Tag Archives: Macro-Evolution

Are the Galapagos finch beaks evidence of Darwinian evolution?

I have a key that will unlock a puzzling mystery
I have a key that will unlock a puzzling mystery

Jonathan Wells has an article about it at Evolution News.

It says:

When Charles Darwin visited the Galápagos Islands in 1835, he collected specimens of the local wildlife. These included some finches that he threw into bags, many of them mislabeled. Although the Galápagos finches had little impact on Darwin’s thinking (he doesn’t even mention them in The Origin of Species), biologists who studied them a century later called them “Darwin’s finches” and invented the myth that Darwin had correlated differences in the finches’ beaks with different food sources (he hadn’t). According to the myth, Darwin was inspired by the finches to formulate his theory of evolution, thoughaccording to historian of science Frank Sulloway “nothing could be further from the truth.”

In the 1970s, biologists studied a population of medium ground finches on one of the islands in great detail. When a severe drought left only large, hard-to-crack seeds, 85 percent of the birds perished. The survivors had beaks that were about 5 percent larger than the average beak size in the original population. The biologists estimated that if similar droughts occurred once every ten years, the population could become a new species in only 200 years. In a 1999 booklet defending evolution, the U.S. National Academy of Sciences called the finches “a particularly compelling example” of the origin of species.

But after the drought, birds with smaller beaks flourished again, and the average beak size of the population returned to normal. No net evolution had occurred. No matter; Darwin’s finches became an icon of evolution that is still featured in most biology textbooks.

In the 1980s, a population of large ground finches, with larger beaks than the medium ground finches, migrated to the island. When a drought in 2004-2005 again reduced the food supply, the medium and large ground finch populations both declined. But since even the largest beaks among the medium ground finches were no match for the beaks of the large ground finches, the latter pretty much monopolized the larger seeds and the former had to make do with smaller seeds. This time, the medium ground finches that survived the drought had beaks that were smaller than the average size in the original population. Biologists studying the finches argued that birds with smaller beaks were better able to eat the tiny seeds that were left after the large ground finches ate the big ones, and they concluded that this was again an example of “evolutionary change.”

[…]Wait a minute. Average beak size increased slightly during one drought, only to return to normal after the rains return. Then average beak size decreased slightly during another drought. A region of DNA is correlated with beak size. And somehow that tells us how finches evolved in the first place?

There is an important distinction to make between micro-evolution and macro-evolution. Changes within a type is micro-evolution. Evolving a new organ type or body plan is macro-evolution. There is plenty of evidence for micro-evolution, but no evidence for macro-evolution.

What needs to be proven by the Darwinists is that the same process that results in different average beak size in a population of finches after a drought can create the finches in the first place. I think that Darwinists are credulous – they believe what they want to believe because they want to believe it, even if the evidence is incredibly weak. Darwinists must demonstrate that heritable variations can result in the generation of new organ types and body plans. Changes in average beak size is not interesting. What is needed is to show how the beaks, much less the wings, evolved in the first place.

Icons of Evolution

Jonathan has actually written about a number of  misleading things that you may mind in Biology textbooks.

Here are the sections in his book “Icons of Evolution“:

  • The Miller-Urey Experiment
  • Darwin’s Tree of Life
  • Homology in Vertebrate Limbs
  • Haeckel’s Embroys
  • Archaeopteryx–The Missing Link
  • Peppered Moths
  • Darwin’s Finches
  • Four-Winged Fruit Flies
  • Fossil Horses and Directed Evolution
  • From Ape to Human: The Ultimate Icon

Dr. Wells holds a Ph.D in Molecular and Cell Biology from the University of California at Berkeley.

New study: natural selection can act to impede speciation

Australian Walking Stick
Australian Walking Stick

My friend KL sent me this press release from the University of Colorado at Boulder.

It says:

An intriguing study involving walking stick insects led by the University of Sheffield in England and the University of Colorado Boulder shows how natural selection, the engine of evolution, can also impede the formation of new species.

The team studied a plant-eating stick insect species from California called Timema cristinae known for its cryptic camouflage that allows it to hide from hungry birds, said CU-Boulder Assistant Professor Samuel Flaxman. T. cristinae comes in several different types — one is green and blends in with the broad green leaves of a particular shrub species, while a second green variant sports a white, vertical stripe that helps disguise it on a different species of shrub with narrow, needle-like leaves.

While Darwinian natural selection has begun pushing the two green forms of walking sticks down separate paths that could lead to the formation of two new species, the team found that a third melanistic, or brown variation of T. cristinae appears to be thwarting the process, said Flaxman. The brown version is known to successfully camouflage itself among the stems of both shrub species inhabited by its green brethren, he said.

