“Those are not short walks,” said Mma Ramotswe. “Although it would not take too long, I think, to get from the middle of town to the Stadium. Perhaps twenty-five minutes if it was not too hot.”

Mma Makutsi sniffed. “How can we tell?” she asked. “These days nobody would know how long it takes to walk anywhere because we have all stopped walking, Mma. We know how long it takes to drive. We know how long a minibus takes. But we do not know how long it takes to walk.”

Mma Ramotswe was silent as she thought about this. She had long understood that one of the features of Mma Makutsi's speeches was that there was often a grain of truth in them, and sometimes even more than that.

“And here's another thing, Mma Ramotswe,” Mma Makutsi continued. “Have you heard of evolution? Well, what will happen if we all carry on being lazy like this and drive everywhere? I can tell you, Mma. We shall start to grow wheels. That is what evolution is all about.”

Mma Ramotswe laughed. “Surely not, Mma!”

But Mma Makutsi was serious. “Oh yes, Mma Ramotswe. Our fingers have evolved so that we can do things like typing. That is well known. Why should our legs not evolve in the same way? They will become circular, I think, and they will turn round and round. That is what will happen, Mma, if we are not careful.”

Mma Ramotswe could not keep herself from smiling. “I do not think that will happen, Mma.”

Mma Makutsi pursed her lips. “We shall see, Mma.”

Mma Ramotswe almost said: But we shall not, Mma Makutsi, because evolution takes a long time, and you and I shall not be around to see the results. But she did not, because Mma Makutsi's remarks had struck a chord within her and she wanted to think about them a bit more.