Mercedes-Benz offers the S-Class sedan with a growing array of options such as carbon-fiber trim, heated and cooled cup holders and four types of caps for the tire valves, and the carmaker’s robots can’t keep up.

With customization key to wooing modern consumers, the flexibility and dexterity of human workers is reclaiming space on Mercedes’s assembly lines. That bucks a trend that has given machines the upper hand over manpower since legendary U.S. railroad worker John Henry died trying to best a motorized hammer more than a century ago.

“Robots can’t deal with the degree of individualization and the many variants that we have today,”  Markus Schaefer, the automaker’s head of production, said at its factory in Sindelfingen, the anchor of the Daimler AG unit’s global manufacturing network. “We’re saving money and safeguarding our future by employing more people.”

Mercedes’s Sindelfingen plant, the manufacturer’s biggest, is an unlikely place to question the benefits of automation. While the factory makes elite models such as the GT sports car and the ultra-luxury S-Class Maybach sedan, the 101-year-old site is far from a boutique assembly shop. The complex processes 1,500 tons of steel a day and churns out more than 400,000 vehicles a year.

That makes efficient, streamlined production as important at Sindelfingen as at any other automotive plant. But the age of individualization is forcing changes to the manufacturing methods that made cars and other goods accessible to the masses. The impetus for the shift is versatility. While robots are good at reliably and repeatedly performing defined tasks, they’re not good at adapting. That’s increasingly in demand amid a broader offering of models, each with more and more features.

“The variety is too much to take on for the machines,” said Schaefer, who’s pushing to reduce the hours needed to produce a car to 30 from 61 in 2005. “They can’t work with all the different options and keep pace with changes.”

With manufacturing focused around a skilled crew of workers, Mercedes can shift a production line in a weekend instead of the weeks needed in the past to reprogram robots and shift assembly patterns, Schaefer said. During that downtime, production would be at a standstill.