Oldest Bird Found in China?

29 05 2013

A very interesting article about the new bird/dinosaur relative Aurornis xui was published this week in the British journal Nature.  It can be found at the Nature News Web site, here:  http://www.nature.com/news/new-contender-for-first-bird-1.13088.

Apparently, A. xui is a strong contender for “earliest bird”.  The extremely complete specimen was unearthed by a farmer in China’s Liaoning Province and acquired by the Fossil and Geology Park in Yizhou, China, through a fossil dealer, where it remained unidentified until being discovered by paleontologist Pascal Godefroit in 2012.

The article states that Godefroit believes that A. xui is “the oldest known member of the Avialae,” the group that includes all animals more closely related to modern birds than to dinosaurs.  This makes it the oldest bird, even older than Archaeopteryx.  A phylogenetic comparison of the specimen with approximately 100 other birds and dinosaurs seems to confirm this.

Godefroit goes on to say, “But these sorts of hypotheses are very controversial. We’re at the origins of a group. The differences between birds and [non-avian] dinosaurs are very thin.”

The American journal Science, also has an article about the find, which can be viewed here:  http://news.sciencemag.org/sciencenow/2013/05/earliest-bird-claim-ruffles-feat.html.  This article provides some additional background information about the evolutionary history of birds and dinosaurs.  It also points out the key remaining issue with the find – it’s authenticity.  There have been several famous fossil fakes from China in the last few years, most of which came to light through fossil dealers, as did A. xui, and one commentator in the Science article noted that scientists need to “take a skeptical look at this specimen.”  He stated that the fact that it is so complete and so “so neatly arranged” raises suspicions that needed to be put to rest before the specimen is completely accepted.

 

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Scientists Discover Link Between Malaria and Red Tides

1 06 2010

A team of scientists has discovered the common ancestor of two creatures that cause the world a considerable amount of trouble and suffering, the malaria parasite and the organism that causes red tides.  The missing link, the thing that connected the two, turned out to be little brown balls called Chromera.

The team, consisting of scientists from the University of British Columbia in Canada and the University of South Bohemia, in the Czech Republic, published their findings in the online early edition of the Proceedings of the National Academy of Sciences (PNAS), an American publication.

Chromera is a symbiont found inside corals. While it has a compartment (called a plastid) used to perform photosynthesis like the dinoflalgellate algae that causes red tide (as well as photosynthesis in plants), Chromera is closely related to apicomplexan parasites, which include malaria.  This discovery, first published in the journal Nature in 2008, gave researchers the idea that the algae and the parasites might be related and that the Chromera was the connection.

The scientists sequenced the genome of Chromera and were able to show for the first time, how the two are connected evolutionarily.

In recent interviews, the scientists said that they hope the knowledge gained by their research will not only advance basic scientific knowledge, but will also open the way for treatments for diseases such as malaria.

The original PNAS article is available here.





Neanderthals in Britain 40,000 Earlier than Believed

1 06 2010

British Archeologists have determined that Neanderthals arrived in Britain approximately 40,000 years earlier than has been believed.

Working with funding by the UK Highways Agency, as part of a study commissioned by Oxford Archaeology, the University of Southampton’s Dr Francis Wenban-Smith discovered two ancient flints at the juncture of the M25 and A2 roads near Dartford, in Kent.  The flints were waste flakes from the manufacture of unknown tools, which would almost certainly have been used to cut up dead animals.  Tests on the sediments in which the flints were buried showed that they date from around 100,000 years ago, proving Neanderthals were living in Britain at the time, even though the country had been assumed by scientists to be uninhabited during that period.

The island was occupied by early pre-Neanderthals, who were there before the last ice age, but were forced south by glaciation sometime around 200,000 year ago.  When the climate warmed up again, between 130,000 and 110,000 years ago, they couldn’t return because, similar to the present day, the sea-level in the English Channel was raised, blocking their path, or so scientists believed.  This discovery shows that they somehow returned earlier than the 60,000 years ago, that previous evidence suggested.

This piece was derived from an article by the University of Southampton (2010, June 1). “Neanderthals walked into frozen Britain 40,000 years earlier than first thought, evidence shows.” ScienceDaily. Retrieved June 1, 2010, from the following URL:
http://www.sciencedaily.com­/releases/2010/06/100601124124.htm.





Mendel’s Manuscript Mess

1 06 2010
Image of Gregor Mendel (1822-1884) the father of modern genetics

Gregor Mendel (1822-1884) the father of modern genetics

One of the most important manuscripts in modern science, long thought lost, has resurfaced in the middle of an ownership dispute.

The original manuscript of Gregor Mendel’s pea-breeding experiments, that allowed him to deduce the laws of heredity, thereby laying the foundations of modern genetics, has turned up in Germany after being missing for more than 50 years.

At the time it was published, Mendel was an Augustinian monk in the Abbey of St. Thomas, in the Austro-Hungarian city of Brünn, now Brno in the Czech Republic.

The importance of Mendel’s work was unrecognized by the international scientific community until 1900 (16 years after Mendel’s death).  The was due mostly to the fact that it was published in the rather obscure Journal of the Brünn Natural History Society.

Once discovered, however, it quickly became one of the most important articles in modern science.  This was because it was the first publised article to describe in detail how genetics operated, even though Mendel (and the rest of the world for that matter) knew nothing about DNA or other elements of genetics.  Indeed, it was Mendel’s paper that set the world on the road to discovering the whole of genetic theory.  In addition, Mendel’s experiment is often cited as one of the most elegant scientific experiments in history.

