The Great Dying 250 million years ago happened slowly, say USC geologists
The greatest mass extinction in Earth’s history also may have been one of the slowest, according to a study that casts further doubt on the extinction-by-meteor theory.
Creeping environmental stress fueled by volcanic eruptions and global warming was the likely cause of the Great Dying 250 million years ago, said USC doctoral student Catherine Powers.
Writing in the November issue of the journal Geology, Powers and her adviser David Bottjer, professor of earth sciences at USC, describe a slow decline in the diversity of some common marine organisms.
The decline began millions of years before the disappearance of 90 percent of Earth’s species at the end of the Permian era, Powers shows in her study.
More damaging to the meteor theory, the study finds that organisms in the deep ocean started dying first, followed by those on ocean shelves and reefs, and finally those living near shore.
“Something has to be coming from the deep ocean,” Powers said. “Something has to be coming up the water column and killing these organisms.”
That something probably was hydrogen sulfide, according to Powers, who cited studies from the University of Washington, Pennsylvania State University, the University of Arizona and the Bottjer laboratory at USC.
Those studies, combined with the new data from Powers and Bottjer, support a model that attributes the extinction to enormous volcanic eruptions that released carbon dioxide and methane, triggering rapid global warming.
The warmer ocean water would have lost some of its ability to retain oxygen, allowing water rich in hydrogen sulfide to well up from the deep (the gas comes from anaerobic bacteria at the bottom of the ocean).
If large amounts of hydrogen sulfide escaped into the atmosphere, the gas would have killed most forms of life and also damaged the ozone shield, increasing the level of harmful ultraviolet radiation reaching the planet’s surface.
Powers and others believe that the same deadly sequence repeated itself for another major extinction 200 million years ago, at the end of the Triassic era.
“There are very few people that hang on to the idea that it was a meteorite impact,” she said. Even if an impact did occur, she added, it could not have been the primary cause of an extinction already in progress.
In her study, Powers analyzed the distribution and diversity of bryozoans, a family of marine invertebrates.
Based on the types of rocks in which the fossils were found, Powers was able to classify the organisms according to age and approximate depth of their habitat.
She found that bryozoan diversity in the deep ocean started to decrease about 270 million years ago and fell sharply in the 10 million years before the mass extinction that marked the end of the Permian era.
But diversity at middle depths and near shore fell off later and gradually, with shoreline bryozoans being affected last, Powers said.
She observed the same pattern before the end-Triassic extinction, 50 million years after the end-Permian.
Thursday, October 25, 2007
Some Neanderthals were redheads
Ancient DNA reveals that some Neanderthals were redheads
Neanderthals' pigmentation possibly as varied as humans', scientists say
Ancient DNA retrieved from the bones of two Neanderthals suggests that at least some of them had red hair and pale skin, scientists report this week in the journal Science. The international team says that Neanderthals' pigmentation may even have been as varied as that of modern humans, and that at least 1 percent of Neanderthals were likely redheads.
The scientists -- led by Holger Römpler of Harvard University and the University of Leipzig, Carles Lalueza-Fox of the University of Barcelona, and Michael Hofreiter of the Max Planck Institute for Evolutionary Anthropology in Leipzig -- extracted, amplified, and sequenced a pigmentation gene called MC1R from the bones of a 43,000-year-old Neanderthal from El Sidrón, Spain, and a 50,000-year-old individual from Monti Lessini, Italy.
"Together with other genes, this MC1R gene dictates hair and skin color in humans and other mammals," says Römpler, a postdoctoral researcher working with Hopi E. Hoekstra in Harvard's Department of Organismic and Evolutionary Biology. "The two Neanderthal individuals we studied showed a point mutation not seen in modern humans. When we induced such a mutation in human cells, we found that it impaired MC1R activity, a condition that leads to red hair and pale skin in modern humans."
To ensure that the MC1R point mutation was not due to contamination from modern humans, the scientists checked some 3,700 people, including those previously sequenced for the gene as well as everyone involved in the excavation and genetic analysis of the two Neanderthals. None showed the mutation, suggesting that Neanderthals and Homo sapiens followed different evolutionary paths to the same redheaded appearance.
With Neanderthals' surviving bones providing few clues, scientists have long sought to flesh out the appearance of this hominid species found across Eurasia some 28,000 to 400,000 years ago. While anthropologists had predicted that Neanderthals might have had pale skin or red hair, the new work by Römpler and colleagues offers the first strong evidence to support this hunch.
