Was Israel the Birthplace of Modern Humans?

ScienceDaily (Dec. 31, 2010) — It has long been believed that modern humans emerged from the continent of Africa 200,000 years ago. Now Tel Aviv University archaeologists have uncovered evidence that Homo sapiens roamed the land now called Israel as early as 400,000 years ago -- the earliest evidence for the existence of modern humans anywhere in the world.



It has long been believed that modern humans emerged from the continent of Africa 200,000 years ago.

The findings were discovered in the Qesem Cave, a pre-historic site located near Rosh Ha'ayin that was first excavated in 2000. Prof. Avi Gopher and Dr. Ran Barkai of Tel Aviv University's Department of Archaeology, who run the excavations, and Prof. Israel Hershkowitz of the university's Department of Anatomy and Anthropology and Sackler School of Medicine, together with an international team of scientists, performed a morphological analysis on eight human teeth found in the Qesem Cave.

This analysis, which included CT scans and X-rays, indicates that the size and shape of the teeth are very similar to those of modern humans. The teeth found in the Qesem Cave are very similar to other evidence of modern humans from Israel, dated to around 100,000 years ago, discovered in the Skhul Cave in the Carmel and Qafzeh Cave in the Lower Galilee near Nazareth. The results of the researchers' findings are being published in the American Journal of Physical Anthropology.

Reading the past

Qesem Cave is dated to a period between 400,000 and 200,000 years ago, and archaeologists working there believe that the findings indicate significant evolution in the behavior of ancient humans. This period of time was crucial in the history of humankind from cultural and biological perspectives. The teeth that are being studied indicate that these changes are apparently related to evolutionary changes taking place at that time.

Prof. Gopher and Dr. Barkai noted that the findings related to the culture of those who dwelled in the Qesem Cave -- including the systematic production of flint blades; the regular use of fire; evidence of hunting, cutting and sharing of animal meat; mining raw materials to produce flint tools from subsurface sources -- reinforce the hypothesis that this was, in fact, innovative and pioneering behavior that may correspond with the appearance of modern humans.

An unprecedented discovery

According to researchers, the discoveries made in the Qesem Cave may overturn the theory that modern humans originated on the continent of Africa. In recent years, archaeological evidence and human skeletons found in Spain and China also undermined this proposition, but the Qesem Cave findings because of their early age is an unprecedented discovery.

Excavations at Qesem Cave continue and the researchers hope to uncover additional finds that will enable them to confirm the findings published up to now and to enhance our understanding of the evolution of humankind -- especially the emergence of modern man.

http://www.sciencedaily.com/releases/2010/12/101230123554.htm

Oxygen-Free Early Oceans Likely Delayed Rise of Life on Planet

ScienceDaily (Jan. 10, 2011) — Geologists at the University of California, Riverside have found chemical evidence in 2.6-billion-year-old rocks that indicates that Earth's ancient oceans were oxygen-free and, surprisingly, contained abundant hydrogen sulfide in some areas.

"We are the first to show that ample hydrogen sulfide in the ocean was possible this early in Earth's history," said Timothy Lyons, a professor of biogeochemistry and the senior investigator in the study, which appears in the February issue of Geology. "This surprising finding adds to growing evidence showing that ancient ocean chemistry was far more complex than previously imagined and likely influenced life's evolution on Earth in unexpected ways -- such as, by delaying the appearance and proliferation of some key groups of organisms."

Ordinarily, hydrogen sulfide in the ocean is tied to the presence of oxygen in the atmosphere. Even small amounts of oxygen favor continental weathering of rocks, resulting in sulfate, which in turn gets transported to the ocean by rivers. Bacteria then convert this sulfate into hydrogen sulfide.

How then did the ancient oceans contain hydrogen sulfide in the near absence of oxygen, as the 2.6-million-year-old rocks indicate? The UC Riverside-led team explains that sulfate delivery in an oxygen-free environment can also occur in sufficient amounts via volcanic sources, with bacteria processing the sulfate into hydrogen sulfide.

