[This theory is very controversial. See post: http://esaus-brethren.blogspot.com/2009/08/human-skull-has-neandertal-feature.html
. and http://esaus-brethren.blogspot.com/2009/05/fossils-anthropology-cultures-evolution.html
Our Species Mated With Other Human Species, Study Says
for National Geographic News
March 6, 2002
A new piece of evidence—one sure to prove controversial—has been flung into the human origins debate.
A study published March 7 in Nature presents genetic evidence that humans left Africa in at least three waves of migration. It suggests that modern humans (Homo sapiens) interbred with archaic humans (Homo erectus and Neandertals) who had migrated earlier from Africa, rather than displacing them.
In the human origins debate, which has been highly charged for at least 15 years, there is a consensus among scientists that Homo erectus, the precursor to modern humans, originated in Africa and expanded to Eurasia beginning around 1.7 million years ago.
Beyond that, opinions diverge.
There are two main points in contention. The first is whether modern humans evolved solely in Africa and then spread outward, or evolved concurrently in several places around the world.
The second area of controversy is whether modern humans completely replaced archaic forms of humans, or whether the process was one of assimilation, with interbreeding between the two groups.
"There are regions of the world, like the Middle East and Portugal, where some fossils look as if they could have been some kind of mix between archaic and modern people," said Rebecca Cann, a geneticist at the University of Hawaii.
"The question is," she said, "if there was mixing, did some archaic genetic lineages enter the modern human gene pool? If there was mixing and yet we have no evidence of those genes—as is indicated from the mitochondrial DNA and y chromosome data—why not?"
Alan Templeton, a geneticist at Washington University in St. Louis who headed the study reported in Nature, has concluded that yes, there was interbreeding between the different groups. "We are all genetically intertwined into a single long-term evolutionary lineage," he said.
To reach his conclusion, Templeton performed a statistical analysis of 11 different haplotype trees. A haplotype is a block of DNA containing gene variations that researchers believe are passed as a unit to successive generations. By comparing genetic differences in haplotypes of populations, researchers hope to track human evolution.
Templeton also concluded that modern humans left Africa in several waves—the first about 1.7 million years ago, another between 800,000 and 400,000 years ago, and a third between 150,000 and 80,000 years ago.
Alison S. Brooks, a paleoanthropologist at George Washington University, is more cautious about Templeton's conclusions. "Archaeological evidence supports multiple dispersals out of Africa," she said. "The question has always been whether these waves are dead ends. Did all of these people die? Templeton says not really, that every wave bred at least a little bit with those in Eurasia
"This has not been the majority viewpoint of geneticists up to this point," said Brooks.
The fossil record shows that about 100,000 years ago, several species of hominids populated Earth.
Homo sapiens could be found in Africa and the Middle East; Homo erectus, as typified by Java Man and Peking Man, occupied Southeast Asia and China; and Neandertals roamed across Europe.
By about 25,000 years ago, the only hominid species that remained was Homo sapiens. Scientists have conducted a considerable amount of both genetic and archaeological research in an effort to understand how this outcome occurred.
The two primary theories in the human origins debate are the "Out of Africa" theory and the multi-regionalism theory. Each has its own variations, and there are intermediate models, such as one favoring assimilation among the different groups. Credible evidence exists to support each theory.
The multi-regionalism theory, which relies on fossil evidence, holds that after members of Homo erectus first left Africa roughly 1.7 million years ago, they settled in different regions of the world and evolved separately but concurrently into Homo sapiens. Despite the vast distances, there was enough gene exchange between groups that an entirely new species did not evolve.
The "Out of Africa" theory relies considerably on DNA evidence. This scenario also holds that Homo erectus first left Africa around 1.7 million years ago. Evolution continued, and anatomically modern humans appeared in Africa between 200,000 and 100,000 years ago.
Beginning about 100,000 years ago, these modern humans expanded outside the continent, making their way across Asia and Europe, where they completely replaced the older species, Homo erectus.
Unlike Templeton's assertions, the "Out of Africa" theory does not support the idea of interbreeding between archaic and modern humans.
Explaining his contention that interbreeding occurred, Templeton said humans "have long shown a pattern of isolation by distance," and at any given time there is some degree of genetic difference between human populations.
"However," he added, "genetic interconnections have long existed among human populations, and this was accentuated by the latest 'Out of Africa' expansion, not eliminated, as under the replacement model."
Templeton's view is "a kind of compromise," said Brooks. "Africa was still the major source of all modern humans, but there was a limited amount of interbreeding with other populations already living in Eurasia," she said.
