Final answer:
Captain James Cook was wrong to describe Australia as terra nullius because the continent was inhabited by Indigenous people with established sovereignty, which he and other Europeans disregarded due to colonial mindset and imperial motives.
Step-by-step explanation:
When Captain James Cook described Australia as terra nullius, he was implying that the land was empty and belonged to no one. This was incorrect because there was an established Indigenous presence on the continent for tens of thousands of years before European arrival. Therefore, the term terra nullius, which translates to 'nobody’s land', does not apply to Australia as it was home to a rich tapestry of Aboriginal tribal groups and cultures. The Europeans chose to disregard the existing Aboriginal sovereignty and land rights due to colonial attitudes and the desire for expansion. This misconception paved the way for British colonization and the subsequent denial of Indigenous Australian rights and claims to their own land.