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Monday, 27 October 2008

Evolution is not dead!

Yep, kisses for all the creationists around :) Seriously, I think people underestimate the power of evolution as a scientific method and theory. Now, you can see some of its strengths. It's about 3 experiments that led to very exciting information.
First, the sexual evolutions got confirmed (or it looks like it)-which means that some traits of our physiology may not be biologically useful-those that are sexually useful, but in strong competition, they are passed to the generation. Second, an intermediate brink of the evolution from the oceans gives new ideas on how life changed to accommodate the new environment. And third, and very very awesome, a new experiment proves that life is not so hard to create from "dead" matter. Enjoy the articles, they are soooooo exciting.

“Other half” of Darwin’s theory passes test

Oct. 13, 2008
World Science staff

Some flir­ta­tious yeast cells have con­firmed a part of Charles Dar­win’s the­o­ry of ev­o­lu­tion that was nev­er tested as suc­cess­fully as the rest of the the­o­ry, bi­ol­o­gists say.

This some­what spe­cial part of the the­o­ry is the con­cept of ev­o­lu­tion through “sex­ual se­lec­tion.”

In gen­er­al, ev­o­lu­tion­ary the­o­ry holds that spe­cies grad­u­ally change be­cause of cer­tain mu­ta­t­ions that spread through their po­p­u­la­t­ions. These mu­ta­t­ions spread if, and only if, they’re ben­e­fi­cial—so that in­di­vid­u­als pos­sess­ing them sur­vive long­er, re­pro­duce more or both. Thus the mu­tat­ed trait ap­pears in­creas­ingly of­ten in suc­ceed­ing genera­t­ions.

Ev­o­lu­tion has been ob­served in ac­tion nu­mer­ous times, be­cause in short-lived spe­cies, many forms of ev­o­lu­tion oc­cur fast enough for hu­mans to watch the changes oc­cur.

But one form of ev­o­lu­tion has not been di­rectly seen: ev­o­lu­tion through sex­u­al se­lec­tion, notes a pa­per in the Oct. 7 on­line is­sue of the re­search jour­nal Pro­ceed­ings of the Roy­al So­ci­e­ty B.

This va­ri­e­ty of ev­o­lu­tion is what bi­ol­o­gists be­lieve ac­counts for the ap­pear­ance of sex­u­al-advertising traits such as a pea­cock’s bright tail, or per­haps mu­si­cal abil­ity.

Such traits are be­lieved to evolve for much the same rea­son as oth­ers: those who have a cer­tain char­ac­ter­is­tic mate more, and thus spread the genes for that fea­ture. The chief dif­fer­ence be­tween this form of ev­o­lu­tion and oth­ers is that with sex­u­al se­lec­tion, the driv­ing fac­tor in the pro­cess is sex­u­al com­pe­ti­tion, rath­er than oth­er ex­i­gen­cies of sur­viv­al more gen­er­ally.

Sex­u­al se­lec­tion is an in­tri­guing as­pect of ev­o­lu­tion be­cause it drives the ev­o­lu­tion of traits that on their face, seem less than clearly ben­e­fi­cial, said Dun­can Greig of Uni­ver­s­ity Col­lege in Lon­don, one of the pa­per’s au­thors.

“For ex­am­ple a pea­cock’s tail might be con­spic­u­ous to preda­tors,” he not­ed in an e­mail. Or for a hu­man equiv­a­lent: “Fer­rari drivers might be more likely to end up splat­ted against a tree than Buick drivers.” For both ex­am­ples, “the sim­ple ex­plana­t­ion is that the cost is more than bal­anced by the ben­e­fit of ex­tra mat­ing.”

In the new pa­per, Greig, along with Da­vid W. Rog­ers of Im­pe­ri­al Col­lege in Lon­don, claim to have ob­served ev­o­lu­tion through sex­u­al se­lec­tion for the first time. “Our yeast sys­tem is a pow­er­ful tool for in­ves­ti­gat­ing the ge­net­ics of sex­u­al se­lec­tion,” they wrote.