Using field investigations, laboratory genetics, modern genome sequencing and computer simulations, the team concluded the brown version of T. cristinae is shuttling enough genes between the green stick insects living on different shrubs to prevent strong divergent adaptation and speciation. The brown variant of the walking stick species also is favored by natural selection because it has a slight advantage in mate selection and a stronger resistance to fungal infections than its green counterparts.

“This is one of the best demonstrations we know of regarding the counteractive effects of natural selection on speciation,” said Flaxman of CU-Boulder’s Department of Ecology and Evolutionary Biology, second author on the new study. “We show how the brown population essentially carries genes back and forth between the green populations, acting as a genetic bridge that causes a slowdown in divergence.”

A paper on the subject appeared in a recent issue of the journal Current Biology. 

[…]“This movement of genes between environments slows down the genetic divergence of these stick insect populations, impeding the formation of new species,” said Aaron Comeault, a former CU-Boulder graduate student and lead study author who conducted the research while at the University of Sheffield.

So, in the past I had read that natural selection can act as a stabilizing force in nature – keeping the organism operating within a type. This study seems to be confirmation of that. That’s a problem for naturalists, who believe that mutations and selection can drive evolution of new body plans or organ types (macro-evolution). I could even agree that mutation and selection drives changes within a kind, but that still wouldn’t explain how one kind changes into another kind.

But there are other problems with generating macro-evolutionary change.

Also related to the problem raised by the study is this problem of genetic drift, which also works against the preservation of beneficial mutations.

Evolution News explains the genetic drift problem:

Evolutionary biologists often assume that once mutations produce a functionally advantageous trait, it will easily spread (become “fixed”) throughout a population by natural selection. For example, imagine a population of brown-haired foxes that lives in a snowy region. One fox is born with a mutation that turns its fur coat white, rather than brown. This fox now has an advantage in hunting prey and escaping predators, because its white fur provides it with camouflage. The white fox survives, passing its genes on to its offspring, which are also adept at surviving and reproducing. Over time, the white-haired trait spreads throughout the population.

This is how it’s supposed to work — in theory. In the real world, however, merely generating a functionally advantageous trait does not guarantee it will persist, or become fixed. For example, what if by chance the white fox trips, breaks a leg, and gets eaten by a predator — never passing on its genes? Random forces or events can prevent a trait from spreading through a population, even if it provides an advantage. These random forces are lumped together under the name “genetic drift.” When biologists run the mathematics of natural selection, they find that unless a trait gives an extremely strong selective advantage, genetic drift will tend to overwhelm the force of selection and prevent adaptations from gaining a foothold in a population.

This underappreciated problem has been recognized by some evolutionary scientists who are skeptical of the ability of natural selection to drive the evolutionary process. One of those scientists is Michael Lynch, an evolutionary biologist at Indiana University, who writes that “random genetic drift can impose a strong barrier to the advancement of molecular refinements by adaptive processes.”2 He notes that the effect of drift is “encouraging the fixation of mildly deleterious mutations and discouraging the promotion of beneficial mutations.”3

I guess the point of this is that if someone wants to convince you that macro-evolution is possible through the mechanisms of random mutation and natural selection, then they have some work to do. And it’s more work than just asserting that it happened.

People who are technical may benefit from reading Michael Behe’s book “The Edge of Evolution”, which studies how likely it is to get several positive adaptations in a row within a reasonable period of time.

UPDATE: A biologist friend tells me that “whether natural selection is driving speciation or preventing it, in neither case is it explaining how these organisms came to be in the first place. It only explains how existing organisms interact with their environment. And this can be explained at least as well through intelligent design as through naturalistic processes.” She also says that natural selection can drive speciation, but still within a kind.

New study: natural selection can act to impede speciation

Australian Walking Stick
Australian Walking Stick

My friend KL sent me this press release from the University of Colorado at Boulder.

It says:

An intriguing study involving walking stick insects led by the University of Sheffield in England and the University of Colorado Boulder shows how natural selection, the engine of evolution, can also impede the formation of new species.

The team studied a plant-eating stick insect species from California called Timema cristinae known for its cryptic camouflage that allows it to hide from hungry birds, said CU-Boulder Assistant Professor Samuel Flaxman. T. cristinae comes in several different types — one is green and blends in with the broad green leaves of a particular shrub species, while a second green variant sports a white, vertical stripe that helps disguise it on a different species of shrub with narrow, needle-like leaves.

While Darwinian natural selection has begun pushing the two green forms of walking sticks down separate paths that could lead to the formation of two new species, the team found that a third melanistic, or brown variation of T. cristinae appears to be thwarting the process, said Flaxman. The brown version is known to successfully camouflage itself among the stems of both shrub species inhabited by its green brethren, he said.

