Tracing Neandertal ancestry in modern human genomes

Leonardo Iasi was awarded the Otto Hahn Medal in recognition of his work on the frequency, duration and biological consequences of gene flow between Neandertals and modern humans. During his doctoral studies, he developed new models to enhance the dating of admixture events, shedding light on the timing and mechanisms by which Neandertal DNA entered the genomes of modern humans. His work shows that Neandertal gene flow into the ancestors of present-day non-Africans occurred over a period of several thousand years around 47,000 years ago. This substantially refines previous estimates of the timing of this mixture. Iasi also revealed patterns of rapid natural selection acting on Neandertal DNA in modern humans shortly after gene flow occurred.

“Receiving the Otto Hahn Medal is a great honour, and I am very grateful for this recognition,” says Iasi. ‘What fascinates me about this work is that present-day genomes still carry traces of encounters between modern humans and Neandertals, even though these events took place tens of thousands of years ago. These traces are incomplete and have been shaped by many evolutionary processes, but with appropriate models, they can reveal surprisingly detailed information about when gene flow occurred and how natural selection acted afterwards. One of the most exciting results for me was discovering that Neandertal admixture was not an isolated event, but rather a process that unfolded over several thousand years.”

Iasi completed his PhD in Biology at Leipzig University and the Max Planck Institute for Evolutionary Anthropology. His dissertation was supervised by Svante Pääbo and Benjamin M. Peter. He has continued his research as a postdoctoral researcher in the Department of Evolutionary Genetics at the Max Planck Institute for Evolutionary Anthropology since January 2025.

Investigating the evolutionary roots of human bipedalism

Rhianna Drummond-Clarke was awarded the Otto Hahn Medal for her study of chimpanzee locomotion and ecology, which tested hypotheses about the evolution of human bipedalism. Her dissertation was the first to examine the locomotion and posture of wild chimpanzees living in open, dry savannah habitats – similar to where our earliest ancestors (hominins) lived. During 20 months of fieldwork in Tanzania's Issa Valley, she observed and documented over 14,000 instances of chimpanzee behaviour, comparing behaviour in closed forests and open woodlands. Contrary to previous assumptions, her work revealed that chimpanzees exhibit more arboreal behaviour in open woodlands than in forests and that bipedalism occurs most frequently in trees. These findings lend weight to the theory that hominin bipedalism first evolved in trees, and are the first to show how arboreal bipedalism could have been adaptive to open woodland.

“I am honoured to receive the Otto Hahn Medal for this research,” says Drummond-Clarke. “Fieldwork at Issa made it very clear to me how important it is to test evolutionary hypotheses in ecologically relevant settings. The chimpanzees did not behave exactly as traditional models might predict – in the more open parts of the landscape, for example, they were often in the trees, and this was also where we most frequently observed bipedal behaviour. I find these findings exciting because they show that the evolution of human bipedalism cannot be understood through simple habitat-based explanations alone, but requires closer examination of how primates interact with their complex environments.”

Drummond-Clarke completed her PhD at Friedrich Schiller University Jena and the Max Planck Institute for Evolutionary Anthropology. Her dissertation was supervised by Tracy Kivell, Manuela Schmidt, and Martin Fischer. Since June 2025, she has been a postdoctoral researcher in the Department of Human Origins at the Max Planck Institute for Evolutionary Anthropology.

Advancing research in evolutionary anthropology

The two awardees have both contributed to key questions in the field of human evolutionary research, such as how interactions with archaic humans have shaped the genomes of present-day people and how the behaviour of our closest living relatives can shed light on the origins of key human traits.

“Leonardo Iasi and Rhianna Drummond-Clarke have both made remarkable contributions to key questions in the field of evolutionary anthropology,” says Johannes Krause, Managing Director at the Max Planck Institute for Evolutionary Anthropology. “Their work demonstrates how innovative methods, long-term field research and interdisciplinary perspectives can transform our understanding of our origins. We warmly congratulate them on this well-deserved recognition.”

Iasi and Drummond-Clarke were awarded the Otto Hahn Medal at the Max Planck Society's Annual Meeting in Frankfurt on 17 June 2026.

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Since 1978, the Max Planck Society has honoured up to 30 young researchers each year with the Otto Hahn Medal in recognition of their outstanding scientific achievements. The medal is named after Otto Hahn (1879–1968), a German chemist and Nobel laureate who served as president of the Society from 1948 to 1960.

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