Born This Day: James Watson

From Today In Science History:

Watson was born on this day in 1928. An American geneticist and biophysicist, he shared the 1962 Nobel Prize for Physiology or Medicine (with Francis Crick and Maurice Wilkins) for the discovery of "the molecular structure of nucleic acids and its significance for information transfer in living material." Deoxyribonucleic acid (DNA) is the substance contained in cells that controls heredity.

Crick and Watson began their collaboration in 1951, and published their paper on the double helix structure on 2 Apr 1953 in Nature. This accomplishment became a cornerstone of genetics and was widely regarded as one of the most important discoveries of 20th-century biology.
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On This Day: AMNH Created

In 1869, the American Museum of Natural History in New York City was officially created with the signing of a bill by the Governor of New York, John Thompson Hoffman.

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The museum began from the efforts of Albert Smith Bickmore, one-time student of Harvard zoologist Louis Agassiz, who was successful in his proposal to create a natural history museum in New York City, with the support of William E. Dodge, Jr., Theodore Roosevelt, Sr., Joseph Choate, and J. Pierpont Morgan. It opened to the public 27 Apr 1871.

With a series of exhibits, the Museum’s collection went on view for the first time in the Central Park Arsenal, the Museum’s original home, on the eastern side of Central Park.

From Today in Science History.

Congratulations to Dr. David Evans!

David successfully defended his Ph.D. dissertation yesterday at the University of Toronto.

Things will slow down at the blog for the Easter weekend. But, we do have this sad news to report. Dr. Bruce Naylor, Director of the Royal Tyrrell Museum of Palaeontology, passed away last night. I’ll post along more details when I have them.

Hagfishes & Evolution

Hagfish embryology with reference to the evolution of the neural crest. 2007. K.G. Ota, et al. Nature 446: 672-675.

Abstract: Hagfish, which lack both jaws and vertebrae, have long been the subject of intense interest owing to their position at a crucial point in the evolutionary transition to a truly vertebrate body plan. However, unlike the comparatively well characterized vertebrate agnathan lamprey, little is known about hagfish development.

The hagfish may be either the sister group of all the other vertebrates (1), or that of lampreys (2). b, c, Hypotheses on neural crest evolution. b, The former hypothesis (1) would agree with the scenario that neural crest evolution had an intermediate epithelial state. c, Alternatively, the crest might have already been established as a population of delaminating cells in the common ancestor to all vertebrates, and this would be coherent with both hypotheses (1 or 2).

The inability to analyse hagfish at early embryonic stages has frustrated attempts to resolve questions with important phylogenetic implications, including fundamental ones relating to the emergence of the neural crest.

Here we report the obtainment of multiple pharyngula-stage embryos of the hagfish species Eptatretus burgeri and our preliminary analyses of their early development. We present histological evidence of putative neural crest cells, which appear as delaminated cells that migrate along pathways corresponding to neural crest cells in fish and amphibians. Molecular cloning studies further revealed the expression of several regulatory genes, including cognates of Pax6, Pax3/7, SoxEa and Sox9, suggesting that the hagfish neural crest is specified by molecular mechanisms that are general to vertebrates.

We propose that the neural crest emerged as a population of de-epithelialized migratory cells in a common vertebrate ancestor, and suggest that the possibility of classical and molecular embryology in hagfish opens up new approaches to clarifying the evolutionary history of vertebrates.

3.2 Billion-Year-Old Earth Had Strong Magnetic Field

Geomagnetic field strength 3.2 billion years ago recorded by single silicate crystals. 2007. JA Tarduno, et al. Nature 446: 657-660.

From the press release:

The Earth's magnetic field was nearly as strong 3.2 billion years ago as it is today. The findings, which are contrary to previous studies, suggest that even in its earliest stages the Earth was already well protected from the solar wind, which can strip away a planet's atmosphere and bathe its surface in lethal radiation.

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Theories of Earth's field say it's generated by the convection of our liquid iron core, but scientists have always been curious to know when Earth's solid inner core formed because this process provides an important energy source to power the magnetic field. Scientists are also interested in when Earth's protective magnetic cocoon formed.

Using a SQUID—a Superconducting Quantum Interface Device—researchers measured the magnetic fields of nano-meter sized magnetic inclusions in rocks that lock in a record of the Earth's magnetic field as they cool from molten magma to hard rock.

