Separation Between Neanderthal and Homo Sapiens Might Have Occurred 500,000 Years Earlier, DNA from Teeth Suggests

ScienceDaily (June 23, 2010) — The separation of Neanderthal and Homo sapiens might have occurred at least one million years ago, more than 500.000 years earlier than previously believed, according to new DNA-based analyses.

A doctoral thesis conducted at the National Center for Research on Human Evolution (Centro Nacional de Investigación sobre la Evolución Humana), associated with the University of Granada, analyzed the teeth of almost all species of hominids that have existed during the past 4 million years. Quantitative methods were employed, and they managed to identify Neanderthal features in ancient European populations.

The main purpose of this research, whose author is Aida Gómez Robles, was to reconstruct the history of evolution of the human species using the information provided by the teeth, which are the most numerous and best preserved remains of the fossil record. To this purpose, a large sample of dental fossils from different sites in Africa, Asia and Europe was analyzed. The morphological differences of each dental class were assessed and the ability of each tooth to identify the species to which its owner belonged was analyzed.

The researcher concluded that it is possible to correctly determine the species to which an isolated tooth belonged with a success rate ranging from 60% to 80%. Although these values are not very high, they increase as different dental classes from the same individual are added. That means that if several teeth from the same individual are analyzed, the probability of correctly identifying the species can reach 100%.

Aida Gómez Robles explains that, from all the species of hominids currently known, "none of them has a probability higher than 5% to be the common ancestor of Neanderthals and Homo sapiens. Therefore, the common ancestor of this lineage is likely to have not been discovered yet."

Computer Simulation

What is innovative about this study is that computer simulation was employed to observe the effects of environmental changes on morphology of the teeth. Similar studies had been conducted on the evolution and development of different groups of mammals, but never on human evolution.

Additionally, the research conducted at CENIEH and at the University of Granada is pioneering -- together with recent studies based on the shape of the skull -- in using mathematical methods to make an estimation of the morphology of the teeth of common ancestors in the evolutionary tree of the human species. "However, in this study, only dental morphology was analyzed. The same methodology can be used to rebuild other parts of the skeleton of that species, which would provide other models that would serve as a reference for future comparative studies of new fossil finds."

To carry out this study, Gómez Robles employed fossils from a number of archaeological-paleontological sites, such as that of the Gran Colina and the Sima de los Huesos, located in Atapuerca range (Burgos, Spain), and the site of Dmanisi in the Republic of Georgia. She also studied different fossil collections by visiting international institutions as the National Museum of Georgia, the Institute of Human Paleontology and the Museum of Mankind in Paris, the European Research Centre Tautavel (France), the Senckenberg Institute Frankfurt, the Museum of Natural History in Berlin, the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and the Museum of Natural History in New York and Cleveland.

The results of this research were disclosed in two articles published in Journal of Human Evolution (2007 and 2008), and they will also be thoroughly presented within a few months.

http://www.sciencedaily.com/releases/2010/06/100623104436.htm

More Than Skin Deep, Tanning Product of Sun's Rays

ScienceDaily (June 22, 2010) — People who remain pale and never tan can blame their distant ancestors for choosing to live in the northern reaches of the globe and those who easily achieve a deep tan can thank their ancestors for living in the subtropical latitudes, according to Penn State anthropologists.



People who remain pale and never tan can blame their distant ancestors for choosing to live in the northern reaches of the globe and those who easily achieve a deep tan can thank their ancestors for living in the subtropical latitudes, according to Penn State anthropologists. (Credit: iStockphoto/Yuliyan Velchev)

"The variation of ultraviolet radiation, especially in the middle and high latitudes is great," said Nina Jablonski, professor of anthropology and chair of Penn State's anthropology department. "Tanning has evolved multiple times around the world as a mechanism to partly protect humans from harmful effects of ultraviolet radiation."

Jablonski, working with George Chaplin, senior research associate in anthropology and an expert in geographic information systems, looked at the way the sun illuminates different parts of the Earth. They looked at levels and angles of incidence of both ultraviolet A and B radiation at various latitudes. Ultraviolet B radiation is much more variable than ultraviolet A as latitude increases due to atmospheric scattering of the light and absorption by oxygen.

