(NewsNation) — Firstborn daughters are having a cultural moment, sparked by viral memes and videos highlighting the perceived joys and burdens of being the responsible eldest sibling – often saddled with familial duties from an early age.

The pop culture term “eldest daughter syndrome” has garnered millions of searches on TikTok where users explain some of the symptoms of the “condition.” Among them: intense feelings of responsibility, people-pleasing tendencies and resentment toward siblings and parents.

While “eldest daughter syndrome” is not an official clinical diagnosis, a new study suggests there may be an evolutionary basis for these perceived tendencies in firstborn daughters.

The University of California, Los Angeles-led research found that in some cases, firstborn daughters show earlier signs of adrenal puberty – bodily changes like acne and body hair that correlate with accelerated brain development and social maturity.

This pattern was specifically observed when the daughters’ mothers experienced high levels of stress during pregnancy.

The findings, published in Psychoneuroendocrinology, suggest an evolutionary adaptation. Early social maturity in eldest daughters allowed them to assist overtaxed mothers, without becoming physically mature enough for their own pregnancies that would redirect their caregiving roles.

The accelerated development was not seen in eldest sons, possibly because male children help less often with direct childcare, according to researchers.

The multi-year study tracked 48 families in Southern California from pregnancy through the teenage years of the children born. Mothers’ stress levels were measured throughout pregnancy, along with signs of puberty onset in their kids over 15 years.

After accounting for other factors like childhood adversity, the correlation between prenatal stress and earlier adrenal maturity emerged only among firstborn daughters.