The more you search the more you find.

"Vennemann proposes that after the last Ice Age, Vasconic people from today's Southern France and Northern Iberia (modern Spain and Portugal) resettled the European continent."

"According to German linguist Theo Vennemann,the vigesimal system in Europe is of Basque (Vasconic) origin and spread from Vasconic languages to other European tongues, such as many Celtic languages, French and Danish."

http://www.math.buffalo.edu/mad/Ancient-Africa/mad_nigeria_pre-colonial.html

Whether the vigesimal (base 20) scale of the West African Yoruba people came with them from the east (perhaps Egypt) or not it was certainly present around 1000 AD during the foundation of the Oyo kingdom. The numeral system itself weighs heavily upon subtraction.

As in our system there are different names for the numbers from one = okan to ten = eewa . As in our system, the numbers eleven = ookanla to fourteen = eerinla could be translated as "one more than ten" to "four more than ten." But once fifteen = aarundinlogun is reached the convention changes, so that fifteen to nineteen = ookandinlogun are expressed as "twenty less five" to "twenty less one," respectively, where twenty = oogun . Similarly, the numbers twenty-one to twenty-four are expressed as additions to thirty = ogbon . At thirty-five = aarundinlogoji , however, there is a change in hte way the first multiple of twenty is referred to: forth is expressed as "two twnenties" = ogoji while 60 = ogota , "three twenties," and 80 = ogerin , "four twenties" and so on to 200 = igba for"ten twenties." It is in the naming of some of hte intermediate numbers that the subtraction principle comes into its own. Examples:

45 = (20*3) - 10 - 5

50 = (20*3) - 10

108 = (20*6) - 10 - 2

300 = 20*(20 - 5)

318 = 400 - (20*4) - 2

525 = (200*3) - (20*4) + 5

All the number from 200 to 2000 (except those that can be directly related to 400 = irinwo ) are reckoned as multiples of 200. From the name egbewa = 2000, names are constructed similar to above.