From: http://www.nytimes.com/2001/01/16/science/16FIRE.html

January 16, 2001 
Of Tubers, Fire and Human Evolution
By MARK DERR

Nearly all of the world's cultures have myths telling how a trickster, a
clever human or some sympathetic deity brought fire to people and changed
their lives. Fire gave rise to cooking and provided protection against
predators and cold. By lighting the night, fire paved the way for music,
art and poetry. In short, for civilization.

While few anthropologists argue with that notion, they are engaged in a
continuing debate over when ancestral humans gained control of fire and
what that says about the way they lived and perhaps even evolved.

"There is even disagreement over what the hominid is who tamed fire," said
Dr. Ofer Bar-Yosef, a professor of anthropology at Harvard.

On one extreme are those anthropologists who argue that Homo erectus,
generally perceived as the first successful human ancestor, evolved with
fire in East Africa some 1.8 million years ago. Armed with fire, stone
tools and weapons, those ancestors soon began spreading throughout much of
Europe and Asia, even into Indonesia.

But the prevailing view among many anthropologists has long been that the
archaeological evidence from East Africa for the early conquest of fire is
ambiguous at best and that, in fact, Homo erectus lived successfully as a
hunter and scavenger of big game for more than a million years without
fire. Homo erectus, and possibly other species of human ancestors, the
theory holds, began to control fire only out of necessity when they moved
into more northern latitudes and had to contend with frozen meat and
bone-chilling cold.

Until recently, the earliest generally accepted evidence for human fire has
come from Zhoukoudian, China — where Peking Man was found — and dates to
around 500,000 years ago, said Dr. Richard Klein, a professor of
anthropology at Stanford. There are also one or two sites in Europe that
contain evidence of human use of fire about 400,000 years ago, Dr. Klein
added.

"But if you want hard evidence for fire in the form of stone hearths and
clay ovens, you are in the last 250,000 years," he said. That is the time
of archaic Homo sapiens in Europe and late Homo erectus in Asia.

Over the last two years, though, several groups of researchers have
published a series of papers that have deepened the debate, casting doubt
on the evidence for human-made fire at Zhoukoudian and lending fresh
support to the argument for very early control of fire.

A team including Dr. Bar-Yosef; Dr. Steve Weiner, professor of structural
biology at the Weizmann Institute of Science in Israel; Dr. Paul Goldberg,
professor of archaeology at Boston University; and Dr. Xu Qin-qi and Dr.
Liu Jin-yi of the Institute of Vertebrate Paleontology and
Paleoanthropology in Beijing found that the ashes archaeologists long
believed were produced by human-made fire 500,000 years ago in Zhoukoudian
washed in from outside and could have natural causes. Burnt bones and stone
tools still suggest the presence of fire, but there is no direct evidence
that humans built it, Dr. Goldberg said.

Meanwhile, two groups of anthropologists, working independently, have
theorized that cooked tubers, corms, rhizomes and other roots played a
pivotal role in human evolution.

Cooking makes tubers more edible and increases their nutritional value by
softening them and in many cases ridding them of toxins, said Dr. Richard
Wrangham, professor of anthropology at Harvard and leader of a group that
includes Dr. David Pilbeam, James Holland Jones and Dr. NancyLou
Conklin-Brittain, all of Harvard, and Dr. Greg Laden, of the University of
Minnesota.

Dr. Wrangham's group theorizes that a population of australopithecines, the
apelike ancestors of Homo erectus, gained control of fire and began cooking
tubers and roots in East Africa about 1.9 million years ago. Within several
hundred generations — a short time in evolutionary terms — the
australopithecines had evolved into Homo erectus. "Evolution is driven by a
cultural event: the capture of fire," Dr. Wrangham said.

Homo erectus, whose early form in Africa is sometimes called Homo ergaster,
is distinguished by physiological and neurological changes from its
australopithecine forebears, including a considerably larger brain, smaller
teeth and an upright gait. Females also began to form individual pair bonds
with males within large social groups, Dr. Wrangham theorizes, largely to
prevent other males from stealing food they collected and prepared around a
fire.

Dr. James F. O'Connell and Dr. Kristin Hawkes, anthropologists at the
University of Utah, with Dr. Nicholas G. Blurton Jones of the University of
California at Los Angeles also tie cooked tubers directly to the evolution,
population growth and migration of Homo erectus.

Dr. O'Connell and his colleagues suggest that in response to a drier,
colder climate, which reduced the availability of traditional plant foods,
like fruit, women in some groups turned to collecting and cooking tubers
and other root stock. These practices, the anthropologists theorize,
allowed women past childbearing age to participate in feeding their
families. The combination of better food and greater contribution to
feeding the family helped lower adult mortality rates and lengthen the
average life span, Dr. O'Connell said, and it improved nutrition for
children and mothers. Other biological and social changes followed.

These "cooked tuber" theories have stirred considerable controversy in
large measure because they posit that control of fire was central to early
human evolution and that meat eating was less important than generally
believed. A number of anthropologists argue that meat eating was central to
the development — especially the increasing brain size — of Homo erectus
and modern humans.

"Conventional wisdom says that hunting and scavenging by males are
responsible for the changes we see in Homo erectus," Dr. O'Connell said.
"But if you do the calculations, you can't find the nutritional resources
needed for that in meat alone."

The proposals have also spurred some researchers to take a new look at
evidence in East Africa for early fire. Sites at Gadeb in Ethiopia, Koobi
Fora and Chesowanja in Kenya, and Olduvai Gorge in Tanzania have produced
evidence in the form of thermally altered stone artifacts and circles of
burned clay dating from 1.5 million to 1.7 million years ago. Burned bones
dating to about 1.5 million years ago have also been found in the
Swartkrans cave in South Africa. 

The material is at least suggestive of human-made fire, said Dr. John W. K.
Harris, professor of anthropology at Rutgers. He studied many of the sites
in the 1970's and 1980's and believes that the new theories on cooking
strengthen the case.

But whether a careful analysis of the East African fire sites would produce
more solid evidence of human involvement is an open question. "It might be
another decade before evidence of early fire comes through more strongly,"
Dr. Wrangham said.

Other researchers are not so certain that the type of definitive evidence
many archaeologists demand will ever be found. Dr. O'Connell, who has
studied fire use among the Hadza, hunters and gatherers who live in
Tanzania, said, "Most archaeologists don't understand how modest fires in
the bush can be. They are small and leave little evidence." What charcoal
and ash remain soon vanish.

Absent physical proof, Dr. Klein said, the only way to answer the question
might be to examine the reasons for increasing brain size in Homo erectus.
"Around 1.8 million years ago brain size increases dramatically, and you
need a high-energy food source for that, and that might require fire to
break down muscle and plant fiber for digestion," Dr. Klein said.

But, Dr. Klein added, until that theory is proven, "the question will
continue to lead to speculation and controversy."