Thought couch potatoes are the product of a modern lifestyle? They may have evolved 7,000 years ago!
A new Cambridge study has shown that couch potatoes have a history that stretches back 7,000 years when humans first picked up the plough.
Research into lower limb bones shows that our early farming ancestors in Central Europe became less active as their tasks diversified and technology improved.
Cambridge University anthropologist Alison Macintosh found that this drop in mobility was particularly marked in men.
Macintosh shows that after the emergence of agriculture in Central Europe from around 5300 BC, the bones of those living in the fertile soils of the Danube river valley became progressively less strong, pointing to a decline in mobility and loading.
Macintosh suggests that male mobility among earliest farmers (around 7,300 years ago) was, on average, at a level near that of today's student cross-country runners.
Within just over 3,000 years, average mobility had dropped to the level of those students rated as sedentary, after which the decline slowed.
Macintosh laser-scanned skeletons found in cemeteries across Central Europe.
The earliest skeletons she examined date from around 5300 BC and the most recent from around 850 AD - a time span of 6,150 years.
Using a portable desktop 3D laser surface scanner to scan femora and tibiae, she found that male tibiae became less rigid and that bones in both males and females became less strengthened to loads in one direction more than another, such as front-to-back in walking.
These findings all indicate a drop in mobility. In other words, it is likely that the people to whom the skeletons belonged became, over generations, less intensely active and probably covered less distance, or carried out less physically demanding tasks, than those who had lived before them.
"My results suggest that, following the transition to agriculture in Central Europe, males were more affected than females by cultural and technological changes that reduced the need for long-distance travel or heavy physical work," said Macintosh.
"This also means that, as people began to specialise in tasks other than just farming and food production, such as metalworking, fewer people were regularly doing tasks that were very strenuous on their legs," Macintosh said.