Based on Mendel’s ideas of inheritance, some human traits offer clues about paternity. Examples include attached or unattached earlobes, the ability to ‘roll’ the tongue, and eye color.
Eye color follows a polygenic inheritance pattern, and is probably controlled by 6 or more genes. Generally, these genes express themselves as one of 8 different eye colors. ‘Dark’ is dominant at each of the 6 genes. The more dominant alleles present, the darker eye color appears.
An eye color paternity test assumes that lighter-eyed parents cannot have darker-eyed children. For example:
- 2 ‘blue’ eyed parents can have a ‘Blue-green’ (or lighter) eyed child, but not hazel or anything darker.
- 1 ‘light brown’ eyed parent and 1 ‘blue-green’ eyed parent can have a child with any of the possible eye colors.
- 2 ‘dark brown or black’ eyed parents can have a child with any of the possible eye colors (but it is unlikely they will have a light eyed child, such as light blue or blue).
While eye color, or blood type, can be an indicator of paternity, they are not consistent enough to be relied on for definitive results.