Specifically, Lyons and colleagues examined rocks rich in pyrite -- an iron sulfide mineral commonly known as fool's gold -- that date back to the Archean eon of geologic history (3.9 to 2.5 billion years ago) and typify very low-oxygen environments. Found in Western Australia, these rocks have preserved chemical signatures that constitute some of the best records of the very early evolutionary history of life on the planet.

The rocks formed 200 million years before oxygen amounts spiked during the so-called "Great Oxidation Event" -- an event 2.4 billion years ago that helped set the stage for life's proliferation on Earth.

"Our previous work showed evidence for hydrogen sulfide in the ocean more than 100 million years before the first appreciable accumulation of oxygen in the atmosphere at the Great Oxidation Event," Lyons said. "The data pointing to this 2.5 billion-year-old hydrogen sulfide are fingerprints of incipient atmospheric oxygenation. Now, in contrast, our evidence for abundant 2.6 billion-year-old hydrogen sulfide in the ocean -- that is, another 100 million years earlier -- shows that oxygen wasn't a prerequisite. The important implication is that hydrogen sulfide was potentially common for a billion or more years before the Great Oxidation Event, and that kind of ocean chemistry has key implications for the evolution of early life."

Clint Scott, the first author of the research paper and a former graduate student in Lyons's lab, said the team was also surprised to find that the Archean rocks recorded no enrichments of the trace element molybdenum, a key micronutrient for life that serves as a proxy for oceanic and atmospheric oxygen amounts.

The absence of molybdenum, Scott explained, indicates the absence of oxidative weathering of the continental rocks at this time (continents are the primary source of molybdenum in the oceans). Moreover, the development of early life, such as cyanobacteria, is determined by the amount of molybdenum in the ocean; without this life-affirming micronutrient, cyanobacteria could not become abundant enough to produce large quantities of oxygen.

"Molybdenum is enriched in our previously studied 2.5 billion-year-old Archean rocks, which ties to the earliest hints of atmospheric oxygenation as a harbinger of the Great Oxidation Event," Scott said. "The scarcity of molybdenum in rocks deposited 100 million years earlier, however, reflects its scarcity also in the overlying water column. Such metal deficiencies suggest that cyanobacteria were probably struggling to produce oxygen when these rocks formed.

"Our research has important implications for the evolutionary history of life on Earth," Scott added, "because biological evolution both initiated and responded to changes in ocean chemistry. We are trying to piece together the cause-and-effect relationships that resulted, billions of years later, in the evolution of animals and, ultimately, humans. This is really the story of how we got here."

The first animals do not appear in the fossil record until around 600 million years ago -- almost two billion years after the rocks studied by Scott and his team formed. The steady build-up of oxygen, which began towards the end of the Archean, played a key role in the evolution of new life forms.

"Future research needs to focus on whether sulfidic and oxygen-free conditions were prevalent throughout the Archean, as our model predicts," Scott said.

Lyons and Scott were accompanied on this project by Christopher Reinhard from UCR; Andrey Bekker from the University of Manitoba, Canada; Bernhard Schnetger from Oldenburg University, Germany; Bryan Krapež from the Curtin University of Technology, Western Australia; and Douglas Rumble III from the Carnegie Institution of Washington, Washington, DC. Currently, Scott is a postdoctoral researcher at McGill University, Canada.

Funding for this work came from the National Science Foundation, the NASA Exobiology Program, the NASA Astrobiology Institute, and through a Canadian National Sciences and Engineering Research Council Discovery Grant.

http://www.sciencedaily.com/releases/2011/01/110110151016.htm

Widespread, Persistent Oxygen-Poor Conditions in Earth's Ancient Oceans Impacted Early Evolution of Animals

ScienceDaily (Jan. 6, 2011) — The conventional view of the history of the Earth is that the oceans became oxygen-rich to approximately the degree they are today in the Late Ediacaran Period (about 600 million years ago) after staying relatively oxygen-poor for the preceding four billion years. But biogeochemists at the University of California, Riverside have found evidence that shows that the ocean went back to being "anoxic" or oxygen-poor around 499 million years ago, soon after the first appearance of animals on the planet, and remained anoxic for 2-4 million years. What's more, the researchers suggest that such anoxic conditions may have been commonplace over a much broader interval of time, with their data capturing a particularly good example.



