Most appealing, perhaps, is the idea that things might have gone smoother if the Europeans had just left the region’s inhabitants to sort things out themselves. This is what happened in the Balkans, where local leaders drew their own borders, and the fighting lasted up through the 1990s.
Africa -- where the creation of new colonial states transformed pre-existing power structures far more radically than in the Middle East -- provides perhaps the best evidence that drawing borders is an inevitably ugly business, no matter who does it. After independence, leaders across the continent initially sought to preserve their countries’ borders unchanged. The fear was that any effort to completely redraw them from scratch would be far more disruptive than accepting the status quo. Of course, this consensus itself met with violent opposition, replicating the conflicts that would likely have accompanied a purely indigenous border-drawing process. To take one discouraging example, Sudan’s government fought for half a century to defend the generous borders it inherited from the British before South Sudan gained its independence in 2011. Subsequently, clashes have continued across this newly formed border, as well as between rival groups within each of the two Sudanese states.
The fundamental problem was, and still is, that the world doesn’t have any authentic or natural borders, just waiting to be identified and transcribed onto a map. Europe’s “real” borders owe their current legitimacy, such as it is, to continent-wide exhaustion following several centuries of fighting. Winston Churchill may have drawn the border between Iraq and Jordan with a pen, but he was just as central in delineating the border between France and Germany when he led the allies to victory in World War II. Determining whether Alsace and Lorraine would be French or German was never as simple as just sending a commission to find out where the French people stopped and the German people started -- rather, the territory was awarded as a prize following each of the Europe’s bloody conflicts. Similarly, no commission, no matter the good intentions, could have been expected to find the magic line that got all the Sunnis on one side, the Shiites on the other, and the oil right in the middle.
Straight lines on maps always appear suspiciously artificial, but in the Middle East they mostly reflect the presence of large swaths of flat, barely-inhabited land (see also: Kansas, Nebraska, et al). Interestingly, one of the most exhaustive efforts to create scientifically accurate borders in a dizzyingly multi-ethnic region was carried out by Soviet anthropologists in the 1920s. The result was today’s Central Asian states, whose borders have repeatedly been denounced as absurdly, unworkably, squiggly. The Soviets felt they could afford to make the borders so excessively precise because, in an example of true, ideologically-driven cynicism, they never expected the countries to become independent in the first place. Local roads that now require three border crossings to pass from one town to the next weren’t a problem when the whole region was politically joined in the Soviet Union.