However, a 60W incandescent bulb puts out about 800 lumens, which is about 64 candela. So one bulb-hour is indeed about 60 candle-hours. This is omnidirectional output, useful output may be less.
The original paper reports a 21 pounds of firewood was measured to produce 2.1 foot-candles (22 lux) for 3.4 hours. Overall useful fireplace output was estimated at about 1.7 lumen-hours per pound of wood, which is 10 lumens (just under 1 candela) on average for that 21 pound fire.
By focusing on light output, and not the heat output, I still think it's an incomplete comparison, as an LED bulb may be very bright and cheap to run, but it won't keep you very warm in a cave in prehistoric Zhoukoudian.
The original paper reports a 21 pounds of firewood was measured to produce 2.1 foot-candles (22 lux) for 3.4 hours. Overall useful fireplace output was estimated at about 1.7 lumen-hours per pound of wood, which is 10 lumens (just under 1 candela) on average for that 21 pound fire.
By focusing on light output, and not the heat output, I still think it's an incomplete comparison, as an LED bulb may be very bright and cheap to run, but it won't keep you very warm in a cave in prehistoric Zhoukoudian.