I am not sure that Dr. Reich (or perhaps the reporter) has got all the qualifiers straight for a sample mentioned in that Economist quote. A google or google scholar search yields quite a few scientific papers with a significantly different breakdown. Check, for example, the abstract of a paper in the Journal of Clinical chemistry and laboratory medicine, 2003:

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The common polymorphism of apolipoprotein E: Geographical aspects and new pathophysiological relations
GERDES Lars Ulrik (Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus Amtssygehus, Aarhus, DANEMARK)

Apolipoprotein E (apoE) has important functions in systemic and local lipid transport, but also has other functions. The gene (APOE) shows a common polymorphism with three alleles - APOE*2, APOE*3, and APOE*4. Their frequencies vary substantially around the world, but APOE*3 is the most common almost everywhere and is often considered to be the ancestral or wild-type allele for that reason. However, there are several arguments for APOE*4 being the ancestral allele. But then, why has APOE*3 become so frequent? And why has APOE*4 not become extinct? The proportion of APOE*4 carriers increases from only 10-15% in southern Europe to 40-50% in the north. The gradient may be a trace of the demic expansion of agriculture that began about 10,000 years ago, but it may also reflect the possibility that APOE*4 carriers are less likely to develop vitamin D deficiency. The common APOE polymorphism is associated with varying risk of cardiovascular disease and Alzheimer's disease, but other interesting aspects may emerge in the future.
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