Mammals' Triassic Emergence
Mammals first appeared during the late Triassic period, around 225 million years ago. These small, nocturnal creatures coexisted with dinosaurs, evolving from synapsid ancestors, the dominant terrestrial vertebrates of the Permian period.
In the Jurassic, mammals diversified into multituberculates, triconodonts, and symmetrodonts. These varied groups possessed specialized teeth and jaws, showcasing an early experimentation with different dietary niches amidst the reign of dinosaurs.
Cretaceous Adaptive Radiation
The Cretaceous period witnessed the rise of eutherians and metatherians, ancestors to modern placental mammals and marsupials. Fossil evidence suggests complex social behaviors and the development of more sophisticated reproductive strategies during this era.
Post-Dinosaur Mammalian Boom
After the Cretaceous-Paleogene extinction event 66 million years ago, mammals rapidly filled ecological niches left vacant by dinosaurs. This adaptive radiation led to an explosion of forms, from tiny shrews to massive whales.
Eocene Epoch Evolution
During the Eocene, around 56 to 34 million years ago, the first true primates emerged. Climate shifts facilitated the spread of mammals, with the formation of the Antarctic ice sheet driving further diversification.
Ice Age Giants
The Pleistocene epoch, 2.6 million to 11,700 years ago, was the age of mammalian megafauna. Creatures like the woolly mammoth and saber-toothed cat roamed alongside early humans, though many species became extinct due to changing climates and human activity.
Humans have significantly impacted mammalian evolution through selective breeding, habitat transformation, and climate change. This has led to numerous adaptations, including the domestication of certain species, and presents ongoing challenges for mammal conservation.