Scientists have traced human tail loss to a short sequence of genetic code

Genetic mechanism of tail loss

• Discussion centers on the TBXT gene and an AluY insertion that disrupts exon 6.
• In mouse models, removing exon 6 from one copy of TBXT produced a spectrum from no tail to full tail; removing it from both copies was non‑viable.
• Higher levels of TBXT missing exon 6 correlated with shorter tails.
• TBXT is a transcription factor, likely controlling a broader “tail machinery” spread across other genes.
• Consensus: this mutation plausibly initiated tail loss, but simply “fixing TBXT” would not regrow tails because other pathways and repurposed genes are now involved.
• Commenters emphasize confusion between “necessary vs sufficient”; this mutation may be the key switch, but not the whole system.

Evolutionary “why” and selection

• Some argue there is no deeper “why” beyond mutations that weren’t selected against; others insist tail loss must have conferred some advantage or came with one.
• Hypotheses include metabolic cost, hygiene issues, and changing locomotion (tree vs ground, size increase), but bipedality is challenged because tail loss predates it.
• Debate over whether mere lack of disadvantage is enough for a trait to spread vs requiring positive selection.

Tails: function, tradeoffs, and combat

• Tails noted as useful for balance, climbing, signaling, fly‑swatting, third leg (e.g., kangaroos), or even prehensility.
• Counterpoint: in large primates tails may be too weak to be useful fifth limbs.
• Extended argument about whether tails are liabilities in fights (grab points) vs less controlling than grabbing a leg due to flexibility.

Human tails and anatomy

• Human “tails” exist but are very rare and often surgically removed; linked material shows they can be non‑innervated and cosmetically odd.
• Some note physical drawbacks (sitting pain) in documented cases, though these may not represent a fully functional ancestral tail.

Genetic engineering and ethics

• Speculation about CRISPR’ing embryos to restore tails, cat ears, or full cat‑people; others stress genetics is far from that simple.
• Concerns raised about germline editing for nonmedical traits; some see vitamin or amino‑acid synthesis restoration as a higher priority but others question necessity and safety.

Cultural, aesthetic, and practical angles

• Many express disappointment we can’t easily “bring back” tails and fantasize about prehensile tails for balance, climbing, cooking, fashion, and sexuality.
• Practical issues raised: chairs, toilets, clothing, sports rules (e.g., tail‑grabbing in football).
• Meta notes: complaints about a clickbait headline and curiosity about the unusually long (∼3‑year) peer‑review timeline for the Nature paper.