The Rise of Mammals: From Tertiary to Quaternary

The Tertiary Period: Mammalian Expansion

Following the demise of the dinosaurs at the end of the Cretaceous period, the Tertiary period (65-1.6 million years ago) marked the first part of the Cenozoic era (65 million years ago to present). This period was characterized by a significant expansion of mammal life. Placental mammals, which nourish and maintain their young in the mother's uterus, saw a dramatic increase in diversity. During the Cretaceous, only a few groups of placental mammals existed, but by the Tertiary, there were several tens of groups, including early human ancestors like Ardipithecus, which appeared in Africa.


By the beginning of the Tertiary period, the continents had nearly reached their present positions. The Tethys Sea, which had separated the northern continents from Africa and India, began to close, forming the Mediterranean Sea and allowing terrestrial animals to migrate between Africa and western Europe. The collision of India with Asia led to the formation of the Himalayas. Midway through the Tertiary period, forest-dwelling and browsing mammals were replaced by grazing mammals such as horses, which thrived on the open savannahs that began to dominate the landscape. Repeated cool periods throughout the Tertiary established Antarctica as an icy island continent.


The Quaternary Period: Ice Ages and Human Evolution

The Quaternary period (1.6 million years ago to present) forms the second part of the Cenozoic era. This period has been characterized by alternating cold (glacial) and warm (interglacial) periods. During cold periods, ice sheets and glaciers repeatedly formed on northern and southern continents. These cold environments in North America and Eurasia, and to a lesser extent in southern South America and parts of Australia, caused many life forms to migrate towards the Equator. Only specialized ice age mammals such as Mammuthus (mammoths) and Coelodonta (woolly rhinoceroses), with their thick wool and fat insulation, were suited to life in very cold climates.


Humans developed throughout the Pleistocene epoch (1.6 million to 10,000 years ago) in Africa and migrated northward into Europe and Asia. Modern humans, Homo sapiens, lived on the cold European continent 50,000 years ago and hunted other mammals. The end of the last ice age and the climatic changes that occurred about 10,000 years ago brought extinction to many Pleistocene mammals, but enabled humans to flourish.

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