The High-Altitude Fiber
On the vast, windswept Changthang plateau of the Himalayas, at elevations over 4,500 meters, lives the Changthangi goat (Capra hircus). This animal endures one of the planet's most extreme climates, with temperatures dropping to -40°C in winter. To survive, the goat develops a remarkable double fleece: a coarse outer coat of guard hairs and a fine, downy undercoat known as pashm. This undercoat is the raw material for pashmina, one of the world's most valued textiles.
The pashmina fibers are exceptionally fine, measuring between 12 and 16 microns in diameter. For comparison, a human hair is typically 50-100 microns thick, and fine merino wool is about 20 microns. This extreme fineness traps air, providing incredible insulation without weight. Each spring, as the goats naturally shed this layer, nomadic Changpa herders harvest it by gently combing the animals, a process that yields only 80 to 170 grams of usable fiber per goat annually.
A Case of Convergent Evolution
The Changthangi goat's ability to produce this fiber and survive in hypoxic and frigid conditions comes from its genetic makeup. Whole-genome sequencing of the goat has identified specific genes related to cold adaptation. These include genes associated with the growth and development of hair follicles, such as those for keratins, which are the structural proteins of hair.
A major discovery is the genetic similarity to an animal living 10,000 kilometers away: the Arctic musk ox (Ovibos moschatus). Despite their separation and distinct evolutionary paths, genomic comparisons reveal that Changthangi goats and musk oxen independently evolved similar genetic solutions to thrive in cold, harsh environments. This is convergent evolution. Studies have identified shared genetic markers related to brown adipose tissue (BAT) thermogenesis—the body's ability to generate heat by burning fat—and lipid metabolism. Both species show adaptations in genes that regulate how their bodies produce and use energy to stay warm, a parallel adaptation written in their DNA.