Born to run?

Here is a report on some developments on the hypothesis that humans are very well evolved to run in the heat. A physical anthropologist told me that while cold adapted peoples can acclimate to tropical conditions, heat adapted peoples are not as good at the reverse. That suggested to me that as a tropical species we have deep and extremely powerful adaptations which allow us to tolerate heat, and these adaptations might have other uses that remained advantageous once we moved north into Eurasia.