Fred Smith, a paleoanthropologist at Northern Illinois University who proposed the assimilation model of human evolution, said Templeton's data support the idea that modern humans evolved in Africa, spread to other continents, and interbred with archaic populations.
"I argued for the assimilation model based on morphology—what could be seen in the fossil record, rather than on genetic evidence. But I'm in agreement with what Templeton has found," Smith said.
Cann, in an accompanying article in Nature, said Templeton's attempt to view the data from a global perspective is over-ambitious given problems with genetic studies of small-scale modern populations.
"I want to see [his methodology and analysis] validated in an area of the world where a variety of scientists from different disciplines think they understand how humans spread and when," she said.
Examples of human migration that might help demonstrate the validity of Templeton's analysis and its limitations, she suggested, include the relatively recent expansion to Polynesia, the spread of farmers from Turkey into Northern Europe, and the migration of Vikings to Iceland.
"We need lots of different tools to study human evolution," Cann pointed out. "Scientists get into trouble when they expect one tool will do everything. Sometimes you need a hammer to attach things, sometimes a screwdriver, and sometimes Velcro works as well!
"Better to keep exploring these different methods with an open mind," she added, "since there are things only fossils can tell you, and things only genetics can reveal."
Erik Trinkaus, professor of anthropology in Arts & Sciences, examines a Neandertal skull. (Photo by Joe Angeles/WUSTL photo)
More Human-Neandertal Mixing Evidence Uncovered
ScienceDaily (Nov. 6, 2006) — A reexamination of ancient human bones from Romania reveals more evidence that humans and Neandertals interbred.
Erik Trinkaus, Ph.D., Washington University Mary Tileston Hemenway Professor in Arts & Sciences, and colleagues radiocarbon-dated and analyzed the shapes of human bones from Romania's Petera Muierii (Cave of the Old Woman). The fossils, discovered in 1952, add to the small number of early modern human remains from Europe known to be more than 28,000 years old.
Results were published in the current issue of the Proceedings of the National Academy of Science.
The team found that the fossils were 30,000 years old and principally have the diagnostic skeletal features of modern humans. They also found that the remains had other features known, among potential ancestors, primarily among the preceding Neandertals, providing more evidence there was mixing of humans and Neandertals as modern humans dispersed across Europe about 35,000 years ago. Their analysis of one skeleton's shoulder blade also shows that these humans did not have the full set of anatomical adaptations for throwing projectiles, like spears, during hunting.
The team says that the mixture of human and Neandertal features indicates that there was a complicated reproductive scenario as humans and Neandertals mixed, and that the hypothesis that the Neandertals were simply replaced should be abandoned.
Telltale Face Betrays Neandertals as Non-Human
for National Geographic News
August 2, 2001
Tens of thousands of years ago, Neandertals—a race of people that somewhat resembled modern humans—crisscrossed the landscapes of Europe and western Asia and lived over a wide range for many millennia.
At times, they lived near or alongside the biological ancestors of modern humans, who had left Africa and were spreading gradually throughout the same regions.
Then, some 20,000 years ago, Neandertals disappeared from Earth.
Anthropologists still aren't certain they know what happened to them, but there are two popular theories.
For decades, scientists have been studying bones, genes, and ancient tools in an effort to determine which of the theories is accurate. Now, two scientists in Switzerland are weighing in with the results of a novel analysis.
One of the two competing theories holds that Neandertals—strong, intelligent, and with the knowledge and dexterity to make simple but effective tools—were barely different from other ancient peoples. Those other groups, the thinking goes, biologically assimilated Neandertals in the process of outcompeting them or perhaps killing them off.
If it's true that Neandertals were absorbed into other groups, their distinctive DNA is likely to have been introduced into the gene pool of the survivors in small amounts and passed down through the generations. In this telling of prehistory, some of us may be descendants of the Neandertals—or at least have a few of them high in the branches of the family tree.
But a popular alternative version maintains that the ancient race left no living legacy. It suggests that Neandertals were a biologically different species that was incapable of mating—and therefore biologically mixing—with the modern humans they may have encountered.
This week in the journal Nature, Marcia S. Ponce de León and Christoph P.E. Zollikofer at the University of Zurich describe their analysis using a computer-modeling technique to reconstruct and compare facial growth patterns in humans and Neandertals. Their study showed that members of the two groups developed in distinct ways and looked quite different from each other from a very young age.
"The developmental evidence is quite strong that we have two species," said Zollikofer.
The findings support the notion that Neandertals were a different species, and that there was little, if any, interbreeding between them and the ancestors of modern peoples.
