ŷ������

Who were these people? The ones who lived in a world populated by animals whose fossils were displayed at the Los Angeles Museum of Natural History; the ones who fashioned the Native American relics his father brought home from a road excavation. Tim White was always traveling in his imagination back in time. As a teen he was fascinated by F. Clark Howell's Early Man, part of the Time-Life Nature Library series. Later, he would read about the Leakey discoveries from the pages of National Geographic.

The illustration “March of Progress�� depicting human evolution by Rudolph Zallinger from Early Man is still iconic. Simple. Intuitive. But wrong, just like most of what we thought we knew about human evolution from catchphrases like “the Missing Link�� or later, “Mitochondrial Eve.�� White was a key figure in shattering these paradigms.

White led a succession of digs in the Afar Depression, the triangular area where three tectonic plates meet at the northeast tail of the Great Rift Valley. It's safe to assume he never said to himself: “Yes, I want to go to war-torn Ethiopia to a remote region plagued by intertribal warfare, venomous snakes, prowling jackals, unpredictable floods, and scalding summers to dig." What is remarkable is that he didn't care about any of this. He wanted to find the oldest human fossil, and the Afar Depression was the most promising location to find it.

In 1994 his team struck paydirt. They unearthed a fossil 4.4 million years old. Up to that time, the oldest fossil was “Lucy�� (Australopithecus afarensis), excavated two decades previously by Donald Johanson. “Lucy�� was estimated to be 3.2 million years old. Eventually, White would conclude that his fossil “Ardi�� represented a new genus which he called Ardipithecus ramidus. Her age alone was enticing. Human ancestry might one day be pushed back from the Pliocene (5.3 to 2.6 million years ago) all the way back to the Miocene (23 to 5.3 million years ago). More eye-opening, however, were the revelations that would take 15 years of careful study, conjecture, and confirmation before being openly published. Ardi's forelimbs were shorter than her legs. Her toes were opposable, consistent with a climber. The spine was upright indicating bipedal locomotion. Diamond-shaped canines that were not self-sharpening were characteristic of humans, not apes. Her habitat was unclear. Woodland? Savannah? Both? “The climate and botany of eastern Africa cycled back and forth in a very spiky fashion between wet periods when huge lakes formed in the rift valley, dry periods when dust collected on the coastal seafloor, and sometimes perplexingly both at the same time....The quest for a master narrative of climate-driven human evolution remains unfulfilled.�� (p.220)

The range of specialized expertise tapped to support these conclusions was staggering. Geology of the Ethiopian rift system and in particular of the Afar Depression (Giday WoldeGabriel, Berhane Asfaw, and Maurice Taieb), isotope decay geochronology and genomic biology (Stan Ambrose), paleoanatomy, comparative anatomy and biomechanics (Owen Lovejoy, Gen Suwa and Scott Simpson), foot anatomy (Bruce Latimer), paleolithic archaeology (Yonas Beyene), paleobotany, and comparative genomics.

Instead of a “missing link,�� some scientists now speak of “ghost lineages.�� Geneticist David Reich states: “Within human populations, there is no simple tree....Instead, the truth is it's more like a trellis with mixing, remixing, and separation again and again going back into deep time.�� (p.403)

Tim White is an iconoclast. He was never cowed by those adhering to conventional wisdom or the criticisms of well-regarded colleagues. His impatience and lack of diplomacy ignited animosities which author Kermit Pattison felt obligated to detail along with opposing interpretations of White's find. The result is a balanced but often meandering narrative. Also interspersed are mini-biographies of the many researchers whom White worked with. Nevertheless, this was a thought-provoking and exhaustive update to the story of human evolution.