Is Evolution Truly Random?

This week's NY Times is a treasure trove of science articles. This is one of them: http://www.nytimes.com/2003/11/11/sc...html?tntemail1

For those who can't access the page, here is the article:

"In nearly every life, there is a moment when a person realizes, with a shudder, how easily she might never have come to be: how her parents nearly missed meeting, or how some other critical genealogical event almost didn't happen.
In the same way, evolutionary biologists have pondered one of their most intractable questions: how much of the living world is here by chance, and might not evolve, if time were turned back and evolutionary history played out again?

A few scientists have begun finding ingenious ways to test the repeatability of evolution. And they are finding that what they thought were the random vagaries of evolution are not so random at all.

"There's a lot of phenomenal data coming out," said Dr. Loren H. Rieseberg, an evolutionary biologist at Indiana University. "There's clearly more to repeatability than we'd suspected a decade ago."

Dr. Richard E. Lenski, an evolutionary biologist at Michigan State, said, "A lot of studies are finding quite a lot of surprising replicability of evolutionary outcomes."

Dr. Stephen Jay Gould, the late Harvard paleontologist, crystallized the question in his book "Wonderful Life." What would happen, he asked, if the tape of the history of life were rewound and replayed? For many, including Dr. Gould, the answer was clear. He wrote that "any replay of the tape would lead evolution down a pathway radically different from the road actually taken."

In fact, to many scientists, it would seem impossible to re-evolve anything like life on earth today, given how life has been shaped by accidents large and small.

But 12 flasks of bacteria in East Lansing, Mich., are beginning to challenge such notions. In 1988, Dr. Lenski and his colleagues set up a dozen genetically identical populations of E. coli bacteria in bottles of broth and have followed their evolutionary fates.

Now, more than 30,000 bacterial generations later, Dr. Lenski and colleagues have what is becoming one of the most striking examples of repeatability yet. All 12 populations show the same patterns of improvement in their ability to compete in a bottle and increases in cell size. All 12 have also lost their ability to break down and use a sugar, called ribose.

More surprising, many genetic changes underlying these adaptations are very similar. Every population, for example, lost its ability to break down ribose by losing a long stretch of DNA from the same gene.

Other scientists studying cichlid fish have observed how the same varieties of cichlids evolve anew every time they invade a new lake. And Dr. Rieseberg and colleagues have found evidence that evolution can repeatedly produce the same species.

These scientists found that one sunflower species on sand dunes has evolved independently three separate times. And each time one of the species newly evolves, genetically it appears to turn out much the same. "With these species, there seems to be only one way to do it," Dr. Rieseberg said.

Some scientists, like Dr. Simon Conway Morris, a paleobiologist at the University of Cambridge and ardent critic of Dr. Gould's view, say the evidence for repeatability is rampant. He argues in his new book, "Life's Solution: Inevitable Humans in a Lonely Universe," that some features are so adaptive that they are essentially inevitable — like the ability to see and, as his title suggests, the intelligence and self-awareness that are the hallmarks of humanity.

Still, scientists say that experimental populations evolving in parallel are not identical. For example, the genetic changes underlying identical adaptations in different populations can differ, even if in minute detail. Are these the subtle differences that could send evolution down a different path?

Only the definitive experiment which remains beyond the scope of the National Science Foundation budget can say.

"What we need are about 1,000 worlds to play evolution back correctly," Dr. Rieseberg said. "Then we can really find out what would happen." "

Basically, what we have is that the physics of the universe sets limits on the designs that will work. There are several genomes that will give those designs, but in the end you need the designs to cope with the environment.

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"If sound science appears to contradict the Bible, we may be sure that it is our interpretation of the Bible that is at fault." Christian Observer, 1832, pg. 437

"Christians should look on evolution simply as the method by which God works." Rev. James McCosh, theologian and President of Princeton, 1890

interesting, but it does seem quite obvious to me that those sorts of things would happen to those kinds of organisms. perhaps it is just lack of imagination on my part since I come from a sample size of 1.

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MSci MSc ARCS DIC PhD..... yes, I am bragging.

You know, this fits in somewhat with one of the alternative theories of human evolution which argues that h. Sapiens evolved independently in isolated regions from a common, pre- h. Sapien ancestor. This is in contrast with the competing "out of Africa" theory which has all h. Sapiens developing in one place, then spreading out.

