Miniature People Add Extra Pieces to Evolutionary Puzzle
By NICHOLAS WADE
Published: November 9, 2004
The miniature people found to have lived on the Indonesian island of Flores until 13,000 years ago may well appeal to the imagination. Even their Australian discoverers refer to them with fanciful names. But the little Floresians have created something of a headache for paleoanthropologists.
The Floresians, whose existence was reported late last month, have shaken up existing views of the human past for three reasons: they are so recent, so small and apparently so smart. None of these findings fits easily into current accounts of human evolution.
The textbooks describe an increase in human brain size that parallels an increasing sophistication in stone tools. Our close cousins the chimpanzees have brains one third the size of ours, as do the Australopithecines, the apelike human ancestors who evolved after the split from the joint human-chimp ancestor six or seven million years ago. But the Australopithecines left no stone tools, and chimps, though they use natural stones to smash things, have no comprehension of fashioning a stone for a specific task.
The little Floresians seem to have made sophisticated stone tools yet did so with brains of 380 cubic centimeters, about the same size as the chimp and Australopithecine brains. This is a thumb in the eye for the tidy textbook explanations that link sophisticated technology with increasing human brain size.
The Australian and Indonesian researchers who found the Floresian bones have an explanation that raises almost as many questions as it resolves. They say the Floresians, who stood three and a half feet high, are downsized versions of Homo erectus, the archaic humans who left Africa 1.5 million years before modern humans. But some critics think the small people may have descended from modern humans - Homo sapiens.
Homo erectus had arrived on the remote island of Flores by 840,000 years ago, according to earlier findings by Dr. Mike Morwood, the Australian archaeologist on the team. The species then became subject to the strange evolutionary pressures that affect island species. If there are no predators and little food, large animals are better off being small. Homo erectus was sharply downsized, as was the pygmy elephant the little Floresians hunted.
But the Morwood theory is not universally accepted. Homo erectus is known to have made crude stone tools but is not generally thought to have spoken or been able to build boats.
Maybe Dr. Morwood's alleged stone tools were just natural pieces of rock. "Many researchers (myself included) doubted these claims," writes Chris Stringer, a paleoanthropologist at the Natural History Museum in London, adding that "nothing could have prepared me" for the surprise of the little Floresians.
It is surprising enough that Homo erectus managed to reach Flores. But not only have the Floresians evolved to be much more advanced than their ancestors ever were, as judged by the stone tools, but they did so at the same time that their brain was being reduced to one-third human size. Getting smaller brained and smarter at the same time is the exact reverse of the textbook progression.
The Floresians' other surprise lies in the time of their flourishing. The skeleton described in Nature lived as recently as 18,000 years ago, but Dr. Morwood said that in the most recent digging season he found six other individuals whose dates range from 95,000 to 13,000 years ago. Modern humans from Africa arrived in the Far East some time after 50,000 years ago and had reached Australia by at least 40,000 years ago.
There has been little evidence until now that Homo erectus long survived its younger cousins' arrival in the region. Modern humans probably exterminated the world's other archaic humans, the Neanderthals in Europe. Yet the little Floresians survived some 30,000 years into modern times, the only archaic human species known to have done so.
All these surprises raise an alternative explanation. What if the Floresians are descended from modern humans, not from Homo erectus?
"I think the issue of whether it derives from H. erectus or H. sapiens is difficult or impossible to answer on the morphology," says Dr. Richard Klein, an archaeologist at Stanford. And if the individual described in the Nature articles indeed made the sophisticated tools found in the same cave, "then it is more likely to be H. sapiens," he says.
The same possibility has been raised by two anthropologists at the University of Cambridge, Dr. Marta Mirazón Lahr and Dr. Robert Foley. Commenting on the sophisticated stone implements found in the cave with the Floresians, they write that "their contrast with tools found anywhere with H. erectus is very striking."
There is the basis here for a fierce dispute. Given what is on the record so far, the argument that the Floresians are descended from Homo sapiens, not erectus, has a certain parsimony. Moderns are known to have been around in the general area, and no Homo erectus is known to have made such sophisticated tools.
Dr. Morwood counters this thesis with data that he has not yet published, and which therefore does not strictly count in scientific arguments. The 95,000-year-old Floresians far antedate the arrival of modern humans in the area. There are modern human remains on Flores, Dr. Morwood says, but the earliest is 11,000 years old, suggesting there was not necessarily any overlap between the two human species.
