Racial tension between ethnic groups fuels the conflict in Darfur, as many nomadic herdsmen consider themselves to be Arabs while many farmers consider themselves to be African.
Many in Sudan consider racism to be at the root of the Darfur conflict, and those who belong to Sudan's ruling Arab elite have often been dismissive of those who belong to African tribes far from the capital, Khartoum.
Intermarriage between Arab traders who arrived 800 or 900 years ago has blurred the color line in Darfur, and nearly all Darfuris, even those who consider themselves to be Arabs, are black.
Yet ethnic and cultural identity remains a cause of tensions in Darfur, more often between nomadic herdsmen (many of whom consider themselves to be Arabs) and farmers (who consider themselves to be African) over access to shrinking supplies of water and pasture land.
Those who call themselves Arabs point to Arab ancestors who arrived as traders both before and after the arrival of Islam, and who gradually converted local Sudanese to the Islamic faith.
Some, especially those who arrived more recently from Egypt or from the Arabian peninsula, are lighter skinned, while others who consider themselves Arab are virtually indistinguishable from other non-Arabic tribes.