Found in cell membranes, MC1R is a receptor that acts as a switch between production of the red-and-yellow pigment pheomelanin and the black-and-brown pigment eumelanin. Modern humans with mutations that cause complete or partial loss of MC1R function tend to be pale and red-haired, although many other pigmentation genes can also result in this phenotype.
In 2006, a team led by Römpler found a mutation in woolly mammoths that may lead to some blond mammoths; together with her colleagues, Hoekstra, the John L. Loeb Associate Professor of the Natural Sciences at Harvard and curator in mammalogy in Harvard's Museum of Comparative Zoology, has shown that this same mutation causes light coloration in mice. Römpler and Hoekstra are now collaborating to identify genetic changes responsible for pigment variation in other extant and extinct species.
"It has only recently become possible to decipher the genomes of species which became extinct thousands of years ago," Römpler says. "The methods used in these Neanderthal and mammoth studies could provide new insights into the coloration of other extinct hominids, animals, and plants."
Neanderthals' pigmentation possibly as varied as humans', scientists say
Ancient DNA retrieved from the bones of two Neanderthals suggests that at least some of them had red hair and pale skin, scientists report this week in the journal Science. The international team says that Neanderthals' pigmentation may even have been as varied as that of modern humans, and that at least 1 percent of Neanderthals were likely redheads.
The scientists -- led by Holger Römpler of Harvard University and the University of Leipzig, Carles Lalueza-Fox of the University of Barcelona, and Michael Hofreiter of the Max Planck Institute for Evolutionary Anthropology in Leipzig -- extracted, amplified, and sequenced a pigmentation gene called MC1R from the bones of a 43,000-year-old Neanderthal from El Sidrón, Spain, and a 50,000-year-old individual from Monti Lessini, Italy.
"Together with other genes, this MC1R gene dictates hair and skin color in humans and other mammals," says Römpler, a postdoctoral researcher working with Hopi E. Hoekstra in Harvard's Department of Organismic and Evolutionary Biology. "The two Neanderthal individuals we studied showed a point mutation not seen in modern humans. When we induced such a mutation in human cells, we found that it impaired MC1R activity, a condition that leads to red hair and pale skin in modern humans."
To ensure that the MC1R point mutation was not due to contamination from modern humans, the scientists checked some 3,700 people, including those previously sequenced for the gene as well as everyone involved in the excavation and genetic analysis of the two Neanderthals. None showed the mutation, suggesting that Neanderthals and Homo sapiens followed different evolutionary paths to the same redheaded appearance.
With Neanderthals' surviving bones providing few clues, scientists have long sought to flesh out the appearance of this hominid species found across Eurasia some 28,000 to 400,000 years ago. While anthropologists had predicted that Neanderthals might have had pale skin or red hair, the new work by Römpler and colleagues offers the first strong evidence to support this hunch.
Found in cell membranes, MC1R is a receptor that acts as a switch between production of the red-and-yellow pigment pheomelanin and the black-and-brown pigment eumelanin. Modern humans with mutations that cause complete or partial loss of MC1R function tend to be pale and red-haired, although many other pigmentation genes can also result in this phenotype.
In 2006, a team led by Römpler found a mutation in woolly mammoths that may lead to some blond mammoths; together with her colleagues, Hoekstra, the John L. Loeb Associate Professor of the Natural Sciences at Harvard and curator in mammalogy in Harvard's Museum of Comparative Zoology, has shown that this same mutation causes light coloration in mice. Römpler and Hoekstra are now collaborating to identify genetic changes responsible for pigment variation in other extant and extinct species.
"It has only recently become possible to decipher the genomes of species which became extinct thousands of years ago," Römpler says. "The methods used in these Neanderthal and mammoth studies could provide new insights into the coloration of other extinct hominids, animals, and plants."
New ideas re human migration from Asia to Americas
Questions about human migration from Asia to the Americas have perplexed anthropologists for decades, but as scenarios about the peopling of the New World come and go, the big questions have remained. Do the ancestors of Native Americans derive from only a small number of “founders” who trekked to the Americas via the Bering land bridge? How did their migration to the New World proceed? What, if anything, did the climate have to do with their migration? And what took them so long?
A team of 21 researchers, led by Ripan Malhi, a geneticist in the department of anthropology at the University of Illinois, has a new set of ideas. One is a striking hypothesis that seems to map the peopling process during the pioneering phase and well beyond, and at the same time show that there was much more genetic diversity in the founder population than was previously thought.
The team’s findings appear in a recent issue of the Public Library of Science in an article titled, “Beringian Standstill and Spread of Native American Founders.”
