Table 2. Frequency of bone signs of treponematosis in consecutive periods of American history.

Periods (CE)	Midpoint dates (BP)*	N cases	N total	Frequency (%)
-6000 - -1000	5500	106	1844	5∙75
-1000- +1000	1950	121	1396	8∙67
1000–1492	700	531	5102	10∙41
1493–1900	300	17	435	3∙91
TOTAL		775	8717	8∙89

*rounded to full/mid centuries.

Chi-squared 50.35 (p < 0.0001), Cramer’s V = 0.076.