[3] On October 21, 1907, Daniel Hartmann, a worker at a sand mine in the Grafenrain open-field system of the Mauer community unearthed a mandible at a depth of 24.63 m (80.81 ft), which he recognized as of human origin.

[4] He was aware of the likelihood of finds, as for 20 years the Heidelberg scholar Otto Schoetensack had asked that the workers at the sand mine be encouraged to look out for fossils, after the well-preserved skull of a straight-tusked elephant had come to light there in 1887.

Schoetensack had the workers taught the characteristics of human bones based on recent examples on his regular visits to the sand mine in search for "traces of mankind".

He presented the results of his studies in autumn the following year in a monograph titled: "The lower jaw of Homo heidelbergensis from the sands of Mauer near Heidelberg".

[7] Further finds from the Mauer sand mine are the Hornstein artefacts, unearthed in 1924 by Karl Friedrich Hormuth, which scholars interpreted as tools of Homo heidelbergensis.

The anatomical analysis of the lower jaw of Mauer in its 1908 original species description by Otto Schoetensack was based largely on the expertise of Breslau professor Hermann Klaatsch, which was only hinted at in a brief acknowledgement in the preface.

[10] Schoetensack concluded a relationship to modern man (Homo sapiens) from the similarity of the dentition and put the lower jaw in the genus Homo—a view that is still being held unanimously by today's palaeo-anthropologists.

"[11] As to the lower jaw of Mauer's precise position in the ancestral chain of modern man Schoetensack expressed only cautious statements.

It is around two million years older than the lower jaw of Mauer and, despite its advanced age, still does not represent the common base of humans and apes.

Otto Schoetensack had the site at the bottom of the sand mine marked with a commemorative stone on which a horizontal line represented the level of the find.

In fact, the part of the mine, in which the lower jaw came to light, was filled with overburden in the 1930s, later re-natured as arable land and declared a nature reserve in 1982.

In the preface to his study he states: "The age of these sands is commonly agreed to as paleo-diluvial (altdiluvial) by reference to embedded mammal remains; although certain species suggest a significant relationship with a more recent section of the Tertiary, namely the Pliocene.

At the 100th anniversary of the discovery in 2007 a scientific commemorative publication complained that there "still existed no satisfactory exact data for the determination of the geological age of the lower jaw of Homo heidelbergensis".

"The anatomy is clearly more primitive than that of Neanderthal, but the harmoniously rounded dental arch and the complete row of teeth...already typically human.

"[18] Based on these circumstances—the chronological delineation from the more recent Neanderthal on the one hand, and from older fossils, denoted as Homo erectus on the other—today's researchers consider it justifiable to declare Mauer 1 as an independent chronospecies.