Biography: Tim D. White
Pioneering Paleoanthropologist

Timothy Douglas White was born in Los Angeles County and grew up near Lake Arrowhead, at the edge of the San Bernardino National Forest, high in the mountains that divide the Mojave Desert from the coastal plain of Southern California. From an early age, he enjoyed exploring the mountains, where he collected snakes and toads, and hunted for relics of the past. One day he might find gear left behind by the miners and loggers who had passed through the area a century before; on another day he might find the obsidian knives and pottery shards of the Native Americans who had preceded them. Young Tim White was also fascinated by prehistoric creatures: the dinosaurs he read about in books, and the extinct mammals whose fossilized remains were discovered in Southern California's La Brea Tar Pits.

In retrospect, it seems obvious that Tim White was an archeologist in the making, but it was not obvious to his parents, teachers or high school counselors. Young people from his community seldom succeeded in college, and he was told to set his sights low. Dissuaded from archeology, he entered the University of California, Riverside, as a biology major. In his junior year, he took his first anthropology course, and the outline of his future career began to take shape. He would apply his love of natural history and archeology to the study of human origins. He graduated with a double major in biology and anthropology, and applied to graduate school at the University of California, Berkeley, hoping to join the school's fossil-hunting expeditions in Kenya and Tanzania. His application to Berkeley was rejected, but White was accepted by the Ph.D. program in physical anthropology at the University of Michigan.

In the summer of 1974, he found the perfect internship: field work with the legendary paleoanthropologist Richard Leakey at Koobi Fora, Kenya. White proved himself a tireless and meticulous field researcher. When Leakey's mother, Mary Leakey, needed an assistant to help her document an extraordinary find of fossils at Laetoli, Tanzania, Richard Leakey recommended the American graduate student. Tim White joined Mary Leakey at Laetoli, participating in the 1976 excavation that unearthed a spine-tingling discovery, the fossilized footprints of an ancient hominid -- an extinct primate, not an ape, but an evolutionary precursor of our own species.

When White received his Ph.D. from Michigan in 1977, he was immediately hired by the anthropology department at Berkeley, the same program that had rejected his application as a graduate student just a few years before. White's expertise in hominid fossils was now well-known in the highest circles of paleoanthropology. He assisted Donald Johanson in analyzing the fossil skeleton known as "Lucy." White was a listed author, along with Johanson, of the 1978 paper that announced their finding that Lucy was not a specimen of Australopithecus africanus, as many believed, but a different species, one they named Australopithecus afarensis. At 3.2 million years of age, Lucy's was the oldest nearly complete hominid skeleton to come to light up to that time. More discoveries lay ahead.

Johanson's expedition had found Lucy's remains at Hadar, in the Afar Basin of Ethiopia, a vast depression in the Earth's crust, where the continental plates of Africa and the Arabian Peninsula are slowly but inexorably pulling away from one another. This movement of the tectonic plates exposes layer upon layer of prehistoric earth, disgorging the fossilized remains of species long extinct, including those of our pre-human ancestors.

Tim White has made the Afar Basin the focus of his field work. The river Awash runs through Afar, and at the midpoint of its course, White has found exceptionally rich deposits of fossils from vastly different eras of prehistoric time. In 1981, he founded the Middle Awash Research Project, based in Berkeley and in Addis Ababa, Ethiopia, to study this unique resource. The project has recruited anthropologists, zoologists, geologists, and paleontologists from all over the world, to take a multidisciplinary approach to unlocking the mysteries of Afar. In particular, Dr. White has concentrated on employing Ethiopians and other Africans, sometimes sponsoring their graduate studies in the United States, so that responsibility for preserving the priceless legacy of Africa's past lies in the hands of its rightful heirs. White serves as Co-Director of the project, with Berhane Asfaw and Giday WoldeGabriel, two of the Ethiopian scientists he has mentored.

In the early '90s, the team's attention was drawn to a site called Aramis, on the western bank of the Awash. In a five-and-a-half-mile arc near a dry streambed, two volcanic eruptions, perhaps a thousand years apart, had preserved a distinct era of fossilized plant and animal life: wood, birds, insects, monkeys, antelopes, rhinoceroses, bears, and hominids. At Aramis, Tim White and his team would make their most dramatic discovery to date.

In the last weeks of 1992, White's associate, Gen Suwa of the University of Tokyo, found a curiously shaped molar, distinctly hominid, but belonging to no known species. A few days later, at the same spot, Berhane Asfaw found a child's jaw and teeth of the same unknown species. In the rainy season that followed, further digging was impossible. A year would pass before White and his crew could return to the site and continue their investigation, but in the following years, they found teeth, arm bones, and pieces of skull and jaw from 17 different individual specimens of the same mysterious creature, preserved in a layer of 4.4 million-year-old sediment. They had discovered a hominid 2 million years older than Lucy, but it would take many years to analyze the bones and determine their significance.

