A FALHA GENÉTICA que Pode Ter Apagado a Cauda dos Nossos Ancestrais

Human embryos form a temporary tail structure before it regresses. In this video, we follow what embryology actually shows—from somites to cell death—and why this doesn't mean development replays evolution like a time-lapse movie. Then, we investigate the study published in Nature about an AluY insertion associated with the TBXT gene. The discovery helps explain how two Alu sequences can alter RNA splicing, delete exon six, and produce an isoform capable of shortening or eliminating tails in experimental models. Finally, we test three separate questions: Is the genetic mechanism convincing? What advantage could have favored the loss of the tail? And did the process bring a biological cost linked to the development of the neural tube? The answer remains within the limits of science: an associated mutation can explain a crucial piece without single-handedly reconstructing the entire evolutionary event. This video does not claim that losing the tail automatically put us upright. Human bipedalism appeared millions of years later, and the pressures that fixed the change in our ancestors are still unknown. #human evolution #genetics #embryology #tbxt #science MAIN REFERENCES 1. XIA, Bo et al. On the genetic basis of tail-loss evolution in humans and apes. Nature, volume 626, pages 1042–1048, 2024. Contribution to the roadmap: Main scientific source. Supports the association between AluY insertion in the TBXT gene and tail loss in hominoids; pairing with AluSx1; alternative deletion of exon six; tests in human stem cells; murine models with reduced or absent tails; and the hypothesis of a possible cost involving neural tube defects. DOI: https://doi.org/10.1038/s41586-024-07... Full text on PubMed Central: https://pmc.ncbi.nlm.nih.gov/articles... PubMed record: https://pubmed.ncbi.nlm.nih.gov/38418... 2. TOJIMA, Sayaka; MAKISHIMA, Haruyuki; TAKAKUWA, Tetsuya; YAMADA, Shigehito. Tail reduction process during human embryonic development. Journal of Anatomy, volume 232, number 5, pages 806–811, 2018. Contribution to the roadmap: Supports the modern description of human embryonic tail regression through three-dimensional reconstruction. The study analyzed embryos between Carnegie stages thirteen and twenty-three, identified the peak number of somites at stage sixteen, and recorded a reduction of approximately five somites during the process. DOI: https://doi.org/10.1111/joa.12774 Full text on PubMed Central: https://pmc.ncbi.nlm.nih.gov/articles... PubMed record: https://pubmed.ncbi.nlm.nih.gov/29315... 3. FALLON, John F.; SIMANDL, Barbara K. Evidence of a role for cell death in the disappearance of the embryonic human tail. American Journal of Anatomy, volume 152, number 1, pages 111–129, 1978. Contribution to the roadmap: Primary source for the embryological overview. Describes the human caudal projection between Carnegie stages fourteen and twenty-two, its anatomical composition, its initial growth, and the central role of cell death in regression until the disappearance of the free tail. DOI: https://doi.org/10.1002/aja.1001520108 PubMed record: https://pubmed.ncbi.nlm.nih.gov/677043/ 4. TUBBS, R. Shane et al. Enigmatic human tails: A review of their history, embryology, classification, and clinical manifestations. Clinical Anatomy, volume 29, number 4, pages 430–438, 2016. Contribution to the roadmap: Reference review on human tails and caudal appendages. It was used as support to distinguish normal embryonic development from rare congenital anomalies and to avoid the simplistic claim that every human caudal appendage represents only a preserved ancestral tail. DOI: https://doi.org/10.1002/ca.22712 PubMed record: https://pubmed.ncbi.nlm.nih.gov/26990... 5. WILDE, Jonathan J.; PETERSEN, Juliette R.; NISWANDER, Lee. Genetic, epigenetic, and environmental contributions to neural tube closure. Annual Review of Genetics, volume 48, pages 583–611, 2014. Contribution to the roadmap: Specialized review used to keep the medical excerpt within the bounds of evidence. Shows that neural tube closure depends on multiple genetic, epigenetic, and environmental factors, preventing attributing current human cases directly to ancestral insertion associated with TBXT. DOI: https://doi.org/10.1146/annurev-genet... Full text on PubMed Central: https://pmc.ncbi.nlm.nih.gov/articles... PubMed record: https://pubmed.ncbi.nlm.nih.gov/25292... EDITORIAL NOTE: Source number one presents the central genetic hypothesis. The remaining studies provide independent confirmation regarding embryology, caudal regression, clinical anomalies, and the multifactorial nature of neural tube defects. None of them demonstrates that tail loss automatically caused human bipedalism; therefore, this relationship was not asserted in the script.