A prehistoric fiction novel where the main character carries embers in a hollowed log lined with clay because people haven't figured out how to start fires themselves yet.

I read this book 16 years ago in middle school. The main character was young and male, I believe. Their family-group or tribe was in Africa. At one point it discusses how if all the embers go out they have to wait for a lightning strike to start a fire to get more. I believe it was supposed to be the start of a series. I've thought of this book on and off for years, so thank you for any help!