 Native Americans are thus made to fit within these groups which often yields false and contradictory assumptions as a result of sample bias.An interdisciplinary analysis of Native American skulls has shown that there is no real evidence, apart from superficial misjudgments and erroneous conclusions, that Native Americans have any link to an African presence in America before the European encounter.Some researchers have argued that the Olmec civilization came into existence with the help of Chinese refugees, particularly at the end of the Shang dynasty.