Researcher Benjamin Gill near the top of a stratigraphic section at Lawsons Cove, Utah. (Credit: Steve Bates.)

The researchers argue that such fluctuation in the ocean's oxygenation state is the most likely explanation for what drove the rapid evolutionary turnover famously recognized in the fossil record of the Cambrian Period (540 to 488 million years ago).

They report in the Jan. 6 issue of Nature that the transition from a generally oxygen-rich ocean during the Cambrian to the fully oxygenated ocean we have today was not a simple turn of the switch, as has been widely accepted until now.

"Our research shows the ocean fluctuated between oxygenation states 499 million years ago," said co-author Timothy Lyons, a professor of biogeochemistry, whose lab led the research, "and such fluctuations played a major, perhaps dominant, role in shaping the early evolution of animals on the planet by driving extinction and clearing the way for new organisms to take their place."

Oxygen is a staple for animal survival, but not for the many bacteria that thrive in and even demand life without oxygen.

Understanding how the environment changed over the course of Earth's history can clue scientists to how exactly life evolved and flourished during the critical, very early stages of animal evolution.

"Life and the environment in which it lives are intimately linked," said Benjamin Gill, the first author of the research paper, who worked in Lyons's lab as a graduate student. Gill explained that when the ocean's oxygenation states changed rapidly in Earth's history, some organisms were not able to cope. Further oceanic oxygen affects cycles of other biologically important elements such as iron, phosphorus and nitrogen.

"Disruption of these cycles is another way to drive biological crises," he said. "Thus both directly and indirectly a switch to an oxygen-poor state of the ocean can cause major extinction of species."

The researchers are now working on finding an explanation for why the oceans became oxygen-poor about 499 million years ago.

"What we have found so far is evidence that it happened," Gill said. "We have the 'effect,' but not the 'cause.' The oxygen-poor state persisted for 2-4 million years, likely until the enhanced burial of organic matter, originally derived from oxygen-producing photosynthesis, resulted in the accumulation of more oxygen in the atmosphere and ocean. As a kind of negative feedback, the abundant burial of organic material facilitated by anoxia may have bounced the ocean to a more oxygen-rich state."

Gill stressed that understanding past events in Earth's distant history can help refine our view of changes happening on the planet presently.

"Today, some sections of the world's oceans are becoming oxygen-poor -- the Chesapeake Bay and the so-called 'dead zone' in the Gulf of Mexico are just two examples," he said. "We know the Earth went through similar scenarios in the past. Understanding the ancient causes and consequences can provide essential clues to what the future has in store for our ocean."

In the study, Lyons, Gill and their team examined the carbon, sulfur and molybdenum contents of rocks they collected from localities in the United States, Sweden, and Australia. Combined, these analyses allowed the team to infer the amount of oxygen present in the ocean at the time the limestones and shales were deposited. By looking at successive rock layers, they were able to compile the biogeochemical history of the ocean.

Lyons and Gill were joined in the research by Seth A. Young of Indiana University, Bloomington; Lee R. Kump of Penn State University; Andrew H. Knoll of Harvard University; and Matthew R. Saltzman of Ohio State University. Currently, Gill is a postdoctoral researcher at Harvard University.

The study was funded by a grant from the U.S. National Science Foundation.

http://www.sciencedaily.com/releases/2011/01/110105131743.htm

Neandertals’ Extinction Not Caused by Deficient Diets, Tooth Analysis Shows

ScienceDaily (Jan. 1, 2011) — Researchers from George Washington University and the Smithsonian Institution have discovered evidence to debunk the theory that Neandertals' disappearance was caused in part by a deficient diet -- one that lacked variety and was overly reliant on meat. After discovering starch granules from plant food trapped in the dental calculus on 40-thousand-year-old Neandertal teeth, the scientists believe that Neandertals ate a wide variety of plants and included cooked grains as part of a more sophisticated, diverse diet similar to early modern humans.

