The archaeological and palaeontological evidence found at Casa Montero reveals five chronological phases covering a period of time stretching from 14 million years ago until the recent past.

Life around a Middle Miocene lake

The oldest remains at the site are Middle Miocene (Tertiary Era) in age (about 14 million years old). These contain an extraordinary fossil record in an excellent state of preservation, and of great scientific interest.

In the southeastern sector of the site, at a depth of about 5 m, there is a layer of sediment that was produced by the drying out of a lake. This sediment contains a great deal of organic matter and many remains of microfauna. Its study has revealed the time when it was deposited, the environmental conditions that reigned at that time, and the identity of the micromammals that lived in the area.

Very nearby, part of the skeleton of a mastodon (Gomphotherium angustidens) was found, along with some 70 footprints (ichnites) made by several such animals in the soft mud near the lake edge. The age of these footprints, plus their almost contemporaneous relationship with the above fossil skeleton, render these finds unique.

Human Activity during the Palaeolithic

The first evidence of human activity appears in the northeastern sector of the site. Several layers (from a depth of 1 m downwards) containing rounded lithic material have been found, as well as an exceptional layer containing the remains of lithic industry next to several structures showing signs of combustion. Some of the worked lithic industry remains recovered from this layer may have their origin in the site’s flint outcrops; if so, this provides the first evidence of their exploitation at what was once the surface. Work currently underway may be able to confirm this.

Neolithic Mining Activity

Around 7400 years ago, in the Early Neolithic, Casa Montero became an area used for the extraction and processing of flint. 3794 shafts have been found, of which 338 have been investigated, providing us with new and valuable information on the first Neolithic societies of the Iberian Peninsula. This type of work has provided a huge amount of archaeological information, and has been the main focus of research at the site in recent years.

Occupation during the Bronze Age

The only archaeological remains suggesting occupation that are not related to flint extraction date from the Bronze Age. These consist of 26 pits in the northern sector that have been interpreted as shallow pits with different functions and some possible storage pits. They contained abundant fragments of carinated vessels, pots with an S-shaped profile, and some lithic remains, largely the by-products of expeditive knapping. Two of these pits were used as graves; each contained a single occupant.

Modern and Contemporary Mining

Evidence of historic mining is provided by signs of modern and contemporary exploitation of the area’s flint. Seventeen pits dating from these times were found at the edge of the area occupied by the prehistoric shafts. The mining strategy followed gave rise to large, circular structures that became filled with mixed, disaggregated material. The aim may have been to extract flint for construction purposes, for the making of threshing boards, and perhaps gun flints.