Scientists have traced human tail loss to a short sequence of genetic code
Genetic research tracing how humans and other apes lost their tails points to a mutation affecting the TBXT gene, likely disrupting the broader “tail-making” machinery rather than acting as a simple on/off switch. Commenters explore what evolutionary advantages tail loss might have conferred, how costly traits get “garbage collected” over time, and why simply reversing this mutation wouldn’t regrow functional tails. The thread branches into wider questions about evolution, speculative human genetic modifications, and how tails (or other added limbs) would affect balance, fighting, daily life, and even fashion.
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.