Molecular anthropology has significantly contributed to studying human evolution, population genetics, and biological variation. However, it is essential to recognize that this subdiscipline is not immune to biases and essentialisms, particularly when interpreting past communities' sex, gender, and sexuality. In this presentation, we will use the case of the Suontaka Vesitorninmäki tomb in Finland (1050-1300 AD) as an example of how biological essentialisms can lead to problematic conclusions that lack historical or anthropological correlation. We will approach this critique from the perspective of decolonial anti-racist trans-feminism. In 2022, a genetic study revealed that the skeleton identified as female actually belonged to a person with Klinefelter syndrome (XXY karyotype). Although the authors of the article highlighted that "chromosomal sex is different from gender, and the XXY karyotype does not automatically define an individual's gender identity or even anatomical appearance," they also suggested that the intersex person was likely non-binary. Intersex people suffer from this type of interpretation and has been denounced numerous times by intersex activism. Molecular anthropology must be careful not to fall into essentialisms when studying past communities, especially regarding the diversity of sex, gender, and sexuality. It is crucial that molecular anthropology addresses these biases and actively promotes anti-bias interpretations when studying human diversity in the past, avoiding falling into essentialisms when studying past communities and respecting the diversity of sex and gender systems throughout human history. This case serves as a reminder that drawing conclusions based on chromosomal anomalies, such as trisomy, may have multiple historical and/or anthropological interpretations. By applying a decolonial, anti-racist trans-feminist lens, we can critically examine and challenge the assumptions and biases that may influence the interpretation of archaeological and genetic evidence, promoting a more nuanced understanding of past societies.