Testosterone levels in saliva correlate well with serum testosterone levels [1, 2]. Studies show:
"among nomadic and settled Ariaal pastoralists of northern Kenya [. . .] salivary testosterone (T) levels (avg. am value = 176.8 +/- 74.8 pmol/l) were low compared to values from Western populations" . A later study reports even lower levels among the Ariaal .
"in Harare, Zimbabwe [. . .] salivary T levels (AM = 196 +/- 96 pmol/l; pm = 172 +/- 98 pmol/l) were much lower [compared to 'Western populations']" .
Among men aged 15 to <30 years, mean salivary T for an American sample from Massachusetts is 335 pmol/l, compared to 286 pmol/l for the Congo sample .
 J Clin Endocrinol Metab. 1981 Nov;53(5):1021-4. Salivary testosterone in men: further evidence of a direct correlation with free serum testosterone. Wang C, Plymate S, Nieschlag E, Paulse
 Clin Chim Acta. 1987 Mar 30;163(3):309-18. Direct assay for testosterone in saliva: relationship with a direct serum free testosterone assay. Johnson SG, Joplin GF, Burrin JM.
 Am J Hum Biol. 2003 Sep-Oct;15(5):697-708. Salivary testosterone and body composition among Ariaal males. Campbell B, O'Rourke MT, Lipson SF.
 Aging Clin Exp Res. 2006 Dec;18(6):470-6. Age-related patterns of body composition and salivary testosterone among Ariaal men of Northern Kenya. Campbell BC, Gray PB, Ellison PT.
 Am J Hum Biol. 2004 Nov-Dec;16(6):704-12. Testosterone, aging, and body composition in men from Harare, Zimbabwe. Lukas WD, Campbell BC, Ellison PT.
 Hum Reprod. 2002 Dec;17(12):3251-3. Population variation in age-related decline in male salivary testosterone. Ellison PT, Bribiescas RG, Bentley GR, Campbell BC, Lipson SF, Panter-Brick C, Hill K.