"The data suggest that the ancient magnetic field strength was at least 50 percent of the present-day field, which typically measures 40 to 60 microteslas," says Tarduno. "This means that a magnetosphere was definitely present, sheltering the Earth 3.2 billion years ago."

Doushantuo Embryos, Again

Doushantuo embryos preserved inside diapause egg cysts. 2007. L. Yin, et al. Nature 446: 661-663.

Abstract: Phosphatized microfossils in the Ediacaran (635–542 Myr ago) Doushantuo Formation, south China, have been interpreted as the embryos of early animals. Despite experimental demonstration that embryos can be preserved, microstructural evidence that the Doushantuo remains are embryonic and an unambiguous record of fossil embryos in Lower Cambrian rocks, questions about the phylogenetic relationships of these fossils remain.

a, Ericiasphaera magna, sample number XFHB-35. b, Appendisphaera tenuis, sample number XFHB-33. c–l, Tianzhushania spinosa; c–h, k, l sample number XFHB-2; i, j sample number XFHB-29. Panels c–h illustrate one (c), two (d, e), eight (f) and 16 (g, with greater detail in h) cell stages of preserved embryos within encompassing structures interpreted as diapause egg cysts; k, l, show details of wall structure in the specimens illustrated in c and g. Panel j, magnified in l, shows a Tianzhushania fossil from 632-Myr-old beds of the lower Doushantuo Formation.

Most recently, some researchers have proposed that Doushantuo microfossils may be giant sulphur-oxidizing bacteria comparable to extant Thiomargarita sp.

Here we report new observations that provide a test of the bacterial hypothesis. The discovery of embryo-like Doushantuo fossils inside large, highly ornamented organic vesicles (acritarchs) indicates that these organisms were eukaryotic, and most probably early cleavage stage embryos preserved within diapause egg cysts. Large acanthomorphic microfossils of the type observed to contain fossil embryos first appear in rocks just above a 632.5 0.5-Myr-old ash bed suggesting that at least stem-group animals inhabited shallow seas in the immediate aftermath of global Neoproterozoic glaciation.

Born This Day: Ralph A. Bagnold

April 3, 1896 - May 28, 1990

From the always excellent Today in Science History:

English geologist who was a leading authority on the mechanics of sediment transport, especially eolian (wind) transport. While serving as a soldier in Egypt prior to WW II, Bagnold first studied sand dune formation and movement. After retiring from the army (1935), he continued his research and wrote the book "Physics of Blown Sand and Desert Dunes", investigating the physics of particles moving through the atmosphere and deposited by wind.

Art © Darwyn Cooke. The Spirit © Estate of Will Eisner

He recognized two basic dune types, the crescentic dune, which he called "barchan," and the linear dune, which he called longitudinal or "sief" (Arabic for "sword"). During WW II, his avocational interest in vehicle performance on blowing sand aided the Allies in North Africa.

Vertebrate Evolution: Humans Closer To Sharks Than Teleost Fish

Survey sequencing and comparative analysis of the elephant shark (Callorhinchus milii) genome. 2007. B. Venkatesh, et al. PLoS Biol 5(4): e101.

From the press release:

Cartilaginous fishes (sharks, rays, skates, and chimaeras) are the phylogenetically oldest group of living jawed vertebrates. They are also an important outgroup for understanding the evolution of bony vertebrates such as human and teleost fishes.

The elephant shark genome, estimated to be about 910 Mb long, comprises about 28% repetitive elements. Comparative analysis of approximately 15,000 elephant shark gene fragments revealed examples of several ancient genes that have been lost differentially during the evolution of human and teleost fish lineages.

Interestingly, the human and elephant shark genomes exhibit a higher degree of synteny and sequence conservation than human and teleost fish (zebrafish and fugu) genomes, even though humans are more closely related to teleost fishes than to the elephant shark.

Unlike teleost fish genomes, the elephant shark genome does not seem to have experienced an additional round of whole-genome duplication. These findings underscore the importance of the elephant shark as a useful "model" cartilaginous fish genome for understanding vertebrate genome evolution.

See Jane. Read Jane.

The Discovery And Mystery of a Dinosaur Named Jane by Judith Williams.

A plug for my friend Judy’s new book on ‘Jane’ the tyrannosaur. Written for ages 9-12 it’s a good read of the young dino-fan in your life.

