A moth made for manufacturing
The silk that defined the trade routes passing through Samarkand originates from an insect that is, genetically speaking, a human invention. The domestic silkmoth, Bombyx mori, is the product of at least 5,000 years of artificial selection from its wild ancestor, Bombyx mandarina. This process has rendered B. mori completely dependent on humans for survival; the adult moths cannot fly, have lost their camouflage pigmentation, and cannot reproduce without assistance.
The genetic divergence from its wild relative is significant. The genome of B. mori, which contains approximately 450 million base pairs, shows major alterations in genes related to growth, metabolism, and, most importantly, silk production. Genes that code for silk proteins—fibroin and sericin—are highly expressed, a direct result of thousands of years of breeders selecting for moths that spun the largest and most commercially viable cocoons. Specific genetic changes have been identified, such as the absence of a particular transposable element called Bm1 in domestic silkworms. This absence increases the activity of a gene known as Mlx, which in turn boosts larval body size and the weight of the cocoon shell. This long-term, targeted breeding transformed a wild moth's protective covering into a part of global textiles.
Samarkand's genetic crossroads
As sericulture spread from its origins in China, the genetics of the silkworms traveled with it. Samarkand, a central hub on the Silk Road, is where different silkworm lineages met and mixed. Genomic analysis of silkworm populations shows that local strains in Uzbekistan occupy a phylogenetic position between ancient local strains from China and modern "improved" strains. This genetic signature shows that Uzbekistan's silkworms originated in China and were carried westward along the trade routes.
Over centuries, sericulturists in Central Asia selected for traits best suited to their local environment. Recent genetic comparisons between Uzbek and Chinese silkworm populations reveal distinct differences. For example, Uzbek strains show greater variation in the number of eggs laid per moth, with an average of 631 compared to 505 in Chinese strains. While there are no differences in average cocoon weight (1.56g for Uzbek strains vs. 1.52g for Chinese), the genetic diversity within Uzbekistan's silkworms is high, particularly on the sex-determining chromosome. This genetic variance points to a long history of local adaptation and selective breeding, creating a unique genetic heritage preserved in the silk workshops of Samarkand today.