Determination of parenthood

Since Roman times fatherhood has been determined with this famous sentence: Mater semper certa; pater est quem nuptiae demonstrant ("The [identity of the] mother is always certain; the father is whom the marriage vows indicate"). The historical approach has been destabilised with the recent emergence of accurate scientific testing, particularly DNA testing. As a result, the law on fatherhood is undergoing rapid changes.

Like mothers, human fathers may be categorized according to their biological, social or legal relationship with the child. Historically, the biological relationship paternity has been determinative of fatherhood. However, proof of paternity has been intrinsically problematic and so social rules often determined who would be regarded as a father, e.g. the husband of the mother.

An individual who is a genetic chimera could theoretically have more than one biological father. No example of this has been reported but human chimeras were unknown to exist until recently and scientists are currently uncertain as to the extent of chimerism within the human population.[8]