Key findings include:

• Overall past-year recreational ketamine use increased by 81.8% from 2015 to 2019 and by 40% from 2021 to 2022.
• Adults with depression were 80% more likely to have used ketamine in the past year in 2015-2019, but this association weakened in later years. In 2021-2022, ketamine use increased only among those without depression.
• In 2021-2022, adults aged 26-34 were 66% more likely to have used ketamine in the past year compared to adults aged 18-25. Those with college degrees were more than twice as likely to have used ketamine compared to people with a high school education or less.
• People were more likely to use ketamine if they used other substances, such as ecstasy/MDMA, GHB, and cocaine.

The researchers recommend expanding prevention outreach to settings like colleges, where younger adults may be at heightened risk, as well as providing education on the harms of polydrug use, particularly in combination with opioids. As medical ketamine becomes more widely available, they also emphasize the need for continued surveillance of recreational ketamine use patterns and further research to understand the factors that contribute to ketamine use.

The study, published online in the Journal of Affective Disorders, was led by Kevin Yang, M.D., a third-year resident physician in the Department of Psychiatry at UC San Diego School of Medicine. The research was supported by the National Institute on Drug Abuse of the National Institutes of Health.

The study, published in PNAS, addresses major gaps in the human genetic history of the Wallacean Archipelago and West Papuan regions of Indonesia — a region with abundant genetic and linguistic diversity that is comparable to the Eurasian continent — including the analysis of 254 newly sequenced genomes.

In combination with linguistic and archaeological evidence, the study shows that Wallacean societies were transformed by the spread of genes and languages from West Papua in the past 3,500 years — the same period that Austronesian seafarers were actively mixing with Wallacean and Papuan groups.

“My colleagues at the Indonesian Genome Diversity Project have been studying Indonesia’s complex genetic structure for more than a decade, but this comprehensive study provides confirmation that Papuan ancestry is widespread across Wallacea, pointing to historical migrations from New Guinea,” says lead author Dr Gludhug Ariyo Purnomo, from the University of Adelaide’s School of Biological Sciences.

“By connecting the dots between genetics, linguistics, and archaeology, we now recognise West Papua as an important bio-cultural hub and the launching place of historical Papuan seafarers that now contribute up to 60% of modern Wallacean ancestry.”

Genomic research is also becoming increasingly important for developing new medicines tailored to specific genetic backgrounds.

“In the era of precision medicine, understanding the genetic structure of human groups is vital for developing treatments that are helpful rather than harmful, with Wallacea and New Guinea having been poorly represented in past genomic surveys,” Dr Purnomo says.

Associate Professor Ray Tobler, from ANU, says Wallacea had been isolated for more than 45,000 years since the arrival of the first human groups, and the more recently arriving Papuan and Austronesian migrants reconfigured Wallacean culture by introducing new languages that diversified and intermingled to create its rich linguistic landscape.

“Our findings suggest that the Papuan and Austronesian migrations were so extensive that they have largely overwritten the ancestry of the first migrants, making the recovery of these ancient migrations from genetic data challenging,” says Professor Tobler, who is also an Adjunct Fellow at the University of Adelaide’s Australian Centre for Ancient DNA.

According to the researchers, there are challenges in reconstructing past movements of people using modern genetic data due to historical migrations and movements.

“There’s also been so much movement in Wallacea in the past couple of thousand years, due to the spice trade and slavery, that it obscures the relationship between geography and genetics,” Associate Professor Tobler says.

“What we know about Wallacea and New Guinea is just the tip of the iceberg, but the use of ancient DNA can help to overcome some of these challenges and help us to understand the origins and legacy of human journeys to the region stretching back tens of thousands of years.”

But now, a newly described dinosaur whose fossils were uncovered by University of Wisconsin-Madison paleontologists is challenging that narrative, with evidence that the reptiles were present in the northern hemisphere millions of years earlier than previously known.

The UW-Madison team has been analyzing the fossil remains since they were first discovered in 2013 in present-day Wyoming, an area that was near the equator on Laurasia. The creature, named Ahvaytum bahndooiveche, is now the oldest known Laurasian dinosaur, and with fossils estimated to be around 230 million years old, it’s comparable in age to the earliest known Gondwanan dinosaurs.

