic bone (is has also been suggested that the adoption of strong lamellar bone rather than pneumatic bone has placed a restriction on the size to which bones can grow). It is therefore quite possible that this adaptation in Ozimek volans was also an adaptation to flight (although in this case unpowered).

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