Skip to comments.Evolution moves more quickly than scientists thought
Posted on 11/19/2006 1:00:27 PM PST by DaveLoneRanger
ST. LOUIS - Evolution happens. But it can also stop and turn on a dime.
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.
But for the scientists themselves, the cases show that evolutionary biology has, well, evolved into a predictive, experimental science like any other.
Losos had the perfect Petri dishes: 12 tiny islands in the Bahamas with small populations of insect-eating Anolis sagrei, six-inch long lizards that normally live on the ground but can adapt to life in trees.
On six of the islands, Losos introduced a predator, a large curly-tailed lizard that can gobble up the lizards. He theorized that at first, the fastest prey would survive as they ran for the trees. Natural selection would reward long legs. Then, as the little lizards adapted to life in trees, nimble twig maneuvers and shorter legs would be rewarded.
At the start of the experiment, the scientists, using dental floss nooses on the ends of 10-foot poles, caught all lizards and carefully measured their hind-limbs. After the first six months, their predictions held up. The average leg length of survivors was 2 percent longer than those that were killed. After a year, leg length was 3 percent shorter. The changes were small in absolute terms but statistically very large, said R. Brian Langerhans, a graduate student with Losos.
The study appeared Friday in the journal Science. Losos did the research while at Washington University, but left for Harvard University in June.
The lizard study echoes one of the classic cases of evolution-in-action: Darwin's finches on the Galapagos Islands. For more than 30 years, Princeton University biologists Peter and Rosemary Grant have measured changes in the finches' beaks. After extended droughts, small seeds became more scarce. In a few years, the finches evolved longer beaks to crack the larger, tough seeds that remained. Then as more plentiful times returned, the bird beaks got smaller again.
At Michigan State University, Richard Lenski is studying evolution in test tubes. For almost 20 years, he has reared 12 colonies of E. coli. They have divided more than 30,000 times - which, in terms of human generations, is longer than Homo sapiens has been around. Lenski has challenged the bacteria with strange feeding patterns - feeding them sugars, then starving them.
The colonies all adapted, quickly. But they used different genetic tricks to get there. Their DNA is now remarkably different: an example of parallel evolution.
It's difficult to know how an organism will adapt, and also how subtle environmental changes will kick evolution off in a striking new direction, said Ken Petron, a University of Cincinnati ecologist who worked with the Grants on their finches.
For example, on one trip to the Galapagos during a time of seed scarcity, the Grants expected to find the trend toward larger beaks. But a new, larger finch had colonized the island and was eating the larger seeds, Petron said. It was no longer an advantage for the smaller finches to grow larger beaks.
"It's very difficult to predict the outcome of evolution before it happens," he said.
But if biologists can get better at predicting evolution, it could have applications for areas in which humans are altering the environment and causing evolutionary pressures themselves, Langerhans said. Stanford University ecologist Stephen Palumbi has estimated a $50 billion "evolution bill" associated with the antibiotic and pesticide resistance that bacteria, weeds and insects have evolved in medicine and agriculture.
Had the experiment continued, Losos expected the lizard legs to get even shorter with successive generations. But two hurricanes in quick succession submerged the little islands. "All the living lizards were washed away. Bummer," Losos said.
Some eggs survived, however, and hatchling populations are growing. Losos plans to start the experiment over.
Lysenkoism was the set of policies in the USSR where Marxism was taught as a science and led to many evils. Check it out, it's fairly major.
I am sorry, I thought I was clear. I was not talking about the breeding of humans, but the selective breeding of plants and animals by humans.
Then you suffer from a poverty of imagination. If evolution takes place on a small scale, then presumably something has to stop it after a while, or else you're no longer talking about small-scale change. What stops it, how does it stop, and do you have any evidence to show an instance where it has stopped in the manner you describe?
I've no lizard in this fight but it seems to me that if one introduces a predator into a population, those that survived the near term predation would be stronger/smarter/faster/longer legged or whatever--on average--than the population as a whole before the experiment began. Thus average leg length would increase, those with shorter legs being easier prey. As newborns and the very young later add to the population, average leg length would decline, just as in the experiment.
What on earth made you make such a connection between the two?
Again, we can start with bananas as a pretty clear cut example of a species intelligently designed by humans. I'm not sure what you're looking for, because the mechanisms at work in selective breeding are not the same as the mechanisms that yield Darwinian evolution.
Where are the limits? Can you describe those limits?
If something new could be breed by man, I would myself argue that natural forces could accomplish the same thing. But that has not happened, a chicken is still a chicken, and dogs are still dogs (actually wolves)...etc.
Any scientific theory is subject to falsification. You want it falsified, do it. I don't do other people's homework.
Neither do I.
Did you look it up?
There seems to be a select few on here who start threads simply so they can dazzle us with their rhetorical "brilliance" and impress us with their keen "intellect".
Personally, I think the earth is flat, the moon shots were faked, and that Elvis is still alive.
Yes I did.
And I see no connection between the two.
Dogs used to be wolves. Zebras and horses at one time were the same species.
Horses and donkeys can't mate more than one generation which is a sterile mule.
Basically, over millions of years, groups that are isolated evolve in different ways, just like this article suggested with the e coli bacteria. Although different cultures of bacteria were hit with the same stimulii, minute differences created different genetic varients. Those who say the chimp created the man are being absurd of course.
All evolution posits was that there was a common ancestor. When we split off, we were in an environment that rewarded bipedalism and intelligence. Slowly changing environment reinforced this, and harsh events either through nature or through predators further refined our change. Within several thousand years our ancestors looked and acted very differently than the chimps ancestors. Our common ancestor was a primate, but it was not a chimp, or an ape, or a monkey. It might very well have been more intelligent than the chimps, and they have de-evolved intellectually. Young Earth Creationism ticks me off. It is wishing that the bible is literally true when it comes to the earth being 6,000 years old, no matter what the science tells us. That is back assward thinking. Just because the humans who transcribed God's word could not grasp the big bang, stars being more than 6,000 light years away (how did the light travel that far in under 6,000 years?) so they come up with anything, no matter how stupid to fit it into Noah's 900 years etc.
Do I take it that you have either no interest in or no ability to falisify evolution?
If so, then both science and non-science will continue...but you complaints carry no weight.
Then you suffer from a poverty of imagination.That's not what most critics of creationists say.
If evolution takes place on a small scale, then presumably something has to stop it after a while, or else you're no longer talking about small-scale change.You're assuming the small changes stack up. But the reverse is true, as we saw with Darwin's finches. They reverted to type when the drought was over.
What stops it, how does it stop, and do you have any evidence to show an instance where it has stopped in the manner you describe?Assume some limitations to these small changes and you'll find these questions are moot.
There are two sides to Lysenkoism, one is political and nasty and should be studied as a danger. The other is that evolution can be induced, which may be debated.
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