While most biologists agree that humans have evolved from earlier species of primates, this article points out that the location of these early ancestors of humans is not established. Some believe the evolution occurred in Africa and that humans spread elsewhere relatively late (80,000 years ago). Two scientists, Robin Dennell and Wil Roebroeks, suggest that we don't have enough evidence from Asia to discount it as a starting point for human evolution.
Another scientist, Spencer Wells, supports the Africa hypothesis, but added, "That Homo erectus could have origins in Asia would be potentially shocking, but I think that what Roebroeks and Dennell are saying reflects the state of the field. We certainly don't have enough fossils. Perhaps we are never going to be able to test the hypothesis."
This shows how open scientists are to having their favored interpretation of the evidence overturned by new evidence. It is how science advances.
Note that if new evidence turns up for humans evolving in Asia, it would not discredit the idea of evolution, only a prominant hypothesis about a particular detail of it.