No Generation Gap
Ponce de León and Zollikofer had assumed that infants of the two groups looked relatively similar. They expected to find that differences in the shape of the face and the head and in the growth pattern of teeth arose only as individuals grew older
"But what we found," said Zollikofer, a paleoanthropologist, "was [that children] had the same differences as adults" of their respective populations.
In juveniles, environmental factors such as physical activity by the individuals couldn't explain the occurrence of such differences. Therefore, he concluded, "the differences were deeply genetic."
The two Swiss researchers studied 16 Neandertal fossils from across the ancient group's geographical range. One specimen came from Gibraltar, off the coast of Spain, and others from as far east as Uzbekistan, in central Asia. Several more came from Israel, but political difficulties left one well-preserved specimen in Iraq off limits.
The scientists spent eight years traveling to study the fossils, which also required packing them carefully in plaster casts and shipping them back to Switzerland for additional examination.
They used a computer-modeling technique to compare these Neandertal fossils with those of modern humans. The latter group of fossils represented people of many ethnicities and included some ancient individuals who could have passed unnoticed among people today.
Eleven of the Neandertal specimens examined were "immature," meaning that not all of the individuals' adult teeth had grown in. That enabled Ponce de León and Zollikofer to reconstruct how different parts of the faces of Neandertals and modern humans changed as both groups grew older.
New Look at Juveniles
About half of the fossils of Neandertals and ancient humans that anthropologists have found are of juveniles. "It's a demographic fact that 50 percent of [those ancient] populations died before reaching maturity," said Zollikofer.
In past scientific studies, the remains of children were usually excluded from the sample because they were assumed not to reflect the developmental patterns that could reveal differences between the adults of two species. Ponce de León and Zollikofer, however, have found that even young members of a species exhibit full-blown growth patterns parallel to those of adults in the groups.
The new research contradicts the claims made by discoverers of a hotly debated fossil find in Portugal's Lapedo Valley two years ago. The so-called Lagar Velho fossil, of a young child who died 24,500 years ago, appears to be Neandertal, but has distinct characteristics of a modern human.
Its discoverers, who included João Zilhão, director-general of the Portuguese Institute of Archaeology, saw it as evidence that humans and Neandertals interbred and produced hybrid offspring. In a paper he wrote about the fossil last year, Zilhão observed: "Neandertals were just people—perhaps a little funny-looking, but people nonetheless."
But most anthropologists still disagree with that conclusion, and Zollikofer's evidence bolsters the argument that humans and Neandertals did not interbreed, and probably were not biologically capable of doing so.
Nevertheless, the Lagar Velho specimen is "amazingly interesting," said Zollikofer. He and Ponce de León have joined a large effort—led by Zilhão, another Portuguese anthropologist, and Erik Trinkhaus of Washington University—to publish a book describing the Lagar Velho find and exploring its implications for our understanding of human evolution.
Zollikofer plans to study the Lagar Velho fossil using the same computer-aided technique he applied to the Neandertal specimens. Determining whether the head and facial growth patterns of the child are more characteristic of Neandertals or of modern humans may help answer uncertainties about its alleged mixed parentage.
Labels: modern humans mated with older species
[First article: Recap of 2004 news of Hobbit discovery. Article of 5 years later follows]
Hobbit-Like Human Ancestor Found in Asia
for National Geographic News
October 27, 2004
Scientists have found skeletons of a hobbit-like species of human that grew no larger than a three-year-old modern child (See pictures). The tiny humans, who had skulls about the size of grapefruits, lived with pygmy elephants and Komodo dragons on a remote island in Indonesia 18,000 years ago.
Australian and Indonesian researchers discovered bones of the miniature humans in a cave on Flores, an island east of Bali and midway between Asia and Australia.
Scientists have determined that the first skeleton they found belongs to a species of human completely new to science. Named Homo floresiensis, after the island on which it was found, the tiny human has also been dubbed by dig workers as the "hobbit," after the tiny creatures from the Lord of the Rings books.
The original skeleton, a female, stood at just 1 meter (3.3 feet) tall, weighed about 25 kilograms (55 pounds), and was around 30 years old at the time of her death 18,000 years ago.
The skeleton was found in the same sediment deposits on Flores that have also been found to contain stone tools and the bones of dwarf elephants, giant rodents, and Komodo dragons, lizards that can grow to 10 feet (3 meters) and that still live today.
Homo floresienses has been described as one of the most spectacular discoveries in paleoanthropology in half a century—and the most extreme human ever discovered.
The species inhabited Flores as recently as 13,000 years ago, which means it would have lived at the same time as modern humans, scientists say.
