Biology
The Neuroethology of Mate Choice and Sensory Bias in Swordtail Fish
Quick fact
Female swordtails prefer males with longer swords, yet this preference may stem from an ancient visual bias for food items—the sword likely evolved because it hijacks a pre-existing sensory pathway, not because it signals male quality.
Why this is interesting
The male swordtail fish carries a long, sword-like extension on its tail—but why do females prefer it? It turns out this preference may have existed long before the sword did.