His view is supported by Dr. G. Philip Rightmire, a paleoanthropologist at Binghamton University in New York and an expert on Homo erectus. "There is no ambiguity about the morphological pattern, and it is erectus-like," Dr. Rightmire says of the Floresian skeleton. "I'm not sure why it should be difficult to accept the reasoning that the little Floresians made progress with stone working and honed their hunting-butchering skills" during their long co-existence on Flores with the pygmy elephants, he said.
Dr. Morwood believes the little Floresians must have had language to cooperate in elephant hunts. Others are not willing to follow him so far, especially given Homo erectus's apparent lack of achievement. Even chimps can hunt cooperatively, Dr. Foley says.
Whether the Floresians' line of descent runs through Homo erectus or through Homo sapiens, a whole new line of human evolution has opened up, even though one that is now all but certainly extinct. The Floresians are not like human pygmies, which have almost normal-size brains but smaller bodies because their growth is retarded during puberty. Nor are they dwarves. The skeleton described last month could be a called a midget, in the sense of a tiny person with the head and body proportions of a full-size person, Dr. Klein said.
"I always tell my students that I've taught for 30 years and I've never given the same lecture twice. Hardly a year goes by when something new isn't found," says Dr. Leslie Aiello, a paleoanthropologist at University College London. Of the Floresian discovery she says, "It's a total knockout."
On island, scientists unearth modern humans' tiny cousin
By Beth Daley, Globe Staff / October 28, 2004
Scientists have unearthed a new species of hobbit-sized humans that may have lived as recently as 12,000 years ago, sharing the earth alongside modern-day man.
The discovery of a skull, bones, and teeth from these Lilliputians on the Indonesian island of Flores, reported in the journal Nature today, paints a far more complex picture of late human evolution, one that counters a long-held belief that Homo sapiens has been alone on the planet for tens of thousands of years.
The 3-foot tall people with grapefruit-sized skulls -- dubbed "Flores Man" -- were apparently able to make stone tools, ignite fires, and organize hunts of young pygmy elephants, based on the charred bones and animal remains found at a cave site called Liang Bua.
Their isolated island, also home to giant lizards and rats, appears to have molded the species in the same way that other island mammals develop into dwarfs or giants, based on what would be advantageous to avoid predators or to gather food.
While legends in Indonesia have long talked about dwarf-sized creatures called "little people," there has never been scientific evidence that they existed.
"When I saw this paper I thought it was a big elaborate hoax -- and it wasn't," said Daniel Lieberman, professor of biological anthropology at Harvard University, who critiqued the paper before it was published. "We are in a very odd time in human history in that we are the only species of humans on the planet now."
Researchers from Australia and Indonesia first discovered the remains of a near-complete female skeleton dating back 18,000 years in a limestone cave on the eastern Indonesian island last year. Since then, they have unearthed bones and teeth of about five to six others dating from 12,000 to 95,000 years ago.
The bones were not fossilized; they had the consistency of "mashed potatoes," researchers said. They believe the species may have been wiped out, along with the tiny elephants, by a volcanic eruption.
"It's rare, extremely rare, to find a hitherto unknown species of human living in the recent geological past," said Bert Roberts of the University of Wollongong in Australia, one of the paper's authors.
The Flores Man is believed to be a descendant of Homo erectus, an African large-brained human ancestor that spread from Africa to Asia about 2 million years ago. Scientists hypothesize the species became isolated on Flores some time in the past few hundred thousand years and evolved into smaller stature. Such evolutionary responses occur on islands, creating animals much smaller or larger than ancestors to adapt to specific conditions.
"I nearly dropped to my knees at one point examining the specimen," said Peter Brown, one of the paper's lead authors and a paleoanthropologist at the University of New England in Australia.
But even more startling, scientists say, is that these dwarfs lived at the same time as homo sapiens. Many scientists believe modern humans originated in Africa about 160,000 years ago, reaching Indonesia about 40,000 years ago.
It is unknown if the two species interacted in any way, or even if either knew the other existed. Scientists' only record of modern man in Flores is after the volcano erupted. However, the two species apparently overlapped in the same part of the world for at least around 20,000 years, the authors of the study estimated.