“Our phylogeographic analysis of a new mitochondrial genome dataset allows us to draw several conclusions,” the authors wrote.
“First, before spreading across the Americas, the ancestral population paused in Beringia long enough for specific mutations to accumulate that separate the New World founder lineages from their Asian sister-clades.” (A clade is a group of mitochondrial DNAs (mtDNAs ) that share a recent common ancestor, Malhi said. Sister-clades would include two groups of mtDNAs that each share a recent common ancestor and the common ancestor for each clade is closely related.)
Or, to express this first conclusion another way, the ancestors of Native Americans who first left Siberia for greener pastures perhaps as much as 30,000 years ago, came to a standstill on Beringia – a landmass that existed during the last glacial maximum that extended from Northeastern Siberia to Western Alaska, including the Bering land bridge – and they were isolated there long enough – as much as 15,000 years – to maturate and differentiate themselves genetically from their Asian sisters.
“Second, founding haplotypes or lineages are uniformly distributed across North and South America instead of exhibiting a nested structure from north to south. Thus, after the Beringian standstill, the initial North to South migration was likely a swift pioneering process, not a gradual diffusion.”
The DNA data also suggest a lot more to-ing and fro-ing than has been suspected of populations during the past 30,000 years in Northeast Asia and North America. The analysis of the dataset shows that after the initial peopling of Beringia, there were a series of back migrations to Northeast Asia as well as forward migrations to the Americas from Beringia, thus “more recent bi-directional gene flow between Siberia and the North American Arctic.”
To investigate the pioneering phase in the Americas, Malhi and his team, a group of geneticists from around the world, pooled their genomic datasets and then analyzed 623 complete mitochondrial DNAs (mtDNAs) from the Americas and Asia, including 20 new complete mtDNAs from the Americas and seven from Asia. The sequence data was used to direct high-resolution genotyping from 20 American and 26 Asian populations. Mitochondrial DNA, that is, DNA found in organelles, rather than in the cell nucleus, is considered to be of separate evolutionary origin, and is inherited from only one parent – the female.
The team identified three new sub-clades that incorporate nearly all of Native American haplogroup C mtDNAs – all of them widely distributed in the New World, but absent in Asia; and they defined two additional founder groups, “which differ by several mutations from the Asian-derived ancestral clades.”
What puzzled them originally was the disconnect between recent archaeological datings. New evidence places Homo sapiens at the Yana Rhinoceros Horn Site in Siberia – as likely a departure point for the migrants as any in the region – as early as 30,000 years before the present, but the earliest archaeological site at the southern end of South America is dated to only 15,000 years ago.
“These archaeological dates suggested two likely scenarios,” the authors wrote: Either the ancestors of Native Americans peopled Beringia before the Last Glacial Maximum, but remained locally isolated – likely because of ecological barriers – until entering the Americas 15,000 years before the present (the Beringian incubation model, BIM); or the ancestors of Native Americans did not reach Beringia until just before 15,000 years before the present, and then moved continuously on into the Americas, being recently derived from a larger parent Asian population (direct colonization model, DCM).
Thus, for this study the team set out to test the two hypotheses: one, that Native Americans’ ancestors moved directly from Northeast Asia to the Americas; the other, that Native American ancestors were isolated from other Northeast Asian populations for a significant period of time before moving rapidly into the Americas all the way down to Tierra del Fuego.
“Our data supports the second hypothesis: The ancestors of Native Americans peopled Beringia before the Last Glacial Maximum, but remained locally isolated until entering the Americas at 15,000 years before the present.”
A team of 21 researchers, led by Ripan Malhi, a geneticist in the department of anthropology at the University of Illinois, has a new set of ideas. One is a striking hypothesis that seems to map the peopling process during the pioneering phase and well beyond, and at the same time show that there was much more genetic diversity in the founder population than was previously thought.
The team’s findings appear in a recent issue of the Public Library of Science in an article titled, “Beringian Standstill and Spread of Native American Founders.”
“Our phylogeographic analysis of a new mitochondrial genome dataset allows us to draw several conclusions,” the authors wrote.
“First, before spreading across the Americas, the ancestral population paused in Beringia long enough for specific mutations to accumulate that separate the New World founder lineages from their Asian sister-clades.” (A clade is a group of mitochondrial DNAs (mtDNAs ) that share a recent common ancestor, Malhi said. Sister-clades would include two groups of mtDNAs that each share a recent common ancestor and the common ancestor for each clade is closely related.)
