New evidence suggests that homids were present in China as early as 1.7 million years ago. An article in the ThaiIndian relates this, regarding the layer where the hominid remains were originally discovered in 1973:
The new team traced that sediment layer - or time horizon - throughout the basin, collecting 318 rock samples from it. The researchers reported that the fossils came from a layer of rock just above a magnetic landmark known as the Olduvai-Matuyama reversal boundary, which is at least 1.77 million years old. This makes the fossil site slightly younger, about 1.7 million years old. This age estimate represents “the oldest definite fossil and archaeological evidence of early hominins in China and mainland East Asia,” according to co-author Rick Potts, a paleoanthropologist at the Smithsonian Institution in Washington, D.C. Taken together, these dates from at least three fossil sites are convincing many researchers that early humans were moving rapidly across Asia 1.77 million to 1.66 million years ago.
Another part of the puzzle. Cool.