There is a fear that we are becoming an increasingly sedentary society, with a number of studies linking time spent sitting with a higher risk of cardiovascular disease, for example.[1] Some have suggested that the human body did not evolve to being sedentary, even though evolutionary pressures should favour such energy-minimising strategies.

To shed light on this, a team of researchers examined inactivity in the Hadza people, an indigenous ethnic group in Tanzania, who are one of the last hunter-gatherer societies remaining.[2] They found that people from both the Hadza tribe and from industrialised populations have similar levels of total non-ambulatory time. However, people from the Hadza tribe predominantly spent this ‘sedentary’ time in ‘active rest’ postures, such as squatting. These postures required significantly more levels of lower limb activity than the equivalent time sitting in a chair.

The authors propose an ‘Inactivity Mismatch Hypothesis’, proposing that human physiology could be adapted to consistently active muscles derived from physical activity and non-ambulatory postures with extensive muscle contraction. This hypothesis may offer a route to reducing the negative impacts associated with our own inactivity.

Peter Chilton, Research Fellow

References:

1. Bailey DP, et al. Sitting Time and Risk of Cardiovascular Disease and Diabetes: A Systematic Review and Meta Analysis. Am J Prevent Med. 2019; 57(3): 408-16.
2. Raichlen DA. et al. Sitting, squatting, and the evolutionary biology of human inactivity. Proc Nat Acad Sci USA. 2020.