Thursday 31 August 2023

Arenaerpeton supinatus: A new species of Temnospondyl Amphibian from the Triassic of New South Wales.

Modern Amphibians all belong to a single group, the Lisamphibians, which are quite closely related to the Amniotes (Reptiles, Birds, and Mammals). However, in the Carboniferous other Amphibian groups, such as the Temnospondyls and Ichthyostegids, which were more distantly related to the Amniotes. Although considered to be 'primitive' compared to modern Tetrapods, some Temnospondyls independently acquired Reptile-like traits such as the scaley skin and the ability to live away from water. The majority of Temnospondyls perished in the End Permian Extinction, but a few groups survived into the Mesozoic, and persisted as long as the Cretaceous. One of these groups was the Chigutisauridae, an exclusively Gondwanan group of wide-headed predatory, aquatic Temnospondyls, which first appeared in the Early Triassic of Australia and persisted across the southern continents until the mid-Cretaceous. However, despite having originated in Australia, the Australian fossil record of Chigutisaurids is very sparse, with three known species from Queensland, one from the Early Triassic, one from the Early Jurassic, and one from the Early Cretaceous, plus a possible species from the Late Triassic of South Australia.

In a paper published in the Journal of Vertebrate Paleontology on 3 August 2023, Lachlan Hart of the Earth and Sustainability Science Research Centre at the University of New South Wales, and the Australian Museum Research Institute, Bryan Gee of the Burke Museum and Department of Biology at the University of Washington, Patrick Smith, also of the Australian Museum Research Institute, and of the Department of Biological Sciences at Macquarie University, and Matthew McCurry, also of the Earth and Sustainability Science Research Centre at the University of New South Wales, and the Australian Museum Research Institute, and of the Department of Paleobiology at the Smithsonian National Museum of Natural History, describe a new species of Chigutisaurid Temnospondyl from the Early–Middle Triassic Terrigal Formation of New South Wales.

The new species is described from a single specimen, AM F125866, which was found among rocks obtained from Kincumber Quarry, approximately 90 km to the north of Sydney on the Central Coast of New South Wales, for the purpose of building a wall on a private property, and donated to the Australian Museum in the mid 1990s. The specimen  is preserved in ventral aspect (belly-up) in a piece of sandstone, with the forward part of the skeleton and the articulated skull preserved, as well as a soft-tissue outline of the body. Only the part (body fossil) of the specimen is known, the counterpart (would of the fossil) was not found, and was apparently lost during the quarrying process. The fossil proved to be impossible to further separate from the matrix without damaging it, and an attempt to X-ray the specimen using a large cargo scanner used by the Australian Border Force proved unsuccessful, as there was to little contrast between the fossil and the matrix.

The new species is named Arenaerpeton supinatus, where 'Arenaerpeton' means 'thing that creeps in the sand' a reference to the sandstone matrix in which the fossil was found, and 'supinatus' means 'on its back' a reference to the position in which the fossil was found. The specimen from which it is described comprises elements of the pre-maxilla, maxilla, vomers, parasphenoid, exoccipital, pterygoid, quadrate, quadratojugal, mandible, and possible remnants of the ectopterygoid, the onterclavicle and clavicle, a possible scapula, a humerus, radius, ulna, and metacarpal, and a near complete precaudal vertebral series with associated ribs. A small piece of what might be the pelvis is present, but no other parts of the pelvic girdle, hindlimbs, or tail.

Arenaerpeton supinatus, AM F125866, articulated skeleton. (A) Full fossil in ventral view. (B) schematic interpretation. Abbreviations:cl, clavicle; cp, cultriform process of the parasphenoid; ect, ectopterygoid; eo, exoccipital; h, humerus; ic, interclavicle; m, mandible; mca, metacarpal; mx, maxilla; p, pelvis; pmx, premaxilla; psph, parasphenoid; pt, pterygoid; q, quadrate; qj, quadratojugal; ra, radius; s, scapula; ul, ulna; v, vomer, ve, vertebrae. Light gray elements represent exposed bone. Darker sections represent cavities in the matrix. Unfilled outlines indicate unexposed bones within the matrix. Thomas Peachey in Hart et al. (2023).