Neandertal teeth from Shanidar cave. (Credit: George Washington University)

"Neandertals are often portrayed as very backwards or primitive," said Amanda Henry, lead researcher and a post-doctoral researcher at GW. "Now we are beginning to understand that they had some quite advanced technologies and behaviors."

Dr. Henry made this discovery together with Alison Brooks, professor of anthropology and international affairs at GW, and Dolores Piperno, a GW research professor and senior scientist and curator of archaeobotany and South American archaeology at the Smithsonian National Museum of Natural History, Washington D.C., and Smithsonian Tropical Research Institute, Panama.

The discovery of starch granules in the calculus on Neandertal teeth provides direct evidence that they made sophisticated, thoughtful food choices and ate more nutrient-rich plants, for example date palms, legumes and grains such as barley. Until now, anthropologists have hypothesized that Neandertals were outlived by early modern humans due in part to the former's primitive, deficient diet, with some scientists arguing Neandertals' diets were specialized for meat-eating. As such, during major climate swings Neandertals could be outcompeted by early humans who incorporated diverse plant foods available in the local environment into their diets.

Drs. Henry, Brooks and Piperno's discovery suggests otherwise. The researchers discovered starch granules in dental calculus, which forms when plaque buildup hardens, on the fossilized teeth of Neandertal skeletons excavated from Shanidar Cave in Iraq and Spy Cave in Belgium. Starch granules are abundant in most human plant foods, but were not known to survive on fossil teeth this old until this study. The researchers' findings indicate that Neandertals' diets were more similar to those of early humans than originally thought. The researchers also determined from alterations they observed in the starch granules that Neandertals prepared and cooked starch-rich foods to make them taste better and easier to digest.

"Neandertals and early humans did not visit the dentist," said Dr. Brooks. "Therefore, the calculus or tartar remained on their teeth, preserving tiny clues to the previously unknown plant portion of their diets."

Dr. Henry is currently a post-doctoral researcher in the Columbian College of Arts and Sciences Hominid Paleobiology program at the George Washington University, where she also received her Ph.D. in Jan. 2010. Her research focuses on the uses of plant foods by human ancestors. In Jan. 2011, Dr. Henry will begin leading an independent research group focusing on the evolution of human diet at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Dr Brooks' research focuses on the evolution of modern human behavior. Dr. Piperno is a pioneer in the detection and study of plant microfossils and the evolution of human diets.

"This significant finding provides new insight on the plight of the Neandertals," said Peg Barratt, dean of GW's Columbian College of Arts and Sciences. "It's also an excellent example of our dynamic partnership with the Smithsonian to further advance learning and discovery."

The research was supported by a National Science Foundation IGERT award, a Wenner Gren Foundation doctoral dissertation award, a Smithsonian Institution pre-doctoral fellowship, a National Science Foundation HOMINID award to the Smithsonian Institution and a selective excellence award from the George Washington University.

http://www.sciencedaily.com/releases/2010/12/101230113723.htm

Heat Helped Hasten Life's Beginnings on Earth, Research Suggests

ScienceDaily (Dec. 5, 2010) — There has been controversy about whether life originated in a hot or cold environment, and about whether enough time has elapsed for life to have evolved to its present complexity.


Lava flow. (Credit: USGS)

But new research at the University of North Carolina at Chapel Hill investigating the effect of temperature on extremely slow chemical reactions suggests that the time required for evolution on a warm earth is shorter than critics might expect.

The findings are published in the Dec. 1, 2010, online early edition of the Proceedings of the National Academy of Sciences.

Enzymes, proteins that jump-start chemical reactions, are essential to life within cells of the human body and throughout nature. These molecules have gradually evolved to become more sophisticated and specific, said lead investigator Richard Wolfenden, PhD, Alumni Distinguished Professor of biochemistry and biophysics at the UNC School of Medicine.

To appreciate how powerful modern enzymes are, and the process of how they evolved, scientists need to know how quickly reactions occur in their absence.

Wolfenden's group measured the speed of chemical reactions, estimating that some of them take more than 2 billion years without an enzyme.

In the process of measuring slow reaction rates, "it gradually dawned on us that the slowest reactions are also the most temperature-dependent," Wolfenden said.

