Chapter 133: The DE Split and the Toba Catastrophe

They disembarked at Yemen, on the green And wetter Arabia of the late Pleistocene. The grass was thick. The seasonal rivers ran. The peninsula was hospitable to the plan Of a small band looking for a new home. And they stayed, and multiplied, and roamed Outward along the southern coast of Asia, Eastward along the shore, the line of their movement easier To follow than to choose: the sea on the right, The dry interior on the left, the site And prompt of the coastal food sources, the shells And the tidepools and the fish, the bells And bowls of the mangrove swamps—these were The conditions of the migration. The blur Of generations of coast-walking. The slow And patient eastward flow. And early in this flow, Within a few thousand years of the crossing, the CT trunk Split. It is called the DE / CF split. The sunk Root of the migration forked into two daughter Clades. One—DE—would do something dramatic. The other— CF—would follow it in the next chapter's account. For now, DE. And within DE, a further count And split: D diverged from E. E, who would one day Return to Africa by land—that is its own chapter. Today We follow D. Haplogroup D was, once, one of the widest Y-lineages on earth. Not just in the dry Corner of the continent we now identify with it. D was everywhere in Asia. D was the fit Of the first wave across the southern route— D's carriers walked along the Indian Ocean's chute, Populated the pre-Dravidian coasts of what is now India, moved into Southeast Asia, crossed to Java, the brow Of the Indonesian islands, pushed northward into what is now Myanmar, Thailand, southwestern China. The vow Of the early coastal migration carried D Across a continent. D was the pioneer, the free And first-arriving lineage, the one whose patient Eastward progress colonized the ancient And un-peopled lands of southern Asia. And then. Seventy-four thousand years ago, give or take, the pen And chronicle of the earth itself recorded the event. In what is now Sumatra, on the island then Attached by land-bridge to the mainland, a volcano Called Toba erupted. Not a small one. Not the flow And cinder-cone of an ordinary outburst. Toba was the largest volcanic eruption Of the last twenty-five million years. The disruption Ejected approximately three thousand cubic kilometers Of rock and ash. The ash fell across the dimmers And shadowed skies of the whole of Asia. The sun Was blocked for years. The temperature dropped. What had been A warming world entered a sudden cold. The stun And hammer-blow of the eruption closed in On the ecosystems of south and east Asia like a fist. Forests died. Food sources vanished. The mist And fog of the ash blocked photosynthesis For whole growing seasons. The whole thesis Of the settled life of the D-carrying populations Collapsed. The first-wave migrants, whose tens of stations And settlements had spread from Iran to Indonesia, Starved. Died. Were buried in the cold pneumonia Of a world without sun. The coastal settlements Were blanketed in ash. The inland encampments Were buried deeper. The great majority of the carriers Of D died in the years after Toba. The barriers To survival were absolute. The second-wave migrations Of later groups, not yet arrived in these stations And settlements, would find them empty. And the lands Where D had been the majority would be taken by the hands Of later arrivals—C and F-descendants pushing in From the west, from populations that had stayed in Less-affected zones and now expanded into the vacancy. D was almost lost. Almost. In three refugia, scattered across the map, against The odds of total extinction, small populations fenced Off from the blast, or buffered by distance, Or lucky in the terrain that broke the ash's persistence, Survived. The first: the Japanese archipelago. Isolated by water from the Asian mainland, the blow Of Toba reached Japan, but not with full force. The ash was thinner. The winds diverged. The coarse And crude geographic luck of a long-faced island Set off the coast was enough to keep the slight stand Of D-carrying people alive. They survived. They became, In the long later centuries, the founding strata of the name Of Japan. Today, roughly half of Japanese men carry D. Half. Of an entire national population. The freely Inherited patrilineal record of the first wave, Preserved in the islands, carried down through the long save And keeping of the Japanese insular line, for tens Of thousands of years. The depth of D in Japan transcends Any later cultural overlay. The Ainu have D. The Yamato have D. The whole of the archipelago, gently But firmly, is the seed-vault of the first southern migration. The second refugium: the high plateau of Tibet. Elevated. Cold. Ash-resistant because the jet Of the ash-plume moved south and east, not north. The Tibetan plateau, already inhospitable, put forth Its strange resilience: the people who had reached it Before Toba stayed. The altitude they'd borne, its piquant Difficulty, was now their salvation. D persisted in Tibet. Today, Tibetan men carry D at rates that echo the fit Of the pre-Toba distribution. The plateau preserved The lineage. The hard land took what the easier lands served Up to disaster, and held it across the millennia. And the third refugium: the Andaman Islands. A tiny