In an article published on Monday (June 31) in The New York Times, writer Nicholas Wade describes what happened to the orignal manuscript after it was published 1865.  According to Wade, the manuscript, the title of which translates into English as Experiments on Plant Hybridization, has been through a lot in the last 145 years.  It languished in the Brünn Natural History Society’s library until 1911, when it was discarded.  Saved from the trash by a local high school teacher, it was returned to the society’s files.  During World War II, a German botany professor (apparently part of the occupying force, who was in chage of the library) keep it in his briefcase.  Afterward, when Soviet forces occupied the area, it disappeared and was presumed destroyed.  Only in 1988 did it resurace, in the hands of a descendent of Mendel’s, who is also an Augustinian monk.  Since then, there have been competing claims to its ownership, with the monk’s order threatening to throw him out and even the German government getting involved.

For the complete story and the details of  the ownership controversy, please see the NY Times article, here.





Coastal Paleontologist Blogs on Early Seal Evolution

29 03 2010
This image is courtesy of Wikimedia Commons.  It is by Vivien Thiessen, and is licensed under the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

The comparative anatomy of an otariid seal and a phocid seal, both of which are discussed in Coastal Paleontologist’s blog piece.

The Coastal Paleontologist has a very interesting piece on early seal evolution.  It can be found at the following location:  Pinniped ancestry: the “Oligocene Seal” from South Carolina.

Following is the first paragraph from the blog, just as a teaser:

One of the most fascinating aspects of the study of marine mammals are the origins of the land to sea transition in various groups. Often marine mammals are so adapted for marine existence, that it is difficult to identify what group (fossil or modern) they descended from. Such has been the case with the origin of whales, for example. While I’m certainly interested in cetaceans, there has been a ton written about them, and I’m currently more intrigued by pinnipeds.





Energy Expenditure and Body Composition in Two Sympatric Lemurs does NOT Support Theories Accounting for Unusual Socio-Ecological Traits and Life History Features

27 03 2010
This image is from Wikimedia Commons and is in the Public Domain

Lemur Catta, also known as the Ring-tailed Lemur

In an article published March 25, in the Online journal PLoS one, researchers present evidence showing no support for the theory that energy conservation behaviors and mechanisms are the result of evolutionary adaptation in response to unusual socio-ecological traits and life history features of those species.

Following is the abstract from the article.  For the complete article, please see the following URL:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0009860.

Abstract

Background

Evolutionary theories that account for the unusual socio-ecological traits and life history features of group-living prosimians, compared with other primates, predict behavioral and physiological mechanisms to conserve energy. Low energy output and possible fattening mechanisms are expected, as either an adaptive response to drastic seasonal fluctuations of food supplies in Madagascar, or persisting traits from previously nocturnal hypometabolic ancestors. Free ranging ring-tailed lemurs (Lemur catta) and brown lemurs (Eulemur sp.) of southern Madagascar have different socio-ecological characteristics which allow a test of these theories: Both gregarious primates have a phytophagous diet but different circadian activity rhythms, degree of arboreality, social systems, and slightly different body size.

Methodology and Results

Daily total energy expenditure and body composition were measured in the field with the doubly labeled water procedure. High body fat content was observed at the end of the rainy season, which supports the notion that individuals need to attain a sufficient physical condition prior to the long dry season. However, ring-tailed lemurs exhibited lower water flux rates and energy expenditure than brown lemurs after controlling for body mass differences. The difference was interpreted to reflect higher efficiency for coping with seasonally low quality foods and water scarcity. Daily energy expenditure of both species was much less than the field metabolic rates predicted by various scaling relationships found across mammals.

Discussion

We argue that low energy output in these species is mainly accounted for by low basal metabolic rate and reflects adaptation to harsh, unpredictable environments. The absence of observed sex differences in body weight, fat content, and daily energy expenditure converge with earlier investigations of physical activity levels in ring-tailed lemurs to suggest the absence of a relationship between energy constraints and the evolution of female dominance over males among lemurs. Nevertheless, additional seasonal data are required to provide a definitive conclusion.





Scientist Shows Post-Mating Pre-Fertilization Barrier to Cross Species Breeding

25 03 2010

Daniel R. Matute of the department of ecology and evolution at the University of Chicago has published a study of two species of Drosophila, that show, for as far as I am aware the first time, the presence of postmating prezygotic isolation.  Specifically, that means a barrier or barriers that act after mating but before fertilization.

The paper appeared on March 23, in the online journal Public Library of Science (PLoS) Biology.  It is important from an evolutionary standpoint as a demonstration of the diversity of ways that reinforcement by gametic isolation can bolster isolation between species or proto-species.

Following is the abstract from the paper.  For the complete paper, please see the following URL:  http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1000341.

Abstract

Reinforcement, a process by which natural selection increases reproductive isolation between populations, has been suggested to be an important force in the formation of new species. However, all existing cases of reinforcement involve an increase in mate discrimination between species. Here, I report the first case of reinforcement of postmating prezygotic isolation (i.e., barriers that act after mating but before fertilization) in animals. On the slopes of the African island of São Tomé, Drosophila yakuba and its endemic sister species D. santomea hybridize within a well-demarcated hybrid zone. I find that D. yakuba females from within this zone, but not from outside it, show an increase in gametic isolation from males of D. santomea, an apparent result of natural selection acting to reduce maladaptive hybridization between species. To determine whether such a barrier could evolve under laboratory conditions, I exposed D. yakuba lines derived from allopatric populations to experimental sympatry with D. santomea, and found that both behavioral and gametic isolation become stronger after only four generations. Reinforcement thus appears to be the best explanation for the heightened gametic isolation seen in sympatry. This appears to be the first example in animals in which natural selection has promoted the evolution of stronger interspecific genetic barriers that act after mating but before fertilization. This suggests that many other genetic barriers between species have been increased by natural selection but have been overlooked because they are difficult to study.