Despite a small number of known fossils, Chigutisaurids are the only group of Temnospondyls which are known to have survived the End Triassic Extinction in Australia. Arenaerpeton supinatus is the second known Triassic species from Australia, along with Keratobrachyops australis, from the Early Triassic of Queensland (another Late Triassic probable Chigutisaurid is known from the South Australia, but this is poorly preserved and has not formally been described). Also known from Queensland are the Early Jurassic Siderops kehli, and the Early Cretaceous Koolasuchus cleelandi. Both of the post-Triassic species were large for Temnospondyls, with Siderops kehli having a total estimated length of 2.6 m, while Koolasuchus cleelandi reached about 3 m, while the Early Triassic Keratobrachyops australis was much smaller; its length cannot be reconstructed from the available material, but the largest known specimen has a maximum skull width of 14.5 cm. Arenaerpeton supinatus appears to be intermediate in size, with a maximum skull width of 23.6 cm, and a bodylength of 94 cm excluding the tail (which was not preserved, comparable with Triassic Chigutisaurids from India and South America. 

Reconstruction of Arenaerpeton supinatus, preying on the Ray-finned Fish Cleithrolepis granulata, which is also known from the Triassic of New South Wales. José Vitor Silva in Hart et al. (2023).

Arenaerpeton supinatus is the second known Temnospondyl from the Terrigal Formation of the Sydney Basin, the other being the Brachyopid Platycepsion wilkinsoni. This is only the second known co-occurrence of Chigutisaurid and Brachyopid Temnospondyls (the only two Temnospondyl groups which survived the End Triassic Extinction), with the two groups otherwise tending to be found in different settings, possibly implying different ecological specializations.

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Tuesday 29 August 2023

Archaeologists uncover ritually buried Red Deer from Bronze Age England.

Archaeologists carrying out exploratory work ahead of the construction of a new water supply network in the east of England have uncovered what appears to be a pair of ritually buried Red Deer at Navenby in Lincolnshire, according to a press release issued by Anglian Water on 9 August 2023. The Deer, which are thought to have been buried about 4000 years ago, were accompanied by pottery associated with the Bell Beaker Culture, a Bronze Age European Culture with appeared about 4800 years ago in Iberia, and spread across Europe and parts of North Africa, reaching Britain about 4450 years ago. The Deer show no signs of butchery (the removal of meat for consumption, which leaves cut marks upon the bones), and were therefore presumably intact when buried, although it is possible that they were ritually sacrificed for some purpose.

Remnants of two Red Deer found in a Bronze Age burrial at Navenby in Lincolnshire, England. Anglian Water.

Other than the burred Deer, no further traces of Bronze Age activity were found at Navenby, although the archaeologists did uncover a small Iron Age settlement, comprising two roundhouses and five smaller structures, which may have been grain stores, as well as the burial of three cremated and one uncremated individuals, which may date from the Roman period.

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Fireball meteor over Colorado

Witnesses in Colorado, Nevada, New Mexico, Utah, and Wyoming have reported observing a bright fireball meteor at around 6.30 am local time (around 9.30 am GMT) on Sunday 27 August 2023. The fireball is described as having moved from north to south, entering the atmosphere to the northeast of Boulder and disappearing over Colorado Springs. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 27 August 2023 Colorado meteor seen from Centennial, Colorado. Tara Barrett/American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings)and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

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Eleven killed by explosion at coal mine in Shaanxi Province, China.

Eleven people have died following an explosion at a coal mine in Shaanxi Province, China, on Monday 21 August 2023. The incident took place at the Xintai Coal Mine close to the city of Yan'An, about 900 km to the southeast of Beijing, at 8.26 pm local time. Ninety people are reported to have been below ground at the time of the evacuation, most of whom were evacuated safely, although two later died of injuries sustained in the explosion, and nine miners who failed to escape from the mine were later found dead by rescue teams. Another eleven people are still being treated in hospital for injuries sustained in the explosion; all are reported to be in a stable condition.

An aerial photograph of the Xintai Coal Mine in Yan'An, Shaanxi, taken on 22 August 2023. Xinhau.

