Looking Backward

At the Hellabrunn Zoo, in Munich, Germany, a small herd of short-maned, pony-sized horses grazed contentedly last week. Fine-boned and broad-skulled, with mouse-grey coats and zebra-striped legs, they look for all the world like tarpans, the fierce wild horses that Roman legionnaires found in Spain. But tarpans are extinct: the last herds vanished in the 19th century, after ranging eastward to the steppes of the Ukraine.

The Hellabrunn horses are a modern throwback to that ancient breed--the end products of careful experiment. Unlike the average horseman, who works at improving the breed, Geneticist Heinz Heck, the Hellabrunn Zoo's director, has spent most of his professional life looking backward. He created the ersatz tarpans by reversing the process of evolution.

Tarpans, explains Dr. Heck in the latest Oryx, journal of Britain's Fauna Preservation Society, flourished as long ago as the Ice Age. Stone-Age man hunted them for food and decorated his caves with their pictures. The last true wild horses were found in the 1880s by the Russian explorer Przewalski. But the shaggy animals which Przewalski brought back from Dzungaria were heavy-boned, with long and awkward heads. They may well have been the ancestors of today's cart horses. There are some Przewalski horses still living in the Hellabrunn Zoo, and Dr. Heck began his experiments in backward breeding with them.

The Przewalski horses have few characteristics of the tarpan, so Dr. Heck brought mares from Iceland and Gotland. Surprisingly like tarpans in skull and build, the mares were bred to Przewalski stallions. Although none of the original brood mares was grey, when crossbred mares were bred to crossbred stallions, they occasionally produced tarpanlike, mouse-grey foals. By discarding the foals that inherited Przewalski heads, by selecting a color here, a skull shape there, working always to reproduce the most backward characteristics, Dr. Heck finally got a herd of horses with tarpan build and the typical tarpan color.

The newborn foals are blond-brown, the color of fresh baked bread. Only after a few months do they change to grey and develop the zebralike tarpan striping on their legs. This change, says Dr. Heck, is the same as the startling color change that takes place so often in domesticated horses. When black and red foals turn to grey, or duns become bays, they are probably imitating their tarpan ancestors.

Since 1928, when he organized the Hellabrunn Zoo and began his experiments in Riickzuechtung (backward breeding), Geneticist Heck has developed his tarpans and a herd of aurochs, the beefy, bison-like ancestors of modern cattle. Neither strain has any domestic value, but both have shown unusual resistance to disease. "The day may come," said Dr. Heck last week, "when our highly bred, high-strung modern breeds will need a shot of their wild ancestors' blood to revitalize them."

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