After a brave fight, our colleague and friend, Dr Tilman Lenssen-Erz - who had only been in so-called retirement for two years - succumbed to an invincible illness on 10 November 2023. He was a research associate at the Africa Archaeology of the Institute of Prehistory Archaeology at the University of Cologne from 1986 to 2021. During this time, he played a key role in shaping rock art research and the development of indigenous knowledge for prehistoric and early historical archaeology, both nationally and internationally.

Tilman Lenssen-Erz studied African Studies, Prehistoric Archaeology and History of Religion at the University of Marburg from 1977 to 1982. His master's thesis was devoted to "Studies on the Verb in Kwang (Chad)". This work was followed by years as a member of staff and local director on various archaeological excavations in Germany, Tunisia and Egypt. With his broad interdisciplinary expertise, he took on the project "Rock paintings in the Upper Brandberg" in Cologne in 1986. This led to his doctoral thesis at the Goethe University Frankfurt in 1997 entitled "Gemeinschaft - Gleichheit - Mobilität. Felsbilder im Brandberg, Namibia, und ihre Bedeutung.  Grundlagen einer textuellen Felsbildarchäologie".

Between 1986 and 2006, Tilman Lenssen-Erz shaped and directed the world's most comprehensive publication of prehistoric rock art, which was accompanied by a data recording system whose innovative methodology benefited from his linguistic knowledge. Based on field documentation compiled by Harald Pager between 1977 and 1985, six volumes were published in the Africa Praehistorica series (Cologne: Heinrich-Barth-Institut).

As a member and applicant in the Cologne Collaborative Research Centre 389 ACACIA (1995-2007), Tilman Lenssen-Erz enriched rock art archaeology in the Ennedi Mountains (Chad) with his research approaches.

Since 2012, he has been co-founder and co-applicant of the African Archaeology Archive Cologne (AAArC), whose development and maintenance extended over several projects, most recently in FAIR.rdm, the central research data management in the DFG priority programme SPP 2143 Entangled Africa.

Since 2008, Tilman Lenssen-Erz has dedicated his research to making indigenous knowledge of recent San hunters in southern Africa accessible to archaeologists. This initially resulted in 'Tracking in Caves' (with Priv.-Doz. Dr habil. Andreas Pastoors), a globally acclaimed project to analyse prehistoric footprints in Palaeolithic European caves in collaboration with indigenous African San trackers. In two further projects entitled 'Indigenous Knowledge and Archaeoinformatics' and 'Modelling of prehistoric human behaviour' (with Prof. Dr Eleftheria Paliou), since 2019 indigenous hunters in Namibia have been accompanied while hunting in order to incorporate empirical data and indigenous explanatory patterns into existing archaeological models.

Archaeology has lost an innovative, widely networked, enormously productive researcher, our institute a colleague who saw science first and foremost as social practice. Deeply well-read, politically and socially committed, blessed with an abundance of humour (including black humour), he had expertise, encouragement, advice and action for everyone right to the end. We believe he will be remembered all over the world as a constructive, exemplary, generous, self-critical and always inspiring colleague, reviewer, expert and mentor. We mourn his loss.