Using field investigations, laboratory genetics, modern genome sequencing and computer simulations, the team concluded the brown version of T. cristinae is shuttling enough genes between the green stick insects living on different shrubs to prevent strong divergent adaptation and speciation. The brown variant of the walking stick species also is favored by natural selection because it has a slight advantage in mate selection and a stronger resistance to fungal infections than its green counterparts.

“This is one of the best demonstrations we know of regarding the counteractive effects of natural selection on speciation,” said Flaxman of CU-Boulder’s Department of Ecology and Evolutionary Biology, second author on the new study. “We show how the brown population essentially carries genes back and forth between the green populations, acting as a genetic bridge that causes a slowdown in divergence.”

A paper on the subject appeared in a recent issue of the journal Current Biology. 

[…]“This movement of genes between environments slows down the genetic divergence of these stick insect populations, impeding the formation of new species,” said Aaron Comeault, a former CU-Boulder graduate student and lead study author who conducted the research while at the University of Sheffield.

So, in the past I had read that natural selection can act as a stabilizing force in nature – keeping the organism operating within a type. This study seems to be confirmation of that. But there are other problems with generating macro-evolutionary change.

Also related to the problem raised by the study is this problem of genetic drift, which also works against the preservation of beneficial mutations.

Evolution News explains the genetic drift problem:

Evolutionary biologists often assume that once mutations produce a functionally advantageous trait, it will easily spread (become “fixed”) throughout a population by natural selection. For example, imagine a population of brown-haired foxes that lives in a snowy region. One fox is born with a mutation that turns its fur coat white, rather than brown. This fox now has an advantage in hunting prey and escaping predators, because its white fur provides it with camouflage. The white fox survives, passing its genes on to its offspring, which are also adept at surviving and reproducing. Over time, the white-haired trait spreads throughout the population.

This is how it’s supposed to work — in theory. In the real world, however, merely generating a functionally advantageous trait does not guarantee it will persist, or become fixed. For example, what if by chance the white fox trips, breaks a leg, and gets eaten by a predator — never passing on its genes? Random forces or events can prevent a trait from spreading through a population, even if it provides an advantage. These random forces are lumped together under the name “genetic drift.” When biologists run the mathematics of natural selection, they find that unless a trait gives an extremely strong selective advantage, genetic drift will tend to overwhelm the force of selection and prevent adaptations from gaining a foothold in a population.

This underappreciated problem has been recognized by some evolutionary scientists who are skeptical of the ability of natural selection to drive the evolutionary process. One of those scientists is Michael Lynch, an evolutionary biologist at Indiana University, who writes that “random genetic drift can impose a strong barrier to the advancement of molecular refinements by adaptive processes.”2 He notes that the effect of drift is “encouraging the fixation of mildly deleterious mutations and discouraging the promotion of beneficial mutations.”3

I guess the point of this is that if someone wants to convince you that macro-evolution is possible through the mechanisms of random mutation and natural selection, then they have some work to do. And it’s more work than just asserting that it happened.

People who are technical may benefit from reading Michael Behe’s book “The Edge of Evolution”, which studies how likely it is to get several positive adaptations in a row within a reasonable period of time.

UPDATE: A biologist friend tells me that “whether natural selection is driving speciation or preventing it, in neither case is it explaining how these organisms came to be in the first place. It only explains how existing organisms interact with their environment. And this can be explained at least as well through intelligent design as through naturalistic processes.” She also says that natural selection can drive speciation, but still within a kind.

Did your science textbook teach that peppered moths prove evolution?

Here’s a post by Jonathan Wells at Evolution News, which re-caps the history of the peppered moths experiment.

Excerpt: (links removed)

The peppered moth story is familiar — even overly familiar — to most readers of ENV, so I will summarize it only briefly here. Before the industrial revolution, most peppered moths in England were light-colored; but after tree trunks around cities were darkened by pollution, a dark-colored (“melanic”) variety became much more common (a phenomenon known as “industrial melanism”). In the 1950s, British physician Bernard Kettlewell performed some experiments that seemed to show that the proportion of melanic moths had increased because they were better camouflaged on darkened tree trunks and thus less likely to be eaten by predatory birds.

Kettlewell’s evidence soon became the classic textbook demonstration of natural selection in action — commonly illustrated with photos of peppered moths resting on light- and dark-colored tree trunks.

By the 1990s, however, biologists had discovered several discrepancies in the classic story– not the least of which was that peppered moths in the wild do not usually rest on tree trunks. Most of the textbook photos had been staged.

