http://www.sun-sentinel.com/news/opinion/sfl-forum09darwinpnfeb09,0, 2858696.story

By Robert McCarthy

February 9, 2009

Feb. 12 marks the 200th anniversary of the birth of Charles Darwin, and 2009 marks the 150th anniversary of the publication of On the Origin of Species. This double-anniversary is the perfect opportunity to assess the impact of Darwin’s ideas on the modern world.

Darwin’s theory is both simple and elegant — adjectives describing the best and most convincing scientific ideas. One hundred and fifty years ago, scientists knew that the Earth was very old, that human births greatly outnumber food supply, and that physical characteristics can be selectively bred in domestic animals. Darwin tied together these disparate observations in a theory, natural selection, that explained how evolution occurred — in short, organisms better adapted to their environment to prosper, contributing a greater proportion of their genes to future generations. Over millennia, these genetic changes give rise to new species.

Darwin’s theory is the centerpiece of modern biology. In the 150 years since its publication, paleontologists have discovered transitional forms (such as Archaeopteryx, a feathered dinosaur) that provide the “missing link” between two species, while other researchers have observed natural selection occurring in both the wild and under laboratory conditions. Of course, scientists have also shown that evolution occurs via other mechanisms and at different levels. These advances expand on Darwin’s original theory without invalidating its central premise.

Darwin’s theory has always been controversial. According to a recent poll, fewer than 50 percent of Americans believe that humans evolved from an earlier species of animal. In Florida, the word “evolution” was only added to the K-12 science standards last year! Despite overwhelming evidence to the contrary, many Americans believe that the world was created 6,000 years ago — and that religious ideas should be taught alongside evolutionary theory in public school science classes. However appealing they may be in other respects, religious convictions are not scientific theories. In science, theories such as evolution (and gravity) are equivalent to fact, and based on more than belief and conviction.

The theory of natural selection is one of the greatest, most misunderstood ideas ever wrought by human intellect. If Charles Darwin were alive to make a wish on his birthday, I think he might have asked for greater scientific literacy, starting with the teaching of facts like evolution in public schools. We owe it to Charles Darwin, and to our children, to see that he gets his wish.

Robert McCarthy is assistant professor of anthropology at Florida Atlantic University.

http://www.world-science.net/exclusives/081013_selection.htm

“Other half” of Darwin’s theory passes test

Oct. 13, 2008 World Science staff

Some flir ­ta ­tious yeast cells have con ­firmed a part of Charles Dar ­win’s the ­o ­ry of ev ­o ­lu ­tion that was nev ­er tested as suc ­cess ­fully as the rest of the the ­o ­ry, bi ­ol ­o ­gists say.

This some ­what spe ­cial part of the the ­o ­ry is the con ­cept of ev ­o ­lu ­tion through “sex ­ual se ­lec ­tion.”

One com ­mon ex ­ample of a re ­sult of evo ­lu ­tion through sex ­ual se ­lec ­t ­ion is the pea ­cock’s tail. (Im ­age cour ­tesy G. Ri ­ta ­ma)

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In gen ­er ­al, ev ­o ­lu ­tion ­ary the ­o ­ry holds that spe ­cies grad ­u ­ally change be ­cause of cer ­tain mu ­ta ­t ­ions that spread through their po ­p ­u ­la ­t ­ions. These mu ­ta ­t ­ions spread if, and only if, they’re ben ­e ­fi ­cial—so that in ­di ­vid ­u ­als pos ­sess ­ing them sur ­vive long ­er, re ­pro ­duce more or both. Thus the mu ­tat ­ed trait ap ­pears in ­creas ­ingly of ­ten in suc ­ceed ­ing genera ­t ­ions.

Ev ­o ­lu ­tion has been ob ­served in ac ­tion nu ­mer ­ous times, be ­cause in short-lived spe ­cies, many forms of ev ­o ­lu ­tion oc ­cur fast enough for hu ­mans to watch the changes oc ­cur.

But one form of ev ­o ­lu ­tion has not been di ­rectly seen: ev ­o ­lu ­tion through sex ­u ­al se ­lec ­tion, notes a pa ­per in the Oct. 7 on ­line is ­sue of the re ­search jour ­nal Pro ­ceed ­ings of the Roy ­al So ­ci ­e ­ty B.

This va ­ri ­e ­ty of ev ­o ­lu ­tion is what bi ­ol ­o ­gists be ­lieve ac ­counts for the ap ­pear ­ance of sex ­u ­al-advertising traits such as a pea ­cock’s bright tail, or per ­haps mu ­si ­cal abil ­ity.

Such traits are be ­lieved to evolve for much the same rea ­son as oth ­ers: those who have a cer ­tain char ­ac ­ter ­is ­tic mate more, and thus spread the genes for that fea ­ture. The chief dif ­fer ­ence be ­tween this form of ev ­o ­lu ­tion and oth ­ers is that with sex ­u ­al se ­lec ­tion, the driv ­ing fac ­tor in the pro ­cess is sex ­u ­al com ­pe ­ti ­tion, rath ­er than oth ­er ex ­i ­gen ­cies of sur ­viv ­al more gen ­er ­ally.

Sex ­u ­al se ­lec ­tion is an in ­tri ­guing as ­pect of ev ­o ­lu ­tion be ­cause it drives the ev ­o ­lu ­tion of traits that on their face, seem less than clearly ben ­e ­fi ­cial, said Dun ­can Greig of Uni ­ver ­s ­ity Col ­lege in Lon ­don, one of the pa ­per’s au ­thors.

