Attached Earlobes
What Do Classrooms Say?
Classrooms teach that earlobes can be divided into two clear categories, free and attached. Free earlobes are those that curve up between the lowest point of the earlobe and the point where the ear joins the head. Attached earlobes blend in with the side of the head. According to textbooks, free earlobes (F) are the dominant trait while attached earlobes are the recessive trait (A). |
What Does the Research Say?
Parents F offspring A offspring Percent F
FxF 12 22 35%
FxA 72 114 39%
AxA 37 90 29%
Conclusion:
Earlobes cannot be divided into just two categories: "free" and "attached". From the picture below it's clear that there is a whole spectrum of earlobes between the two categories. While some earlobe attachments start from up near the ear cartilage others go to well below the ear. While there is probably some genetic influence on the earlobe attachment point, the family studies above show that it does not fit the simple one-locus, two-allele myth.
- Powell and Whitney (1937) published a pedigree that supported the hypothesis that ear lobe attachment's inheritance was autosomal dominance. Their research looked into one family for three successive generations.
- Wiener (1937) responded to Powell and Whitney (1937) by pointing out that the "arbitrary classification into two sharply defined types...gives a false picture, since all gradations between the two extremes are encountered." In his experiment he divided earlobes into four groups: 0 (completely free) to 3 (completely attached). After looking into every possible combination between 0x0 and 3x3, Wiener (1937) concluded that earlobes were determined by more than one gene, or by a single gene with more than two alleles.
- Lai and Walsh (1966) studied the genetics of earlobes of families in New Guinea. They classified earlobes in which the lowest point of the earlobe was the attachment point "attached", and classified all other earlobes as "free". After looking at 347 families they concluded that "a simple Mendelian gene effect is unlikely to be responsible for the earlobe types". The table below is the data they recorded:
Parents F offspring A offspring Percent F
FxF 12 22 35%
FxA 72 114 39%
AxA 37 90 29%
Conclusion:
Earlobes cannot be divided into just two categories: "free" and "attached". From the picture below it's clear that there is a whole spectrum of earlobes between the two categories. While some earlobe attachments start from up near the ear cartilage others go to well below the ear. While there is probably some genetic influence on the earlobe attachment point, the family studies above show that it does not fit the simple one-locus, two-allele myth.
Sources:
Jones, Kristin. "Genetics Unit." Biology Class. Novi High School, Novi. 8 Dec. 2010. Lecture.
Lai, L.Y.C., and R.J. Walsh. 1966. Observations on ear lobe types. Acta Genetica 16: 250-257.
Powell, E.F., and D.D. Whitney. 1937. Ear lobe inheritance: an unusual three-generation photographic pedigree chart. Journal of Heredity 28: 184-186.
Wiener, A.S. 1937. Complications in ear genetics. Journal of Heredity 28: 425-426.
Jones, Kristin. "Genetics Unit." Biology Class. Novi High School, Novi. 8 Dec. 2010. Lecture.
Lai, L.Y.C., and R.J. Walsh. 1966. Observations on ear lobe types. Acta Genetica 16: 250-257.
Powell, E.F., and D.D. Whitney. 1937. Ear lobe inheritance: an unusual three-generation photographic pedigree chart. Journal of Heredity 28: 184-186.
Wiener, A.S. 1937. Complications in ear genetics. Journal of Heredity 28: 425-426.