Alexandra van der Geer

Searching for evidence of dwarf elephants

I am a palaeontologist, specialised in the evolution of mammals on islands worldwide. The inclusion of extant, endemic island species and introduced species in my research enables me to measure the effect of time. As a crucial extension, I analyse the impact of humans on island ecosystems since the Pleistocene.


Island biogeography; island biodiversity; insularity; mammals; vertebrate palaeontology; extinctions; palaeoecology; taxonomy


The evolution and extinction of insular mammals worldwide, past and present.

Body size evolution is perhaps the best known aspect of island mammals, with pony-sized elephants and gorilla-sized lemurs. Many exceptions to this 'island rule' exist, because many variables influence the direction and degree of size evolution. Crucial variables are competitors, predators and island geography. The extinction of island biodiversity is an ongoing problem on islands worldwide. Understanding the impact of humans is crucial to prevent further loss.

Dwarf elephants with their mainland ancestors


A selection of my research topics .

Island biodiversity and human impact

Island faunas differ from those on the mainland. Endemic species live here isolated from competing species and free from terrestrial predators. They often evolve unique and sometimes bizarre adaptations. When humans settle on the islands, this unique…
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Changing invaders

How introduced rats have changed during their colonization of Pacific islands. Humans have been transporting vertebrates to islands worldwide since prehistory, often with dramatic impact on native fauna. These introduced species appear to change very…
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  • van der Geer, A., Lyras G., de Vos, J. (2021) Evolution of Island Mammals: Adaptation and Extinction of Placental Mammals on Islands. Oxford, Wiley-Blackwell
  • van der Geer A.A.E., Claessens L.P.A.M., Rijsdijk K.F., Lyras G.A. (2021) The changing face of the dodo (Aves: Columbidae: Raphus cucullatus): iconography of the Walghvogel of Mauritius. Historical Biology Early View. doi: 10.1080/08912963.2021.1940996
  • Louys J., Braje T.J., Chang C.-H., Cosgrove R., Fitzpatrick S.M., Fujita M., Hawkins S., Ingicco T., Kawamura A. MacPhee R.D.E., McDowell M.C., Meijer H.J.M., Piper P.J., Roberts P., Simmons A.H., van den Bergh G., van der Geer A., Kealy S., O’Connor S. (2021) No evidence for widespread island extinctions after Pleistocene hominin arrival. Proceedings of the National Academy of Sciences of the USA 118(20), e2023005118. doi:10.1073/pnas.2023005118
  • Van der Geer, A.A.E., Lyras, G., MacPhee, R.D.E., Mitteroecker, P. (2018) From Jumbo to Dumbo: cranial shape changes in elephants and hippos during phyletic dwarfing. Evolutionary Biology 45 (3): 303-317. DOI: 10.1007/s11692-018-9451-1
  • Van der Geer, A.A.E. (2018) Uniformity in variety: antler morphology and evolution in a predator-free environment. Palaeontologia Electronica 21.1: 9A. DOI: 10.26879/834
  • Van der Geer, A.A.E., Lomolino, M., Lyras, G.A. (2018) On being the right size – do aliens follow the rules.Journal of Biogeography 45: 515-529. DOI: 10.1111/jbi.13159.
  • van der Geer A. Animals in Stone. Indian fauna sculptured through time. Handbook of Oriental Studies, Section 2 South Asia, 21. Leiden, Brill, 461 + lxv pp., 528 figs. + 49 pl.

All publications on Google Scholar


MSc and BSc Leiden University:  coordinator MSc Introduction to Evolutionary Biology (Sept 2022, 2023); BSc Biodiversity Animals 'Vertebrates' (March 2022);  MSc Evolutionary Biology 'Island Evolution' (Sept 2020, 2021, 2022, 2023); MSc Evolutionary Biology 'Carnivore Evolution' (Sept 2022, 2023). Elsewhere: 'Evolution of the Horse' (Veterinary Medicine, Utrecht University; 2012, 2013, 2014, 2016); 'Collection Management Vertebrates' (Athens University; 2006-2013).

PhD Students (ongoing)

Pauline Basilia (Griffith University, Brisbane) "Beyond dwarfing: examining insular dwarfism of Stegodon fossil remains from Southeast Asia". External supervisor.

Anne-Jifke Haarsma (Radboud University, Nijmegen) "Habitat and diet segregation of pond bats". External advisor.

PhD Students (past):

Benjamin Jentgen (2022; Vrije Universiteit, Brussels) "Histological and remodelling patterns among neosauropods in insular environments". Examination committee.

Leila D'Souza (2019; Bristol University, UK) "An endemic radiation of deer in the Late Pleistocene of Malta". External examiner.

Matthew Scarborough (2018; University of Cape Town, South Africa) "Insular adaptations in the appendicular skeleton of Sicilian and Maltese dwarf elephants". External examiner.

MSc Students (current):

Demi Kuhne (Leiden University) "Ecomorphology of the Falkland Island Wolf"

Daniëlle Snijders (Leiden University) "Cranium and lower jaw development of Pond bat"

BSc Students (current):

Tessa Oberoi (Leiden University) "Cranium and lower jaw development of Pond bat"

Casper Braams and Laurenz Kilian (Leiden University) "Sexual dimorphism in roe deer skulls"

Jochem Noordzij (Leiden University) "Evolution and biogeography of island dwarf elephants"

MSc/BSc Students (2022)

Laura van Duijn (MSc 2022; Leiden) "Phylogeny of Lydekker’s deer of Pleistocene Java"; Tristan van Laar (MSc 2022; Leiden) "Body mass evolution in native island pigs"; Rebecca Davies (2022; Maastricht) "Scientific illustration of the Cretan dwarf deer".

Lisa van Eulem and Victor Huijer (BSc 2022; Leiden) "Evolution and biogeography of island deer"; Eline Hilbers (2022; Leiden) "Pachyostosis degree in an island deer"