What does that refer to in the passage? I think it refers to 'movement' but someone else argues it 'physiology,' which I think makes little sense. Which is right?
Let’s go back to our ancestors, back before elevators, escalators, cars, and even horses. This is the time when our human physiology was coming of age. Our ancestors had to move to survive. Not unlike most other mammals, humans had to expend much energy in order to acquire food and water. These early humans, with whom we share most of our physiology, were nomadic, and therefore moving was an essential part of their lives. As descendants of these nomadic people, our physiology is based on abundant movement and a diet of vegetables, fruits, nuts, fish, and infrequent, small portions of meat. To the extent we have that, we are more likely to be healthy. To the extent we don’t have that, problems arise. If you look at photos of crowds just over half a century ago, before exercise was a word, before the term jogging had meaning, before fitness centers, and before the hundreds of diet plans, you’ll see that the people in these photos are lean. Almost every person―lean. Movement was an inherent part of daily life―walking, biking, work, play―and obesity was rare. Not exactly like our distant ancestors, but closer than we are today.
*source : Authentic Health and Successful Aging By Roger Landry