Scatter of islands in the Bay of Bengal, between India And Myanmar, isolated, small, with no infinity Of land to spare—but also, crucially, too far away From the Toba plume to be smothered. The Andamanese— The Jarawa, the Onge, the Sentinelese—they, these Three remaining peoples, carry D in what may Be the purest form surviving. The un-diluted relay Of the first-wave migration, held in a population That has, until recent centuries, lived in a station Of total isolation from the rest of the human world. And there is no cultural connection between them. The Gaiad is emphatic on this point. It is tempting— It is very tempting—to look at the three surviving stem- Carriers of D and weave a story. Japan and Tibet And the Andaman Islands share a haplogroup. Don't they exhibit, Then, some deep kinship? Some residue of the old D culture? Does Japan carry, in its mold, Some trace of what the first-wave migrants knew, That Tibet also carries, that the Sentinelese cue Into as well? Is there a lost D civilization we could Reconstruct if we put them together? Or should We say, more particularly, that Japan's spirituality, Its Shinto, its reverence for the mountain, its locality In the islands, bears some ancient inheritance from The shared source? The Gaiad says: no. Stop. The story is the catastrophe. The story is not A hidden cultural unity. The hot And almost-total extinction of the lineage Is what the three survivals mean. Not an old pedigree Of civilizational inheritance. Seventy thousand years Is long. Languages die a thousand times in seventy thousand years. Cultures are rebuilt and rebuilt and rebuilt, from the ground Up, over and over. The fact that a patrilineal marker is found In three disconnected populations is a fact about The Y-chromosome alone. It tells us nothing about the shout Or silence of the culture that these men carried in their mouths Seventy thousand years ago, which is lost, which died with the droughts And cold years after Toba, and which no living person remembers. The three populations are cultural islands, each in their own embers Of their own long local development. Japan is Japan. Tibet is Tibet. The Andamans are themselves. No plan Of a buried common inheritance. The haplogroup is not A culture. The chromosome is not a soul. The spot And flag on the genetic map is a fact about biology. It is not a fact about religion, or about philosophy, Or about the story that the living members of the populations Tell themselves about who they are. The trepidations And fantasies of those who want to weave Shinto Into Tibetan Buddhism by way of the Andamanese—they go Into the ash of their own speculation. There is no such thread. The Gaiad is careful. The Gaiad does not build a bed For a myth that the evidence does not support. But the catastrophe itself, the short And terrible story of Toba and what it did To the first wave—that story is real, and the Gaiad bid To tell it. Seventy-four thousand years ago, one volcano Erased, very nearly, an entire branch of humanity. The low Bottleneck that D passed through is visible in its genes: The small population sizes after the eruption, the means And standard deviations of the genetic diversity Of modern D-carriers, confirm that the adversity Was extreme. The lineage almost did not make it. It did make it. Three refugia. Three survivals. The lit And dim-lit remainder of what had been a wide And spreading first wave, now reduced to the tide Pools of the very lucky. And from these three survivals, Across the coming millennia, the slow revivals Of population, the slow rebuilding of the lineage, the long And patient continuation of the D-carrying throng Into the present. Japan would become a country. Tibet would become a plateau-empire. The sentry Islands of the Andaman Sea would stay themselves, small And uncontacted. The D-carriers of the world, in their call And inheritance, survived. And half of Japanese men Walk today with the same Y that once was the bend And backbone of a continent's first-wave population. They do not know. They go about their day. The station Of the marker in the blood is silent. It does not speak. It does not call. It does not ask. It is meek And lives, and lives, and lives, and lives, and lives. Somewhere in their bodies, an ancestor who survives The largest volcanic eruption of the last twenty-five Million years, whose own ancestors had crossed alive The Bab al-Mandab, whose own ancestors had walked Out of Africa, whose own ancestors had stalked Back to the origin man Adam—is carried, unnoticed, Through the subway of Tokyo, or through the bused And commuter traffic of Sapporo, or over The trails of Kyoto's old stone paths, a rover In the bloodstream of a salaryman who does not know That he carries the salvaged relic of the blow That nearly erased his line. He does. He does. He does. This is the shape of haplogroup D. The buzz And quiet signal of a first wave almost erased, Preserved in three refugia, unbraced By cultural unity but preserved in its letters Nonetheless. The body remembers what the mind forgets. The Gaiad tells the catastrophe and the survival. Not the false unity. Not the romantic revival Of a common religion or shared soul. The stark And simple fact: a volcano, an ash-dark World, a near-extinction, and three refugia. That is what the Y remembers. That is D's aria.