There are a lot of simple things out there that aren’t really simple once you start trying to understand and explain them. The concept of “species” is one of those non-simple concepts. I had assumed that I had a good gut understanding of “species” until I read an article called “Speciation,” by Andrew P. Hendry, published in the March 12, 2009 edition of Nature (available online only to subscribers). Hendry suggests that the term “species” as a technical classification in the field of biology is “ambiguous and amorphous.” He starts by quoting Darwin, from on the origin of species:
In short, we shall have to treat species in the same manner as those naturalists treat genera, who admit that genera are merrily artificial combinations made for convenience. This may not be a cheering prospect; but we shall at least be free from the vain search for the undiscovered and undiscoverable essence of the term species.
Hendry suggests that modern biological research has proved Darwin. No universal easily applicable concept of “species” exists; instead, more than two dozen approaches exist with regard to “species.” The most common version is the “biological species concept” (BSC). This definition holds that species are “groups of actually or potentially interbreeding individuals that are reproductively isolated from other such groups (that is, they exchange few genes). Hendry elaborates:
The BSC is sometimes interpreted to imply the extreme situation where two groups are separate species only when successful hybrids cannot ever be produced-and any two such groups certainly are separate species. But many other groups that are widely accepted to represent separate species frequently violate the strict criteria; for example, some estimates hold that 25% of all plant species and 10% of all animal species hybridize successfully with at least one other species. Probably for this reason, the BSC is often relaxed to the point that different groups are considered separate species if they can maintain their genetic integrity and nature. This more useful, albeit more ambiguous, criterion allows for some genetic exchange (gene flow) between species as long as they do not become homogenized.
Hendry then goes on to discuss various challenges to BSC.
In Darwin’s dangerous Idea: Evolution and the Meanings of Life, Daniel Dennett describes Darwin’s idea as the “best idea anyone has ever had.”
In a single stroke, the idea of evolution by natural selection unifies the realm of life, meaning, and purpose with the realm of space and time, cause and effect, mechanism and a physical law. But it is not just a wonderful scientific idea. It is a dangerous idea.
What exactly was Darwin’s dangerous idea? According to Dennett, it was “not the idea of evolution, but the idea of evolution by natural selection, an idea he himself could never formulate with sufficient rigor and detail to prove, though he presented a brilliant case for it.” (42) Dennett considers Darwin’s idea to be “dangerous” because it has so many fruitful applications in so many fields above and beyond biology. When Dennett was a schoolboy, he and some of his friends imagined that there was such a thing as “universal acid,”
a liquid “so corrosive that it will eat through anything! The problem is: what do you keep it in? It dissolves glass bottles and stainless steel canisters as readily as paper bags. What would happen if you somehow came upon or created a dollop of universal acid? With the whole planet eventually be destroyed? What would it leave in its wake? After everything had been transformed by its encounter with universal acid, what would the world look like? Little did I realize that in a few years I would encounter an idea-Darwin’s idea-bearing an unmistakable likeness to universal acid: eats through just about every traditional concept, and leaves in its wake a revolutionized world-view, with most of the old landmarks are still recognizable, but transformed in fundamental ways.
(63) Darwin’s idea is powerful, indeed. Many people see it as having the power to ruin the meaning of life.
People fear that once this universal acid has passed through the monuments we cherish, they will cease to exist, dissolved in an unrecognizable and unlovable puddle of scientific destruction.
Dennett characterizes this fear is unwarranted:
We might learn some surprising or even shocking things about these treasures, but unless our valuing these things was based all long on confusion or mistaken identity, how could increase understanding of them diminish their value in our eyes? (82)
Over the past few weeks, in commemoration of the 200th anniversary of Darwin’s birthday, we’ve seen many articles published on the topic of evolution. The November 20, 2008 edition of Nature contains a drawing of Darwin on the cover, and the entire issue is titled “Beyond the Origin.” Inside this issue is an article by Marek Kohn titled “The Needs of the Many,” an article summarizing current thinking on group selection.
Kohn carefully sets out some definitions at the beginning of his article. For instance, he recognizes that modern evolutionary theory is based on the idea that selection “sees” individuals and acts on them through the genes they embody. Compare that to “group selection”:
The idea that evolution can choose between groups, not just the individuals that make them up–has a higher profile today than at any time since its apparent banishment from mainstream evolutionary theory. And it gets better press, too. This is in part owing to the efforts of David Sloan Wilson of Binghamton University in New York, who argues that the dismissal of group selection was a major historical error that needs to be rectified. And it does not hurt that he has been joined by Edward O. Wilson, the great naturalist and authority on social insects. They and many others have worked to reposition group selection within the broader theme of selection that acts simultaneously at multiple levels.
