The division of humanity into temporarily perceived
ethnic groups cannot really be anything other than harmful.
After all it is these groups that originally created a sense of nationalism that inspired most of the wars that have plagued human existence. These percieved differences in nature because of physical and cultural characteristics are superficial and only damaging to our basic humanity.
While many would argue that they need the definition of ethnic groups to instill a sense of identity, I would argue that this sense of identity is false, and robs you of your true sense of self as a moral human being judged on the basis of your qualities and not on some academic notion of slotted humanity. In many cases these ethnic boundaries isolate people into untenable identities. After all what does it mean to be an Indian? Or an American? Or an American-Indian? All these are (or can be construed as) ethnic groups but they are only vaguely related to personal characteristics, or lineage, or many of the things that people would use to classify each other. Don't get me wrong, I don't mind anthropologists, at least not the non-patronizing ones who contribute something to the sum total of human knowledge by deep contemplation of peoples expressions of humanity, but as one finds, most of these people find underlying causes to cross the pre-defined notions of race, and culture, and accept each other through understanding just how much we are influenced by culture, and just how much our basic humanity shines through anyway all over the world!
We need greater awareness of the fact that the very ways we speak about things can cause harm, and a little forethought would be good before deciding who our neighbour is.