Jaekel was born in Neusalz (Nowa Sól), Prussian Silesia, the son of a builder and the youngest of seven children.

[3] Furthermore, his collection of Japanese Ukiyo-e wood block prints was among the most important in Germany and featured in several exhibitions and catalogs.

[4] Apart from his publications, Jaekel's most prominent contribution to vertebrate paleontology lies in the excavations in Wildungen (1890-1903) and Halberstadt (1909-1912), both of which he supervised.

In Wildungen, various forms of Devonian fishes were excavated, while Halberstadt yielded a large number (more than thirty) of the dinosaur Plateosaurus.

During World War I, in which he served as a Hauptmann (Captain) in the 210th Prussian Infantry Regiment, Jaekel attempted to re-start excavations at the southern Belgian town of Bernissart, where several dozen specimens of the dinosaur Iguanodon had been dug up in the 1870s.