"To find that as recently as perhaps 13,000 years ago, there was another upright, bipedal—although small-brained—creature walking the planet at the same time as modern humans is as exciting as it was unexpected," said Peter Brown, a paleoanthropologist at the University of New England in New South Wales, Australia.
Brown is a co-author of the study describing the findings, which appears in the October 28 issue of the science journal Nature. The National Geographic Society's Committee for Research and Exploration has sponsored research related to the discovery. The find will be covered in greater detail in a documentary airing early next year on the National Geographic Channel.
"It is totally unexpected," said Chris Stringer, director of the Human Origins program at the Natural History Museum in London. "To have early humans on the remote island of Flores is surprising enough. That some are only about a meter tall with a chimp-size brain is even more remarkable. That they were still there less than 20,000 years ago, and [that] modern humans must have met them, is astonishing."
The researchers estimate that the tiny people lived on Flores from about 95,000 years ago until at least 13,000 years ago. The scientists base their theory on charred bones and stone tools found on the island. The blades, perforators, points, and other cutting and chopping utensils were apparently used to hunt big game.
In an accompanying Nature commentary, Marta Mirazón Lahr and Robert Foley, both with the Leverhulme Centre for Human Evolutionary Studies at the University of Cambridge, England, describe Homo floresiensis as changing our understanding of late human evolutionary geography, biology, and culture.
The discovery shows that the genus Homo is more varied and more flexible in its ability to adapt than previously thought. (The genus Homo also includes modern humans, Homo erectus, Homo habilis, and Neandertals—all of which are marked by relatively large braincases, erect posture, opposable thumbs, and the ability to make tools.)
"Homo floresiensis is an addition to the short list of other human species that lived at the same time as modern humans. I think people will be surprised to learn that not so long ago, we were not alone," said Brown.
Lost World of Tiny People
Despite its smaller body size, smaller brain, and mixture of primitive and advanced anatomical features, the new species falls firmly within the genus Homo. The researchers speculate that the hobbit and her peers evolved from a normal-size, island-hopping Homo erectus population that reached Flores around 840,000 years ago.
"Physically, they were about the size of a three-year old Homo sapiens [modern human] child, but with a braincase only one-third as large," said Richard Roberts, a geochronologist at the University of Wollongong, Australia, and one on the co-authors of the research paper. "They had slightly longer arms than us. More conspicuously, they had hard, thicker eyebrow ridges than us, a sharply sloping forehead, and no chin."
"While they don't look like modern humans, some of their behaviors were surprisingly human," said Brown, the study co-author.
The Flores people used fire in hearths for cooking and hunted stegodon, a primitive dwarf elephant found on the island. Although small, the stegodon still weighed about 1,000 kilograms (2,200 pounds), and would pose a significant challenge to a hunter the size of a three-year-old modern human child. Hunting must have required joint communication and planning, the researchers say.
Almost all of the stegodon bones associated with the human artifacts are of juveniles, suggesting the tiny humans selectively hunted the smallest stegodons. The Flores humans' diets also included fish, frogs, snakes, tortoises, birds, and rodents.
"The hobbit was nobody's fool," Roberts said. "They survived alongside us [Homo sapiens] for at least 30,000 years, and we're not known for being very amiable eco-companions. And the hobbits were managing some extraordinary things—manufacturing sophisticated stone tools, hunting pygmy elephants, and crossing at least two water barriers to reach Flores from mainland Asia—with a brain only one-third the size of ours.
"Given that Homo floresiensis is the smallest human species ever discovered, they out-punch every known human intellectually, pound for pound."
Both the tiny humans and the dwarfed elephants appear to have become extinct at about the same time as the result of a major volcanic eruption.
Mingling of the Human Tribes
There is no evidence of modern humans reaching Flores before 11,000 years ago, so it is unknown whether the hobbit intermingled with modern humans. The researchers found hobbit and pygmy stegodon remains only below a 12,000-year-old volcanic ash layer. Modern human remains were found only above the layer.
Still, rumors, myths, and legends of tiny creatures have swirled around the isolated island for centuries. It's certainly possible that they interacted with modern humans, according to the researchers.
"Looked at from a regional perspective, we definitely have modern humans in Australia from at least 40,000 years ago, and in Borneo from at least 43,000 years ago," Roberts said. "So there was temporal overlap between the hobbits and ourselves from at least 40,000 years ago until at least 18,000 years ago—more than 20,000 years minimum. What was the nature of their interaction? We have absolutely no idea. We need more sites and more hard evidence, and that's the next phase of our investigation."
