Related Experiment Video
Updated: Aug 8, 2026
13:55
Combined Immunofluorescence and DNA FISH on 3D-preserved Interphase Nuclei to Study Changes in 3D Nuclear Organization
Published on: February 3, 2013
Population differences in finger-length ratios: ethnicity or latitude?
John C Loehlin1, Dennis McFadden, Sarah E Medland
1Department of Psychology, University of Texas, Austin, Texas 78712-0187, USA. loehlin@psy.utexas.edu
Archives of Sexual Behavior
|May 12, 2006
Summary
The 2D:4D finger ratio, an indicator of prenatal testosterone, showed Australian males resembled British males, not US males. This suggests genetic differences, not latitude, explain variations in this trait among Caucasian populations.
Area of Science:
- Behavioral endocrinology
- Human genetics
- Anthropometry
Background:
- The 2D:4D finger ratio is a proposed marker for prenatal testosterone exposure.
- Previous studies noted differences in 2D:4D ratios between Caucasian males in Britain and the U.S.
- These differences raised questions about genetic versus environmental (e.g., latitude) influences.
Purpose of the Study:
- To investigate the factors influencing 2D:4D finger ratio variations in Caucasian populations.
- To differentiate between genetic and environmental (latitude-related) explanations for observed 2D:4D ratio differences.
Main Methods:
- Examined the 2D:4D finger ratios of an Australian adolescent sample.
- Compared Australian 2D:4D ratios with existing data from British and U.S. Caucasian males.
Main Results:
- Australian 2D:4D ratios were found to be similar to those reported for British males.
- The Australian results did not align with the 2D:4D ratios observed in U.S. males.
- The findings suggest latitude-related environmental factors are less likely explanations.
Conclusions:
- Genetic differences between Caucasian gene pools may be a more plausible explanation for 2D:4D ratio variations.
- The study provides evidence against latitude as a primary environmental determinant for 2D:4D ratios in these populations.
Related Concept Videos
01:18Polygenic Traits
When more than one gene is responsible for a given phenotype, the trait is considered polygenic. Human height is a polygenic trait. Studies have uncovered hundreds of loci that influence height, and there are believed to be many more. Due to the high number of genes involved, as well as environmental and nutritional factors, height varies significantly within a given population. The distribution of height forms a bell-shaped curve, with relatively few individuals in the population at the...
02:45The Ratio of X Chromosome to Autosomes
In most organisms, sex is determined by the ratio of X and Y chromosomes. However, in some organisms, such as Drosophila and C.elegans, sex is determined by the ratio of the number of X chromosomes to the number of sets of autosomes. The Y chromosome in Drosophila is active but does not determine sex. It contains genes responsible for the production of sperms in adult flies.
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
01:14Wilcoxon Signed-Ranks Test for Median of Single Population
The Wilcoxon signed-rank test for the median of a single population is a nonparametric test used to evaluate whether the median of a population differs from a specified value. Unlike parametric tests, it does not require data to follow a normal distribution, making it suitable for non-normal or small samples. The test begins by calculating the difference (d) between each observation and the hypothesized median. The absolute values of these differences are ranked in ascending order, with ties...
01:10Nature and Nurture
Many human characteristics, like height, are shaped by both nature—in other words, by our genes—and by nurture, or our environment. For example, chronic stress during childhood inhibits the production of growth hormones and consequently reduces bone growth and height. Scientists estimate that 70-90% of variation in height is due to genetic differences among individuals, and 10-30% of variation in height is due to differences in the environments that individuals experience, such as differences...
01:21Testing a Claim about Mean: Unknown Population SD
A complete procedure of testing a hypothesis about a population mean when the population standard deviation is unknown is explained here.
Estimating a population mean requires the samples to be approximately normally distributed. The data should be collected from the randomly selected samples having no sampling bias. There is no specific requirement for sample size. But if the sample size is less than 30, and we don't know the population standard deviation, a different approach is used; instead...
Estimating a population mean requires the samples to be approximately normally distributed. The data should be collected from the randomly selected samples having no sampling bias. There is no specific requirement for sample size. But if the sample size is less than 30, and we don't know the population standard deviation, a different approach is used; instead...
01:19F Distribution
The F distribution was named after Sir Ronald Fisher, an English statistician. The F statistic is a ratio (a fraction) with two sets of degrees of freedom; one for the numerator and one for the denominator. The F distribution is derived from the Student's t distribution. The values of the F distribution are squares of the corresponding values of the t distribution. One-Way ANOVA expands the t test for comparing more than two groups. The scope of that derivation is beyond the level of this...