Researchers comparing DNA from various primates and humans have identified a genetic feature that may have driven tail reduction in human ancestors. The study, published in Nature, highlights a shared trend across species and points to specific genetic changes that could explain how tails were lost over millions of years.
Earlier work shows that more than 100 genes are linked to tail formation in different vertebrates. The new analysis suggests that disruption or variation in one or more of these genes could stop tail development, leading to tail absence in certain lineages. To explore this, scientists examined the genomes of great apes and humans to see how tail-related genetic programs may have diverged over time.
Scientists found that the loss of tails in human ancestors may be tied to a distinctive genetic insertion labeled Aluy within the TBXT gene. Although Aluy does not represent a classical mutation, it alters the reading of the TBXT gene in a way that changes its function. Studies in animals engineered to carry this insertion showed various tail defects, including the complete absence of a tail. In some cases, the alteration was associated with neural tube anomalies, suggesting that similar developmental changes could influence newborn outcomes today.
Estimates place the tail loss event within a primate lineage that includes gorillas, chimpanzees, and humans around 25 million years ago. The researchers propose that shedding the tail may have facilitated the shift from an arboreal to a more terrestrial mode of life, enabling new ecological opportunities and evolution of diverse bodies and behaviors among descendants.
In a separate line of discovery, researchers in Luxembourg reported a fossilized vampiremorph believed to date about 183 million years old, underscoring the ongoing expansion of the deep past in the study of primate evolution and vertebrate development.