So. The Ishango Bone.
No-one is entirely sure of course. But for me at least, the second side represents the importance of 10 as a number, by omission. 9 and 11, at either end, bracket 10; and 19 and 21, in the centre, bracket 20. Remember that 10 and 20 are very natural human numbers of importance, given our digits.
The third side is the most stunning. It gives 11, 13, 17 and 19 – the prime numbers between 10 and 20, in order. The remaining 7 and 5 on the first side extend the sequence of primes to include all the prime numbers below 20 occurring after 4… the first non-prime number.
Not entirely sure, understandable, but note there is a second Ishango rod, revealed by the discoverer on his death bed, though he discovered it just like the first rod in the 1950s.