Dwarfing of fossil mammals on Mediterranean islands

Museum palaeontologists are leading a project to study the effect of dramatic environmental changes over the last 800,000 years on the evolution and survival of dwarf elephants and dwarf deer. Such work may help us understand how mammals might respond to climate change today.

Project background

Rapid evolution

Dwarf elephants and dwarf deer are now extinct, but between 800,000 and 3,000 years ago they lived on islands throughout the Mediterranean, Indonesia and off the coasts of Siberia and California.

They are remarkable examples of rapid evolutionary change. For example, some dwarf elephants, like those that lived on Sicily and Cyprus, were only about 1m tall as adults, the size of a new-born African elephant. However, their ancestor on the mainland was larger than the adult African elephant today.

We also know that dwarf deer on Jersey took less than 6,000 years to halve their body size. In evolutionary time this is very fast indeed.

A fluctuating climate

When dwarf elephants and dwarf deer lived in the Mediterranean, the climate fluctuated between ice ages and warm stages every 100,000 years.

Global sea levels dropped during ice ages as water froze to form ice sheets, and then rose again in warmer stages as the ice melted. This altered the size of the islands and their distance from the mainland. A land bridge may even have formed at times.

Island populations

We know from present-day islands that the bigger the island and the closer it is to the mainland, the more species inhabit it. The number of species able to live on the island will be affected if either of these factors changes.

Island species are often unique or endemic to a particular island, so they are vulnerable to extinction. They also evolve more quickly. We therefore expect island species to be affected by climate change to a greater extent and at a faster rate than those on the mainland. They are the front line of response to climate change.

Current research

  1. Dating fossils
    Previously, no one had considered the evolution of Mediterranean dwarf elephants and deer in the context of climate change. This is because uncertainty over the age of most of the fossils meant the corresponding climatic conditions could not be precisely determined. We are using the latest state-of-the-art techniques to get accurate and reliable dates for when dwarf elephants and deer lived on Mediterranean islands.

  2. New excavations
    We are also carrying out new excavations on Cyprus, Crete, Sicily and Malta to gather more fossil evidence for dwarf elephant and dwarf deer evolution and the environmental pressures that may have caused it.

The research is being carried out by a team of scientists from the UK, the USA and Mediterranean countries. It was supported by a Natural Environment Research Council (NERC) grant between 2009-2012, and is currently supported by a Leverhulme Trust grant, 2013-2016.

Staff involved in this project:

Project staff

References

  • Lister, AM & Hall, C (2014). Variation in body and tooth size with island area in small mammals: a study of Scottish and Faroese house mice (Mus musculus). Ann. Zool. Fennici 51: 95–110.
  • Herridge, VL & Lister, AM (2012). Extreme insular dwarfism evolved in a mammoth. Proc. R. Soc. B 279: 3193-3200.
  • Weston EM and Lister AM (2009) Brain size and insular dwarfism: implications for Homo floresiensis. Nature, 459: 85-88.
  • Lister AM (1995) Sea levels and the evolution of island endemics: the dwarf red deer of Jersey. Geological Society Special Publications, 96: 151-172.