When I was getting born, Zatopek was taking the 10,000 WR to 28:54. About 13 years later, Clarke took it down by 75 seconds. At the time, if you'd told anyone who followed the sport that the WR in forty years or so would be another 75 seconds or so beyond what Clarke had done, none of us would have been surprised. If you'd told us that tracks would be at least a second per lap faster, that runers would be able to make a living from the sport and do nothing but train, that pacemaking would not only be legal but professionalized and that at least some people would take checmicals that can improve performances by 10% or so, we might have expected the record to be two or three minutes better by now.
The fact that Africans hold all the records now is as much because westerners have pretty much given up on the quest to be at the top at a time when Africans have picked it up.
I see no reason why non-Africans shouldn't have been able to match the times that today's Africans are posting.
Yes, there are tons of them. But if you look at the Boston Marathon, a good race for comparison because it's run on the same course as ever and has never used pacemakers, you see that the times turned in are very comparable to what was turned in 20-30 years ago If guys like DeCastella and Steve Jones could run 2:07s other westerners can too, even today.
You guys who are big on pointing out that yesterday's runners didn't have to contend with TODAY'S Africans also forget that today's Africans didn't have to contend with yesterday's westerners. You always present this as "What would happen if you took (Shorter, Mills, Rodgers, Virgin, Clarke, etc) and brought them to a race today against the Africans. You never ask what would happen if you took today's Africans and had them born in 1950 or so. If you could do that, you wouldn't find them running sub 13:00-27:00. They might well be the best runners of their era, as some Africans were back then, but their times would not be what they're posting now. Times progress over the years.