Coal is formed when buried organic material, principally wood, in heated and pressurised, forcing off hydrogen and oxygen (i.e. water) and leaving more-or-less pure carbon. Methane is formed by the decay of organic material within the coal. There is typically little pore-space within coal, but the methane can be trapped in a liquid form under pressure. Some countries have started to extract this gas as a fuel in its own right. When this pressure is released suddenly, as by mining activity, then the methane turns back to a gas, expanding rapidly causing, an explosion. This is a bit like the pressure being released on a carbonated drink; the term 'explosion' does not necessarily imply fire in this context, although as methane is flammable this is quite likely.

Fire is much feared in coal mines due to this combination of flammable gas and solids, with methane and coal dust both potentially explosive when they come into contact with naked flames. To make matters worse, the limited oxygen supply in mines often means that such fires will involve incomplete combustion, in which all the oxygen is used up, but instead of forming carbon dioxide forms the much more deadly carbon dioxide, with potentially lethal consequences for anyone in the mine.

As coal is comprised more-or-less of pure carbon, and therefore reacts freely with oxygen (particularly when in dust form), to create carbon dioxide and (more-deadly) carbon monoxide, while at the same time depleting the supply of oxygen. This means that subterranean coal mines need good ventilation systems, and that fatalities can occur if these break down. 

Despite attempts to modernise its energy network, China is still reliant on coal for much of its energy, with 400 000 tonnes of coal mined in China in July 2023, and over 200 million tonnes of coal imported each year, most of it from Indonesia, Australia, South Africa, the United States, and Russia. China has been trying to reduce its dependence on foreign coal by expanding its own coal industry with new mines such as Xintai, but this has come at the cost of more accidents within the industry. 

An investigation into the cause of the explosion has now begun, with seven people reported to have been arrested, including the mine's owner and a major shareholder.

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Monday 28 August 2023

First images from NASA's air quality-monitoring TEMPO satellite released.

NASA has released the first set of images from its new Tropospheric Emissions: Monitoring of Pollution (TEMPO) satellite, which is intended to measure the concentrations of pollutant gasses over North America, and which was launched April 2023. The images, featured in a press release issued on 24 August 2023, shows the distribution of nitrogen dioxide, which is produced as a biproduct of burning fossil fuels and which is harmful to the respiratory tract, around major cities, and thoroughfares in North America on 2 August 2023. 

Nitrogen dioxide levels over the DC/Philadelphia/New York region at 4:24 p.m. on 2 August 2023, as measured by TEMPO. Kel Elkins/Trent Schindler/Cindy Starr/NASA Scientific Visualization Studio.

The satellite has been placed in a geostationary orbit 35 400 km above the equator and will continuously monitor an area between the Atlantic Ocean to the east, the Pacific Ocean to the west, the latitude of Mexico City to the south, and approximately mid-Canada to the north. It forms part of a network which now monitors much of the Northern Hemisphere for atmospheric pollution, including the South Korean Geostationary Environment Monitoring Spectrometer, and the European Space Agency's Sentinel 4 satellite.

Image showing nitrogen dioxide levels over Southern California at 12:14on 2 August 2023, as measured by TEMPOKel Elkins/Trent Schindler/Cindy Starr/NASA Scientific Visualization Studio.

The TEMPO satellite works by monitoring wave lengths at which gas molecules emit light. All molecules will absorb light at some wavelengths and emit it at others, and spectrographic instruments such as TEMPO are able to utilise this to determine the presence and concentration of individual molecules. For example, nitrogen, which makes up 80% of the Earth's atmosphere, emits light in the blue part of the spectrum, giving the sky its distinctive blue colour. Nitrogen dioxide has a distinctive orange-brown colour, while gasses such as methane and carbon dioxide radiate light in the infra-red part of the spectrum, which we experience as heat, leading to them being regarded as greenhouse gasses.

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Nautilus shell beads from the End Pleistocene and Early Holocene of Alor Island, Indonesia.

