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.