The confirmation that a woman became pregnant by two men at the same time confirms the “commonplace” maxim that reality is stranger than fiction. Let us remember that in 2018 a genetics laboratory in Colombia treated a woman who requested paternity tests for her twins. The results were surprising: both children were children of the same mother, but different fathers, a rare phenomenon known as heteropaternal superfertilization.
To determine paternity, scientists from the Population Genetics and Identification Laboratory of the National University of Colombia used microsatellite markers to compare DNA fragments between the mother, the twins and the alleged father. This analysis, which involves multiple stages, made it possible to confirm that one child’s DNA matched that of the father, while the other did not.
In order to clarify this unusual event, the tests were repeated from the beginning, obtaining the same surprising result. This discovery was the first of its kind in a laboratory, which highlights its importance in the field of genetics.
“We take the DNA of each of them, we look at between 15 and 22 points, which are called microsatellites, and we compare them one by one,” explained Professor William Usaquén, director of the laboratory, to BBC World.
So, when half of the child’s genetic profile matches that of the mother and the other half matches that of the alleged father, paternity is confirmed.
The strange thing about heteropaternal superfertilization
Heteropaternal superfertilization is unusual due to the combination of several factors: the woman must have relations with two men in a short period and release multiple eggs. According to experts, the time between fertilizations must be critical for this phenomenon to occur.
“We had heard from other reports that these cases were observed in very low frequency in the world,” he told the BBC Andrea Casas, genetics expert and researcher at the Genetics Institute.
Studies have documented few cases worldwide, highlighting the low frequency of this condition. A study in the United States, for example, only found three cases in a data crunch of 39,000 paternity tests.
Ethical and social aspects
Researchers face ethical limitations when addressing the private lives of their subjects. Paternity tests are carried out respecting individual integrity and privacy, so the details of the applicants’ relationships are not inquired into.
It is anticipated that, with the advancement of technology, heteropaternal superfecundation could become less atypical as more people access paternity testing, which could eventually lead to greater understanding of this phenomenon.
Legal implications
This phenomenon generates disputes over who assumes obligations such as support and custody, since traditional law presumes only one parent for twins. It requires DNA testing to determine the paternity of each child, which can lead to judicial processes of challenge or voluntary recognition.
Inheritance rights. It complicates the succession, since each twin inherits only from the corresponding biological father, affecting property distributions. Courts must intervene to clarify family ties and avoid appropriate neglect of parents or children.
Legal challenges. It is a rare case (less than 20 registered globally), and the rules are not always prepared, generating ethical and legal conflicts regarding the renunciation of parental rights. In countries like Colombia, it is resolved through affiliation actions effectively. erga omnes (“regarding all”).
Custody rights. Custody is settled on a case-by-case basis, evaluating the impact on the child’s well-being; Genetic tests are key to assigning precise rights and avoiding errors in pensions or visits. It does not alter the status of twins as siblings, but may involve four parents (mother + two fathers), requiring appropriate adaptation.
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