The essence

Bats are the only mammals that fly. They did not invent new genes; they changed when and where common genes switch on. In most mammals, the thin skin between early fingers disappears before birth through apoptosis (planned cell death). In bats, that skin stays and becomes the wing membrane.

What the study shows

Researchers examined the bat wing membrane, the chiropatagium, and found active fibroblasts with high expression of two limb genes—MEIS2 and TBX3. In other mammals these genes are turned off before fingers form. In bats they switch back on in the distal limb, helping suppress interdigital cell death so the membrane persists.

Proof in a mouse model

When scientists engineered mice to express MEIS2 and TBX3 during limb development, embryos formed webbed, thickened tissue between digits and partial fusions—an early bat-like pattern. This is regulatory evolution: small shifts in gene control that yield big anatomical change.

Why it matters

• Explains how wings can arise by reusing existing genes.
  
• Offers clues for regenerative medicine and birth-defect biology where tissue shaping goes wrong.
  
• For India, such work aligns with long-horizon support under the Anusandhan National Research Foundation; any animal research follows Committee for the Purpose of Control and Supervision of Experiments on Animals norms.
  

Key terms
Regulatory evolution; apoptosis; interdigital region; chiropatagium; fibroblasts; MEIS2; TBX3; distal limb.

Exam hook

Key takeaways

• Bat flight reflects regulatory evolution, not new genes.
  
• Reactivating MEIS2 and TBX3 in the distal limb suppresses apoptosis, preserving wing membrane.
  
• Mouse experiments that switch on these genes produce bat-like webbing, confirming the mechanism.
  

UPSC Prelims (MCQ)
Q. Which statements are correct?

1. In mammals, loss of tissue between digits normally occurs through apoptosis.
   
2. In bats, reactivation of MEIS2 and TBX3 helps retain interdigital tissue.
   
3. Regulatory evolution means creating brand-new genes.
   Answer: 1 and 2 only.
   

One-line wrap: Bats became flyers by changing gene timing—old genes, new pattern, a wing from webbing.