UW-Madison scientists and their research partners detail their discovery Jan. 8, 2025, in the Zoological Journal of the Linnean Society.

“We have, with these fossils, the oldest equatorial dinosaur in the world — it’s also North America’s oldest dinosaur,” says Dave Lovelace, a research scientist at the University of Wisconsin Geology Museum who co-led the work with graduate student Aaron Kufner.

Discovered in a layer of rock known as the Popo Agie Formation, it took years of careful work by Lovelace and his colleagues to analyze the fossils, establish them as a new dinosaur species and determine their estimated age.

While the team doesn’t have a complete specimen — that’s an exceedingly rare occurrence for early dinosaurs — they did find enough fossils, particularly parts of the species’ legs, to positively identify Ahvaytum bahndooiveche as a dinosaur, and likely as a very early sauropod relative. Sauropods were a group of herbivorous dinosaurs that included some famously gigantic species like those in the aptly named group of titanosaurs. The distantly related Ahvaytum bahndooiveche lived millions of years earlier and was smaller — much smaller.

“It was basically the size of a chicken but with a really long tail,” says Lovelace. “We think of dinosaurs as these giant behemoths, but they didn’t start out that way.”

Indeed, the type specimen of Ahvaytum bahndooiveche, which was full-grown but could have been slightly bigger at its maximum age, stood a little over one foot tall and was around three feet long from head to tail. Although scientists haven’t found its skull material, which could help illuminate what it ate, other closely related early sauropod-line dinosaurs were eating meat and would likely have been omnivorous.

The researchers found the few known bones of Ahvaytum in a layer of rock just a little bit above those of a newly described amphibian that they also discovered. The evidence suggests that Ahvaytum bahndooiveche lived in Laurasia during or soon after a period of immense climatic change known as the Carnian pluvial episode that has previously been connected to an early period of diversification of dinosaur species.

The climate during that period, lasting from about 234 to 232 million years ago, was much wetter than it had been previously, transforming large, hot stretches of desert into more hospitable habitats for early dinosaurs.

Lovelace and his colleagues performed high-precision radioisotopic dating of rocks in the formation that held Ahvaytum’s fossils, which revealed that the dinosaur was present in the northern hemisphere around 230 million years ago. The researchers also found an early dinosaur-like track in slightly older rocks, demonstrating that dinosaurs or their cousins were already in the region a few million years prior to Ahvaytum.

“We’re kind of filling in some of this story, and we’re showing that the ideas that we’ve held for so long — ideas that were supported by the fragmented evidence that we had — weren’t quite right,” Lovelace says. “We now have this piece of evidence that shows dinosaurs were here in the northern hemisphere much earlier than we thought.”

While the scientific team is confident they’ve discovered North America’s oldest dinosaur, it’s also the first dinosaur species to be named in the language of the Eastern Shoshone Tribe, whose ancestral lands include the site where the fossils were found. Eastern Shoshone tribal elders and middle school students were integral to the naming process. Ahvaytum bahndooiveche broadly translates to “long ago dinosaur” in the Shoshone language.

Several tribal members also partnered with Lovelace and his UW-Madison colleagues as the researchers sought to evolve their field practices and better respect the land by incorporating the knowledge and perspectives of the Indigenous peoples into their work.

“The continuous relationship developed between Dr. Lovelace, his team, our school district, and our community is one of the most important outcomes of the discovery and naming of Ahvaytum bahndooiveche,” says Amanda LeClair-Diaz, a co-author on the paper and a member of the Eastern Shoshone and Northern Arapaho Tribes. LeClair-Diaz is the Indian education coordinator at Fort Washakie school and coordinated the naming process with students and tribal elders — a process that started under her predecessor, Lynette St. Clair.

“Typically, the research process in communities, especially Indigenous communities, has been one sided, with the researchers fully benefiting from studies,” says LeClair-Diaz. “The work we have done with Dr. Lovelace breaks this cycle and creates an opportunity for reciprocity in the research process.”