 However, despite these physical differences, genetic studies have shown that they are more closely related to other Eurasian populations than to Africans.These early population groups originally lacked watercraft technology, and thus could only cross narrow interisland seas with primitive floats or rafts (likely bamboo or log rafts) or through accidental means.Especially the deeper waters of the Wallace Line, Weber Line, and Lydekker Line with islands disconnected from mainland Asia even in the lower sea levels of the last glacial period.