"These [little people] are sort of like WordPerfect 1.2 and then you don't bother to find out if there are any upgrades," said Bernard Wood, Henry Luce professor of human origins at George Washington University, who is not connected to the study. "You forget what the rest of the world is doing. If you take one of these creatures and put them in a slightly different environment, they change. What is extraordinary is how [flexible] evolution is."
There remain many unanswered questions about the dwarfs. Scientists don't know if the Flores Man was relatively short-lived species in evolutionary terms or survived for a very long time. Scientists say evidence now places the species back about 95,000 years, but it might extend up to eight times longer ago than that.
Most scientists contacted said yesterday they were deeply excited that there might be other modern-day "twigs" of failed human evolutionary branches elsewhere in the world. The authors of the paper are stepping up research on Flores and other nearby islands.
"You don't know until you find them," said Tim White, a paleobiologist at the University of California Berkeley. He said the research does underscore an important point in evolution: "We are not the goal, but one product of the evolutionary process. What they found on Flores is another product."
(COMTEX) B: ACLU to Sue Over Pa. Evolution Debate ( AP Online )
HARRISBURG, Pa., Dec 14, 2004 (AP Online via COMTEX) -- Eight families have filed a lawsuit against a school district that is requiring students to learn about alternatives to the theory of evolution, claiming the curriculum violates the separation of church and state.
The ACLU and Americans United for Separation of Church and State said the lawsuit is the first to challenge whether public schools should teach "intelligent design," which holds that the universe is so complex that it must have been created by some higher power. The two organizations are representing the parents in the federal lawsuit.
The Dover Area School District voted 6-3 on Oct. 18 to include intelligent design in the ninth-grade science curriculum, in what is believed to be the first such requirement in the country.
The American Civil Liberties Union contends intelligent design is a more secular form of creationism - a biblical-based view that credits the origin of species to God - and may violate the constitutional separation of church and state.
One of the parents bringing suit, Tammy Kitzmiller, expressed concern that the school board would mandate the teaching of "something that isn't accepted as science." Kitzmiller has two children who attend Dover High School, where teachers of ninth-grade biology are expected to discuss evolution sometime next month.
School officials had no immediate comment on the lawsuit.
At least one other district has recently become embroiled in federal litigation over teaching evolution. A federal judge in Georgia is considering the constitutionality of a suburban Atlanta district's decision to include a warning sticker about evolution in biology textbooks.
Two of the three dissenting board members have resigned in protest. Angie Yingling, a board member who originally supported the policy, said she later reconsidered her vote.
"Anyone with half a brain should have known we were going to be sued," she said. "You can't do this."
(COMTEX) B: Rapid brain expansion propelled human intelligence, study finds ( Chicago Tribune )
CHICAGO, Dec 29, 2004 (Chicago Tribune - Knight Ridder/Tribune News Service via COMTEX) -- The first study of genes that build and operate the brain shows that humans underwent a unique period of rapid brain expansion that endowed them with a special form of intelligence not shared by any other animal, according to University of Chicago researchers.
The colossal leap forward grew the human brain to three or four times the size of that of a chimpanzee - man's closest genetic relative - when body sizes are equalized. That vast computing power pushed human intelligence over the threshold of basic instincts and into an unparalleled realm of cognition, self-awareness and consciousness.
"We tend to think of our species as categorically different, being on top of the food chain," said University of Chicago geneticist Bruce Lahn. "There is some justification for that."
The dark side of this magnificent gift is that some of the genes that make for a bigger and better brain may also be the ones that predispose people to mental disorders and addiction. Learning more about what happens when these genes go wrong could lead to new prevention strategies and treatments.
Reporting in the cover article in Wednesday's issue of the journal Cell, Lahn and his colleagues, Eric Vallender and Steve Dorus, found that 17 brain-building genes mutated at a tremendously rapid rate in humans, compared with the brains of chimpanzees, macaque monkeys, rats and mice.
In a species that was social and cooperative but had few other survival skills, being smarter meant a lot to early humans, said Lahn. Genetic mutations that enhanced intelligence amid the pressure to survive were quickly passed on to future generations. Those not possessing the new genes eventually died off.
Once started, the selection of brain-building genes snowballed, resulting in thousands of changes to thousands of genes in a relatively short period, Lahn explained.
"Humans evolved their cognitive abilities not due to a few accidental mutations, but rather from an enormous number of mutations acquired through exceptionally intense selection favoring more complex cognitive abilities," he said.
