Final answer:
Homo erectus populations likely created boats or rafts and migrated to Australia, although no direct evidence has been found. They likely used these watercraft to cross short distances between islands and settle in Australia.
Step-by-step explanation:
According to the available evidence, Homo erectus populations likely created boats or rafts and migrated to Australia. Although no direct evidence such as crafts have been found, the presence of Homo erectus populations in Australia suggests that they must have used some form of watercraft. It is believed that they used rafts or boats to cross short distances between islands and eventually settled in Australia.