Ultraviolet B radiation produces vitamin D in human skin. Ultraviolet radiation can, however, destroy folate. Folate is important for the rapid growth of cells, especially during pregnancy where its deficiency can cause neural tube defects.

"What we now recognize is that some of the medical problems seen in darkly pigmented people may be linked at some level to vitamin D deficiency," said Jablonski. "Things like certain types of cancer in darkly pigmented people and in people who use a lot of sunscreen or always stay inside could be partly related to vitamin D deficiency."

Scientists have understood for years that evolutionary selection of skin pigmentation was caused by the sun. As human ancestors gradually lost their pelts to allow evaporative cooling through sweating, their naked skin was directly exposed to sunlight. In the tropics, where human ancestors evolved and where both ultraviolet radiations are high throughout the year, natural selection created darkly pigmented individuals to protect against the sun.

"Past arguments about the selective value of dark pigmentation focused on the protective effects of melanin against sunburn, skin cancer, and overproduction of vitamin D. These factors can no longer be considered significant selective pressures," the Jablonski and Chaplin report in a recent issue of the Proceedings of the National Academy of Sciences.

Sunburn and most skin cancers do not alter an individual's ability to procreate, so they are not selection factors. The human body also has a mechanism to prevent overproduction of vitamin D.

Previously, the researchers concluded that dark skin pigmentation in the tropics protects people from folate destruction by ultraviolet B, but, because levels of ultraviolet B are high year round, the skin can still allow enough in to manufacture vitamin D.

As humans moved out of Africa, they moved into the subtropics and eventually inhabited areas up to the Arctic Circle. Ultraviolet radiation in these areas is neither consistent nor strong. North or south of 46 degrees latitude, which includes all of Canada, Russia, Scandinavia, Western Europe and Mongolia, there is insufficient ultraviolet B through most of the year to produce vitamin D. Populations in these areas evolved to have little skin pigmentation.

In the latitudes between 23 and 46 degrees, an area that encompasses North Africa, South America, the Mediterranean and most of China, ultraviolet B radiation is much more variable. Heavily pigmented skin in the winter would block the development of vitamin D, and lightly pigmented skin during the summer would allow destruction of folate.

"We actually demonstrate that in those middle latitudes where highly fluctuating levels of ultraviolet radiation occur throughout the year, tanning has evolved multiple times as a mechanism to partly protect humans from harmful effect of the sun," said Jablonski.

The tanning process evolved for humans who by and large were naked all the time. As the ultraviolet B radiation began to increase in the early spring, the skin would begin to gradually darken. As the sun became stronger, the tan became deeper. During the winter, as ultraviolet B waned, so did the tan, allowing Vitamin D production and protecting folate.

The researchers note that the ability to tan developed in a wide variety of peoples and while the outcome, tanablity, is the same, the underlying genetic mechanisms are not necessarily identical. They also note that depigmentated skin also developed at least three times through different genetic mechanisms.

Implications for today focus on the fact that depigmented people now live in tropical and subtropical areas where besides getting sunburned they run the risk of losing folate. Highly pigmented people live in higher latitudes where they may become vitamin D deficient, especially if they use sunscreens.

"It is a conspiracy of modernity," said Jablonski. "The rapidity at which we can move long distances and live far away from our ancestral homelands. The fact that we can live and work indoors. All this has happened within the last 500 years and especially within the last 200 years."

http://www.sciencedaily.com/releases/2010/06/100621125137.htm

3.6 Million-Year-Old Relative of 'Lucy' Discovered: Early Hominid Skeleton Confirms Human-Like Walking Is Ancient

ScienceDaily (June 21, 2010) — Meet "Lucy's" Great-Grandfather. Cleveland Museum of Natural History Curator and Head of Physical Anthropology Dr. Yohnannes Haile-Selassie led an international team that discovered and analyzed a 3.6 million-year-old partial skeleton found in Ethiopia. The early hominid is 400,000 years older than the famous "Lucy" skeleton and is significantly larger in size. Research on the new specimen reveals that advanced human-like, upright walking occurred much earlier in the evolutionary timeline than previously thought.