Body ornamentation appears to have been a key piece of Human behaviour from the dawn of our species, and in Island Southeast Asia traces of such ornamentation, or other forms of artistic expression, is often the first evidence of Homo sapiens moving into an area. For a long time, rock art and shell beads from this region have automatically been assumed to be of Holocene age, but in the past decade it has become clear that many such items are much older, and that Modern Humans may have been active in the area as much as 50 000 years ago.

In a paper published in the journal Antiquity on 15 August 2023, Michelle Langley of the Australian Research Centre for Human Evolution and School of Environment and Science at Griffith UniversityShimona Kealy of Archaeology and Natural History and the ARC Centre of Excellence for Australian Biodiversity and Heritage ar the Australian National UniversityMahirta of the Departemen Arkeologi at the Universitas Gadjah Mada, and Sue O’Connor, also of Archaeology and Natural History and the ARC Centre of Excellence for Australian Biodiversity and Heritage ar the Australian National University, report the discovery of crafted beads made from the shells of Nautilus pompilius from Alor Island in the Eastern Lesser Sunda Islands, which can be directly dated to about 12 000 years before the present.

The beads were found in Makpan Cave, a lava tube between the modern villages of Halmin and Ling Al on the southwest coast of the island. The entrance to the cave is currently 386 m from the shoreline, and 37.5 m above sealevel. Since Alor Island is extremely steep sided, the cave would have been within easy walking distance of the sea, even during Pleistocene low sealevel stands.

Location of Makpan on Alor Island, Indonesia (A)–(B) and site context showing main excavation pit outlined with range poles (C)–(D). Shimona Kealy in Langley et al. (2023).

Excavations at the cave were carried out by a joint team from the Australian National University and Universitas Gadjah Mada in June-July 2016. A 2 m x 2 m trench was excavated in four blocks (A, B, C, and D) in a series of 5 mm 'spits', down to a depth of 1.5 m, then a single block (B) was further excavated down to a depth of 3.5 m, where beach sand sterile of artefacts was found. Because only block B was excavated tor the full extent of the occupation, Langley et al. concentrate on this block in their study.

Stratigraphic sections for the upper 2 × 2m excavation at Makpan. Langley et al. (2023).

Dating of the sequence was based upon charcoal where this was found, and marine shells where it was not. Occupation of the site was divided into five phases. Phase 1 began about 43 076 years before the present, and lasted for about 28 000 years, incorporating spits 68-58. Phase 2 covers the Terminal Pleistocene, beginning from about 13 965 years before the present, and incorporates spits 57-37. Phase 3 is a substantial shell midden comprising spits 36-21, believed to have been laid down at the Pleistocene–Holocene transition, starting from about 11 805 years before the present. Phase 4 covers the Early-Middle Holocene, starting from about 10 430 years before the present, and comprising spits 20-9. Phase 5 comprises Neolithic deposits, starting from about 3663 years before the present, and comprises spits 8-1. There are some detectable gaps in this record, most notably one of about 3500 years between the end of Phase 2 and the start of Phase 1, with a shorted gap between Phase 3 and Phase 4. The rate at which sediments were deposited appears to have changed over time, with the highest sedimentation rate during Phase 3 and the lowest during Phase 1.

Stratigraphic sections for the lower 1 × 1m square B excavation at Makpan. Langley et al. (2023).

Langley et al. recovered at total of 577 shell beads and bead fragments, of which 36 were deemed to be complete or near complete (i.e. more than 75% of the original bead was present. Of the 36 complete or near complete beads, 33 are of an ovoid shape, with two central holes, while the remaining three are roughly circular with a single hole at their centre.

‘Intact’ (more than 75% intact) beads recovered from Makpan. Bead provenance (Square and Spit) is listed below each artefact, along with their analysis identifier shown in parentheses. Michelle Langley in Langley et al. (2023).

The majority of the beads were found within the midden layer, and are estimated to be dated to between 11 805 and 11 223 years before the present. However, some beads were found within Phase 4, potentially as late as 7284 years before the present, as well as in phases 2 (11 000-13 500 years before the present) and 1 (21 500-40 500 years before the present). The layers within the deposits at Makpan are generally considered to have good stratigraphic integrity, with little movement between the layers, however, small beads would have a high potential for working themselves downwards in loose deposits, so, since the lowest two beads came from spits 63 and 60 (likely to be more than 20 000 years old, and potentially significantly so), Langley et al. decided that it would be prudent to directly date these before including them in the study. Unfortunately, it was not possible to relocate either of these beads, which had apparently been lost since the excavation. 

