TPO 5 The Origin of the Pacific Island People

TPO 5 The Origin of the Pacific Island People
第二段中，有这样一段话：
Speculation on the origin of these Pacific islanders began as soon as outsiders encountered them, in the absence of solid linguistic, archaeological, and biological data, many fanciful and mutually exclusive theories were devised. Pacific islanders are variously thought to have come from North America, South America, Egypt, Israel, and India, as well as Southeast Asia. Many older theories implicitly deprecated the navigational abilities and overall cultural creativity of the Pacific islanders. For example, British anthropologists G. Elliot Smith and W. J. Perry assumed that only Egyptians would have been skilled enough to navigate and colonize the Pacific.
其中，older theories 觉得 Pacific islanders 的 navigational abilities 很差，却有举了个例子,Elliot等人发现只有埃及人的航海技术足够好去殖民Pacific
这个内在逻辑是什么啊？搞不明白作者的写作思路~