Or, to express this first conclusion another way, the ancestors of Native Americans who first left Siberia for greener pastures perhaps as much as 30,000 years ago, came to a standstill on Beringia – a landmass that existed during the last glacial maximum that extended from Northeastern Siberia to Western Alaska, including the Bering land bridge – and they were isolated there long enough – as much as 15,000 years – to maturate and differentiate themselves genetically from their Asian sisters.
“Second, founding haplotypes or lineages are uniformly distributed across North and South America instead of exhibiting a nested structure from north to south. Thus, after the Beringian standstill, the initial North to South migration was likely a swift pioneering process, not a gradual diffusion.”
The DNA data also suggest a lot more to-ing and fro-ing than has been suspected of populations during the past 30,000 years in Northeast Asia and North America. The analysis of the dataset shows that after the initial peopling of Beringia, there were a series of back migrations to Northeast Asia as well as forward migrations to the Americas from Beringia, thus “more recent bi-directional gene flow between Siberia and the North American Arctic.”
To investigate the pioneering phase in the Americas, Malhi and his team, a group of geneticists from around the world, pooled their genomic datasets and then analyzed 623 complete mitochondrial DNAs (mtDNAs) from the Americas and Asia, including 20 new complete mtDNAs from the Americas and seven from Asia. The sequence data was used to direct high-resolution genotyping from 20 American and 26 Asian populations. Mitochondrial DNA, that is, DNA found in organelles, rather than in the cell nucleus, is considered to be of separate evolutionary origin, and is inherited from only one parent – the female.
The team identified three new sub-clades that incorporate nearly all of Native American haplogroup C mtDNAs – all of them widely distributed in the New World, but absent in Asia; and they defined two additional founder groups, “which differ by several mutations from the Asian-derived ancestral clades.”
What puzzled them originally was the disconnect between recent archaeological datings. New evidence places Homo sapiens at the Yana Rhinoceros Horn Site in Siberia – as likely a departure point for the migrants as any in the region – as early as 30,000 years before the present, but the earliest archaeological site at the southern end of South America is dated to only 15,000 years ago.
“These archaeological dates suggested two likely scenarios,” the authors wrote: Either the ancestors of Native Americans peopled Beringia before the Last Glacial Maximum, but remained locally isolated – likely because of ecological barriers – until entering the Americas 15,000 years before the present (the Beringian incubation model, BIM); or the ancestors of Native Americans did not reach Beringia until just before 15,000 years before the present, and then moved continuously on into the Americas, being recently derived from a larger parent Asian population (direct colonization model, DCM).
Thus, for this study the team set out to test the two hypotheses: one, that Native Americans’ ancestors moved directly from Northeast Asia to the Americas; the other, that Native American ancestors were isolated from other Northeast Asian populations for a significant period of time before moving rapidly into the Americas all the way down to Tierra del Fuego.
“Our data supports the second hypothesis: The ancestors of Native Americans peopled Beringia before the Last Glacial Maximum, but remained locally isolated until entering the Americas at 15,000 years before the present.”
Wednesday, October 17, 2007
Earliest modern human behavior in South Africa
Evidence of early humans living on the coast in South Africa, harvesting food from the sea, employing complex bladelet tools and using red pigments in symbolic behavior 164,000 years ago, far earlier than previously documented, is being reported in the Oct. 18 issue of the journal Nature. The international team of researchers reporting the findings include Curtis Marean, a paleoanthropologist with the Institute of Human Origins at Arizona State University and three graduate students in the School of Human Evolution and Social Change.
“Our findings show that at 164,000 years ago in coastal South Africa humans expanded their diet to include shellfish and other marine resources, perhaps as a response to harsh environmental conditions,” notes Marean, a professor in ASU’s School of Human Evolution and Social Change. “This is the earliest dated observation of this behavior.”
Further, the researchers report that co-occurring with this diet expansion is a very early use of pigment, likely for symbolic behavior, as well as the use of bladelet stone tool technology, previously dating to 70,000 years ago.
These new findings not only move back the timeline for the evolution of modern humans, they show that lifestyles focused on coastal habitats and resources may have been crucial to the evolution and survival of these early humans.
Searching for beginnings
After decades of debate, paleoanthropologists now agree the genetic and fossil evidence suggests that the modern human species – Homo sapiens – evolved in Africa between 100,000 and 200,000 years ago.
Yet, archaeological sites during that time period are rare in Africa. And, given the enormous expanse of the continent, where in Africa did this crucial step to modern humans occur.
