Some people have earlobes that curve up between the lowest point of the earlobe and the point where the ear joins the head; these are known as \"free\" or \"unattached\" earlobes, as shown in the upper left of the picture below. Other people have earlobes that blend in with the side of the head, known as \"attached\" or \"adherent\" earlobes, as shown in the lower right. <\/p>\n
Attached vs. free earlobes are often used to illustrate basic genetics. The myth is that earlobes can be divided into into two clear categories, free and attached, and that a single gene controls the trait, with the allele for free earlobes being dominant. Neither part of the myth is true. <\/p>\n
Classroom exercises on earlobe genetics say that there are two distinct categories, free (F) and attached (A). However, many of the papers on earlobe genetics have pointed out that there are many people with intermediate earlobes (Quelprud 1934, Wiener 1937, Dutta and Ganguly 1965). El Kollali (2009) classified earlobes into three types, based on whether the attachment angle was acute, right, or obtuse. To make the picture above, I searched for pictures of professional bicyclists (because they have short hair), found 12 with their ears showing, and arranged them from free to attached. It doesn't look to me as if there are just two categories; instead, there is continuous variation in the height of the attachment point (the \"otobasion inferius\") relative to the lowest point on the earlobe (the \"subaurale\"). My own earlobes are exactly halfway in between the two extremes; I couldn't tell you whether my earlobes should be considered free or attached. <\/p>\n
Carrire (1922) and Hilden (1922) were among the first to study the genetics of earlobes, and they reached opposite conclusions. Carrire (1922) looked at 15 families and concluded that attached earlobes were dominant. However, all of the offspring of A x A matings had attached earlobes, and there were no F x F matings, so his data are consistent with either free or attached being dominant. <\/p>\n
Powell and Whitney (1937) looked at one family and concluded that attached earlobes were recessive. Wiener (1937) responded 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.\" He divided earlobes into four arbitrary groups, from 0 (completely free) to 3 (completely attached). All possible matings, from completely 0 x 0 to 3 x 3, produced some intermediate earlobes. Wiener (1937) concluded that earlobes were determined by more than one gene, or by a singe gene with more than two alleles. <\/p>\n
Lai and Walsh (1966) called earlobes in which the lowest point on the earlobe was the attachment point \"attached,\" and they classified all other earlobes as \"free.\" They recorded the following data on families in New Guinea: <\/p>\n
If the myth were true, two parents with attached earlobes could not have a child with a free earlobe. There are slightly more A offspring from A x A matings, but the large numbers of F offspring from A x A matings and A offspring from F x F matings indicate that this is not a one-locus, two-allele trait. <\/p>\n
Mohanraju and Mukherjee (1973) performed a similar study in India and found similar results: <\/p>\n
They found a much stronger association between parents and offspring, but the five F offspring of A x A matings are inconsistent with the myth that this is a one-locus, two-allele trait. <\/p>\n
Earlobes do not fall into two categories, \"free\" and \"attached\"; there is continuous variation in attachment point, from up near the ear cartilage to well below the ear. While there is probably some genetic influence on earlobe attachment point, family studies show that it does not fit the simple one-locus, two-allele myth. You should not use earlobe attachment to demonstrate basic genetics. <\/p>\n
Carrire, R. 1922. ber erbliche Orhformen, insbesondere das angewachsene Ohrlppchen. Zeitschrift fr Induktive Abstammungs- und Vererbungslehre 28: 288-242. <\/p>\n
Dutta, P., and P. Ganguly. 1965. Further observations on ear lobe attachment. Acta Genetica 15: 77-86. <\/p>\n
El Kollali, R. 2009. Earlobe morphology: a simple classification of normal earlobes. Journal of Plastic, Reconstructive and Aesthetic Surgery 62: 277-280. <\/p>\n
Hilden, K. 1922. ber die Form des Ohrlppchens beim Menschen und ihre Abhngigkeit von Erblanglagen. Hereditas 3: 351-357. <\/p>\n
Lai, L.Y.C., and R.J. Walsh. 1966. Observations on ear lobe types. Acta Genetica 16: 250-257. <\/p>\n
Mohanraju, C., and D.P. Mukherjee. 1973. Ear lobe attachment in an Andhra village and other parts of India. Human Heredity 23: 288-297. <\/p>\n
Mowlavi, A., D.G. Meldrum, and B.J. Wilhelmi. 2004. Earlobe morphology delineated by two components: the attached cephalic segment and the free caudal segment. Plastic and Reconstructive Surgery 113: 1075-1076.[not seen yet] <\/p>\n
Powell, E.F., and D.D. Whitney. 1937. Ear lobe inheritance: an unusual three-generation photographic pedigree chart. Journal of Heredity 28: 184-186. <\/p>\n
Quelprud, T. 1934. Familienforschungen ber Merkmale des usseren Ohres. Zeitschrift f Induktive Abstammungs- und Vererbungslehre 67: 296-299. <\/p>\n
Wiener, A.S. 1937. Complications in ear genetics. Journal of Heredity 28: 425-426. <\/p>\n
OMIM entry <\/p>\n
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Myths of Human Genetics: Earlobes<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Some people have earlobes that curve up between the lowest point of the earlobe and the point where the ear joins the head; these are known as \"free\" or \"unattached\" earlobes, as shown in the upper left of the picture below. Other people have earlobes that blend in with the side of the head, known as \"attached\" or \"adherent\" earlobes, as shown in the lower right Continue reading