World’s Oldest Homo sapiens Fossils Discovered

hominin skull

These images show two views of a composite reconstruction of the earliest known Homo sapiens fossils discovered in Jebel Irhoud, Morocco. (Photo credit: Philipp Gunz/Max Planck Institute for Evolutionary Anthropology)

It’s time to rewrite the textbooks. Until now, the oldest known Homo sapiens fossils, found in Omo Kibish in Ethiopia, dated to 195,000 years ago. The new fossils, discovered in Jebel Irhoud in Morocco, date to approximately 300,000 years ago. This means the new findings predate the previous oldest-known fossils by over 100,000 years.

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Modern Genetics Confirms Evolutionary Relationship Between Fins and Hands

spotted gar

The spotted gar, an ancient freshwater fish species, provides genetic evidence for the evolutionary relationship between fins and hands. (Photo credit: blickwinkel/Hartl Alamy)

The news that hands evolved from fins is not a new one. In fact, fossil evidence in the form of Tiktaalik roseae, an ancient creature with characteristics of both fish and amphibians, confirms the connection. [Read more…]

Koalas: Australia’s Pickiest Eaters

Koalas, one of nature’s pickiest eaters, choose to only dine on eucalyptus leaves. (Photo credit: Purestock/Getty Images)

Many people have favorite foods. But the koala takes favorite food to the extreme. These Australian marsupials have evolved to live almost exclusively on eucalyptus leaves. And if that isn’t picky enough, recent research suggests that koalas are highly selective as to the species of eucalyptus they prefer and even the individual trees from which they choose to eat. How have these animals become so picky, and how can scientists use this information to aid in koala conservation efforts? [Read more…]

The Appendix: More Useful Than Once Thought

For a long time, it was thought that the human appendix had no use. Instead, it was thought of as a vestigial organ, that is, an organ that functioned in an earlier ancestor, but no longer held that same use. However, new research indicates that the appendix is far from pointless. In fact, it may have an important role in survival.

The appendix is a pinky-finger sized organ located just below the junction between the small and large intestines. Though its function has been debated over the years, scientists have known for a while that the appendix is formed from immune system tissue.

appendix

The appendix is a pinky-finger sized organ located just below the junction of the large and small intestines.

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Warmer Climate, Shrinking Species?

Research indicates rising global temperatures may result in smaller plant and animal species. (Photo credit: Evgeny Dubinchuk/Fotolia)

Plants and animals are already beginning to change their behavior due to a warmer climate. Animals are beginning to migrate earlier, plants have changed their flowering periods, and many plants and animals have shifted their distribution away from the equator and closer to the cooler north and south poles. Recent research indicates that these modified behaviors are not the only change that species will undergo if the climate continues to warm as expected. These studies show that plant and animals may actually shrink in size as the climate continues to change.

Jennifer Sheridan, a professor of conservation biology at the University of Alabama, and David Bickford, a professor of environmental science at the National University of Singapore collaborated together on an article published in the journal Nature Climate Change. In the article, the scientists evaluated data from the fossil record, as well as modern-day studies to hypothesize what might happen if plant and animal sizes shrink due to a warming climate.

Their studies of the fossil record indicate that animals such as beetles, spiders, and pocket gophers significantly shrank in size during the Paleocene-Eocene Thermal Maximum, which occurred around 55.8 million years ago. Modern-day observations indicate that over the last 100 years, a variety of plant and animal species have decreased in size as average global temperatures have increased.

In addition to synthesizing data from the fossil record and current literature, the scientists also conducted two experiments. In one experiment, the scientists exposed ocean-dwelling creatures such as scallops, oysters, and scallops to conditions mimicking ocean water with increasing levels of acidity. As the acidity of the water increased, the marine animals ability to form their shells decreased, leading to an overall decrease in size. In a second experiment in which plants were grown under controlled climate conditions, the scientists found that for every 2 degrees that the temperature was increased, fruit size decreased by 3 to 17 percent. Similarly, when a variety of animals, including fish, beetles, marine invertebrates, and salamanders were exposed to increasing temperatures, they decreased in size, too. Fish, in particular, decreased between 6 and 22 percent in size.

ome species of salamanders are decreasing in size due to increased temperatures. (Photo credit: Carsten Meyer/Fotolia)

Research published in the journal The American Naturalist corroborates this data. This study focused on ectotherms, also known as cold-blooded animals, and how increased temperatures affect their growth rate and development. Experiments conducted with copepods, which are tiny aquatic crustaceans, showed that when exposed to warmer temperatures, the copepods go through their life stages at a quicker pace, meaning they reach adulthood at a smaller size than normal. This observation held true for a range of copepod species.

Why are species shrinking? Scientists point to a few explanations. Smaller plant size is linked to warmer and drier conditions and scarce water supplies. In addition, drought conditions often lead to forest fires, which diminish the amount of nitrogen, a nutrient necessary for plant growth, in the soil. These smaller plants in turn provide less of a satisfying meal for the herbivores that eat them. If the herbivores are unable to eat enough of their plant food source, or cannot find a replacement plant to eat, they will likely be unable to grow to their full size. Smaller herbivores in turn require predators to find more prey to eat to maintain their body size, or they too, will shrink in size.