“Archaeologists have had a hard time finding material residues of these earliest modern humans,” Marean says. “The world was in a glacial stage 125,000 to 195,000 years ago, and much of Africa was dry to mostly desert; in many areas food would have been difficult to acquire. The paleoenvironmental data indicate there are only five or six places in all of Africa where humans could have survived these harsh conditions.”
In seeking the “perfect site” to explore, Marean analyzed ocean currents, climate data, geological formations and other data to pin down a location where he felt sure to find one of these progenitor populations: the Cape of South Africa at Pinnacle Point.
“It was important that we knew exactly where to look and what we were looking for,” says Marean. This type of research is expensive and funding is competitive. Marean and the team of scientists who set out to Pinnacle Point to search for this elusive population, did so with the help of a $2.5 million grant from the National Science Foundation’s Human Origins: Moving in New Directions (HOMINID) program.
Their findings are reported in the Nature paper “Early human use of marine resources and pigment in South Africa during the Middle Pleistocene.” In addition to Marean, authors on the paper include three graduate students in ASU’s School of Human Evolution and Social Change: Erin Thompson, Hope Williams and Jocelyn Bernatchez. Other authors are Miryam Bar-Matthews of the Geological Survey of Israel, Erich Fisher of the University of Florida, Paul Goldberg of Boston University, Andy I.R. Herries of the University of New South Wales (Australia), Zenobia Jacobs of the University of Wollongong (Australia), Antonieta Jerardino of the University of Cape Town (South Africa), Panagiotis Karkanas of Greece’s Ministry of Culture, Tom Minichillo of the University of Washington, Ian Watts from London and excavation co-director Peter J. Nilssen of the Iziko South African Museum.
The Middle Stone Age, dated between 35,000 and 300,000 years ago, is the technological stage when anatomically modern humans emerged in Africa, along with modern cognitive behavior, says Marean. When, however, within that stage modern human behavior arose is currently debated, he adds.
“This time is beyond the range of radiocarbon dating, yet the dates on the finds published here are more secure than is typical due to the use of two advanced and independent techniques,” Marean says.
Uranium series dates were attained by Bar-Matthews on speleothem (the material of stalagmites), and optically stimulated luminescence dates were developed by Jacobs. According to Marean, the latter technique dates the last time that individual grains of sand were exposed to light, and thousands of grains were measured.
Migrating along the coast
“Generally speaking, coastal areas were of no use to early humans – unless they knew how to use the sea as a food source” says Marean. “For millions of years, our earliest hunter-gatherer relatives only ate terrestrial plants and animals. Shellfish was one of the last additions to the human diet before domesticated plants and animals were introduced.”
Before, the earliest evidence for human use of marine resources and coastal habitats was dated about 125,000 years ago. “Our research shows that humans started doing this at least 40,000 years earlier. This could have very well been a response to the extreme environmental conditions they were experiencing,” he says.
“We also found what archaeologists call bladelets – little blades less than 10 millimeters in width, about the size of your little finger,” Marean says. “These could be attached to the end of a stick to form a point for a spear, or lined up like barbs on a dart – which shows they were already using complex compound tools. And, we found evidence that they were using pigments, especially red ochre, in ways that we believe were symbolic,” he describes.
Archaeologists view symbolic behavior as one of the clues that modern language may have been present. The earliest bladelet technology was previously dated to 70,000 years ago, near the end of the Middle Stone Age, and the modified pigments are the earliest securely dated and published evidence for pigment use.
“Coastlines generally make great migration routes,” Marean says. “Knowing how to exploit the sea for food meant these early humans could now use coastlines as productive home ranges and move long distances.”
Results reporting early use of coastlines are especially significant to scientists interested in the migration of humans out of Africa. Physical evidence that this coastal population was practicing modern human behavior is particularly important to geneticists and physical anthropologists seeking to identify the progenitor population for modern humans.
“This evidence shows that Africa, and particularly southern Africa, was precocious in the development of modern human biology and behavior. We believe that on the far southern shore of Africa there was a small population of modern humans who struggled through this glacial period using shellfish and advanced technologies, and symbolism was important to their social relations. It is possible that this population could be the progenitor population for all modern humans,” Marean says."
“Our findings show that at 164,000 years ago in coastal South Africa humans expanded their diet to include shellfish and other marine resources, perhaps as a response to harsh environmental conditions,” notes Marean, a professor in ASU’s School of Human Evolution and Social Change. “This is the earliest dated observation of this behavior.”
