Editing Digit ratio (section)

==Sexual dimorphism and age==
Studies measuring the 2D:4D of fetuses have found the ratio to be [[sexually dimorphic]], being lower in males than females.<ref name="Malas_2006" /><ref name="Galis_2010">{{cite journal | vauthors = Galis F, Ten Broek CM, Van Dongen S, Wijnaendts LC | title = Sexual dimorphism in the prenatal digit ratio (2D:4D) | journal = Archives of Sexual Behavior | volume = 39 | issue = 1 | pages = 57–62 | date = February 2010 | pmid = 19301112 | pmc = 2811245 | doi = 10.1007/s10508-009-9485-7 }}</ref>

However, when examining the extent of sexual dimorphism evident after birth, adults were found to demonstrate more dimorphism than children, who show the same extent of dimorphism as fetuses.<ref>{{Cite journal |last1=Galis |first1=Frietson |last2=Ten Broek |first2=Clara M. A. |last3=Van Dongen |first3=Stefan |last4=Wijnaendts |first4=Liliane C. D. |date=February 2010 |title=Sexual Dimorphism in the Prenatal Digit Ratio (2D:4D) |journal=Archives of Sexual Behavior |language=en |volume=39 |issue=1 |pages=57–62 |doi=10.1007/s10508-009-9485-7 |issn=0004-0002 |pmc=2811245 |pmid=19301112}}</ref> This has led the authors to suggest that digit ratio is also affected by postnatal development. Similarly, a study of people from Poland found statistically significant variation in 2D:4D between age groups (children, young adults and adults) for both males and females in the left hand, but only for women with the right hand.<ref>{{Cite journal |last1=Pruszkowska-Przybylska |first1=Paulina |last2=Kobus |first2=Magdalena |last3=Żądzińska |first3=Elżbieta |last4=Rosset |first4=Iwona |last5=Pruszkowska |first5=Milena |last6=Kuczyński |first6=Wojciech |last7=Sitek |first7=Aneta |date=2023-12-21 |title=The age difference in 2D:4D among the Polish population: An exploratory study |url=https://czasopisma.uni.lodz.pl/ar/article/view/18751 |journal=Anthropological Review |language=en |volume=86 |issue=4 |pages=99–110 |doi=10.18778/1898-6773.86.4.08 |issn=2083-4594 |doi-access=free |access-date=25 December 2023 |archive-date=3 January 2024 |archive-url=https://web.archive.org/web/20240103094435/https://czasopisma.uni.lodz.pl/ar/article/view/18751 |url-status=live |hdl=11089/49401 |hdl-access=free }}</ref>

Sexual dimorphism is strongest in digit ratios involving digit 2 with palmar measurements.<ref>{{cite journal | vauthors = Loehlin JC, Medland SE, Martin NG | title = Relative finger lengths, sex differences, and psychological traits | url = https://archive.org/details/sim_archives-of-sexual-behavior_2009-04_38_2/page/298 | journal = Archives of Sexual Behavior | volume = 38 | issue = 2 | pages = 298–305 | date = April 2009 | pmid = 18340520 | doi = 10.1007/s10508-007-9303-z | s2cid = 12340685 }}</ref><ref name = "McFadden_2002">{{cite journal | vauthors = McFadden D, Shubel E | title = Relative lengths of fingers and toes in human males and females | journal = Hormones and Behavior | volume = 42 | issue = 4 | pages = 492–500 | date = December 2002 | pmid = 12488115 | doi = 10.1006/hbeh.2002.1833 | s2cid = 1360679 }}</ref><ref>{{cite journal | vauthors = Voracek M | title = Comparative study of digit ratios (2D:4D and other) and novel measures of relative finger length: testing magnitude and consistency of sex differences across samples | journal = Perceptual and Motor Skills | volume = 108 | issue = 1 | pages = 83–93 | date = February 2009 | pmid = 19425449 | doi = 10.2466/pms.108.1.83-93 | s2cid = 10076143 }}</ref> However, when measured dorsally, digit ratios involving digit 5 showed strongest dimorphism, with women having shorter fifth digits on average.<ref name="Kumar_2017"/> Overall, dorsal digit ratios demonstrate stronger sexual dimorphism than palmar digit ratios,<ref name="Kumar_2017"/> including the palmar 2D:4D ratio that has been the basis of most study.<ref>{{cite journal | vauthors = Hönekopp J, Watson S | title = Meta-analysis of digit ratio 2D:4D shows greater sex difference in the right hand | journal = American Journal of Human Biology | volume = 22 | issue = 5 | pages = 619–630 | date = September 2010 | pmid = 20737609 | doi = 10.1002/ajhb.21054 | s2cid = 29503255 }}</ref> Moreover, compared to palmar digit ratio, dorsal digit ratio is a better indicator of bone digit ratio.<ref name="Auger_2011"/> Thus, while most of the earlier research has focused on palmar 2D:4D ratio, study of other digit ratios is also promising.

A 2009 study in ''[[Biology Letters]]'' argues: "Sexual differences in 2D:4D are mainly caused by the shift along the common [[allometric]] line with non-zero intercept, which means 2D:4D necessarily decreases with increasing finger length, and the fact that men have longer fingers than women",<ref>{{cite journal | vauthors = Kratochvíl L, Flegr J | title = Differences in the 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line | journal = Biology Letters | volume = 5 | issue = 5 | pages = 643–646 | date = October 2009 | pmid = 19553247 | pmc = 2781964 | doi = 10.1098/rsbl.2009.0346 }}</ref> which the authors claim may be the basis for the sex differences in 2D:4D and/or any putative hormonal influence on the ratios.

There has been no reliable correlation reported between 2D:4D and sex hormone levels in adulthood.<ref name="Hönekopp_2007">{{cite journal | vauthors = Hönekopp J, Bartholdt L, Beier L, Liebert A | title = Second to fourth digit length ratio (2D:4D) and adult sex hormone levels: new data and a meta-analytic review | journal = Psychoneuroendocrinology | volume = 32 | issue = 4 | pages = 313–321 | date = May 2007 | pmid = 17400395 | doi = 10.1016/j.psyneuen.2007.01.007 | s2cid = 44238240 }}</ref><ref name="No relationship between the digit r"/> Marta Kowal has suggested that testosterone levels are correlated with other factors (such as smoking, body weight and diet) that would impact the relationship between 2D:4D and an adult's testosterone level.<ref name="No relationship between the digit r"/>