The team collected remains of 6,000 vertebrate animals at Aramis; most of them had been picked clean and scattered by scavengers shortly after death, but one hominid skeleton was more complete. It would take two years to recover 125 bone fragments of this one specimen, an adult female. By 1994 they had hand and foot bones, a shinbone, the partial jaw and teeth, and pieces of a crushed skull and pelvis, all belonging to the same creature. It appeared to have been trampled into the mud by larger animals, and had lain undisturbed for 4.4 million years -- an incredible fluke that preserved enough of the skeleton for White and his team to reconstruct. It would take many years to painstakingly clean and preserve the precious fossils. In many cases, the fragments were too fragile to handle and had to be scanned digitally for virtual reconstruction. For 15 years, only Tim White and a handful of his closest colleagues had access to these bones.

The hominid remains found at Aramis belonged to a bipedal creature -- that is, one that walked upright -- but in other respects was far more primitive than any hominid previously known to science. At first, White conjectured that the Aramis hominid was a species of the genus Australopithecus (Southern ape), the genus of Lucy and many other finds. Anthropologists had long believed that natural selection for bipedalism occurred in the savanna, open grassland where walking upright through the tall grass would confer advantages over traveling on all fours. But the other plant and animal specimens found at Aramis were those of a dense forest, like the habitat of modern tree-dwelling apes. What biological advantage could walking upright have had in the forest?

After years of examination, Tim White and his colleagues concluded that the hominid remains found at Aramis were not specimens of Australopithecus, like Johanson's Lucy, Meave Leakey's Au. amanensis, or White's Au. garhi. White announced that the specimens belonged to a different, previously unknown genus, one he named Ardipithecus (from the Afar word for "ground"), the "ground ape" as opposed to the tree-dwelling apes of today. The hominids of Aramis are now known as Ardipithecus ramidus.

In October 2009, Tim White and his colleagues unveiled their reconstruction of the adult female A. ramidus they had nicknamed "Ardi." At 4.4 million years old, she is more than a million years older than Lucy. Although Ardi is a hominid, born long after the human and chimpanzee lineages diverged, she gives us the best indication to date of what the common ancestor of human and chimpanzee might have been.

Ardi and her A. ramidus brothers and sisters stood about four feet tall, and weighed perhaps 65 pounds. While Lucy was exclusively bipedal, Ardi was capable of walking both upright and on all fours. Her foot was long, strong, and flat enough for walking upright, like a human's, but had an opposing big toe, like a chimpanzee's, useful for gripping tree branches. Her hands were flexible enough for a variety of tasks, but also suitable for walking on all fours. While modern apes walk with their weight on their knuckles, Ardi would have walked with her weight resting on the palms of her hands.

The jaws of A. ramidus males lacked the large canine teeth that chimpanzees and other apes use to express aggression, particularly when competing with other males for access to females. This small difference in the male of the species, and the ability of A. ramidus to walk upright, led White to a provocative hypothesis. The male ramidus, able to gather and carry large quantities of food by hand while walking upright, might have used his skills as a provider to attract a mate. Natural selection would have favored the male who provided food for his own mate and young exclusively, and favored the female who mated exclusively with the most efficient provider. In this way, White suggests, walking upright may be linked to the development of human family dynamics.

While White and his colleagues analyzed the ramidus fossils, they continued to explore other sites in the Middle Awash, finding hominid remains from 14 different time periods, ranging from creatures even older and more primitive than A. ramidus to early specimens of our own species, Homo sapiens.

In 1994, a dig in Awash uncovered a fossil hominid jawbone similar to that of the Australopithecus amanensis found by Meave Leakey in the Great Rift Valley in Kenya. Older than Lucy, (Au. afarensis), but younger than the Aramis find, the anamensis was also undoubtedly bipedal. In 1996 the team found remains of a previously unknown species of Australopithecus, one they named Au. garhi ("surprise" in the Afar language) a creature with a skull like that of other Australopithecus species, but with teeth similar to those of the genus Homo that includes modern man.

In 1997, near the village of Herto, the team recovered two nearly complete adult skulls, and one child's, recognizably human -- genus Homo, not Australopithecus -- but older than any specimen of truly human remains ever seen. Fragments from similar skulls and body parts were found nearby, all roughly at 160,000 to 154,000 years old. The Herto specimens had a larger brain capacity than the average human of today, but in other respects, they resembled far older hominids. Animal bones found nearby had evidently been cut with stone knives, indicating the Herto man's taste for meat and facility with making and using tools. The child's skull appeared to have been polished, as though by repeated handling, suggesting the possibility of a religious or cultural practice. Specimens of Homo erectus have also been found in the Middle Awash. Erectus was probably the first species of hominid to leave Africa; remains have been found as far abroad as the Indonesian archipelago.

In addition to his work with the Middle Awash Research Project, Tim White is still based at the University of California, Berkeley, where he is curator of biological anthropology for the Phoebe A. Hearst Museum of Anthropology, a research paleoanthropologist at the Museum of Vertebrate Zoology, a Professor in the Department of Integrative Biology, and Director of the Human Evolution Research Center.

Since the discovery of A. ramidus, Tim White and the Awash project have found fragments of an even older hominid, Ardipithecus kadabba, an ancestor of A. ramidus that could be nearly 5.8 million years old. Hominid bones found in Kenya and Chad take us back six and seven million years, tantalizingly close to the moment when humans and chimpanzees parted company from their common ancestor, but these remains are so fragmentary we can draw no conclusions as yet. For now, Ardi is the oldest hominid we can picture clearly, but Tim White plans to keep digging.