Further, the researchers report that co-occurring with this diet expansion is a very early use of pigment, likely for symbolic behavior, as well as the use of bladelet stone tool technology, previously dating to 70,000 years ago.
These new findings not only move back the timeline for the evolution of modern humans, they show that lifestyles focused on coastal habitats and resources may have been crucial to the evolution and survival of these early humans.
Searching for beginnings
After decades of debate, paleoanthropologists now agree the genetic and fossil evidence suggests that the modern human species – Homo sapiens – evolved in Africa between 100,000 and 200,000 years ago.
Yet, archaeological sites during that time period are rare in Africa. And, given the enormous expanse of the continent, where in Africa did this crucial step to modern humans occur.
“Archaeologists have had a hard time finding material residues of these earliest modern humans,” Marean says. “The world was in a glacial stage 125,000 to 195,000 years ago, and much of Africa was dry to mostly desert; in many areas food would have been difficult to acquire. The paleoenvironmental data indicate there are only five or six places in all of Africa where humans could have survived these harsh conditions.”
In seeking the “perfect site” to explore, Marean analyzed ocean currents, climate data, geological formations and other data to pin down a location where he felt sure to find one of these progenitor populations: the Cape of South Africa at Pinnacle Point.
“It was important that we knew exactly where to look and what we were looking for,” says Marean. This type of research is expensive and funding is competitive. Marean and the team of scientists who set out to Pinnacle Point to search for this elusive population, did so with the help of a $2.5 million grant from the National Science Foundation’s Human Origins: Moving in New Directions (HOMINID) program.
Their findings are reported in the Nature paper “Early human use of marine resources and pigment in South Africa during the Middle Pleistocene.” In addition to Marean, authors on the paper include three graduate students in ASU’s School of Human Evolution and Social Change: Erin Thompson, Hope Williams and Jocelyn Bernatchez. Other authors are Miryam Bar-Matthews of the Geological Survey of Israel, Erich Fisher of the University of Florida, Paul Goldberg of Boston University, Andy I.R. Herries of the University of New South Wales (Australia), Zenobia Jacobs of the University of Wollongong (Australia), Antonieta Jerardino of the University of Cape Town (South Africa), Panagiotis Karkanas of Greece’s Ministry of Culture, Tom Minichillo of the University of Washington, Ian Watts from London and excavation co-director Peter J. Nilssen of the Iziko South African Museum.
The Middle Stone Age, dated between 35,000 and 300,000 years ago, is the technological stage when anatomically modern humans emerged in Africa, along with modern cognitive behavior, says Marean. When, however, within that stage modern human behavior arose is currently debated, he adds.
“This time is beyond the range of radiocarbon dating, yet the dates on the finds published here are more secure than is typical due to the use of two advanced and independent techniques,” Marean says.
Uranium series dates were attained by Bar-Matthews on speleothem (the material of stalagmites), and optically stimulated luminescence dates were developed by Jacobs. According to Marean, the latter technique dates the last time that individual grains of sand were exposed to light, and thousands of grains were measured.
Migrating along the coast
“Generally speaking, coastal areas were of no use to early humans – unless they knew how to use the sea as a food source” says Marean. “For millions of years, our earliest hunter-gatherer relatives only ate terrestrial plants and animals. Shellfish was one of the last additions to the human diet before domesticated plants and animals were introduced.”
Before, the earliest evidence for human use of marine resources and coastal habitats was dated about 125,000 years ago. “Our research shows that humans started doing this at least 40,000 years earlier. This could have very well been a response to the extreme environmental conditions they were experiencing,” he says.
“We also found what archaeologists call bladelets – little blades less than 10 millimeters in width, about the size of your little finger,” Marean says. “These could be attached to the end of a stick to form a point for a spear, or lined up like barbs on a dart – which shows they were already using complex compound tools. And, we found evidence that they were using pigments, especially red ochre, in ways that we believe were symbolic,” he describes.
Archaeologists view symbolic behavior as one of the clues that modern language may have been present. The earliest bladelet technology was previously dated to 70,000 years ago, near the end of the Middle Stone Age, and the modified pigments are the earliest securely dated and published evidence for pigment use.
“Coastlines generally make great migration routes,” Marean says. “Knowing how to exploit the sea for food meant these early humans could now use coastlines as productive home ranges and move long distances.”
Results reporting early use of coastlines are especially significant to scientists interested in the migration of humans out of Africa. Physical evidence that this coastal population was practicing modern human behavior is particularly important to geneticists and physical anthropologists seeking to identify the progenitor population for modern humans.