In the 2000s the story began disappearing from the textbooks. British biologist Michael Majerus then did some studies that he felt supported the camouflage-predation explanation. But before he died of cancer in 2009, he only managed to publish a report of his study in the Darwin lobby’s in-house magazine Evolution: Education and Outreach. Now four other British biologists have presented his results posthumously in the Royal Society’s peer-reviewed Biology Letters. In an accompanying supplement, the authors presented their version of what they call “the peppered moth debacle.” And a debacle it certainly is, but not in the way they think.

According to Charles Darwin, natural selection has been “the most important” factor in the descent with modification of all living things from one or a few common ancestors, yet he had no actual evidence for it. All he could offer in The Origin of Species were “one or two imaginary illustrations.” It wasn’t until almost a century later that Kettlewell seemed to provide “Darwin’s missing evidence” by marking and releasing light- and dark-colored moths in polluted and unpolluted woodlands and recovering some of them the next day. Consistent with the camouflage-predation explanation, the proportion of better-camouflaged moths increased between their release and recapture.

Throughout the 1970s and 1980s, however, researchers reported various problems with the camouflage-predation explanation, and in 1998 University of Massachusetts biologist Theodore Sargent and two colleagues published an article in volume 30 of Evolutionary Biology concluding “there is little persuasive evidence, in the form of rigorous and replicated observations and experiments, to support this explanation at the present time.” (p. 318)

The same year, Michael Majerus published a book in which he concluded that evidence gathered in the forty years since Kettlewell’s work showed that “the basic peppered moth story is wrong, inaccurate, or incomplete, with respect to most of the story’s component parts.” (p. 116) In a review of Majerus’s book published in Nature, University of Chicago evolutionary biologist Jerry Coyne wrote: “From time to time, evolutionists re-examine a classic experimental study and find, to their horror, that it is flawed or downright wrong.” According to Coyne, the fact that peppered moths in the wild rarely rest on tree trunks “alone invalidates Kettlewell’s release-and-recapture experiments, as moths were released by placing them directly onto tree trunks.”

In 1999, I published an article in The Scientist summarizing these and other criticisms of the peppered moth story, and in 2000 I included a chapter on peppered moths in my book Icons of Evolution. Then, in 2002, journalist Judith Hooper published a book about the controversy titled Of Moths and Men. Hooper accused Kettlewell of fraud, though I never did; my criticism was directed primarily at textbook writers who ignored problems with the story and continued to use staged photos even after they were known to misrepresent natural conditions.

Jonathan has actually written about a number of  misleading things that you may mind in Biology textbooks.

Here are the sections in his book “Icons of Evolution“:

  • The Miller-Urey Experiment
  • Darwin’s Tree of Life
  • Homology in Vertebrate Limbs
  • Haeckel’s Embroys
  • Archaeopteryx–The Missing Link
  • Peppered Moths
  • Darwin’s Finches
  • Four-Winged Fruit Flies
  • Fossil Horses and Directed Evolution
  • From Ape to Human: The Ultimate Icon

Dr. Wells holds a Ph.D in Molecular and Cell Biology from the University of California at Berkeley.

Is there a smooth pathway from micro-evolution to macro-evolution?

From Luke Nix who blogs at Faithful Thinkers.

Excerpt:

Macroevolutionary changes are a lot of microevolutionary changes, but they are in a specific series that follow a specific pathway. The missing premise in this argument is that the pathway from ancestor to claimed offspring (many generations down the road) is clear of obstacles.

In his book, “The Edge of Evolution” Michael Behe shows that scientists have observed such an obstacle in the lab. The obstacle was not time, it is in the genetic pathway that must be traversed if macroevolutionary changes are to take place in reality. Since an obstacle has been observed, we now have a false premise in the argument. Since there is a false premise, the argument fails. There is a difference between micro- and macro-evolutionary changes. A lot of microevolutionary changes are necessary for macroevolution, but they are not sufficient. The other sufficient condition (a clear genetic pathway) still has yet to be met. Since both sufficient conditions for macroevolution have not been met, it has not been demonstrated. And since changes over time has been demonstrated, there is a need to distinguish between the two. To prevent confusion about what we know to be true and what we don’t, this distinction must be made.

There is only one way that this can be overcome by the naturalist: find a pathway that would be clear by default in nature. Notice that I have added one more piece to the missing premise above: “…clear by default in nature“. I have to add that last qualification because as scientists are looking for a way to overcome this obstacle, they are introducing their own intelligence- fine-tuning the process, then “allowing nature to take its course”. Their conclusion of naturalistic macroevolution will depend on a premise that is founded on intelligence. That would undermine the whole argument for naturalistic (macro)evolution.

This is one of the ways to show that evolution is true – by showing a pathway to macro-evolutionary change in the lab. If people expect me to believe in the grandiose claims of fully naturalistic evolution through a stepwise process, then why can’t I see the pathway myself? If you make the claim that it happened, then I want to see the evidence for the claim.

Related posts