Just finished watching a fabulous new BBC2 series The Origins of Us, with Dr Alice Roberts, and learned how 5 million years of evolution took us from four-legged climbers to consummate two-legged runners.
The physical characteristics that we possess today have been profoundly determined by the need for our ancestors to run. Expanding savannah grasslands 1.5 million years ago took early humans out on to the plains where we flourished, but only because we could escape from new predators and exploit an opportunity to hunt down other animals over long distances in the heat of the African sun.
We developed longer legs, bigger hips, gluteus maximus muscles, a long narrow waist to enable us to twist our torsos and counterbalance the destabilising leg movement of running, and crucially the nuchal ligament at the back of our necks to stop our heads pitching forward.
With the additional ability to regulate our body temperature through sweating, we can run down any animal over a long distance in the heat.
Something to think about on the next run!