In general, the amount of influence temperature has on reaction speeds varies drastically, the group found. In one slow reaction, for instance, raising the temperature from 25 to 100 degrees Celsius increases the rate 10 million fold. "That is a shocker," Wolfenden said. "That's what's going to surprise people most, as it did me."

That is surprising, Wolfenden said, because a textbook rule in chemistry -- for more than a century -- has been that the influence of temperature is modest. In particular, a doubling in reaction rate occurs when the temperature rises 10 degree Celsius, according to experiments done in 1866.

High temperatures were probably a crucial influence on reaction rates when life began forming in hot springs and submarine vents, Wolfenden said. Later, the cooling of the earth provided selective pressure for primitive enzymes to evolve and become more sophisticated, the Wolfenden's group hypothesizes.

Using two different reaction catalysts -- which are not protein enzymes but that may have resembled early precursors to enzymes -- the group put the hypothesis to the test. The catalyzed reactions are indeed far less sensitive to temperature, compared with reactions that are accelerated by catalysts. The results are consistent with our hypothesis, Wolfenden said.

Wolfenden's group plans to test the hypothesis using other catalysts. In the meantime, these findings are likely to influence how scientists think of the first primitive forms of life on earth, and may affect how researchers design and enhance the power of artificial catalysts, he added.

Study co-authors from UNC are Randy Stockbridge, PhD, Charles Lewis, Jr., PhD and research specialist Yang Yuan, MS. Support for the research came from the National Institute of General Medicine, a component of the National Institutes of Health.

http://www.sciencedaily.com/releases/2010/12/101202124321.htm

Sewage Water Bacteria: 'Missing Link' in Early Evolution of Life on Earth?

ScienceDaily (Nov. 27, 2010) — A common group of bacteria found in acid bogs and sewage treatment plants has provided scientists with evidence of a 'missing link' in one of the most important steps in the evolution of life on Earth -- the emergence of cells with a nucleus containing DNA (eukaryotic cells).


New research shows that PVC (Planctomycetes, Verrucomicrobiae, Chlamydiae) bacteria -- members of which are commonly found in today's sewage treatment plants or acid bogs -- represent an intermediate type of cell structure. (Credit: iStockphoto/Viktor Balabanov).

For billions of years, bacteria (single celled organisms without a nucleus) were the only cellular life form on Earth. Then, about 1.6 to 2.1 billion years ago, eukaryotic cells emerged. These cells (with a nucleus) heralded the evolution of multi-cellular life on Earth including: plants, insects, animals and humans.

Until now scientists have been unable to identify an 'ancestral cell' linking the early prokaryotes with the later eukaryotes, so fusion theory -- where two cells merge to form a new cell -- is often put forward to explain the appearance of these new cell types.

But new findings by scientists from University College Dublin, Ireland, and the European Molecular Biology Laboratory in Heidelberg, Germany, published in Science (Nov. 26, 2010), have put paid to the fusion theory explanation, and suggest that an intermediate or 'missing link' cell did exist all those billions of years ago.

"Our discovery means that the appearance of eukaryotic cells on Earth can be explained by Darwinian evolution over billions of years rather than a 'big bang' fusion theory," says cell biologist Dr Emmanuel Reynaud from University College Dublin, one of the co-authors of the scientific paper.

"Our analysis shows that PVC [Planctomycetes, Verrucomicrobiae, Chlamydiae] bacteria, members of which are commonly found in today's sewage treatment plants or acid bogs, represent an intermediate type of cell structure. They are slightly bigger than other known bacteria, and they also divide more slowly."

"The structure of PVC suggests that it is an ancestor of a 'missing link' cell which connected prokaryotic to eukaryotic cells along an evolutionary path all those billions of years ago," says Dr Damien P Devos from the European Molecular Biology Laboratory, Heidelberg, Germany, who co-authored the scientific paper.

http://www.sciencedaily.com/releases/2010/11/101126094444.htm

Age Doesn't Matter: New Genes Are as Essential as Ancient Ones

ScienceDaily (Dec. 16, 2010) — New genes that have evolved in species as little as one million years ago -- a virtual blink in evolutionary history -- can be just as essential for life as ancient genes, startling new research has discovered.


