Dehaene, Izard, Spelke, and Pica carried out experiments with an indigenous Amazonian tribe, and discovered that Mundurucu adults retain their logarithmic number line intuitions:
This indicates that the mapping of numbers onto space is a universal intuition and that this initial intuition of number is logarithmic. The concept of a linear number line appears to be a cultural invention that fails to develop in the absence of formal education.
Mundurucu numbers are also pretty interesting. They have a limited and approximate number vocabulary, so that:
"xep xep" = 2
"pug pogbi" = "one handful" = 5-ish
"pug pogbi xep xep bodi" = "one handful and two on the side" = 7-ish
"xep xep pogbi" = two handfuls = 10-ish
Hmm, the same issue of Science has a note about "Culture, Gender, and Math, which presents data showing that the 'gender gap' in math disappears in countries that have greater gender equality. Also, the girls increase their humongous lead in reading. Bitches.