A recent Scientific American issue on human evolution sets out the competing theories in two different articles.

This is a strange parallel with Star Trek's theory of why all their characters are human-like (besides the fact that the actors are human). They said that adaptability and evolution each led to this form of sentient life.

I thought that it was a little unrealistic, but it now seems a possibility.

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I thought they explained it in one episode where we were all seeded from one ancestor. oh well, that's ST for you. personally I don't see it working that tightly really though. while bilateral symmetry has alot of sense, I see no problem with multiple limbs and so on.

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MSci MSc ARCS DIC PhD..... yes, I am bragging.

I wouldn't mind having a third arm, myself...

Originally Posted by Vance

You know, this fits in somewhat with one of the alternative theories of human evolution which argues that h. Sapiens evolved independently in isolated regions from a common, pre- h. Sapien ancestor. This is in contrast with the competing "out of Africa" theory which has all h. Sapiens developing in one place, then spreading out.

A recent Scientific American issue on human evolution sets out the competing theories in two different articles.

Not really. Notice that the species of bacteria are not identical or evolving toward a single species. The sunflower paper shows that a species forming by hybridization has only one stable genome to go to.

But, Multiregional has never been seen in any other species that I can see. That is, that semi-isolated populations over a wide geographical area all simultaneously undergo anagenesis to a new common species. What happens instead is that either 1) each population becomes a new species under disruptive selection or 2) one isolated population undergoes directional selection to form a new species which then replaces the populations of the original species. The second is, of course, Out of Africa.

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"If sound science appears to contradict the Bible, we may be sure that it is our interpretation of the Bible that is at fault." Christian Observer, 1832, pg. 437

"Christians should look on evolution simply as the method by which God works." Rev. James McCosh, theologian and President of Princeton, 1890

Originally Posted by Michali

This is a strange parallel with Star Trek's theory of why all their characters are human-like (besides the fact that the actors are human). They said that adaptability and evolution each led to this form of sentient life.

I thought that it was a little unrealistic, but it now seems a possibility.

STNG explained that all the humanoid species were descended from an ancestral species that seeded the inhabitable planets. Thus the similarity of DNA such that many of the humanoid species could interbreed with little or no genetic manipulation.

However, the requirements for tool use may dictate that the design be similar.

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"If sound science appears to contradict the Bible, we may be sure that it is our interpretation of the Bible that is at fault." Christian Observer, 1832, pg. 437

"Christians should look on evolution simply as the method by which God works." Rev. James McCosh, theologian and President of Princeton, 1890

must.....resist....jokes.....about.....third......leg........

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MSci MSc ARCS DIC PhD..... yes, I am bragging.

The results are interesting no doubt, but there are plenty of examples of similar solutions arising in completly different fashions. See Gould's book on the Panda's Thumb.

But as to whether human-like beings are inevitable, I'm with Gould and think the chances of anything like us arising again get less and less likely as the clocks get rolled back further and further. How many mamalian species have failed to develop intelligence? Those that do posess some intelligence don't appear to have been selected for more intelligence. Add to that the millions of years that dinosaurs have flourished without any selective pressure for intelligence.

Take flight: it has arisen independantly a number of times in a number of different ways (insects, birds, bats, flying squirrels, flying fish), and has progressed to different points. In each, it was likely the side-effect of other changes. First, some initial changes were necessary which would directly help the organism (temperature control, for example) which could, as a side-effect, provide some limited flight and allow selective pressures to work.

But after the history of all life on this planet, we appear to be the only creature who was able to gain enough intelligence (in the right place, in the right time) to allow selection for intelligence itself. I don't think there's any good reason to imagine that this is an inevitable or even a predictable outcome.

Again, going back to Gould, he shows the fossil life of the Burgess Shale and asks whether survival after an extinction event could be determined but he throws his hands up in figurative despair. As we trace back our origins, it quickly becomes humble and obscure, lost in the might of the giants of the dinosaur age. Can anyone show that our ancestors were somehow better adapted for survival? What if a smaller meteor hit, or a bigger one? In a different place? The centre of a continent instead of the Yucutan?

While some mutations may arise time and time again, and some forms arise in different ways in different animals, I don't think that eliminates the huge factor of chance and randomness which has influenced the individual mutations in species, and their ultimate survival.