Homo heidelbergensis evolved around 700,000 years ago in the Old World (probably in Africa) from Homo ergaster, with the main shift being an increase in brain size from a mean for the earlier species of around 900 ml. to a mean of some 1100 ml. for the later species. This fossil, found in 1921 in Kabwe, Zambia, by Tom Zwigelaar, has a cranial capacity of 1280 ml. - a brain size well within the modern human range. It dates at around 300,000 years ago.
At the same time this individual has an extremely rugged skull build, with a set of brow ridges among the largest known in the hominid/human fossil record. Clearly a male, this individual skull has the nickname "Broken Hill Man" in recognition of the place where he was found.
This fossil skull is historically interesting in that it was the first fossil of any pre-modern human to be found in Africa, and stimulated the search there for early human fossils which has yielded prodigious numbers of extremely important finds in the eight decades since its discovery.
What the larger brain size of Homo heidelbergensis (con-trasted with H. ergaster) probably signifies, given that there is no increase in body size in this more recent species (lasting from around 700,000 to about 130,000 years ago) is the increasingly complex and important issue of human social structures in the form of alliances, friendships, competition, and cooperation - one of the main drivers of larger brain size and increased intelligence of our hominid ancestors at least since the emergence of the genus Homo some 2 1/2 million years ago.
So far as lithic tool technology was concerned these people made the same Acheulean tools (hand axes etc.) as their H. ergaster ancestors had been producing. What these people did accomplish, during the warmer interglacial periods of the Pleistocene Ice Age, was to move into Europe for the first time. At least no fossil evidence in Europe of humans older than this stage has yet been found.