title: Selective breeding for a behavioral trait changes digit ratio.
abstract: The ratio of the length of the second digit (index finger) divided by the fourth digit (ring finger) tends to be lower in men than in women. This 2D:4D digit ratio is often used as a proxy for prenatal androgen exposure in studies of human health and behavior. For example, 2D:4D ratio is lower (i.e. more "masculinized") in both men and women of greater physical fitness and/or sporting ability. Lab mice have also shown variation in 2D:4D as a function of uterine environment, and mouse digit ratios seem also to correlate with behavioral traits, including daily activity levels. Selective breeding for increased rates of voluntary exercise (wheel running) in four lines of mice has caused correlated increases in aerobic exercise capacity, circulating corticosterone level, and predatory aggression. Here, we show that this selection regime has also increased 2D:4D. This apparent "feminization" in mice is opposite to the relationship seen between 2D:4D and physical fitness in human beings. The present results are difficult to reconcile with the notion that 2D:4D is an effective proxy for prenatal androgen exposure; instead, it may more accurately reflect effects of glucocorticoids, or other factors that regulate any of many genes.
authors.affiliation: Department of Psychology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Reginia H Y
authors.initials: RH
authors.lastname: Yan
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Malisch
authors.forename: Robert M
authors.initials: RM
authors.lastname: Hannon
authors.forename: Peter L
authors.initials: PL
authors.lastname: Hurd
authors.forename: Theodore
authors.initials: T
authors.lastname: Garland
mesh_terms: D000728:Androgens / Q000378:metabolism; D000818:Animals; D001522:Behavior, Animal; D005121:Extremities / Q000033:anatomy & histology* / Q000502:physiology; D005260:Female; D005385:Fingers / Q000033:anatomy & histology* / Q000502:physiology; D006801:Humans; D008297:Male; D051379:Mice; D015233:Models, Statistical; D012727:Sex Characteristics; D012737:Sex Factors; D012984:Software; D013045:Species Specificity
chemical_list: D000728:Androgens
references.citation: Anat Rec. 2002 Jul 1;267(3):231-4
references.pmid: 12115273
references.citation: Naturwissenschaften. 2007 Mar;94(3):207-12
references.pmid: 17136513
references.citation: Proc Biol Sci. 2005 Dec 22;272(1581):2641-9
references.pmid: 16321787
references.citation: Arch Sex Behav. 2008 Feb;37(1):112-8
references.pmid: 18074216
references.citation: Genes Brain Behav. 2006 Apr;5(3):299-300; author reply 300-2
references.pmid: 16594983
references.citation: Horm Behav. 2004 Dec;46(5):558-64
references.pmid: 15555497
references.citation: Horm Behav. 2006 Mar;49(3):315-9
references.pmid: 16143332
references.citation: Behav Genet. 1998 May;28(3):227-37
references.pmid: 9670598
references.citation: Am J Hum Biol. 2007 May-Jun;19(3):416-21
references.pmid: 17420996
references.citation: Anat Rec (Hoboken). 2008 Apr;291(4):433-40
references.pmid: 18286614
references.citation: Evol Hum Behav. 2001 Jan;22(1):61-69
references.pmid: 11182575
references.citation: Horm Behav. 2006 Apr;49(4):545-9
references.pmid: 16403410
references.citation: Gen Comp Endocrinol. 2008 Apr 1;156(2):210-7
references.pmid: 18329645
references.citation: Ann Hum Biol. 2003 Sep-Oct;30(5):579-88
references.pmid: 12959899
references.citation: Arch Dis Child Fetal Neonatal Ed. 2005 Mar;90(2):F166-9
references.pmid: 15724043
references.citation: Physiol Biochem Zool. 2007 Jan-Feb;80(1):146-56
references.pmid: 17160887
references.citation: Twin Res Hum Genet. 2006 Apr;9(2):215-9
references.pmid: 16611491
references.citation: J Sports Med Phys Fitness. 2002 Dec;42(4):446-50
references.pmid: 12391439
references.citation: Horm Behav. 2005 Sep;48(3):342-6
references.pmid: 15878573
references.citation: Br J Sports Med. 2006 Dec;40(12):981-3
references.pmid: 17008344
references.citation: Reprod Biol Endocrinol. 2006 Feb 26;4:10
references.pmid: 16504142
references.citation: Arch Sex Behav. 2008 Feb;37(1):9-18
references.pmid: 18080736
references.citation: Early Hum Dev. 2004 Apr;77(1-2):23-8
references.pmid: 15113628
references.citation: Anat Rec A Discov Mol Cell Evol Biol. 2006 May;288(5):491-7
references.pmid: 16604562
references.citation: Am J Hum Genet. 1952 Jun;4(2):72-89
references.pmid: 14943709
references.citation: Am J Hum Biol. 2005 Nov-Dec;17(6):796-800
references.pmid: 16254897
references.citation: Med Hypotheses. 2003 Mar;60(3):340-3
references.pmid: 12581609
references.citation: Horm Behav. 2002 Dec;42(4):380-6
references.pmid: 12488105
references.citation: Genes Brain Behav. 2005 Jul;4(5):318-23
references.pmid: 16011578
references.citation: Early Hum Dev. 2002 Dec;70(1-2):47-54
references.pmid: 12441204
references.citation: Horm Behav. 2003 Sep;44(3):209-21
references.pmid: 14609543
references.citation: Biol Psychol. 2005 Mar;68(3):215-22
references.pmid: 15620791
references.citation: Proc Biol Sci. 2004 Feb 7;271(1536):239-44
references.pmid: 15058433
references.citation: Arch Sex Behav. 2006 Dec;35(6):739-42
references.pmid: 16688484
references.citation: Evol Hum Behav. 2000 May 1;21(3):163-183
references.pmid: 10828555
references.citation: Ann Eugen. 1946 Apr;13:35-71
references.pmid: 20982098
references.citation: J Appl Physiol (1985). 2006 Aug;101(2):477-85
references.pmid: 16601309