Cave-dwelling humans in the Stone Age didn't have flashlights, but they didn't necessarily live in complete darkness. To shed light on how our ancestors lit up their Paleolithic caves, archaeologists in Spain recreated ancient lighting techniques: torches, grease lamps and fireplaces.
Ars Technica explains:
... measurements showed that the various lighting sources had very different characteristics and, thus, were probably used in different contexts. The wooden torches, for instance, emitted light in all directions, up to nearly six meters (19.6 feet), and lasted an average of 41 minutes. The torches exhibited uneven light intensity and often needed to be relit by waving them from side to side, and they produced a lot of smoke, so they worked best for exploring caves or crossing wide spaces. The team also found that adding resin intensified the flame, while adding animal fat extended its duration.
By contrast, the grease lamps emitted weaker light akin to the intensity of a candle over a span of three meters (9.8 feet) or so. They burned consistently, and didn't smoke, for over an hour, but they had a dazzling effect if the person was moving and didn't illuminate the floor very well.
Research paper at PLOS ONE
Remains of paleolithic lighting remains, including semi-charred juniper branches, pine wood, torch, fixed lamp and a fireplace pit.
Torch experiment
Stone grease lamp experiment
Fireplace in a pit experiment.
Images: Mariangeles Medina-Alcaide et al, 2021.