The actual levelof intensity depends on such factors as the physical layout, population density, and productive activities of a metropolis.
实际的强度水平取决于诸如大城市的物理布局、人口密度和生产活动之类的因素。
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"In the general population today, at this genetic, environmental level, we've pretty much gone as far as we can go," says anthropologist William Cameron Chumlea of Wright State University.
One reason to suspect this is that a country's levelof Toxoplasma infection seems to be related to the levelof neuroticism displayed by its population.