***The cross-hatched engravings***
Tic-tac-toe? No wonder they never got anywhere if they put the X in the middle.
http://www.newscientist.com/article/dn26134-first-neanderthal-etching-is-a-stoneagehashtag.html?cmpid=RSS|NSNS|2012-GLOBAL|online-news#.VATZCaPVkdV