Researchers are also anxious to investigate how and why the hobbits came to be so small. When scientists discovered the hobbit remains, they thought it was the skeleton of a child. There was no record of human adults that were that small. Modern pygmies are considerably taller at about 1.4 to 1.5 meters (4.6 to nearly 5 feet) tall.
"H. floresiensis presents an intriguing problem in evolutionary biology," Brown said.
The most likely explanation is that, over thousands of years, the species became smaller because environmental conditions favored smaller body size. Dwarfing of mammals on islands is a well-known process and seen worldwide. Islands frequently provide a limited food supply, few predators, and few species competing for the same environmental niche. Survival would depend on minimizing daily energy requirements.
But there is no absolute proof that this is what in fact happened with this small human.
"While there are stone tools dated as far back as 840,000 years ago, no fossils of large-bodied ancestors have ever been found" on Flores, Brown said. "There is some possibility [Homo floresiensis] arrived on the island small-bodied."
"I could not have predicted such a discovery in a million years," said Stringer, of London's Natural History Museum. "This find shows us how much we still have to learn about human evolution, particularly in Southeast Asia."
The 3-D landmarks superimposed from the front of the LB1 Skull of Homo floresiensis, also known as the Hobbit, helped researchers conclude that the fossil is not human. (Credit: P. Brown)
'Hobbit' Skull Study Finds Hobbit Is Not Human
ScienceDaily (Jan. 21, 2009) — In a an analysis of the size, shape and asymmetry of the cranium of Homo floresiensis, Karen Baab, Ph.D., a researcher in the Department of Anatomical Scienes at Stony Brook University, and colleagues conclude that the fossil, found in Indonesia in 2003 and known as the “Hobbit,” is not human.
They used 3-D shape analysis to study the LB1 skull of the hobbit and found the shape of the skull to be consistent with a scaled down human ancestor but not modern humans. Their findings, reported in the current online edition of the Journal of Human Evolution, add to the evidence that the hobbit is a new species.
The question as to whether the hobbit was human or another species remains controversial. Some scientists claim the hobbit was a diminutive human that suffered from some type of disease that causes microcephaly, which results in abnormal growth of the brain and causes the cranium to be much smaller than the normal human cranium. But Dr. Baab and co-author Kieran McNulty, Professor of Anthropology at the University of Minnesota, believe their findings counter the microcephaly theory.
“A skull can provide researchers with a lot of important information about a fossil species, particularly regarding their evolutionary relationships to other fossil species,” explains Dr. Baab. “The overall shape of the LB1 skull, particularly the part that surrounds the brain (neurocranium) looks similar to fossils more than 1.5 million years older from Africa and Eurasia, rather than modern humans, even though Homo floresiensis is documented from 17,000 to 95,000 years ago.”
To carry out the study, Dr. Baab and colleagues collected 3D landmark data on the LB1 skull and a large sample of fossils representing other extinct hominin species, as well as a comparative sample of modern humans and apes. They performed several analyses of different regions of the skulls. Taken together, these analyses indicated that the LB1 skull shape is that of a scaled down Homo fossil not a scaled down modern human.
The results of the analysis of the asymmetry of the skulls, which refers to differences between the right and left sides of the skull, refutes the suggestion that the LB1 skull was that of a modern human with a diagnosis of microcephaly. In modern humans, a high degree of asymmetry may indicate that the individual was diseased. At least one scientific study on the asymmetry of LB1 supported the argument that this individual had microcephaly. Conversely, Dr. Baab and colleagues found the degree of asymmetry of the LB1 skull was not unexpectedly high and therefore not supportive of the diagnosis of microcephaly.
“The degree of asymmetry in LB1 was within the range of apes and was very similar to that seen in other fossil skulls,” says Dr. Baab. “We suggest that the degree of asymmetry is within expectations for this population of hominins, particular given that the conditions of the cave in Indonesia in which the skull was preserved may have contributed to asymmetry.”
Dr. Baab recognizes that the controversy as to the evolutionary origins of Homo floresiensis will continue, perhaps without an answer. However, all the evidence that she and colleagues illustrate in their article “Size, shape, and asymmetry in fossil hominins: The status of the LB1cranium based on 3D morphometric analyses,” suggest that Homo floresiensis was most likely the diminutive descendant of a species of archaic Homo.
The results of this study are also in line with what other researchers in the Department of Anatomical Sciences at Stony Brook University have found regarding the rest of the hobbit skeleton. Drs. William Jungers and Susan Larson have documented a range of primitive features in both the upper and lower limbs of Homo floresiensis, highlighting the many ways that these hominins were unlike modern humans.