Yeast cells oc­cur in two dif­fer­ent mat­ing types, some­what akin to male and fema­le. Each type sig­nals to po­ten­tial part­ners of the oth­er type by pro­duc­ing an at­trac­tive chem­i­cal, called a pher­o­mone. But cells vary widely in how strongly they can sig­nal; the dif­fer­ences are ge­net­ic.

Rog­ers and Greig en­gi­neered one of the “sex­es” of yeast cells, called MAT-alpha, to have ei­ther very high or very low sig­naling strength. They then mixed both types of cells with those of the op­po­site “sex” group, called MATa. This mix­ing was done in two dif­fer­ent ways: in one, the MAT-alpha cells were few, and so faced lit­tle com­pe­ti­tion among each oth­er; in the oth­er, they were many, so that they faced tough com­pe­ti­tion for mat­ing op­por­tun­i­ties.

Only un­der the high-com­pe­ti­tion situa­t­ion, the strong-sig­nalling gene var­i­ant spread quickly through the popula­t­ion at the ex­pense of the weak-sig­nalling var­i­ant, Rog­ers and Greig found. This matched the pre­dic­tions of sex­u­al se­lec­tion the­o­ry, they added. source

My comment: That is absolutely awesome! I mean they really have saw it! That's so unbelievable. And in such a simple way. Simply amazing. That's what science is about. Proving complicated things in elegant way.

Head skeleton sheds light on intermediate steps

October 15, 2008

New research has provided the first detailed look at the internal head skeleton of Tiktaalik roseae, the 375-million-year-old fossil animal that represents an important intermediate step in the evolutionary transition from fish to animals that walked on land.

Results of the study, published in this week's issue of the journal Nature, show that the transition from aquatic to terrestrial lifestyle involved complex changes not only to appendages (fins to limbs) but also to the internal head skeleton.

"Exquisite specimens of Tiktaalik roseae discovered several years ago continue to function as rosetta stones for understanding the emergence of quadripeds on land," said H. Richard Lane, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research.

A team co-led by scientist Ted Daeschler at the Academy of Natural Sciences in Philadelphia discovered Tiktaalik roseae (tik-TAHL-ik RO-zay) in 2004, in Devonian-age rock on Ellesmere Island in Canada, more than 700 miles above the Arctic Circle.

The creature was a large aquatic predator with a flattened head and body.

The body plan and nature of the deposits where the fossils were found suggest an animal that lived on the bottom in shallow water, and perhaps out of the water for short periods.

Tiktaalik roseae has features of the skull, neck, ribs and appendages that are shared with the earliest limbed animals (tetrapods), as well as fishlike features such as scales and fin rays. This mosaic of features makes it a textbook example of a transitional fossil, say paleontologists.

Jason Downs, a scientist at the Academy of Natural Sciences and lead author of this week's paper, said the examination of the internal head skeleton further demonstrates the intermediacy of Tiktaalik roseae.

"The braincase, palate and gill arches of Tiktaalik help reveal the pattern of evolutionary change in this part of the skeleton," said Downs. "We see that cranial features once associated with land-living animals were in fact the first adaptations for life in shallow water."

"The gradual evolutionary transition from fish to tetrapod, and the transition from aquatic to terrestrial lifestyles required much more than the evolution of limbs," said Daeschler. "The head of these animals was becoming more solidly constructed and, at the same time, more mobile with respect to the body across this transition."

Trends in head shape include a flattening of the skull and a lengthening of the snout.

Using several well-preserved specimens of Tiktaalik roseae, the research helps document the relative timing of the particular skeletal changes associated with changes in head shape.

"We used to think of this transition of the neck and skull as a rapid event, largely because we lacked information about the intermediate animals," said Neil Shubin of the University of Chicago, who co-led the team that discovered Tiktaalik roseae. "Tiktaalik neatly fills this morphological gap, and helps to resolve the timing of this complex transition."

During this transition, interactions among the different parts of the head skeleton also were changing.

