Giant four-legged kangaroo survived until 20,000 years ago, study reveals

A four-legged giant kangaroo that formerly roamed Papua New Guinea (PNG) may have lived as recently as 20,000 years ago, a press release announced on Friday.

The fresh analysis indicates the kangaroo lived long after other large-bodied 'megafauna' on mainland Australia went extinct and underscores the significance of the use of modern analytical techniques to confirm timelines of life on Earth.

Megafauna bones from the prolific Nombe Rock Shelter fossil site reveal an unexpected survival

To learn more about the fascinating natural history of PNG, paleontologists from Flinders University and archaeologists and geoscientists from Australian National University reexamined megafauna bones from the prolific Nombe Rock Shelter fossil site in Chimbu Province.

New dating methods from the analysis reveal that when people first arrived in the PNG Highlands, possibly 60,000 years ago, numerous large mammal species, including the extinct thylacine and a marsupial that resembled a panda (named Hulitherium tomasettii), were still present there.

Surprisingly, two sizable extinct kangaroo species, one of which bounded on four legs rather than two, may have survived in the area for 40,000 years longer.

In a press release, Prof. Tim Denham, co-leader of the new study reveals, "If these megafaunal species did indeed survive in the PNG Highlands for much longer than their Australian equivalents, then it may have been because people only visited the Nombe area infrequently and in low numbers until after 20,000 years ago."

Denham explains that the Nombe rock shelter is the only location in New Guinea where it is known that people have lived there for tens of thousands of years. The area also contains the remnants of extinct megafaunal species, most of which are exclusively found in New Guinea.

Knowledge of New Guinea's faunal and human history is poor compared with that of mainland Australia

The professor who first conducted fieldwork in the highlands of Papua New Guinea in the 1990s adds, "New Guinea is a forested, mountainous, northern part of the formerly more extensive Australian continent called 'Sahul' but our knowledge of its faunal and human history is poor compared with that of mainland Australia."

The latest Nombe study, according to study co-author Professor Gavin Prideaux of the Flinders University Palaeontology Laboratory, is consistent with earlier research from Kangaroo Island. Such research also suggests megafaunal kangaroos may have survived until about 20,000 years ago in some of the more remote regions of the continent.

A reminder that broad generalizations about extinction are 'more harmful than helpful'

Prideaux claims that many broad generalizations concerning the extinction rates of megafauna have been "more harmful than helpful."

"Although it is often assumed that all of the megafaunal species in Australia and New Guinea became extinct coast to coast by 40,000 years ago, this generalisation is not based on very much actual evidence," Prideaux explains.

Archaeologists first discovered the concealed rock shelter in the 1960s. Still, the most intense fieldwork was carried out between 1971 and 1980 by Dr. Mary-Jane Mountain of the Australian National University- also one of the authors of the most recent paper.

Mountain's work provided the first description and interpretation of the Nombe site, which contributed significantly to knowledge of the human history of the PNG Highlands. 

An early hypothesis now confirmed with the advent of new dating techniques in science

"Mary-Jane (Mountain) initially hypothesised that megafauna at the site may have survived for tens of millennia after human colonisation, but this has only been confirmed with the advent of new techniques in archaeology, dating and palaeontological science," says Professor Denham.

According to Professor Prideaux, these novel uses of cutting-edge analytical methods or fresh digs at the Nombe site will further support timings for late-existing megafauna and the length of human settlement in PNG.

The new study was published in Archaeology in Ocean. 

Study Abstract:

Australian continent have long been controversial. This is due, in no small part, to inadequate knowledge of exactly when these species were lost from different ecosystems. The Nombe rockshelter in the highlands of Papua New Guinea is one of very few sites on Sahul with as-yet-unrefuted evidence for the survival of megafaunal species until more recently than 40 thousand years (ka) ago. However, our understanding of the age of this site has been based on radiocarbon dating. Here we present new U–Th ages on large marsupial specimens from the deposit and identify a range of postcranial elements to species that include the diprotodontid Hulitherium tomasettii, kangaroo Protemnodon tumbuna and thylacine Thylacinus cynocephalus. Direct U–Th ages of 27–22 ka ago on faunal remains of Protemnodon tumbuna and another large unidentified macropodid are consistent with the existing radiocarbon chronology, yet are minimum ages due to the potential for post-depositional uptake of 238U and stratigraphic reworking. Pollen analyses indicate perhumid, montane forests dominated by Nothofaguspersisted, with minimal human disturbance from at least c.26–20 ka ago up to the terminal Pleistocene. Collagen fingerprinting (ZooMS) demonstrates the potential of protein-based identification of megafaunal remains at Nombe in the future. This study leaves open the possibility of extended coexistence between some megafaunal species in the montane rainforests of New Guinea and intermittently visiting groups of people, and underscores the need for further investigation of the Nombe deposit. Although preliminary, these findings reinforce the view that debates regarding megafaunal extinctions on Sahul require a greater appreciation of species-specific temporalities and the degrees of human impact on diverse habitats across the continent.