A direct radiocarbon date was therefore obtained from the third and fourth lowest beads found, a fragment and whole bead recovered from spit 58, at the end of Phase 1. This produced ages of 12 800-11 400 years for the fragment and 12 440-11 810 for the whole bead, slightly younger than a marine shell from spit 57 (the beginning of Phase 2), which was dated to 13 276-12 930 years before the present. This supports an End Pleistocene age for the beads, and suggests a revision of a dating system where Phase 2 starts with spit 57 may need to be revised, given that direct dates have not previously been obtained from spits 58 or 59, and the similarity between the deposits of phases 1 and 2, which makes differentiating a boundary difficult.

All of the beads appear to have been made from the shells of Nautilus pompilius, a Cephalopod Mollusc with an nacreous aragonitic shell which typically lives 200-300 m beneath the surface, but can survive as deep as 800 m. Nautilus are occasionally eaten by Humans, but are more often collected for their distinctive shells, which have an attractive orange, brown, and white pattern on their outer surface and an  iridescent nacreous interior.  Nautilus are caught by fishermen in the Philippines today, who use Bamboo and Rattan traps lowered to depths of 150-200 m. It is possible that the ancient inhabitants of Alor Island caught Nautilus, either intentionally or as a bycatch from other fishing activities (they are known to have been proficient fishermen), but more likely that they were collected from beaches, where they still wash up today.

Nautilus pompilius shell reaches to around 200mm in length, providing a large quantity of nacreous shell for material culture production. Michelle Langley in Langley et al. (2023).

All the intact and fragmentary beads were examined under a light microscope to look for traces of manufacture and use. Nacre is also known to have been used to make fishhooks at Makpan, so it was particularly important to be able to differentiate between bead fragments and fishhook fragments. Usefully, the examined fishhooks were all found to have been made from the shells of marine Gastropods of the genera Rochia and Turbo. Thus, the beads tend to be smaller and flatter than the hooks, which have a distinctive plano-convex shape. 

Typical fragments of two-holed beads. Scale bar is 1mm. Michelle Langley in Langley et al. (2023).

All the beads from Makpan are small, with intact specimens having a maximum width of between 4.4 mm and 11.6 mm. The overall shape of the bead, oval or circular, appears to have been achieved by controlled flaking, followed by grinding of the outer surface, though a significant proportion were never ground and retain a scalloped outer surface. The perforations were made with a handheld unifacial drill, which left striations on the shell surface, which do not form a full circle and have a wavey trajectory. This drilling was done from the inner, nacreous side of the shell, resulting in chips breaking away from the outer surface as the drill broke through. The striations left by the drilling suggest a stone tool was used.

Features of the Makpan Nautilus two-holed beads. (A) Near-complete example for Square B, Spit 18 with red ochrous residue between and in perforations; (B) & (C) Chipping on the outer shell surface created during unifacial drilling. From Square B, Spits 36 and 23, respectively; (D) & (E) Striations and red ochrous residue on back of bead from Square B, Spit 23; (E) Hand-held drilling of perforations on bead from Square B, Spit 23; Restriction of red ochrous residue to between the two perforations on bead from Square B, Spit 36; (G) polish on edge of bead from Square B, Spit 32. Scale bars are 1mm. Michelle Langley in Langley et al. (2023).

Surprisingly for small objects recovered from a site in a tropical environment, use wear and evidence of polishing can be observed on the beads. The high points of the outer (non-naceous) side of the beads are well polished, and the outer edges of the beads appear well rounded. The perforations are also well rounded, showing notching associated with a thread or string, with a distinct wear-notch between the two holes on the double-holed beads, as well as often having traces of a red, haematite-based pigment. This suggests that the beads were sewn, with their shiny nacreous side out, onto some form of soft fabric as a form of appliqué.