"Fish in deep water move and feed in three-dimensional space, and can easily orient their bodies in the direction of their prey," said Farish Jenkins, Jr., an evolutionary biologist at Harvard University and co-author of the paper. "A mobile neck is advantageous in settings where the body is relatively fixed, as is the case in shallow water and on land." source

My comment: Nice, nice, nice. I wonder what would a undersea human would look like. They claim fixed head is ok in 3D, but after all, it depends on the environment, more precisely the predators they have to evade. It's not so simple I guess. And if the "thing" has to live in water and on the Earth, then it gets even more complicated. But it's so nice to see they found that intermediate level. And that evolution still get some attention.

New Results from a 1953 Experiment Offer Hints to the Origin of Life

Vials holding the results of a famous chemistry experiment conducted 55 years ago have been discovered in dusty cardboard boxes, and a new analysis of their contents has revealed fresh insights into a big question: the origin of life on earth. In 1953, chemist Stanley Miller tried to duplicate the conditions present on the primordial earth in laboratory flasks, and while some of his results were published to great acclaim, other results were packed away and forgotten–until now.

Miller’s classic experiment involved putting atmospheric components thought to reflect those of the early Earth (ammonia, hydrogen, methane, and water) in a closed system and stimulating that mixture with an electric current to mimic the effects of lightning storms. He generated a small number of biochemically significant compounds, including amino acids, hydroxy acids, and urea, showing that conditions of primitive earth can create the building blocks of life [Ars Technica]. These results generated considerable excitement, but later researchers argued that Miller was wrong about the composition of the young earth’s atmosphere, and the experiment was written off as a novelty.

In the new study, published in Science , researchers analyzed vials of material that were produced by a slightly different process that Miller had viewed as a flop; in that process, the gases were also mixed with a jet of steam to replicate conditions around an erupting volcano. Using modern methods to analyze the samples, researchers found they contained a total of 22 amino acids (including some that Miller had never identified in any of his experiments), the most complex mix yet produced by Miller’s method.

Study coauthor Jeffrey Bada, who was a graduate student of Miller’s, says the findings suggest that life could have originated on earth in the fiery and turbulent regions around volcanoes. “The model is that you have these small pockets, volcanic hot spots,” explains Bada, in which a volatile reducing atmosphere, one in which chemicals are more likely to react with one another, may have produced amino acids. The team’s reanalysis makes it plausible that a shallow tide pool tucked into the side of a volcano and a fortuitous bolt of lightning could have led to an abundance of amino acids [Science News].

However, theories on the origin of life have moved on since the days of Miller’s original experiments, and have taken decidedly new directions. The discovery of amino acids in meteorites suggested that the building blocks of life came from space, eliminating the need for finding chemical processes that could produce them on Earth. Some scientists have since suggested places like the ocean bottom as most likely to be where the building blocks first came together as a living organism…. “My take on this is you want to consider everything,” Dr. Bada said. source

My comment:And my opinion is that life is obviously much more common than we think. If we can produce its building blocks with 2 different processes, how many more we're missing? And that's even without the clear understanding what life is.

The comment I left on the site:
If you can recreate building blocks of life with two different experiments, imagine how much Nature can do. On every planet, on all the different situations-volcano, particles emissions on the poles, earthquakes, lightnings- you name it.
For me, this experiment proves that life is much more common than we think. And probably that the whole theory that something brought "it" is wrong, because maybe it wasn't a single lucky even, but a multiplicity of events-from above, from below, from everywhere, that sparkled and spread over, some died away, some evolved and in the end-we had so much life, it simply flourished.
Why it doesn''t happen everywhere? Two possible reasons: A) it requires some basic elements and you can find it where they are present-unlikely since on Earth there are bacteria like everywhere. B) it is all around, we just can't see it so easily, because it's based on different building blocks or is on different scale-too big or too small.
In any case, Mars exploration is going on, Europa is also a good candidate for life, so sooner or later, we'll find out how common life in space is.

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