If, has been fairly convincingly argued by Frank Salter, there is a genetic basis to human ethnic identity, this by no means means it's a good thing. Descriptive does not equal prescriptive.

(PDF file) http://www.mankindquarterly.org/samples/SalterMQXLVIII-3.pdf

But it is useful to know if it is true. Fighting, apparently for one's ethnic group, might be understood scientifically. The August 4, 1914 vote in favor of the 'fatherland' by Germany's social democrats was regarded by Marxists and other utopians as a 'betrayal' of the ideals of international working class solidarity. If ethnic consciousness is deeper than class or human identity, you should find out, whether your political views are left, right, or anywhere. It's not enough to analyze wars as simply attacks by one class on another  http://f.acetio.us/wildcat/Yugoslavia.html

Ethnic identity doesn't necessarily lead to war. Britain's declaration of war on Germany in 1939 was not caused by it.

Here is a wonderfully utopian letter to the Eugene newspaper by a typical old hippie, claiming that people aren't naturally ethnic:

    "How many citizens in Israel and Palestine would rather be considered citizens of the Middle East instead of as members of groups in conflict, like team members, members of special interest groups?" 

  http://www.registerguard.com/csp/cms/sites/web/opinion/24519190-47/story.csp

Not very many, I suspect.

'Ethnic identity' is altruism toward people who may be more closely related to you than the average human being, based on appearance. 'Racism' is ethnic identity among white Europeans.