This office certifies Assam tea, not Chinese tea, but a reader who has ever seen "Assam type" listed against a Yunnan tea deserves the straight answer: it is not the same plant as the one in this valley, and it never was. Two separate teams of geneticists, working from nuclear microsatellites and chloroplast DNA, traced the tea plant's family tree and found three branches, not two: classic small-leafed China-type tea, a big-leafed "Assam type" that grows wild in southwestern Yunnan, and India's own big-leafed Assam type, rooted here in the Brahmaputra valley. All three were domesticated on their own, in their own place, by their own people. China's "Assam type" and Assam's Assam type share a name, a rough silhouette, and a common ancestor from deep in the last Ice Age. They do not share a domestication.

Three plants, one name doing double duty

The confusion is understandable, because "Assam type" is a description of the plant, not a claim about where it grows. Botanically, Camellia sinensis splits into two broad varieties: var. sinensis, the small-leafed China type long cultivated across southern and eastern China, and var. assamica, a bigger-leafed form built for a wetter, warmer climate. Big-leafed assamica populations turn out to grow wild in two places that have nothing to do with each other administratively: the hills of southwestern Yunnan, and the Brahmaputra valley where this office does its certifying. Both got called "Assam type" tea by botanists, because both look like the plant Robert Bruce found growing wild near Sadiya in the 1820s. Same look, same rough classification. The genetics, checked properly, say the resemblance ends there.

The dates the DNA gives up

Working from nuclear microsatellite markers and chloroplast DNA sampled across wild and cultivated tea populations in both countries, the research team, led by D.K. Meegahakumbura, found genetic clustering that split cleanly into three groups: China-type tea, Chinese Assam-type tea (found in southern and western Yunnan), and Indian Assam-type tea (this valley's own population). Each cluster carried its own distinct genetic signature, with no haplotype shared between the Chinese and Indian Assam populations despite their shared name and shared leaf shape. The team's later, refined dating put China-type and Assam-type tea diverging from a common ancestor roughly 22,000 years ago, during the last glacial period, itself a wide estimate the method admits could run anywhere from a few thousand to over a million years. The two Assam-type populations, Chinese and Indian, then went their separate ways much more recently: an estimated 2,770 years ago, still long before either the British or the Ahom kings had any part in the story. India's Assam type did not migrate from Yunnan and settle in, in other words. It was domesticated from a local wild population that had already been on its own for millennia.

What "independently domesticated" is actually certifying

Three independent domestication events means three separate human populations, in three separate places, took a wild tea plant already growing near them and began managing it, without one group's crop simply spreading to become another's. That is a different, and more interesting, claim than "tea spread from China to India," the version that gets repeated most often. It means the wild ancestor of the tea in an Assam garden was never China's plant wearing a different climate. It was its own population the whole time, related to Yunnan's Assam type only as a distant cousin, not a parent.

This does not overturn what this office has already certified about the plant in the ground here. The clonal breeding record traces a genome-backed split between Assam-type and China-type tea to roughly 5.5 million years ago, a figure from a completely different study, the 2024 chromosome-scale sequencing of the TV1 clone. That number and this one are not in conflict; they are answering two different questions. The 5.5-million-year figure is how long ago the China-type and Assam-type lineages parted ways at all. The 2,770-year figure is how long ago the two populations that both ended up called "Assam type," China's and India's, stopped being one population and became two. The China-type/Assam-type split is ancient and geological. The split inside "Assam type" itself is recent enough to sit comfortably within recorded human history, and it happened without India's tea ever touching Yunnan's.

The bottom line

Three tea lineages, not two, each domesticated on its own: classic China type in southern China, a separate "Assam type" native to Yunnan, and Assam's own Assam type, native to this valley and nowhere else. The last two share a name because they share a look, big leaves built for warm, wet ground, and a common ancestor from the depths of the last Ice Age. They do not share a domestication, a population, or, the genetics say plainly, so much as a single haplotype. The next time a bag claims "Assam type" and the leaf inside it grew in Yunnan, this office is on record: it is kin to what grows here, by a distant and glacial-era relation. It is not the same tea.

Sources

1. Indications for Three Independent Domestication Events for the Tea Plant, Meegahakumbura et al., PLOS ONE, 2016, on the three-way genetic clustering into China-type, Chinese Assam-type, and Indian Assam-type tea, and the finding that Chinese and Indian Assam-type tea share no haplotype despite the shared name.
2. Domestication Origin and Breeding History of the Tea Plant, Meegahakumbura et al., Frontiers in Plant Science, 2018, on the refined divergence dating: roughly 22,000 years between China-type and Assam-type tea, and roughly 2,770 years between the Chinese and Indian Assam-type populations.