DMT Depression Trial, Epibatidine Poison in Navalny Case, and the Mystery of the Chin | Science Weekly

Three science headlines anchor this week’s Science Weekly. First, a small trial finds that DMT, administered with psychotherapy, can provoke rapid antidepressant effects in treatment-resistant depression, with benefits lasting several months and the therapy potentially easier to scale than longer psychedelic sessions. Second, five countries claim Navalny was killed with the frog poison epibatidine, discussing detection methods and possible signals behind such a choice. Third, a chin mystery is revisited: researchers show that modern humans’ chins may be an evolutionary byproduct rather than a selected trait. The hosts contrast DMT with psilocybin therapies and reflect on how these discoveries fit into the broader landscape of mental health treatment and brain science.

Overview: DMT and psychedelic-assisted therapy

The episode begins with a discussion of a small clinical trial on dimethyltryptamine, or DMT, as part of psychedelic-assisted therapy for treatment-resistant depression. The study involved 34 participants who received a single infusion of DMT (over about 10 minutes) and were supported by skilled psychotherapists, with placebo controls for comparison. Depression symptoms were assessed before treatment and at several follow-up points. Reporters note an immediate antidepressant effect in those who received DMT, with effects lasting up to three months and in some cases six months, alongside a range of subjective experiences such as visual and auditory hallucinations and ego dissolution. The host draws a comparison to psilocybin-assisted therapy, highlighting that psilocybin typically produces longer, two-hour experiences, whereas DMT sessions are shorter and potentially easier to scale. A key idea from the lead investigator, described through an analogy, is that the drug may "shake up" entrenched thinking patterns and enable new cognitive pathways while psychotherapy helps reinforce new patterns. A host quote from a leading researcher emphasizes how psychedelics may reset rigid brain-plasticity patterns, enabling more flexible thinking—and that broader, real-world application will require larger, more robust trials. A quote is used to illustrate the concept of reshaping cognition in depressive states, and the section ends by acknowledging that this is a small, early study, with more work needed to understand long-term outcomes and practical implementation.

"If you think of your patterns of thinking as tracks in a snowy landscape, let's say some of those tracks are sort of quite entrenched... what the drug seems to do as an analogy is basically shake up all the snow on the landscape, redistribute it" - David Eritzo

Epibatidine and the Navalny poisoning case

The transcript then covers 5 countries’ dramatic statement that Navalny was murdered using epibatidine, a potent toxin found on the skin of certain South American dart frogs. The discussion explains that epibatidine is a very strong analgesic with significant toxicity, and researchers note that the chemical could be synthesized in the lab. Detection of the toxin in Navalny’s body is attributed to methods such as gas chromatography and mass spectrometry, though the exact analytic steps have not been released publicly. Toxicology expert Alistair Hay explains that epibatidine acts by binding to nicotine receptors in the nervous system, causing paralysis and potentially suffocation if muscles fail to relax and allow breathing. The hosts and experts consider why such an unusual poison might be chosen, acknowledging that while a dramatic message could be intended, others question that interpretation. Swansea University’s Luca Trento offers multiple possibilities, including messaging about capability or revenge, reflecting a long history of poison use in statecraft. The discussion emphasizes the complexities of attributing intent and the need for careful, evidence-based inference as more samples and data become available.

"there's this idea that perhaps it's sending a message of look at our capabilities. We have the capability to use all sorts of weird and wacky poisons to do away with people we don't like" - Doctor Luca Trento

The chin mystery: an evolutionary byproduct

Finally, the podcast returns to a curious anatomical question: why do humans have chins when other primates do not? A University of Buffalo team conducted precise skull measurements across multiple species, reconstructing the last common ancestor skull and analyzing how facial features could change due to genetic drift. Their findings suggest that on six of nine measured aspects, the human chin shows no evidence of selective pressure; instead, the chin may be a byproduct of broader facial evolution as brains grew and faces became more vertical and flatter. The upper jaw receded, allowing the lower jaw to project beyond the teeth, producing the chin as a byproduct rather than a chosen trait. The discussion invokes Stephen Jay Gould’s concept of an evolutionary spandrel, using the navel as another example of a byproduct rather than an adaptation. The hosts reflect on how this challenges the habit of assigning purposeful explanations to every quirk in anatomy and highlights the value of evolutionary perspectives in understanding human uniqueness.

"the chin arose, but not because it was useful to have a chin, it just arose because other things were happening in the evolution of our face that produced a chin along the way" - Ian Sample

All three topics are explored with careful caveats about sample sizes, replication, and real-world applicability, underscoring the ongoing nature of research. The episode closes with a reminder to readers to follow Guardian Science reporting for updates and further analysis of these evolving stories.