Though not much is yet known about how worldwide food webs will be affected by a potential decrease in size across species, scientists hypothesize that changes in one species could have a ripple-effect on other species within their food web. They also foresee some species not feeling any affects due to a changing climate, which could also lead to imbalances within a food web, as some species thrive while others decline. Though computer models can help to show how shrinking species size may affect ecosystems in the future, only time will tell the actual impact these changes. As described above, current research indicates that shrinking species size could have a significant impact, though more research is necessary.

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Scientists Uncover Mystery of Flu Virus Evolution

Researchers at the University of Rochester Medical Center (URMC) have uncovered the mechanism that lets the flu virus evolve so efficiently within and between host species. In their research, the scientists found that the secret to the flu virus’s evolutionary success lies in its unique replication process. Previously, scientists thought that the flu virus evolved so quickly due to an error-prone replication process. However, this new research refutes that hypothesis. Instead, the researchers discovered that the flu virus’s unique replication process lets enough mutations form that the virus can easily spread and adapt to its host environment. In addition, this replication process allows just enough mutations to occur without causing catastrophic mutagenesis—that is, without killing itself in the process.

These new findings give us insights into how we may be able to control viral evolution,” Baek Kim, Ph.D., professor in the department of Microbiology and Immunology at UMRC and lead study author, said in a press release about the discovery. This research presents an attractive strategy for tackling the flu—making the influenza virus kill itself by amplifying the number of mutations made beyond the desired level, which is lethal for the virus.

In their study of the mechanisms behind flu virus evolution, the researchers used biochemical analysis methods to compare flu virus replication with human-immunodeficiency virus (HIV) replication. The scientists found that while the polymerases, that is, the enzymes, behind replication are quite error-prone in HIV, they are much more accurate in the flu virus. Though both viruses depend on mutations for survival, HIV is only able to replicate its genome a few times during an infection, meaning it isn’t able to produce that many mutations. In contrast, the flu virus replicates itself a number of times during an infection, and this gives it ample time to produce a huge number of mutations that allow the virus to thrive.

The results of the scientists’ research was published online in the April 29, 2010 edition of the open-access journal PLoS One. Researchers who contributed to this study included Shilpa Aggarwal, Birgit Bradel-Tretheway, Toru Takimoto, Stephen Dewhurst, and Baek Kim.

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Sponges Descended from Unique Ancestor

Researchers have discovered that sponges evolved from a separate ancestor than all other animals. This finding is contrary to popular thought that places a sponge-like creature as the ancient ancestor of all other animals.

Research indicates that sponges evolved from a separate ancestor than all other animals. (Photo credit:  Andrew David, NOAA/NMFS/SEFSC Panama City; Lance Horn, UNCW/NURC - Phantom II ROV operator.)

Research indicates that sponges evolved from a separate ancestor than all other animals. (Photo credit: Andrew David, NOAA/NMFS/SEFSC Panama City; Lance Horn, UNCW/NURC – Phantom II ROV operator.)

The three main researchers associated with this study include Herv Philippe of the Universit de Montral in Montreal, Canada, Gert Wrheide of the Ludwig-Maximillians Universistt in Munich, Germany; and Michael Manuel of the University of Paris in Paris, France. In their research, the scientists studied 128 genes from 55 different species. These species included 9 poriferans, 8 cnidarians, 3 ctenophores, and 1 placozoan. The scientists used a technique called phylogenomics. This technique uses computers to analyze and compare large datasets of gene sequences to determine evolutionary relationships. By determining evolutionary relationships, the scientists were able to develop a phylogenetic tree to show how related each animal was to another. In studying these relationships, the scientists found that poriferans developed from a separate ancestor than the other groups of animals. They also found evidence that cnidiarians and ctenophores belong to a common group.

Future research plans include determining when specific features evolved in animals. The scientists are especially interested in determining how the “genetic toolkit” necessary for the development of animal nervous systems, muscles, and sensory organs evolved.

The research was published in the April 2, 2009 edition of the journal Current Biology. The study was funded by the Deutsche Forschungsgemeinschaft as a part of the Priority Program 1174 “Deep Metazoan Phylogeny.”

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Bacterium Evolves Stealth Strategy Against Tomatoes

Suppose a species has one defense against bacterial infection, then the bacteria evolve to get around the defense. The host species will succumb to infection until another defense evolves to stop the attack. This is known as an evolutionary arms race — a continuous battle between two organisms to outdo each others tactics. Now, Tracy Rosebrock, a plant pathology student at Boyce Thompson Institute for Plant Research at Cornell University, published molecular data supporting the evolutionary arms race theory.

Tomatoes use a protein called Fen to protect themselves from an infectious bacterium, Pseudomonas syringae. Fen triggers an immune response in the tomatoes as soon as it comes across P. syringae.

Now, some strains of P. syringae produce a protein that acts like a tomato enzyme called E3 ubiquitin ligase. E3 ubiquitin ligase binds to proteins that the tomato plant should destroy. The copycat bacterial protein binds to Fen, causing tomato plant to eliminate Fen from its system. P. syringae evolved an effective way to turn off the tomato plants defensive system. The bacterium avoids detection and infects the plant.

The host resistance mechanism of the tomato against P. syringae and now the blocking of this immune response is now understood at the molecular level.

“Plant breeders often find that five or six years after their release, resistant plant varieties become susceptible because pathogens can evolve very quickly to overcome plant defenses,” notes Gregory Martin, Cornell professor of plant pathology and senior author of the research paper. Agricultural scientists and growers may need to look more often at disease resistance at molecular to mount a successful defense in the ongoing evolutionary arms race.

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