Twenty-one humanoid robots joined thousands of runners at the Yizhuang half-marathon in Beijing on Saturday, the first time these machines have raced alongside humans over a 21-km (13-mile) course. The robots from Chinese manufacturers such as DroidUP and Noetix Robotics came in all shapes and sizes, some shorter than 120 cm (3.9 ft), others as tall as 1.8 m (5.9 ft). One company boasted that its robot looked almost human, with feminine features and the ability to wink and smile. Some firms tested their robots for weeks before the race. Beijing officials have described the event as more akin to…