Haile-Selassie is the first author of the initial analysis of the specimen, which will be published in the online early edition of the Proceedings of the National Academy of Sciences during the week of June 21, 2010.

The partial skeleton belongs to "Lucy's" species, Australopithecus afarensis. It was found in the Woranso-Mille area of Ethiopia's Afar region by a team led by Haile-Selassie that excavated of the skeleton over five years following the discovery in 2005 of the lower arm bone. The team recovered the most complete clavicle and one of the most complete shoulder blades ever found in the human fossil record. A significant portion of the rib cage was also found.

The specimen was nicknamed "Kadanuumuu" (kah-dah-nuu-muu) by the authors. This means "big man" in the Afar language and reflects its large size. The male hominid stood between 5 to 5 ½ feet tall, while "Lucy" stood only 3 ½ feet tall.

"This individual was fully bipedal and had the ability to walk almost like modern humans," said Haile-Selassie. "As a result of this discovery, we can now confidently say that 'Lucy' and her relatives were almost as proficient walking on two legs as we are, and that the elongation of our legs came earlier in our evolution that previously thought."

He explained, "All of our understanding of Australopithecus afarenis' locomotion was dependent on 'Lucy.' Because she was an exceptionally small female with absolutely short legs, this gave some researchers the impression that she was not fully adapted to upright walking. This new skeleton falsifies that impression because if 'Lucy's' frame had been as large as this specimen, her legs would also have been proportionally longer."

Kent State University Professor Dr. C. Owen Lovejoy was a co-author of the research and helped analyze the skeleton. When comparing it to "Lucy," Lovejoy said, "They both have pelves, a complete lower limb bone and elements of the forelimb, vertebral column and thorax. However, the new specimen has more complete ribs and a nearly complete scapula, which tells us much more about body form in Australopithecus afarensis than 'Lucy' was able to alone."

Authors of the research include Cleveland scientists Dr. Bruce Latimer, interim director of the Center for Human Origins of the Institute for the Science of Origins at Case Western Reserve University, and Dr. Beverly Saylor, associate professor of geological sciences at Case Western Reserve University. Other co-authors are from Addis Ababa University in Ethiopia, Berkeley Geochronology Center and Stanford University.

Australopithecus afarenis is the best-known direct early human ancestor. Until now, the only partial skeleton assigned to this species was "Lucy," a 3.2 million-year-old female individual, which was discovered in 1974 by a team led by then Museum curator Dr. Donald Johanson.

The analysis of "Kadanuumuu" indicates that the shoulder and rib cage of this species were different from those of chimpanzees. "These findings further confirm what we concluded from the 'Ardi' specimen -- that chimpanzees have undergone a great deal of specialized evolution since we shared a last common ancestor with them," said Lovejoy.

"Ardi," or Ardipithecus ramidus is a 4.4 milion-year-old hominid species that was unveiled in October 2009 by a team that included Haile-Selassie, Lovejoy, and Museum scientists and associate researchers Dr. Linda Spurlock, Dr. Bruce Latimer and Dr. Scott Simpson. "Ardi" was named by the journal Science as breakthrough discovery of the year. Click here to find out more about "Ardi."

http://www.sciencedaily.com/releases/2010/06/100621151119.htm

Flowering Plants May Be Considerably Older Than Previously Thought

ScienceDaily (Mar. 17, 2010) — Flowering plants may be considerably older than previously thought, says a new analysis of the plant family tree.


A new analysis of the land plant family tree suggests that flowering plants may have lived much earlier than previously thought. (Credit: Wikimedia Commons)

Previous studies suggest that flowering plants, or angiosperms, first arose 140 to 190 million years ago. Now, a paper to be published in the Proceedings of the National Academy of Sciences pushes back the age of angiosperms to 215 million years ago, some 25 to 75 million years earlier than either the fossil record or previous molecular studies suggest.

