Are Armspan and Height Genetically Determined?

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Updated on Apr 08, 2013

Are you a square or a rectangle? You can figure it out by measuring your height and the length between your fingertips when you spread your arms apart. If these measurements are almost equal, you’re a square. If one is much larger than the other, you’re a rectangle. But is this trait genetic? Find out with this science experiment.


Is the relationship between a person’s height and armspan genetic?


  • Tape measure
  • Calculator


  1. Using a tape measure, measure your height to the nearest inch.
  2. Stretch your arms out to either side as far as they can go. Measure the distance between your fingertips.
  3. Record your data in a chart.
  4. Divide your height by your armspan to get the ratio between the two values.
  5. Repeat this process with at least three family members (siblings, parents, and grandparents) and at least three unrelated friends.
  6. Calculate the average of the ratios for your family, and the average of the ratios for your friends. Do not include yourself in these calculations, and record this data.
  7. Calculate the average deviation for your family. To do this, subtract your family average (from Step 6) from your own ratio (from Step 4), and divide by the family average again. Record this data.
  8. Repeat this process to find the average deviation for your friends. Just subtract your friend average (from Step 6) from your own ratio (from Step 4), and divide this by your friend average again. Record this data.
  9. Compare the two average deviations. Which is smaller? The smaller of the two belongs to the group of people whose ratio is closest to yours. Use this information to support or reject your hypothesis.
  10. If you’d like, you can repeat this process with several other people, as well as their friends and relatives. This will give you more accurate results.


First Place Science Fair Projects for Inquisitive Kids, by Elizabeth Snoke Harris. Pp. 29-30.

Keren Perles has worked as an educational writer, editor, teacher, and tutor of all ages. Her experience spans the subject areas, from science and math, to English and the Hebrew language.

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