“This evidence shows that Africa, and particularly southern Africa, was precocious in the development of modern human biology and behavior. We believe that on the far southern shore of Africa there was a small population of modern humans who struggled through this glacial period using shellfish and advanced technologies, and symbolism was important to their social relations. It is possible that this population could be the progenitor population for all modern humans,” Marean says."
Thursday, October 11, 2007
New findings solve human origins mystery
An extraordinary advance in human origins research reveals evidence of the emergence of the upright human body plan over 15 million years earlier than most experts have believed. More dramatically, the study confirms preliminary evidence that many early hominoid apes were most likely upright bipedal walkers sharing the basic body form of modern humans. On October 10th, online, open-access journal PLoS ONE will publish the report based on research from Harvard University’s Museum of Comparative Zoology and from the Cedars Sinai Institute for Spinal Disorders that connects several recent fossil discoveries to older fossils finds that have eluded adequate explanation in the past.
Recent advances in the field of homeotic genetics together with a series of discoveries of hominoid fossils vertebrae now strongly suggest that a specific genetic change that generated the upright bipedal human body form may soon be identified. The various upright “hominiform” hominoids appear to share this morphogenetic innovation with modern humans. Homeotics concerns the embryological assembly program for midline repeating structures such as the human vertebral column and the insect body segments.
The report analyses changes in homeotic embryological assembly of the spine in more than 200 mammalian species across a 250 million year time scale. It identifies a series of modular changes in genetic assembly program that have taken place at the origin point of several major groups of mammals including the newly designated ‘hominiform’ hominoids that share the modern human body plan.
The critical event involves a dramatic embryological change unique to the human lineage that was not previously understood because the unusual human condition was viewed as “normal.”
“From an embryological point of view, what took place is literally breathtaking,” says Dr. Aaron Filler, a Harvard trained evolutionary biologist and a medical director at Cedars Sinai Medical Center’s Institute for Spinal Disorders. Dr. Filler is an expert in spinal biology and the author of three books about the spine – “Axial Character Seriation in Mammals” (BrownWalker 2007), “The Upright Ape” (New Page Books 2007), and “Do You Really Need Back Surgery” (Oxford University Press 2007).
In most vertebrates (including most mammals), he explains, the dividing plane between the front (ventral) part of the body and the back (dorsal) part is a “horizontal septum” that runs in front of the spinal canal. This is a fundamental aspect of animal architecture. A bizarre birth defect in what may have been the first direct human ancestor led to the “transposition” of the septum to a position behind the spinal cord in the lumbar region. Oddly enough, this configuration is more typical of invertebrates.
The mechanical effect of the transposition was to make horizontal or quadrupedal stance inefficient. “Any mammal with this set of changes would only be comfortable standing upright. I would envision this malformed young hominiform – the first true ancestral human – as standing upright from a young age while its siblings walked around on all fours.”
The earliest example of the transformed hominiform type of lumbar spine is found in Morotopithecus bishopi an extinct hominoid species that lived in Uganda more than 21 million years ago. “From a number of points of view,” Filler says, “humanity can be redefined as having its origin with Morotopithecus. This greatly demotes the importance of the bipedalism of Australopithecus species such as Lucy (Australopithecus afarensis) since we now know of four upright bipedal species that precede her, found from various time periods on out to Morotopithecus in the Early Miocene.”
Recent advances in the field of homeotic genetics together with a series of discoveries of hominoid fossils vertebrae now strongly suggest that a specific genetic change that generated the upright bipedal human body form may soon be identified. The various upright “hominiform” hominoids appear to share this morphogenetic innovation with modern humans. Homeotics concerns the embryological assembly program for midline repeating structures such as the human vertebral column and the insect body segments.
The report analyses changes in homeotic embryological assembly of the spine in more than 200 mammalian species across a 250 million year time scale. It identifies a series of modular changes in genetic assembly program that have taken place at the origin point of several major groups of mammals including the newly designated ‘hominiform’ hominoids that share the modern human body plan.
The critical event involves a dramatic embryological change unique to the human lineage that was not previously understood because the unusual human condition was viewed as “normal.”
“From an embryological point of view, what took place is literally breathtaking,” says Dr. Aaron Filler, a Harvard trained evolutionary biologist and a medical director at Cedars Sinai Medical Center’s Institute for Spinal Disorders. Dr. Filler is an expert in spinal biology and the author of three books about the spine – “Axial Character Seriation in Mammals” (BrownWalker 2007), “The Upright Ape” (New Page Books 2007), and “Do You Really Need Back Surgery” (Oxford University Press 2007).
