Today we're going to discuss the history of the bicycle. One key figure is Kirkpatrick Macmillan, a Scottish blacksmith, who in 1839 built the first rear-wheel-driven bicycle. Unlike earlier models that were pushed by the rider's feet, Macmillan's design used pedals connected to the rear wheel by rods. However, his invention was not widely adopted, partly because it was considered dangerous and partly because it was expensive. It wasn't until the 1860s, with the introduction of the pedal-crank system on the front wheel, that bicycles became more popular, especially among young men in urban areas.
❓ According to the lecture, why was Macmillan's bicycle not widely adopted?