Basel researchers unravel evolution’s mystery

The most comprehensive evidence of evolution in ruminant animals: An international research team led by paleontologists Bastien Mennecart and Loïc Costeur from the Basel Museum of Natural History has succeeded in tracing the 35-million-year evolution of the mammal group. The researchers published the results in the famous journal “Nature Communications.”

Secret organ as the key to success

The inner ear has been the key to success: no other organ can be so clearly distinguished among animal families. The hearing and vestibular organs have been extensively studied before and have long been accepted as evidence of mammalian evolution. The rounded cochlea, typical for mammals, developed about 150 million years ago.

Using modern methods, the research team led by Mennecart and Costeur were able to depict in three dimensions the ear canals of nearly 200 living and extinct ruminants. They showed how inner ear shape evolves depending on climatic factors. For example, giraffe species spread particularly well in warm regions, while other animals such as cattle and deer show themselves primarily in cool conditions. The more diverse the climate in the areas of their distribution, the more diverse the species developed.

Landmass shift gave rise to new species

Not only did the climate affect the development of ruminant animals. The displacement of the continents also had a significant impact. For example, about three million years ago, deer migrated from North America to South America when a land bridge was created between the two continents. Numerous species of deer evolved as a result of their new habitat, as researchers can show by the change in the shape of the inner ear. Almost half of all known deer species still live in South America.