The development process for Drosophila melanogaster stopped at the pharate stage when the new gene G32376 was knocked down. This gene originated 18 million years ago. (Credit: Manyuan Long Lab/University of Chicago)

Evolutionary biologists have long proposed that the genes most important to life are ancient and conserved, handed down from species to species as the "bread and butter" of biology. New genes that arise as species split off from their ancestors were thought to serve less critical roles -- the "vinegar" that adds flavor to the core genes.

But when nearly 200 new genes in the fruit fly species Drosophila melanogaster were individually silenced in laboratory experiments at the University of Chicago, more than 30 percent of the knockdowns were found to kill the fly. The study, published December 17 in Science, suggests that new genes are equally important for the successful development and survival of an organism as older genes.

"A new gene is as essential as any other gene; the importance of a gene is independent of its age," said Manyuan Long, PhD, Professor of Ecology & Evolution and senior author of the paper. "New genes are no longer just vinegar, they are now equally likely to be butter and bread. We were shocked."

The study used technology called RNA interference to permanently block the transcription of each targeted gene into its functional product from the beginning of a fly's life. Of the 195 young genes tested, 59 were lethal (30 percent), causing the fly to die during its development. When the same method was applied to a sample of older genes, a statistically similar figure was found: 86 of 245 genes (35 percent) were lethal when silenced.

Because the young genes tested only appeared between 1 and 35 million years ago, the data suggests that new genes with new functions can become an essential part of a species' biology much faster than previously thought. A new gene may become indispensable by forming interactions with older genes that control important functions, said Sidi Chen, University of Chicago graduate student and first author of the study.

"New genes come in and quickly interact with older genes, and if that interaction is favorable by helping the organism survive or reproduce better, it is favored by natural selection and stays in the genome," Chen said. "After a while, it becomes essential, and the organism literally cannot live without the gene any more. It's something like love: You fall in love with someone and then you cannot live without them."

The indispensable nature of new genes also questions long-held beliefs about the shared features of development across different species. In 1866, German zoologist Ernst Haeckel famously hypothesized that "ontogeny recapitulates phylogeny" after observing that the early steps of development are shared by animals as different as fly and man.

Biologists subsequently predicted and confirmed that the same ancient, essential genes would be the conductors of this early development in all species. This principle enabled the use of model organisms, including flies, mice, and rats, to be used for research on the mechanisms of human disease.

Intriguingly, in the new study, deleting many of the new genes causes flies to die during middle or late stages of development, while older genes were lethal during early development. So while ancient genes essential for the early steps of development are shared, newer genes unique to each species may take over the later developmental stages that make each species unique. For example, many new genes in the study were found to be involved with metamorphosis, the mid-life stage that drastically transforms the body plan in animals.

"This may change the way we view the developmental program," Long said. "Each species has a different species-specific developmental program shaped by natural selection, and we can no longer say that from Drosophila to humans the development of different organisms is just encoded by the same genetic program. The story is much more complicated than what we used to believe."

As such, a full understanding of biological diversity may require a new focus on genes unique to each organism.

"I think it has important implications on human health," Chen said. "Animal models have proven to be very useful and important for dissecting human disease. But if our intuition is correct, some important health information for humans will reside in the unique parts of the human genome."

The newfound importance of young genes and unique developmental programs may have a dramatic impact on the field, Long said. The discovery will also inspire new research directions examining how quickly new genes can become essential and their exact role in species-specific development.

"Biologists have long assumed, quite reasonably, that ancient genes have survived natural selection because they are essential to life and that new genes are generally less critical to an organism's development," said Irene Eckstrand, PhD, who manages Dr. Long's and other evolutionary biology grants at the National Institutes of Health. "This important study suggests that this assumption is flawed, unlocking new questions that could lead to a deeper understanding of evolutionary processes and their impact on human health."

The work was funded by grants from the National Institute of General Medical Sciences, the National Science Foundation, and the Chicago Biomedical Consortium.

http://www.sciencedaily.com/releases/2010/12/101216142523.htm