"If you just looked at the fossil record, you would say that angiosperms originated in the early Cretaceous or late Jurassic," said Michael Donoghue of Yale University. "Most molecular divergence times have shown that they might be older than that," added Yale biologist Jeremy Beaulieu. "But we actually find that they might be Triassic in origin," said Beaulieu. "No one has found a result like that before."

If confirmed, the study could bolster the idea that early angiosperms promoted the rise of certain insects. Modern insects like bees and wasps rely on flowers for nectar and pollen. "The fossil record suggests that a lot of these insect groups originated before angiosperms appeared," said Stephen Smith of the National Evolutionary Synthesis Center. This study shifts the oldest angiosperms back farther in time towards the origin of groups like bees and flies, the scientists say. "If you take our dates and superimpose them on the evolutionary tree for these insect groups, all of a sudden you get a match," said Beaulieu.

To trace the origins of flowering plants, the researchers used genetic comparisons of living plants and clues from fossils to reconstruct the relationships among more than 150 terrestrial plant species. Though their results contradict previous age estimates for angiosperms, they support estimates for other plant groups. "Many of the dates that we get correspond really well to the known fossil record, at least for the origin of land plants and the origin of vascular plants and seed plants," said Donoghue. "But we got a much older date for the origin of angiosperms -- one that's really out of whack with the fossil record," Smith added.

This disconnect between molecular and fossil estimates is not unheard of, the authors explained. "We see the same kind of discrepancy in other groups too, like mammals and birds," said Donoghue.

Why the mismatch between different approaches to dating the tree of life?

One possibility, the researchers explained, is that the first flowering plants weren't diverse or abundant enough to leave their mark in the fossil record. "We would expect there to be a time lag between the time of origin and when they became abundant enough to get fossilized," said Smith. "The debate would just be how long."

"Imagine a long fuse burning and then KABOOM! There's a big explosion. Maybe angiosperms were in that fuse state," said Donoghue. "But it's hard to imagine flowering plants would have had a big impact on the origin of major insect groups if that were the case," he added.

Another possibility, the researchers allow, is that the molecular methods may be amiss. "If the angiosperms originated 215 million years ago, then why don't we find them in the fossil record for almost 80 million years?" said Beaulieu. "It could also suggest that our dates are wrong."

"We've done the best analysis we know how to do with the current tools and information," said Donoghue. To improve on previous studies, the researchers used a method that allows for variable rates of evolution across the plant family tree. "Rates of molecular evolution in plants seem to be correlated with changes in life history," he explained. "Older methods assume that rates of molecular evolution don't change too radically from one branch of the evolutionary tree to another. But this newer method can accommodate some fairly major rate shifts." Although researchers have come up with some savvy statistical tricks to account for rate shifts, Donoghue explained, the problem hasn't entirely disappeared.

"As we develop better molecular methods, people would like it if the molecular dates reconciled with the fossil record. Then everybody would be happy," said Donoghue. "But instead the gap is getting wider," he said. "And in the end, that might actually be interesting."

The team's findings will be published early online in the March 15 issue of Proceedings of the National Academy of Sciences.

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Move Over Predators: Plants Can Control the Food Chain Too -- From the Bottom Up

ScienceDaily (Mar. 25, 2010) — Forget top-to-bottom only. New Cornell University evolutionary biology research published in the journal Science shows how plants at the bottom of the food chain have evolved mechanisms that influence ecosystem dynamics as well.

"The ecology and interactions of most organisms is dictated by their evolutionary history," said Anurag Agrawal, associate professor of ecology and evolutionary biology (EEB), the study's senior author.

In food webs, predators help suppress populations of prey by eating them; that frees species lower in the food chain, such as plants, to flourish, a dynamic called a "trophic cascade." Most trophic cascade studies have focused on the ability of predators to increase plant biomass by eating herbivores. Such studies typically find strong trophic cascades in aquatic environments, where big fish eat minnows, which eat the tiny algae-eating crustaceans called daphnia.

Agrawal, first author Kailen Mooney, who is a former Cornell postdoctoral researcher and now assistant professor at the University of California-Irvine, and colleagues studied trophic cascades in 16 milkweed species, famed for their interactions with monarch butterflies, and also fed upon by aphids.

