The initial migration out of Africa is associated with Homo erectus who first originate in Africa and spread out into other areas. This migration probably takes place around 1.5 million years ago and involves populations thought to be related to Homo ergaster, one of the varieties of Homo erectus that emerges in African around 2 million years ago. There are clear differences that develop with time and separation between African and Javan and Chinese Homo erectus.

Note the rough features of this drawing
of a Javan H. erectus. The regional differences are an interesting
question relative to evolutionary processes affecting hominid populations
as they spread over the landscape.
This QuickTime movie enables us to view the potential
pathways between African and Javan hominids. This movie takes us from a
stage at about 2.0 million years ago with an early form of Homo from Africa
(Koobi Fora specifically). The movie is a morph first between that early
homo fossil and one from Africa and then Java. It shows how one could transition
from this form into a later Javan H. erectus (from the site of Sangiran)
as well as into an African H. erectus (also from Koobi Fora). This
forms the basis of a common origin in Africa for both regions. [These fossils
have been scaled.]
The remains of H. erectus in China have been found at both Zhoukoudian
and Lantian. These show affinities to finds from Java and Africa. Yet, in
China as with Java, hominid divergence begins to show as regional variations
can be noted. Eventually, there are regional varieties in Europe, African,
China, and Java that become clear as evolutionary process relating to population
genetics and adaption take hold.
What is clear is that the technology found in context with Chinese and Javan
H. erectus is distinctive from that found in Europe and Africa. There
are no Acheulean hand axes in China or Java. It has been suggested that
bamboo may have replaced the needs for more advanced hand axes in this region.
Given that bamboo is so hard and durable, it may have been an effective
replacement for stone tools. Yet, it may also support the idea of an early
migration from Africa as a source of H. erectus populations in Asia
since that would have occurred prior to the advent of hand axes at about
1.3 million years ago in Africa. The connection with Europe in terms of
technology may suggest a migration connection with Africa after 900,000
years ago.
How Recent might Homo Erectus be?