In most vertebrates (including most mammals), he explains, the dividing plane between the front (ventral) part of the body and the back (dorsal) part is a “horizontal septum” that runs in front of the spinal canal. This is a fundamental aspect of animal architecture. A bizarre birth defect in what may have been the first direct human ancestor led to the “transposition” of the septum to a position behind the spinal cord in the lumbar region. Oddly enough, this configuration is more typical of invertebrates.
The mechanical effect of the transposition was to make horizontal or quadrupedal stance inefficient. “Any mammal with this set of changes would only be comfortable standing upright. I would envision this malformed young hominiform – the first true ancestral human – as standing upright from a young age while its siblings walked around on all fours.”
The earliest example of the transformed hominiform type of lumbar spine is found in Morotopithecus bishopi an extinct hominoid species that lived in Uganda more than 21 million years ago. “From a number of points of view,” Filler says, “humanity can be redefined as having its origin with Morotopithecus. This greatly demotes the importance of the bipedalism of Australopithecus species such as Lucy (Australopithecus afarensis) since we now know of four upright bipedal species that precede her, found from various time periods on out to Morotopithecus in the Early Miocene.”
Human migrations in the circum-Pacific Region
A new study by Kevin Pope of Geo Eco Arc Research and John Terrell of The Field Museum adds insight into the migration of anatomically modern humans out of Africa and into Asia less than 100,000 years before present (BP). The comprehensive review of human genetic, environmental, and archaeological data from the circum-Pacific region supports the hypothesis, originally based largely on genetic evidence, that modern humans migrated into eastern Asia via a southern coastal route. The expansion of modern human populations into the circum-Pacific region occurred in at least four pulses, in part controlled by climate and sea level changes in the Late Pleistocene and Holocene epochs. The initial “out of Africa” migration was thwarted by dramatic changes in both sea level and climate and extreme drought in the coastal zone. A period of stable climate and sea level 45,000-40,000 years BP gave rise to the first major pulse of migration, when modern humans spread from India, throughout much of coastal southeast Asia, Australia, and Melanesia, extending northward to eastern Russia and Japan by 37,000 years BP.
The northward push of modern humans along the eastern coast of Asia stalled north of 43° N latitude, probably due to the inability of the populations to adjust to cold waters and tundra/steppe vegetation. The ensuing cold and dry Last Glacial period, ~33,000-16,000 year BP, once again brought dramatic changes in sea level and climate, which caused abandonment of many coastal sites. After 16,000 years BP, climates began to warm, but sea level was still 100 m below modern levels, creating conditions amenable for a second pulse of human migration into North America across an ice-free coastal plain now covered by the Bering Sea.
The stabilization of climate and sea level in the early Holocene (8,000-6,000 years BP) supported the expansion of coastal wetlands, lagoons, and coral reefs, which in turn gave rise to a third pulse of coastal settlement, filling in most of the circum-Pacific region. A slight drop in sea level in the western Pacific in the mid-Holocene (~6,000-4,000 year BP), caused a reduction in productive coastal habitats, leading to a brief disruption in human subsistence along the then densely settled coast. This disruption may have helped initiate the last major pulse of human migration in the circum-Pacific region, that of the migration to Oceania, which began about 3,500 years BP and culminated in the settlement of Hawaii and Easter Island by 2000-1000 years BP.
The northward push of modern humans along the eastern coast of Asia stalled north of 43° N latitude, probably due to the inability of the populations to adjust to cold waters and tundra/steppe vegetation. The ensuing cold and dry Last Glacial period, ~33,000-16,000 year BP, once again brought dramatic changes in sea level and climate, which caused abandonment of many coastal sites. After 16,000 years BP, climates began to warm, but sea level was still 100 m below modern levels, creating conditions amenable for a second pulse of human migration into North America across an ice-free coastal plain now covered by the Bering Sea.
The stabilization of climate and sea level in the early Holocene (8,000-6,000 years BP) supported the expansion of coastal wetlands, lagoons, and coral reefs, which in turn gave rise to a third pulse of coastal settlement, filling in most of the circum-Pacific region. A slight drop in sea level in the western Pacific in the mid-Holocene (~6,000-4,000 year BP), caused a reduction in productive coastal habitats, leading to a brief disruption in human subsistence along the then densely settled coast. This disruption may have helped initiate the last major pulse of human migration in the circum-Pacific region, that of the migration to Oceania, which began about 3,500 years BP and culminated in the settlement of Hawaii and Easter Island by 2000-1000 years BP.
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