Mammals: Patterns of evolution

Mammalian evolution is less linear than previously thought, suggests a new study. The study uses the newly improved fossil record to build up a more complex picture of the evolution of key anatomical features.

Mammals are an important group for understanding life and its evolution. From the bumblebee bat to the blue whale, the group has evolved through time to display spectacular diversity and specialization. The evolution of mammals is commonly thought to involve a steady, orderly acquisition of key features from the reptile group - the ancestors from which mammals diverged. Characters such as the middle ear evolved from the reptilian jaw joint, and the ‘tribosphenic’ (crushing and biting) molar is thought to have come from the simpler, pointed teeth of reptiles.

Zhe-Xi Luo analyses a host of recently discovered fossils that alters this view radically, showing that mammal evolution was not quite so linear but more chaotic and subject to frequent changes - with many ‘dead-end’ lineages evolving. Lineage splits were accompanied by significant ecological diversification, with independent evolutionary ‘experiments’ evolving. The rapid accumulation of new data from recent finds and increasingly comprehensive ‘phylogenies’ have all contributed to this new approach of understanding how mammals evolved.

CONTACT
Zhe-Xi Luo (Carnegie Museum of Natural History, Pittsburgh, PA, USA)
Tel: +1 412 622 6578; E-mail: luoz@carnegiemnh.org