Another Kong Cartoon

Art © Steve Hickman

One more Kong cartoon via our friends at Atomic Surgery.

Chinook Center T. rex Albertosaurus

Photos © M. Ryan

While I was in Calgary recently I stopped into the Chinook Mall on the south side to photograph this T. rex made out of junk. I meant to write down the info on the sculptor, but didn't.

Update: Jordan Mallon informs me that it’s an Albertosaurus that was sculpted by Russell Zeid entirely of scraps from junkyards around Alberta.

Fish Feet

© Larry Gonick

Reader Sarda Sahney has a fun blog called FISH FEET that is worth visiting. Apparently Sarda is presently on a mysterious trip into the heart of India in search of ancient secrets--what wonders will she return with? All will be revealed on her blog....

Floral Gigantism Strikes Back

Floral Gigantism in Rafflesiaceae. 2007. C. C. Davis, et al. Science 315: 1812

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Abstract: Species of Rafflesiaceae possess the world's largest flowers (up to 1 meter in diameter), yet their precise evolutionary relationships have been elusive, hindering our understanding of the evolution of their extraordinary reproductive morphology.

We present results of phylogenetic analyses of mitochondrial, nuclear, and plastid data showing that Rafflesiaceae are derived from within Euphorbiaceae, the spurge family. Most euphorbs produce minute flowers, suggesting that the enormous flowers of Rafflesiaceae evolved from ancestors with tiny flowers.

Given the inferred phylogeny, we estimate that there was a circa 79-fold increase in flower diameter on the stem lineage of Rafflesiaceae, making this one of the most dramatic cases of size evolution reported for eukaryotes.

Return of the Giant Hogweed:

Mammoths With Hollow Feet

All photos © Kipling West

While I was in Calgary last week I had the pleasure of meeting up with two of the 7 Deadly Sinners, Tom Bagley and Kipling West. Kipling revealed that the Mammoth at the Calgary Zoo has hollow feet (probably related to its fibreglass nature) and kindly sent along these pix.

Hungry? Try some of Kipling's FRESH SPAM!

Classification of Geological Eras

In 1759, Italian geologist Giovanni Arduino (1714-1795) dated a letter to Professor A.Vallisneri the younger, in which Arduino proposed a classification of Earth's surface rocks according to four brackets of successively younger orders: Primary, Secondary, Tertiary and Quaternary. These are the four geological eras used today.

© Meyerowitz & Beard

The volcanic rocks without fossils which he saw in the Atesine Alps that formed the cores of large mountains he called Primary. Overlying them, the fossil rich rocks of limestone and clay that were found on the prealpine flanks of the mountains he called Secondary. The less consolidated fossil-bearing rocks of the subalpine foothills, he named Tertiary, and the alluvial rock deposits in the plains were the Quaternary. link.

The Golden Age of Dino Discoveries

From BBC News:

Peter Dodson & Steve Wang created a computer model that came up with an astonishing prediction--it estimated that the museums and research institutes in the world only hold around 30% of the dinosaur fossils that may exist - the other 70% are still in the ground.

"When we submitted our study, we knew of 527 kinds of dinosaur," he said.

"Based on what has gone before, we projected into the future and found that at some point - we can't say when, but sometime in the next century or two, when we've found all the dinosaurs out there to find - the total number will be about 1,850 genres, or kinds, of dinosaur."

Estimating the diversity of dinosaurs. 2006. S. C. Wang and P. Dodson. PNAS 103 (37): 13601-13605.

Abstract: Despite current interest in estimating the diversity of fossil and extant groups, little effort has been devoted to estimating the diversity of dinosaurs. Here we estimate the diversity of nonavian dinosaurs at 1,850 genera, including those that remain to be discovered. With 527 genera currently described, at least 71% of dinosaur genera thus remain unknown. Although known diversity declined in the last stage of the Cretaceous, estimated diversity was steady, suggesting that dinosaurs as a whole were not in decline in the 10 million years before their ultimate extinction. We also show that known diversity is biased by the availability of fossiliferous rock outcrop. Finally, by using a logistic model, we predict that 75% of discoverable genera will be known within 60–100 years and 90% within 100–140 years. Because of nonrandom factors affecting the process of fossil discovery (which preclude the possibility of computing realistic confidence bounds), our estimate of diversity is likely to be a lower bound.

Dead Dinos ≠ More Mammals

The delayed rise of present-day mammals. 2007. O. R. P. Bininda-Emonds, et al. Nature 446: 507-512.