Plants have evolved three main strategies for increasing their biomass as much as they can against the forces that limit their growth, said the researchers: They grow as quickly as possible; develop direct defenses, such as toxins or prickly leaves, against herbivores; and attract such predators as ladybugs that eat their pests.

But plants do not have the resources to develop all three defenses. Since Darwin, evolutionary biologists have hypothesized that over millions of years of evolution, plant species are subject to trade-offs, developing some defense strategies in lieu of others; a key finding of the new study is that these evolutionary trade-offs drive how modern ecosystems are structured.

In the case of milkweed, some favored fast growth and the ability to attract predators while putting less energy into resisting herbivores.

The study found that one of the major factors leading to greater milkweed biomass (or growth) is the production of volatile compounds called sesquiterpenes, which attract such predators as aphid-eating ladybugs. But surprisingly, the plants' biomass increases regardless of whether ladybugs or other aphid predators are present.

The reason, the researchers suggest, is because the trait to produce sesquiterpenes appears genetically linked to faster growth; the strategy here is to replace leaves faster than they can be eaten. At the same time, milkweed species that put more energy into growing faster put less energy into resisting such pests as aphids.

"Because no species can do everything, milkweeds that grow fast necessarily have lower resistance to aphids," said Agrawal. "Thus species that grow fast benefit the most from predators" of aphids.

The findings have implications for agriculture, as conventional strategies for controlling pests often involve spraying insecticides, said Agrawal. "By including the evolutionary history in our understanding of natural pest management, we gain insight into plant strategies that have stood the test of time, and this may provide hints for breeding crops with traits that ensure robust lines of defense," he added.

*Science, March 26, 2010.

Co-authors include Andre Kessler, assistant professor, and postdoctoral researcher Rayko Halitschke, both in EEB at Cornell.

The study was funded by the National Science Foundation, Cornell Center for a Sustainable Future and University of California-Irvine's School of Biological Sciences.

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Evolution More Rapid Than Darwin Thought

ScienceDaily (Mar. 22, 2010) — Evolution can proceed much more rapidly than has long been thought. This is shown by Magnus Karlsson, a doctoral candidate at Linnaeus University in Kalmar, in his dissertation about the impact of genetics and the environment on the color patterns of pygmy grasshoppers.

It has been the accepted view among evolutionary biologists since Darwin published his Origin of Species in 1859 that measurable evolutionary changes occur slowly, often taking hundreds of generations. This view may now be about to change.

Pygmy grasshoppers exist in many different color variants and in many types of environment. Through a series of experiments and studies in nature, Magnus Karlsson discovered that the distribution between the color variants of pygmy grasshoppers differs across different environments. In recently burnt over areas, a very high proportion of the grasshoppers are black. In unburnt areas, on the other hand, the black variant is unusual. What's more, the proportion of black grasshoppers changes very rapidly between generations in the burnt areas, whereas the proportion in unburnt areas remains the same over the same period of time.

Magnus Karlsson presents data that show that the pygmy grasshoppers' color changes by natural selection. He believes that the primary cause of these changes is birds and other animals that hunt using their vision. The black grasshoppers are simply less visible against the burnt background, so they survive more often. But as the environment changes and becomes more complex, the advantage of being dark diminishes, and other color variants can once again increase in number.

In his experiments, Magnus Karlsson has also shown that the color pattern of the pygmy grasshopper is genetically conditioned and is passed on from parent to offspring. On the other hand, various environmental factors, such as crowdedness or the substrate the grasshoppers grow up on, do not affect their color. In other words, there is no indication that the grasshoppers themselves can change their color depending on what environment they are surrounded by. Therefore, the great differences that exist between burnt and unburnt environments are the result of unusually rapid evolutionary change.

But it is not only that evolution sometimes proceeds rapidly; variation itself also offers major advantages. In groups consisting of many different color variants, survival is higher than in groups with less color variation. This means quite simply that variable groups may find it easier to adapt to environmental changes and that they are more productive.

The practical significance of Magnus Karlsson's discoveries is broad and just as varied as his grasshoppers. He believes this new knowledge can be used in planning preservation projects for threatened species and to improve yields in agriculture.

