Homo heidelbergensis is a controversial and somewhat poorly defined species of archaic human from the Middle Pleistocene of Europe and Africa, as well as potentially Asia depending on the taxonomic convention used. The species-level classification of Homo during the Middle Pleistocene is controversial, called the "muddle in the middle", owing to the wide anatomical range of variation that populations exhibited during this time. H. heidelbergensis has been regarded as either the last common ancestor of modern humans, Neanderthals, and Denisovans; or as a completely separate lineage.