Abstract: Did the end-Cretaceous mass extinction event, by eliminating non-avian dinosaurs and most of the existing fauna, trigger the evolutionary radiation of present-day mammals? Here we construct, date and analyse a species-level phylogeny of nearly all extant Mammalia to bring a new perspective to this question. Our analyses of how extant lineages accumulated through time show that net per-lineage diversification rates barely changed across the Cretaceous/Tertiary boundary. Instead, these rates spiked significantly with the origins of the currently recognized placental superorders and orders approximately 93 million years ago, before falling and remaining low until accelerating again throughout the Eocene and Oligocene epochs. Our results show that the phylogenetic 'fuses' leading to the explosion of extant placental orders are not only very much longer than suspected previously, but also challenge the hypothesis that the end-Cretaceous mass extinction event had a major, direct influence on the diversification of today's mammals.

Hey everyone, let’s put out a press release, and another one, and one more:

A new, complete 'tree of life' tracing the history of mammals on Earth shows that they did not diversify as a result of the death of the dinosaurs. It contradicts the previously accepted theory that the Mass Extinction Event that wiped out the dinosaurs 65 million years ago prompted the rapid rise of the mammals we see on the earth today.

Research shows that after the mass exteinxtion certain mammals did experience a rapid period of diversification and evolution. However, most of these groups have since either died out completely or declined in diversity.

The researchers believe that our 'ancestors', and those of all other mammals on earth now, began to radiate around the time of a sudden increase in the temperature of the planet – ten million years after the death of the dinosaurs.

Read the comment at Nature News.

FYI, the lead author is another fellow graduate (M.Sc., I think) from a few years back of the U of Calgary studying under Dr. A. P. Russell.

The tendonitis has improved so I'll be slowing bring the blog back up to speed, although I'll probably not hit 100% of what I was doing before.

New Mongolian Raptors

From LiveScience.com:

A new dromaeosaurid theropod from Ukhaa Tolgod (Ömnögov, Mongolia). 2006. Mark A. Norell et al. American Museum Novitates.

Tsaagan mangas was unearthed in 1993 but only recently identified as a new raptor species. Credit: Mark Norell

Tsaagan mangas, was found in the Ukhaa Tolgod region of Mongolia. Tsaagan was slightly larger than a turkey and its skull is one of the best preserved dromaeosaurid skulls ever found.

A small derived theropod from Öösh, early Cretaceous, Baykhangor Mongolia 2007. Alan H. Turner, et al. American Museum Novitates.

Fragments of a jawbone from the second raptor, Shanag ashile (above), was found in the Oosh region of Mongolia. It lived about 20 million years before Tsaagan and was probably much smaller, about the size of a small raven. Shanag likely resembled Microraptor, Turner said, a feathered bird-like dinosaur discovered in China that scientists think coasted between trees on two sets of wings.

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Monkey In The Mirror: Man's earliest ancestor had apelike face

Left: Dr. Richard Leakey’s reconstruction shows an erroneous vertical facial profile on a 1.9 million-year-old early human skull. Right: Bromage’s computer-simulated reconstruction shows the same skull with a distinctly protruding jaw. Green and red lines compare the location of the eyes, ears, and mouth, which must be in precise relationship to one another in all mammals. Credit: Dr. Timothy Bromage

From the press release:

A computer-generated reconstruction shows a 1.9 million-year-old skull belonging to Homo rudolfensis, the earliest member of the human genus, with a surprisingly small brain and distinctly protruding jaw, features commonly associated with more apelike members of the hominid family living as much as three million years ago.

Dr. Bromage's findings call into question the extent to which H. rudolfensis differed from earlier, more apelike hominid species. Specifically, he is the first scientist to produce a reconstruction of the skull that questions renowned paleontologist and archeologist Richard Leakey"s depiction of modern man"s earliest direct ancestor as having a vertical facial profile and a relatively large brain – an interpretation widely accepted until now.

Dr. Bromage's reconstruction also suggests that humans developed a larger brain and more vertical face with a less pronounced jaw and smaller teeth at least 300,000 years later than commonly believed, perhaps as recently as 1.6 million to one million years ago, when two later species, H. ergaster and H. erectus, lived. Dr. Bromage presented his findings today at the annual scientific session of the International Association for Dental Research in New Orleans.