Dwarfing of fossil mammals on Mediterranean islands

We are studying the effect of dramatic environmental changes over the last 800,000 years on the origin and diversification of dwarf elephants and dwarf deer. This work forms a natural experiment in evolution responding to changes in the environment.

We are using state-of-the-art techniques to study dwarf mammal fossils. This is giving us accurate dates for when dwarf elephants and dwarf deer lived on Mediterranean islands. We will then be able to match the fossils with climate data and explore the link between climate and sea-level change and evolution.This hasn't been possible before because of uncertainty over the age of most of the fossils.

We have also carried out new excavations in Cyprus, Crete, and especially Sicily and Malta to gather more fossil evidence.

The research is being carried out by a team of scientists from the UK, Italy, Malta and Greece, led by Museum palaeontologists. We are also collaborating with colleagues in Germany in the first ancient DNA study into the origins of Mediterranean dwarf elephants.

Rapid evolution

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

These dwarf mammals are remarkable examples of rapid evolutionary change. For example, some dwarf elephants - such as those that lived on Sicily and Cyprus - were only about one metre tall as adults, the same size as a newborn African elephant. Their mainland ancestors, however, were larger as adults than adult African elephants today.

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

A fluctuating climate

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

Global sea levels dropped during ice ages as water froze to form ice sheets, and rose again in warmer times as the ice melted. This altered the size of islands and their distance from the mainland. Land bridges formed at times.

Island populations

Island species are often unique to a particular island, making them vulnerable to extinction. They also evolve quicker than non-island species. As a result, climate change tends to affect island species to a greater extent and at a faster rate than those on the mainland. Island species are on the front line of response to climate change.