Sunday, November 26, 2006

A recent search for articles and papers providing evidence for evolution turned up a wide variety of examples.

Evolution of typhoid bacteria
This is fairly technical and I'm not qualified to sumarize it or elaborate on the evidence, but the opening summary reads as follows:

In a study published in the latest issue of Science (24 November, 2006), an international consortium from the Max-Planck Society, Wellcome Trust Institutes in Britain and Vietnam, and the Institut Pasteur in France have elucidated the
evolutionary history of Salmonella Typhi. Typhi is the cause of typhoid fever, a disease that sickens 21 million people and kills 200,000 worldwide every year. The results indicate that asymptomatic carriers played an essential role in the evolution and global transmission of Typhi.

Clearly, these biologists have no difficulty understanding this disease in terms of evolution, and we are fortunate for this, as they are working to keep us one step ahead of diseases that clearly demonstrate a propensity to evolve. This is a growing problem in hospitals, since strains of bacteria are evolving that are not killed by standard antibiotics.

This article opens, "Virginia scientists are finding pockets of oysters in the Chesapeake Bay that have adapted to genetically resist the deadly diseases that threaten the broader population. 'We have what appears to be an evolution of disease-resistant oysters,' said Ryan Carnegie, an assistant research scientist at the Virginia Institute of Marine Science." This shows the other side of the "arms race" between bacteria and the organisms they infect. Some have even suggested that this to some extent accounts for continuing evolution rather than a steady-state situation in which all organisms have evolved to some peak level of survival ability.
Wheat's lost gene helps nutrition

Domesticated varieties of wheat have a gene that normally is not turned on. That is, the gene is present, but another gene is needed to turn it on, so that it acts on the development of the plant. By figuring out a way to turn this gene on, scientists have increased the nutritional quality and decreased the time to reach maturity. For those worried about eating genetically modified foods, the scientists have found a way to turn the gene on by cross-breeding domestic and wild strains of wheat. This may help improve the nutrition for people all over the world. These kinds of advances can never be provided by "intelligent design" theory. How would you predict something like this if you had no way to fathom the designs created by this intelligent designer?

New Gene Map Reveals Surprising Differences

This article reports on a new way of comparing gene maps that picks up on subtle differences from individual to individual in something called 'copy number variants' or CNPs. This may be a revolutionary development because it may enable scientists to identify genetic causes of certain diseases. This says to me that the genetic reproduction process is very complex and so there can be lots of variation before something becomes significant enough to cause an evolutionary change.

Evolution can happen quickly, study finds

I'll quote the first few paragraphs, since they say better than I many important points about evolution and how new research is confirming the theory, rather than challenging it.

A new study of lizards in the Bahamas shows that the natural selection pressures that drive evolution can flip-flop faster than previously thought -- even in months.

"Darwin was right about so many things," said Jonathan Losos, a former Washington University biologist who led the study. "In this case he was wrong. He thought that evolution must occur slowly and gradually."

The lizards and their changing leg lengths are yet another case of evolution occurring in real time. From finches that evolve longer beaks in a few years to bacteria that adapt to strange feeding regimens in days, evolution, as a science, has leapt out of musty museums and into the field. Scientists say that, from a political perspective, the cases offer a vivid reminder of the continuous process that some people imagine proceeding only in fossilized fits and starts: first monkey, then man.

The article goes on to describe science at work, testing hypotheses, improving theories. Scientists measured leg length of a lizard on various islands in the Bahamas. Then they introduced a predator and used evolution to predict how the lizards' legs would change in response. They thought the legs would grow longer initially, since the longer legs would allow the normally ground-dwelling lizards better chances to survive by running up trees. Once the population had lived in the trees a while, however, they expected leg length to decrease again, as it provides a better way to get around in the trees. They found the predicted changes.

For another example of how scientists are testing and verifying evolution, see the next article.

Robot Tadpole Sex Sheds Light on Vertebrate Evolution

Quoting the first few paragraphs:

The distant forebears of humans and other vertebrates were much squashier than their descendants. They possessed flexible rods known as notochords that served as primitive backbones, but no vertebrae. Scientists think vertebrae evolved to
help our ancient predecessors swim more powerfully by stiffening the body so attached muscles could generate more force.

"The fossil record shows vertebrae evolved independently at least four separate times. That shows they must really be functionally important," said vertebrate physiologist John Long at Vassar College in Poughkeepsie, N.Y.

To test this idea, Long and his colleagues built robot fish with backbones of varying strength to simulate extinct animals. They then "mated" the best swimmers to see how generations of "offspring" evolved to swim better.

Here again, a test of the idea of evolution, with no guarantee that the results would confirm the hypothesis. This is a physical version of something that is often done on computers, creating "genetic algorithms." It demonstrated that the hypothesis was confirmed. The faster swimmers, when "mated," (that is when "computer simulations that modeled the genetic mixing that occurs during sex to produce the next generation" were used to generate new designs for the swimmers), produced a structure that does stiffen the region down the center where the spinal cord would be in primative organisms.

But they also found that the hypothesized evolution only accounted for 40% of the improved swimming speed. Evolution found other ways which the scientists had not thought of to improve the "design" of the model. They plan to introduce a robot predator to test how well visual sensing device similar to something in fish can improve through evolution.

0 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home