"But the most important part of the dissertation is that I have shown that evolution sometimes proceeds incredibly rapidly. This is huge," says Magnus Karlsson.

His dissertation is titled Evolution in Changing Environments Revealed by Fire Melanism in Pygmy Grasshoppers.

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First Ever Southern Tyrannosaur Dinosaur Discovered

ScienceDaily (Mar. 26, 2010) — Scientists from Cambridge, London and Melbourne have found the first ever evidence that tyrannosaur dinosaurs existed in the southern continents. They identified a hip bone found at Dinosaur Cove in Victoria, Australia as belonging to an ancestor of Tyrannosaurus rex.
Tyrannosaurus rex. (Credit: iStockphoto)

The find sheds new light on the evolutionary history of this group of dinosaurs. It also raises the crucial question of why it was only in the north that tyrannosaurs evolved into the giant predators like T. rex.

The 30cm-long pubis bone from Dinosaur Cove looks like a rod with two expanded ends, one of which is flattened and connects to the hip and the other looks like a 'boot'.

According to Dr Roger Benson of the Department of Earth Sciences at the University of Cambridge, who identified the find: "The bone is unambiguously identifiable as a tyrannosaur because these dinosaurs have very distinctive hip bones."

The discovery lays to rest the belief held by some scientists that tyrannosaurs never made it to the southern continents.

"This is an exciting discovery because tyrannosaur fossils had only ever been found in the northern hemisphere before and some scientists thought tyrannosaurs never made it down south.

"Although we only have one bone, it shows that 110 million years ago small tyrannosaurs like ours might have been found worldwide. This find has major significance for our knowledge of how this group of dinosaurs evolved." says Dr Benson.

Dr Paul Barrett, Palaeontologist at the Natural History Museum, London and member of the research team commented: "The absence of tyrannosauroids from the southern continents was becoming more and more anomalous as representatives of other 'northern' dinosaur groups started to show up in the south. This find shows that tyrannosauroids were able to reach these areas early in their evolutionary history and also hints at the possibility that others remain to be discovered in Africa, South America and India."

The bone would have come from an animal about three metres long and weighing around 80 kg, similar to a human, and would have had the large head and small arms that make tyrannosaurs so distinctive.

The newly identified dinosaur, known as NMV P186069, was much smaller than T. rex, which was 12 metres long and weighed around four tonnes. Giant size like this only evolved late in the tyrannosaur lineage.

Compared with T. rex, which lived about 70 million years ago at the end of Cretaceous period, NMV P186069 lived earlier during the Cretaceous, around 110 million years ago.

During the time of the dinosaurs the continents gradually went from a single supercontinent towards something like their present-day arrangement. This tyrannosaur is from the mid-stages of this continental break-up, when the southern continents of South America, Antarctica, Africa and Australia had separated from the northern continents, but had not separated from each other.

While answering the question of whether or not tyrannosaurs lived in both the southern and northern hemispheres, the new find leaves another, deeper mystery: why did tyrannosaurs evolve into giant predators such as T. rex only in the northern hemisphere?

According to Dr Benson: "It is difficult to explain why different groups succeeded in the north and the south if they originally existed in both places. What we need to know now is just how diverse the early radiation of tyrannosaurs was, why they went extinct, leaving only giant-sized, short-armed species like T. rex, and how successful they might have been in the southern hemisphere. We can only answer these questions with new discoveries."

About the excavation: Dinosaur Cove is in south-east Australia, where the Otway ranges meet the sea to the west of Cape Otway, along the Great Ocean road. The fossil-bearing rock layers consist of sand-, silt- and mudstones around 106 million years old.

The site was excavated during the 1980s and 1990s. Work at the site was challenging: access involved either climbing down dangerous cliffs or landing a boat or helicopter on rock platforms at low tide, and the hardness of the rock meant heavy mining equipment and dynamite was required to uncover the fossil-bearing rock layers. Swedish mining company Atlas Copco donated some of the equipment used and the excavation was funded by the National Geographic Society.

Read more here!