Buried in the dispute about the extent to which group selection occurs are numerous definitional issues such as the proper way to define “group,” “altruism,” and “selfishness.”
My growing impatience with creationists: a side by side comparison of evolutionary biology and creationism
Over the past three years of writing for DI, I have discussed evolution with many creationists who have posted comments at this site. These exchanges have been good for me. They have forced me to think harder about exactly what it is that I understand about evolution and what evidence supports my understanding. These exchanges have also helped me to understand the concerns and mental gymnastics of creationists.
I now find myself getting increasingly impatient with the creationists, however. It was initially interesting to banter with creationists because I enjoyed the challenge of trying to understand why they claimed the things they claimed. I’m now getting annoyed with these creationists arguments, and it mostly has to do with the refusal of creationists to acknowledge relevant scientific observations from the real world.
My frustration also stems from the anti-scientific mindset of creationists. As a group, creationists refuse to argue even-handedly. They become skeptical only when it suits their immediate needs—they don’t apply skepticism equally both to their own claims and to the claims of those with whom they disagree. As a group, they scurry to find disingenuous arguments to support points that they actually learned in churches, not in science books. Many of them are consciously dishonest, and when you call attention to their obvious untruths, they try to change the subject. There are exceptions to this rule. There are some creationists who aren’t consciously being dishonest, but those creationists tend to be so incredibly ignorant of the principles of the scientific theory of evolution that they lack the ability to meaningfully criticize evolution. Their arguments are aimed at things that no competent scientist has ever claimed. For numerous excellent examples of this problem, see these videos by AronRa here and here.
It is well-established that humans are susceptible to committing errors caused by the confirmation bias. We seek out evidence that supports our current beliefs. Scientists are imminently aware of this danger and they work hard to design experiments to counteract this bias. Creationists (who don’t even try to run experiments) excel at feeding their confirmation biases. They proudly exclude evidence that threatens their opinions. Creationists come to mind when I consider David Hume’s quote: “Reason is and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them.” [A Treatise of Human Nature, (2nd Ed.), Book II, Part I, Section III (“Of the influencing motives of the will”) (1739)].
Once again the orchids are on display at the Missouri Botanical Garden. I snapped some photos or these incredible beings. After all, they are our cousins. Richard Dawkins estimates that animals diverged from the plant kingdom about two billion years ago.
I’ve written previously about Darwin’s fascination with orchids here. For today, I will simply paste in a few new photos of these incredibly beautiful plants. I’ve posted many more of my photos of today’s show at one of my public web albums at Picasa.
In today’s speech, Barack Obama extolled the virtues of Abraham Lincoln, mentioning Charles Darwin along the way. It’s a terrific speech articulating the balance between individual liberties and the common good. A key quote: What if we were “consumed with small things–petty things–when were were called upon to do great things.”
To hear an American President actually mentioning the work of Charles Darwin in a good light, listen in starting about the 6-minute mark.
I have Darwin on my mind these days, perhaps because tomorrow is Darwin Day.
To celebrate Darwin Day, I sat down to read the February 2009 edition of National Geographic, which, according to the front cover, features an article entitled “What Darwin Didn’t Know.” Once you get inside the magazine, however, you’ll see that the main article is actually entitled “Darwin’s First Clues.” It is an extraordinary article setting straight some of the misconceptions about the manner in which Darwin developed his theory of evolution by natural selection. You can read that article online here. you can also watch a short introductory video by writer David Quammen, who explains that Darwin “is a man who just will not go away,” and whose ideas are not only still relevant, but “central” to the field of biology.
If you read this article, you’ll see that Darwin’s first clue toward evolution occurred not in the Galapagos, but three years earlier on the northern coast of Argentina, where Darwin found fossils of giant sloths. You read about his numerous fossil finds of giant mammals, “extinct Pleistocene giants.”
Quammen’s article points out that, for all of his gifts, Dawn was not a comparative anatomist. For this reason, he entrusted much of that work to others, including John Stevens Henslow, a botanist at Cambridge and Richard Owens, “an up-and-coming authority on extinct mammals.”
Darwin was certainly aware of the implications of the diversity and distributions of the flora and fauna he studied. The fact that fossils of giant extinct mammals could be found in the same places as still-living relatives suggested the idea of “relatedness and succession among closely allied species” rather than a God who had specially created species, placing them on the planet in arbitrary locations. Darwin’s explanation was certainly “more economical, more inductive and more persuasive than the creationist scenario.”