Our species, Homo sapiens, inhabited the world at the same time as other human species, often living in close proximity. In fact, Homo erectus, Homo floresiensis, Homo neaderthalensis, and Homo sapiens all co-inhabited the earth only 70,000 years ago.
When our species, Homo sapiens, left Africa for Europe and Asia about 80,000 years ago, they almost certainly would've encountered other early human species. Our ancestor, Homo erectus, had made it to Europe and Asia 1 million years earlier!
Homo sapiens arrived in Australia about 50,000 years ago. Although the sea level was much lower at this time and much of Southeast Asia was a single land mass (referred to as Sunda), the trip still would've required traveling many kilometers across open water.