Study in Namibia points out that males & females with a low 2D:4D digit ratio tend to get married at an early age:

The second to fourth digit ratio (2D:4D) is used as a potential marker for prenatal androgen exposure. It is associated with many behavioral and biological variables, including fertility and sexual behavior. However, direct association between 2D:4D and reproductive success—in populations where no contraceptives are used—has not been investigated. Here, we present a study conducted among the semi-nomad Himba population living in northern Namibia. 2D:4D ratios were calculated for a sample of this population (N = 99; 60 women, 39 men), and the results were correlated with age, marital status, age at first marriage, number of children, and number of marriages. As found in the majority of previous studies, males had lower 2D:4D ratios than females. The 2D:4D ratio did not correlate with number of children. Females and males with a more masculine 2D:4D were married earlier and were more likely to have a husband or wife. We suggest that mating preferences for females with masculine 2D:4D are related to masculinity of phenotypic and personality traits of such women, which are beneficial in harsh environmental conditions and/or higher facial masculinity, which influences the perceived age of an individual. At the same time, masculine (physically strong, dominant, and hardworking) males might gather resources necessary to marry their first wife earlier.

NOTICE: 2D:4D digit ratio is known to correlate with many aspects of marriage/relationships, including e.g. the age of the partner, the number of partners, the offspring & the wearing of wedding rings.

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Digit ratio: A Pointer to Fertility, Behavior and Health

Digit Ratio: A Pointer to Fertility, Behavior and Health

Book Review:

Digit Ratio: A Pointer to Fertility, Behavior and Health – author: John T. Manning

Publisher: Rutgers University Press 2002

Review by Michael Mills, Psychology Department, Los Angeles.

Michael Mills writes about John Manning’s book Digit Ratio:

“Take a look at your right-hand. Which of your fingers is longer: your ring finger, or your index finger? Surprisingly, a passing stranger who noticed a difference in length between these two fingers (and who had handy a copy of John Manning’s book Digit Ratio: A Pointer to Fertility, Behavior and Health) might infer some very personal characteristics about you. With no more data than that gleaned from a passing glance at your hands, a stranger might infer whether you are likely to have homosexual inclinations, are highly fertile, may eventually suffer from a heart attack or breast cancer, have musical aptitude or sporting prowess, and a surprisingly long list of other characteristics.

…Females typically have index and ring fingers of about the same length. The ratio of index finger length to ring finger length is called the “2D:4D digit ratio,” or more simply, the “digit ratio.” Manning reports that, for males, the index finger is generally about 96 percent of the length of the ring finger, which gives an average digit ratio for males of .96.

…Manning devotes separate chapters to explore the relationship between digit ratio and a variety of characteristics, including assertiveness and attractiveness (chapter 3), reproductive success (chapter 4), hand preference, verbal fluency, autism, and depression (chapter 5), health and disease (chapter 6), homosexuality (chapter 7), musical aptitude (chapter 8 ) and sports aptitude (chapter 9). A brief summary Manning’s findings (some of which he notes are quite preliminary) is presented in the table below.”

 

Low 2D:4D ratio

High 2D:4D ratio

Males

* More fertile
* Higher lifetime reproductive success
* More aggressive and assertive
* Greater proclivity toward homosexuality/bisexuality
* Higher musical and sports aptitude
* Lower SES (?)

* Higher risk of early heart disease

Females

* Greater proclivity toward homosexuality/bisexuality
* More aggressive and assertive

* More fertile
* Higher lifetime reproductive success
* Higher risk of breast cancer

digit ratio

A short history of major the developments in the concept of ‘digit ratio’:

  • In 1888 antropologist and biologist Dr. Frank Baker noticed that the index finger is usually short than the ring finger:
  • More than a hundred years ago, a very entertaining paper concerning various customs and superstitions associated with the hand – titled: Anthropological Notes on the Human Hand (1888) – was presented to the Antropological Society of Washington by Frank Baker, Professor of Anatomy at the University of Georgetown. Following some fascinating tales, and a debunking of palmistry, he concluded by discussing the comparative lengths of the digits, and noted that the second (index) finger is usually shorter than the fourth (ring) finger.

  • In 1930 antropologist Ruggles George noticed a sex difference in the index finger and the ring finger:
  • Some years later R. George described in a paper – titled: Human Finger types (1930) – a sex difference in the distribution of finger length ratios in that males are more likely to show the 2 < 4 pattern (i.e. a longer ring finger relative to the index finger), while females are more likely to show the opposite pattern (2 > 4).

  • In 1952 antropologist V.R. Phelps discovered that finger length is stable throughout life:
  • Two decades later the sex difference findings reported by George (1930) were confirmed in the work of V.R. Phelps – titled: Relative index finger length as a sex-influenced trait in man (1952) – noting that such differences were observed in foetuses, and then appeared to be stable throughout life.

    Psychologist Glenn Wilson

    Psychologist Glenn Wilson

    * In 1983 Psychologist Glenn Wilson introduced the word ‘digit ratio’:

    Dr Glenn Wilson of King’s College, London published a study – titled: ‘Finger length as an index of assertiveness in women‘ – which introduced the 2D/4D ‘digit ratio’ as a marker of exposure to prenatal testosterone + examining the correlation between assertiveness in women and their digit ratio. This was the first study to examine the correlation between digit ratio and a psychological trait within members of the same sex.

    Psychologist John T. Manning

    Psychologist John T. Manning

    * In 1998 Psychologist John T. Manning presented a link between ‘digit ratio’ and testosterone + sperm counts:

    This link was described by Manning in a study – titled: ‘The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone‘.

    'Digit ratio' - the book

    Digit Ratio - the book

    * In 2002 Psychologist John T. Manning presented the book ‘Digit ratio’:

    Psychologist John T. Manning presented his first book about the 2D:4D ratio – titled: ‘Digit ratio: A Pointer to Fertility, Behavior and Health‘.

    In this book Manning presents a first overview of the digit ratio research which has been presented uptill the year 2002.

    The finger book

    The finger book

    * In 2008 Psychologist John T. Manning presented the book ‘The finger book’:

    Psychologist John T. Manning presented his first book about the 2D:4D ratio – titled: ‘The finger book‘.

    Quote from New Scientist:

    “According to evolutionary psychologist John Manning, who has spent years researching the secrets they betray, your digits reveal all sorts of things, from your sexuality to whether you are socially disadvantaged or likely to suffer a heart attack. They even, as the legend goes, give away the size of a man’s penis.”