In 1917, the legal framework in Sweden concerning non-marital parenting was changed in order to provide for the children born out of wedlock. Before 1917, maternity and paternity outside marriage were conditional on the parents' willingness to recognize a child. The law on children born out of wedlock changed the rights of these children by ending the anonymous childbirth and imposing the designation of a father. The mother could not refuse the maternity of the child. The right of the child to know its origins was opposed to the rights of the parents to remain anonymous. The parents also had to provide the child with care and education, thus to take responsibility for the child in a way which attests to the recognition of family ties outside of marriage.

We explore the development of the search for paternity since the adoption of the law of 1917 until today in Sweden. We begin with the legislative debates during the preparation of this law. We then analyse the modalities provided by this law to the practices of paternity research. We trace the history of paternity research until today by studying how the responsibilities (allowances) towards children that are not spontaneously recognized by fathers have developed and what rights it implies concerning inheritance.

Finally we look upon how the dilemma of combining the quest for equal rights for the children to know their parents may become unequal rights for adults to have children. How anonymity among potential fathers (for instance sperm donors) may clash with the law that claims equal rights for the children to know their parents. How the law clashes with single mothers who refuse to give the name of the father, or homosexual couples who do not want to involve a sperm donor or a surrogate mother as parent.