Engraved lunar calendar (Abri Blanchard plaque)

What it is

A bone plaque with 69 marks in a serpentine pattern whose shape changes like the phases of the Moon, according to Marshack's interpretation. The first attempt to record astronomical time.

Marshack's lunar reading is hypothetical; recent studies (Bacon et al. 2023) propose that the signs alongside animals in cave art encode breeding months.

What it led to

• Prediction of cycles: migrations, tides, gestation
• Coordination of meetings between scattered bands on fixed dates
• The origin of astronomy and of temporal notation systems

Built on

• Abstract geometric engraving on ochrec. 75 ka
• Tally stick (Lebombo bone)c. 43 ka
• Lunar cycle tallies and earliest calendarsc. 30000 BCE
• Tally stick (Lebombo bone)
• Abstract geometric engraving on ochre

Made possible

• Ishango bonec. 20000 BCE
• Engraved stone mapc. 13.7 ka
• Ishango bone
• Engraved stone map

Links

Sources✓ verified 2026-09-25

• https://www.sciencenews.org/article/mysterious-marks-ice-age-cave-art
• https://link.springer.com/article/10.1007/s41982-023-00158-8