Paleontologists have presented a description of the oldest representative of the carnivorous marsupial family (Dasyuridae). This species, named Miyumba chrisdickmani, inhabited the state of Queensland about 18.24 million years ago, at the beginning of the Miocene.
Miyumba chrisdickmani was a very small mammal, weighing approximately between 23 and 33.5 grams. It hibernated and fed on insects and various invertebrates. According to data published in the journal Australian Zoologist, scientists had previously been unable to find reliable representatives of Dasyurids in geological layers older than 5.3 million years.
The family Dasyuridae includes about 70 species, existing or extinct in the past, and is found in Australia, as well as on the islands of Tasmania and New Guinea. Known representatives include Tasmanian devils (Sarcophilus harrisii), spotted quolls (Dasyurus), and antechinus mice (Antechinus). Larger and medium-sized species of this group feed on carrion and vertebrates, while smaller species specialize in hunting insects and other invertebrates.
According to modern scientific models, this group of Dasyurids appeared in the early Miocene, around 18 million years ago. However, in fossil records, its representatives only appear for the first time in the early Pliocene, about 5.3 million years ago. A team of paleontologists led by Timothy Churchill from the University of New South Wales managed to describe the first undisputed representative of Dasyurids from pre-Pliocene deposits.
The focus of the scientists was seven samples of lower jaws containing teeth—premolars and molars. These finds were discovered at the UNESCO World Heritage site of Riversleigh, located in northwestern Queensland, Australia. The age of these remains has been determined to be 18.24 million years, corresponding to the early Miocene. Churchill and his staff concluded that the owner of these jaws belonged to a previously unknown species and genus in the order of carnivorous marsupials, based on the structure of the molars. Additional analysis allowed it to be classified within the family of carnivorous marsupials as a clade that is sister to all other members of the family. The new species has been named Miyumba chrisdickmani. The genus name comes from the Australian word waanyi, which denotes the area around Riversleigh, and the specific epithet is dedicated to ecologist Christopher Dickman for his contribution to the study of modern dasyurids.
Calculations showed that M. chrisdickmani weighed only 23.3–33.5 grams, comparable to the smallest extant carnivorous marsupials, such as antechinus mice and sminthopsis mice (Sminthopsis). The authors suggest that representatives of this species lived in the humid tropical forests covering northern Australia in the middle and early Miocene, and judging by their size, hunted insects and other invertebrates, resembling modern New Guinean marsupial mice (Murexia).
By integrating M. chrisdickmani into the evolutionary scheme of the order of carnivorous marsupials, Churchill and his co-authors also established that another presumed pre-Pliocene representative of the Dasyurid family, Mayigriphus orbus, indeed belongs to this group. This species lived in Riversleigh in the early late Miocene and, like M. chrisdickmani, was very small, weighing about 20 grams. It is assumed that M. orbus was an early representative of the subfamily Sminthopsinae, which is adapted to arid open landscapes.
Thanks to the discoveries of M. chrisdickmani and the recognition of M. orbus as a member of the family, previous ideas about the origin of Dasyurids have been corrected. According to the updated reconstruction, Dasyurids appeared at the end of the Oligocene or beginning of the Miocene, approximately 23.2 million years ago, five million years earlier than previous estimates. Initially, these species inhabited humid tropical forests, but later some of their descendants managed to adapt to other environments, including deserts and savannas.
In the context of paleontology, three new fossils of Obdurodon insignis—a toothed ancestor of platypuses—were also described. These finds were made in the Namba formation of South Australia during the Late Oligocene and date back to about 25 million years ago. Analysis of the scapulocoracoid showed that O. insignis likely closely resembled extant platypuses and possessed good swimming skills. Researchers believe that these animals inhabited a large lake or lake system alongside many freshwater inhabitants, including small dolphins. The results of this study were also published in the journal Australian Zoologist.
Paleogeneticists analyzed DNA extracted from the remains of ancient people buried on the island of Gotland during the Neolithic period. The research established that several individuals living at different times suffered from the plague. One of these cases dates back to approximately 3490–3110 BCE, making it one of the earliest recorded globally.
The plague is known as one of the most devastating infectious diseases in human history, claiming millions of lives. The most famous outbreaks include the Justinianic Plague and the Black Death, which occurred in the Middle Ages. Although modern people face this threat, the scale of such epidemics today is significantly different.
Thanks to the study of ancient DNA, scientists have concluded over the past decade that human contact with the plague bacillus (Yersinia pestis) occurred long before medieval pandemics. Genetic data indicates that prehistoric inhabitants of Eurasia were infected with this infection more than five thousand years ago. Confirmations of this were found through the analysis of remains from Lake Baikal and the Baltic region, as well as in other regions, including Germany and Scandinavia.
A team of scientists from the UK, Mexico, Turkey, France, and Sweden, led by Matthias Jakobsson from Uppsala University, focused on DNA taken from ancient residents of Gotland. The main focus was on farmers and herders of the Funnel Beaker culture (approximately 4000–2800 BCE) and hunter-gatherers/fishermen of the Pit Pottery culture (approximately 3300–2300 BCE), who coexisted on the island for five hundred years during the Middle Neolithic. Additionally, the genome of one late Neolithic individual (around 2030–1890 BCE) was sequenced.
According to geneticists, the late Neolithic individual was a male and represents the earliest known case in Gotland to possess a steppe ancestral component associated with carriers of the Yamnaya archaeological culture. Researchers also found long homozygous segments in a representative of the Funnel Beaker culture, indicating kinship between his parents (e.g., cousins).
The search for ancient pathogen DNA generated the greatest scientific interest. Analysis of samples from 32 people from Gotland showed that the only late Neolithic male in the sample was infected with the plague bacterium. Furthermore, he was also found to be infected with the bacterium Y. enterocolitica, the causative agent of enteric yersiniosis. A similar co-infection was previously identified when studying ancient remains from mainland Sweden.
Although the DNA of the plague bacillus was presumably present in the remains of four other individuals, confirming this proved more difficult than in the case of the late Neolithic male. Nevertheless, scientists concluded that various strains of this bacterium circulated repeatedly in Gotland during the Neolithic era. The earliest probable case of infection dates back to the Ansärva megalithic tomb, whose remains date to the period 3490–3110 BCE.
Previous studies have shown that not only humans but also dogs could contract the plague bacillus in Gotland. DNA analysis of about fifteen animals revealed an infected specimen. This pet of Pit Pottery culture carriers lived at least 4500 years ago, and its burial dates back to the 2nd century BCE.
Geneticists studied the DNA of two adult individuals buried together in the 2nd century BCE in the Fanagoria crypt. It was determined that these remains belonged to an elderly man and woman from different populations. The man had genetic proximity to ancient populations of Asia Minor and the Middle East, while the woman descended from a population presumed to have lived in Eastern or Northern Europe.
