All of the fossils from Gran Dolina date back to the Pleistocene epoch. The Pleistocene, which began around 1.8 million years ago and lasted until around 10,000 years ago, is sometimes called the Great Ice Age—although this term is rather misleading. The Earth’s climate actually cycled between periods of bitter cold and more moderate temperatures during this time.

Layer 10 Illustration by Mauricio Antón

Around 375,000 years ago, the Atapuerca region had entered an interglacial period of relatively mild conditions. Fossil remains of animals and pollen indicate a fairly wet environment for much of the time. But there were colder and drier seasons over the years, as depicted in this illustration.

Layer 10 (TD 10)
Researchers excavating Layer 10 of Gran Dolina (also known as TD10) have found numerous fossils dating back to 375,000 years ago from large and medium-size animals such as bison, lion and deer, as well as smaller mammals like rodents, cats and other carnivores. Stone tools have been uncovered from Layer 10, but no human fossils or other evidence of human activity such as fire use have been discovered here.

This layer is one of the most recent ones and sits close to the top of the Gran Dolina cliff. The sediment in Layer 10 consists primarily of yellow-red mud containing pebbles and cobbles.

What does TD mean?
The Spanish team working at Gran Dolina refers to the layers of the cliff as TD layers. TD stands for Trinchera Dolina, or the Dolina trench, in reference to the railway trench where the site is located.