Homo erectus (Latin for ‘upright man’) is an extinct human species from the Pleistocene. The species lived mainly after Homo habilis, but cannot be ruled out that both species were contemporaries for a period of time, and so share an unknown common ancestor. Its earliest occurrence is about 2 million years BC.

At the beginning, Homo erectus coexisted with several other species in East Africa. We think about Homo rudolfensis and Homo habilis. Sometimes they were found at the same fossil sites. At the end of its time, Homo erectus coexisted with Homo sapiens and possibly Homo florensiensis.

Homo erectus was the first human ancestor to spread throughout the Old World, having a distribution in Eurasia. African Homo erectus are likely to be the ancestors to several human species, e.g. Homo heidelbergensis. The Asian Homo erectus may be the ancestor of the Homo florensiensis. There are several proposed subspecies with varying levels of recognition.

Early African Homo erectus, also known as the Homo erectus ergaster, are the oldest known early humans to have possessed modern human like proportions, with a flat face, prominent nose and possibly sparse body hair coverage. These features are considered adaptations to a life lived on the ground. It indicates the loss of earlier tree-climbing adaptations. The most complete fossil individual of this species (2021) is known as the "Turkana Boy", dating about 1,6 million years BC. Fossil evidence showed that the species cared for the old and weak individuals. Their appearance is often related with the earliest hand axes. The species consumed medium to large animals, e.g. elephants. The finds suggest the development of predatory behavior and coordinated hunting. Also is postulated to have been able to use fire. They hunted, gathered in groups, cared for injured or sick people.

The men and women of the species may have been roughly the same size as each other like modern humans. The size ranged widely from 1,46 m to 1,85 m in height and weighted between 40 to 68 kg. It is unclear if the Homo erectus was capable of speech, thought it is postulated they communicated using some proto-language.

The discoveries form the "Peking Man" in China comprise the classic examples of this species. Because they were spread over two continents and expanded Africa as the first species, it is considered a highly variable species. The tall bodies and large brains required a lot of energy on a regular basis to function. Eating meat and other types of protein, that could be fast digested, made it possible to absorb nutrients with a more shorter digestive treat.

If we return to the stone tool tradition, we see evidence for the first stone tool innovation in technology. This tradition is called the Acheulian. It consisted of the creation of large cutting tools like hand axes and cleavers.

There is also proof of hearths (= campfires) during the time of Homo erectus. They were using fire for cooking food, they probably have been places for social interaction, and used for warmth and keep predators away.

But as always, there is place for discussion. Some scientists distinguish between the African Homo ergaster and Asian Homo erectus sensu stricto. Others lump them together as Homo erectus sensu lato. But there is a general agreement that Homo erectus descended from an earlier species, Homo habilis. It is likely that the Homo erectus led to the emergence of later hominin species, e.g. Homo heidelbergensis.