Lahn, also a Howard Hughes Medical Institute investigator at the University of Chicago, argues that the evolutionary forces that led to the big brain continue to act on humans today and are likely to produce bigger and better brains in the future.
Jianzhi George Zhang, an assistant professor of ecology and evolutionary biology at the University of Michigan, said the "work suggests that we humans might be most distinct in our brains. It documents for the first time that there is a general trend of accelerated evolution of proteins involved in human and primate brain development."
The findings, Lahn said, disprove the contention of other scientists who say the evolutionary process leading to the bigger human brain was simple adaptation to change - like growing bigger antlers, longer tusks or gaily colored feathers.
"We've proven that there is a big distinction," he said. "To accomplish so much in so little evolutionary time - a few tens of millions of years - requires a selective process that is categorically different from the typical processes of acquiring new biological traits."
Many people desperately want to feel special and the findings from the Cell paper indicate that humans really are, said Arthur Caplan, director of the University of Pennsylvania's Center for Bioethics.
"There is this desire for humans to have a privileged position in terms of other animals," he said. "We try to find in intelligence or language or something that seems to distinguish us, because we want to be more like the angels than like the animals.
"But, unfortunately, the animals keep talking and being social and using tools. Every time we come up with something, they do it too."
The difference is that while some animals may have one or two of these attributes in rudimentary form, humans have all of them in abundance, he said.
"The new findings look like the human brain and its hyper-evolutionary development might give us that special status relative to all the other living things around us," Caplan said.
For this study the University of Chicago researchers looked at 214 genes involved in brain development in humans, macaques, rats and mice. (They had studied chimp genes previously.)
Ninety-five of the genes, those involved in the most basic cellular functions such as energy production, remained basically the same in all four species for the last 80 million years, or since primates split from rodents on the evolutionary tree.
But mutations in genes that build the brain exploded in the human line when humans split from monkeys 20 to 25 million years ago, Lahn said. Rats, meanwhile, split from mice around the same time - 16 to 23 million years ago - but did not undergo comparable changes.
The researchers found 24 genes that had undergone rapid evolutionary changes in humans and not in the other three species. Seventeen are involved in building the brain and regulating behavior, and their rate of mutational change was two to three times greater than that of chimps and monkeys.
The functions of two of these genes have already been studied in Lahn's laboratory. They are called ASPM and Microcephalin, and they play a key role in making the brain bigger. Humans born with major malfunctions in either of these genes develop microcephaly, a severe reduction in the size of the cerebral cortex, which is the part of the brain responsible for planning, abstract reasoning and other higher cognitive function.
Among the earliest humans, it was social interactions that pushed for bigger brains, Lahn said. The social structure could be manipulated to gain more resources for all of its members, and those who were the best resource providers thrived and passed their genes to future generations.
A second set of evolutionary pressures on the brain set in about 4 million years ago with the development of primitive tools and other cultural accomplishments, he said. Cultural development meant new information could be passed on by learning and not only by genes.
The brain is tremendously plastic, meaning that most of it gets built after birth from the experiences it encounters in its environment. That helps account for the long dependency of childhood, a time in which the brain's software is being installed, Lahn said.
"Animals are born with a set of instincts," he said. "They can run, eat and swim right away. Humans cannot. The reason for that is that given this large complex brain you're better off not to be born with so many instincts but with the ability to learn. It allows you to adapt to different environments."
Although human brain development appears to have undergone unique changes, it is still based on similar basic genes common to all animals, Caplan said.
"It's not like we're a silicon life form and the rest of the planet is carbon," he said. "It's just that the pressures on us once we began to have a brain were very powerful. To survive we needed to get a whole lot smarter in evolutionary terms relatively quickly."
And humans are going to continue to become smarter, Lahn said. "If anything, intelligence matters even more now than it has even in the recent past. Kids go through all kinds of hurdles to rise up in society, and people are constantly competing largely based on their mental capacities.
"I think that these genes are still evolving," he said. "Within human populations there are still mutations that are arising very recently that make some people a little smarter than others."
Brain size was thought to have hit its maximum because a larger skull would not be able to squeeze through the birth canal. But Caesarean sections - the modern practice of surgically removing a baby from the womb - could eliminate those limitations, Lahn noted.
"With the C-section we have just lifted a huge barrier to how big the brain can be," he said. "I wouldn't be surprised if in a few hundred years C-sections become almost 100 percent."
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