Indications of the mode of attachment on the two-holed beads. (Above) Examples of larger fragments from two-holed beads; (Below) mid-region of two-holed beads showing concentrations of residues and notches (indicated by red arrows). (A) Artefact 131; (B) Artefact 117; (C) Artefact 155. White scale bars are 1mm. Michelle Langley in Langley et al. (2023).

Many of the fragmentary beads appear to have broken across the centre part of the bead, and from the perforations to the outer edge by the shortest route. This supports the idea that they were sewn tightly to a cloth surface, creating a pressure point in the centre. Several beads also show signs of being delibarely ground or scratched with an rock on their exposed surface, possibly to increase their reflectivity. 

Langley et al. were able to split the double holed oval beads into four distinct groups, which they term A, B, C, and D. Type A have a distinctive elongated ellipse shape, while types B, C, and D are closer to round in shape, but fall into distinct size categories, Type B having a mean width of 10.5 mm, Type C having a mean width of 7 mm, and Type D having a mean width of 5.5 mm. Type A, B, and D beads were found throughout the sequence, but type C beads were only found in spits 30-34 (within the End Pleistocene shell midden).

Nautilus shell beads first appear at Makpan between 12 800 and 11 400 years ago and persist for about 5000 years. These beads present the oldest know evidence for appliqué decoration in Island Southeast Asia, although pigment-stained fragments of Nautilus shell have been found at Asitau Kuru on Timor-Leste which date back to at least 42 000 years ago. Further afield, the use of red pigments for both body decoration and for other forms of art is documented in Southeast Asia from a range of Pleistocene and Holocene sites, and such pigments appear to have been adopted by Homo sapiens in Africa and the Levant early in the history of our species. The Makpan beads appear to represent a new example of a persistent habit of combining red pigments with light or bright coloured objects.

Appliqué beads are widely documented in the Eurasian Palaeolithic archaeological record, using both shell and ivory as a material. Examples of this include the Arene Candide 1 burial from Italy, dated to between 28 000 and 27 000 years before the present, which had a cap with appliqué shell beads, and the Sunghir individuals from Vladimir Oblast in southern Russia, dating from between 33 000 and 30 000 years before the present, which had garments covered with ivory beads, both of which are attributed to the Gravettian Culture. The Gravettian is the oldest known culture to which the use of appliqué can confidently be attributed, although some older Aurignacian sites, such as Hohle Fels in Germany and Solutré in France have yielded beads which could have been used in appliqué decoration.

Although the Makpan beads are much later than the Eurasian examples, they form part of a shared cultural tradition found across several islands in southern Wallacea. Similar double-holed beads have been found on Kisar Island to the east of Alor Island, and Timor-Leste to the south, with one bead from Matja Kuru 2 on Timor-Leste directly dated to between 10 110 and 9629 years before the present, and another from Here Sorot Entapa on Kisar Island dated to 12 019–12 400 years before the present. This shows that the decorative tradition was shared between at least three islands in the region during the End Pleistocene and Early Holocene. Making garments covered with appliqué beads in this way would have required a considerable investment in time and labour, and such effort across multiple sites implies a shared worldview and culture across these sites, and the transmission of social information between these sites. 

The date at which these beads first appear correlates with the first appearance of obsidian tools on these islands; made with a material not found on any of the islands, and comes only very slightly after the appearance of fishhooks in the area, itself a manifestation of an increased investment in gaining resources from the sea. Polished shell adzes, considered another part of this shift to utilizing maritime resources, first appear on Obi Island in the Maluku islands in north-eastern Wallacea, and reach Timor by the early Holocene. These adzes are a rare part of these assemblages, with the oldest examples identified by pieces of shell which flaked from them during drilling, making it likely that the technology was in use quite a while before the oldest known examples which have been found.

It is likely that a trade  and social network which passed along technologies such as appliqué beads and materials such as obsidian would also have involved some genetic exchange, important for isolated communities on small islands, and such interchange of marriage partners across islands would have further deepened cultural ties and furthered the exchange of ideas, something potentially more important than the exchange of physical goods between islands, and which has been supported by recent genetic studies of End Pleistocene populations in Wallacea.

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