“For ex ­am ­ple a pea ­cock’s tail might be con ­spic ­u ­ous to preda ­tors,” he not ­ed in an e ­mail. Or for a hu ­man equiv ­a ­lent: “Fer ­rari drivers might be more likely to end up splat ­ted against a tree than Buick drivers.” For both ex ­am ­ples, “the sim ­ple ex ­plana ­t ­ion is that the cost is more than bal ­anced by the ben ­e ­fit of ex ­tra mat ­ing.”

In the new pa ­per, Greig, along with Da ­vid W. Rog ­ers of Im ­pe ­ri ­al Col ­lege in Lon ­don, claim to have ob ­served ev ­o ­lu ­tion through sex ­u ­al se ­lec ­tion for the first time. “Our yeast sys ­tem is a pow ­er ­ful tool for in ­ves ­ti ­gat ­ing the ge ­net ­ics of sex ­u ­al se ­lec ­tion,” they wrote.

Yeast cells oc ­cur in two dif ­fer ­ent mat ­ing types, some ­what akin to male and fema ­le. Each type sig ­nals to po ­ten ­tial part ­ners of the oth ­er type by pro ­duc ­ing an at ­trac ­tive chem ­i ­cal, called a pher ­o ­mone. But cells vary widely in how strongly they can sig ­nal; the dif ­fer ­ences are ge ­net ­ic.

Rog ­ers and Greig en ­gi ­neered one of the “sex ­es” of yeast cells, called MAT-alpha, to have ei ­ther very high or very low sig ­naling strength. They then mixed both types of cells with those of the op ­po ­site “sex” group, called MATa. This mix ­ing was done in two dif ­fer ­ent ways: in one, the MAT-alpha cells were few, and so faced lit ­tle com ­pe ­ti ­tion among each oth ­er; in the oth ­er, they were many, so that they faced tough com ­pe ­ti ­tion for mat ­ing op ­por ­tun ­i ­ties.

Only un ­der the high-com ­pe ­ti ­tion situa ­t ­ion, the strong-sig ­nalling gene var ­i ­ant spread quickly through the popula ­t ­ion at the ex ­pense of the weak-sig ­nalling var ­i ­ant, Rog ­ers and Greig found. This matched the pre ­dic ­tions of sex ­u ­al se ­lec ­tion the ­o ­ry, they added.

“We have tested the sim ­plest pos ­si ­ble sex ­u ­al se ­lec ­tion sce ­na ­rio,” they wrote. “Ob ­serv ­ing the real time ev ­o ­lu ­tion of nov ­el sex ­u ­ally se ­lected traits, and pref ­er ­ences for them, is the ul ­ti ­mate test for sex ­u ­al se ­lec ­tion the ­o ­ry.”

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http://www.lethbridgeherald.com/content/view/26421/92/

Darwin’s theories stand test of time Written by Dan Johnson Saturday, 27 December 2008

On Dec 27, 1831, a wooden ship sailed from Plymouth, England, on a voyage of exploration. Aboard was 22-year-old Charles Darwin, recently graduated and pleased with the dream job he had secured as the naturalist on the HMS Beagle. The four-year trip around the world was in part meant to document the surprisingly different sets of species in separated regions. During the trip, Darwin found many previously unknown mammals, birds, insects, plants, crustaceans, fish and fossils. When he returned to England, his experiences provided the basis for his popular books on geology and natural history. Darwin never left England again. After decades of further study in his home lab and library, Darwin presented a simple but shocking idea that has stood the tests of science and time.

Darwin was a thoughtful observer of nature, who wrote detailed accounts of many living things. Nonetheless, he was a regular person, who even made blunders (like forgetting to label his collections of the famous Galapagos Finches with the names of the exact islands each came from). Although he spent long hours with books and a microscope, he also enjoyed playing billiards, raising pigeons and collecting beetles. He and his wife Emma had 10 children who were witness to his fascination for living things.

The children were so familiar with his intense studies that one of his sons, while visiting a neighbour’s house and noting there was no lab, asked, “Where does your father do his barnacles?”

Given the enormous impact on science, and the public ruckus that ensued and still flares up, it might seem what Darwin had to say was strange and complicated. On the contrary, the idea is pure simplicity, and therein is the genius.

Darwin was well aware of the methods of selection used by animal breeders to produce new forms of livestock and pets. Selection of traits works because of the considerable genetic variation present in populations of living things, and because many of the traits of interest are inherited. Darwin saw that such variation exists in natural populations as well. A large surplus of offspring are produced by wild organisms, which are then reduced in number by limited resources, competition, harsh conditions, predators, parasites and pathogens. Only a fraction survives. The survivor traits are passed to the next generation, resulting in a slight shift in the typical traits in the breeding population. Slowly, the traits of those individuals who have the survival edge or some breeding advantage become more dominant in subsequent generations. Given enough time, this can produce new varieties and species. Changes in environmental conditions can result in new species similar to their ancestors in some ways, but better adapted to challenges.

The mechanism, “natural selection,” successfully explains changes seen in plants, animals and microbes over time. Darwin’s idea was the start of modern evolutionary theory.

By the way, theory means a body of knowledge, not that it is unproven. Someone who says evolution is “just a theory and not a law” has failed to grasp this most basic definition in science.

Evolutionary theory is no longer directed only at understanding how the living world came to its current state. It is opening new doors, including developing new medical technologies based on an understanding of genetic change and evolution of pathogens, and on our own genetic heritage. The science started by Darwin just might save your life.

Dan Johnson is professor of Environmental Science and Canada Research Chair (Evolution and Ecology) at the University of Lethbridge.