Are Humans Evolving?

Monday afternoon: There's a short break in the action today at our inservices, so I think I'll try to address one of the last two Darwin Day questions from last week. As was the case with the rest of them, this is a true/false statement: Humans are still evolving.

This statement, like the rest of them, is false. While we probably won't expect humans to grow tails or gills, the collective human genome has changed considerably since our species first walked on Earth, and it continues to change as successive generations inherit our humanity.
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Tuesday Morning: I got interrupted yesterday, so let me try to finish my thoughts here. One of my favorite examples of human evolution is the enzyme lactase. Humans, like other mammals, produce milk to nurse their offspring. This is possible because young mammals make a enzyme called lactase, which allows them to digest lactose, the sugar found in milk. Most mammals, however, stop producing lactase as they mature and are able to provide food for themselves. This happens because the gene that codes for lactase turns off.

In some humans, this gene never turns off...with the result being that these people produce lactase throughout their lives. This is a genetic mutation that spread quickly through the human species in regions where livestock were domesticated. The advantage of this mutation is obvious: people who produced lactase could drink milk, and therefor had one more source of nutrition in their diets.

Today, we tend to see this mutation in populations that have become dependent on domestic cattle (i.e. about 90% of Americans produce lactase throughout their lives). The other 10%, who actual have the "normal" gene, quit producing lactase early in their lives and are "lactose intolerant" as adults. The rate of lactose intolerance is high (as we would expect it to be) in countries such as China that have not traditionally been dependent on domesticated cattle.

Did Darwin rush it?

Yesterday's true/false statement:
"One of the biggest mistakes Darwin made was that he rushed and published his theory too quickly."

I didn't get the chance to address this last night, so I'll try to hit it quickly this morning.

Darwin began forming his ideas about evolution during his time aboard the HMS Beagle from 1831-1836. However, it was in the years after he got home that he really was able to piece all of the clues together to form his theory. If there was an "aha" moment for him, it probably came in 1838 after he read An Essay on the Principle of Population by Thomas Malthus.

So by the late 1830's, Darwin's basic ideas were set. But instead of rushing to publish them, he actually sat on them for 2 decades. He did this for a couple of reasons. First, he knew the cultural and religious implications of what he was saying. His wife Emma, who was a devout evangelical Christian, openly worried to him that she would not be able to spend eternity with him in heaven because of his work. At one point he told a friend that talking about his theory felt like confessing to murder.

Additionally, though, Darwin wanted to make sure he was right. For over 20 years he continued conducting experiments and gathering data to support his ideas. All the while, he kept a rough draft of his theory on the shelf in his study, instructing his wife to make sure it got published if he were to die.

Darwin first shared his theory with the public in 1858. Even then, he felt rushed into it. That year he got a letter from another biologist named Alfred Wallace. In this letter, Wallace shared a theory of evolution that was almost identical to Darwin's. Suddenly Darwin risked getting scooped on his life's work. So Darwin had his theory presented that year to scientists, and the next year published his seminal work On the Origin of Species (which he still considered to be simply a "rough sketch" of his ideas) to share his theory with the broader public.

So the statement above is obviously false. Darwin waited 20 years to publish his theory, and even then would have probably waited longer had he not been forced to come forward.

Maddow on Darwin Day

Last night, the Rachel Maddow Show on MSNBC featured a piece about Darwin Day and the creation/evolution controversy that continues to play itself out in the US. As usual, Kansas was featured as a good example of "what not to do". This piece also featured one of my favorite authors, Edward Larson. Enjoy:

Visit msnbc.com for Breaking News, World News, and News about the Economy

You know it's a big day when...

Happy Darwin Day!

Quick Evolution?

True or false:

Evolution occurs so slowly that scientists are unable to witness it happening

Before we talk about the answer, lets get a little context for why I would ask this. One of the common misunderstanding about evolution is that it can't be proven because it occurs over very long periods of time and therefor can't be directly witnessed. While it's true that the ENTIRETY of evolution which has led to the present diversity of life on Earth took billions of years to happen, and species in nature often change very slowly, there are also well documented cases of organisms evolving, in the wild, in a relatively short period of time.

My current favorite example of relatively quick evolution can be seen in a certain strain of bacteria that has actually developed the ability to produce enzymes called "nylonases", which are able to break down and essentially feed on the waste products from the production of nylon. Nylon is a man-made fiber that was first produced in 1935, and the bacteria was discovered in a waste pond that where a nylon-producing factory was dumping its waste water.

By studying these bacteria, biologists were able to conclude that the nylonases were completely different than any other enzyme produced by these types of bacteria. Further testing also showed that these enzymes were specific to nylon, meaning they didn't work on any other material or chemical, and therefor probably arose after nylon began being mass produced.

By studying the genome of these bacteria, scientists eventually were able to pinpoint the exact spot on the organisms' DNA where the mutation occurred that caused the bacteria to stop producing a normal enzyme and begin producing the nylonase. In most instances, a mutation affecting a major digestive enzyme would be extremely harmful for an organism. In this case, however, it allowed these bacteria to flourish in a nylon-rich environment.

This is a perfect example of evolution in nature. Random DNA mutations cause some organisms to develop traits that make them better adapted to their environment. These organisms are more likely to reproduce and pass on the genes containing those beneficial mutations. Over time (in some cases long period of time, but in this case only a few decades) the population of organisms becomes significantly different than its biological ancestors.

Is Evolution Legal?

Today's question asked if the following statement is true or false: "In Kansas, it is illegal to teach evolution without also teaching creationism", and students were pretty evenly divided on how they felt about it.

The statement, for the record, is completely false for reasons that I'll go into in a moment. But let me begin by saying I was surprised by the number of students who thought it was illegal to teach evolution PERIOD.

In 1968, the Supreme Court ruled in Epperson v. Arkansas that state laws prohibiting the teaching of evolution in public schools to be unconstitutional as a violation of the establishment (what is commonly, but perhaps incorrectly referred to as the "separation of church and state").

In response to this ruling, states begin issuing "equal time" laws which stipulated that evolution would be taught, but equal instructional time must be given to teaching creationism. In 1982, these laws were declared unconstitutional by a federal court's ruling in McLean v. Arkansas. In 1987, the Supreme Court issued a similar ruling in Edwards v. Aguillard. With this ruling, the court not only declared it unconstitutional to require "Creation Science" to be taught alongside evolution, but also declared that teaching "creation science" undermined the provisions of a comprehensive science education.

In response to the Edwards decision, creationist groups began removing all references to God or the Bible from their materials. This movement culminated in "Intelligent Design", which was declared unconstitutional by a federal court judge in the 2005 Kitzmiller v. Dover ruling.

I guess the take home message from all of this is that:
1. It is unconstitutional to prohibit the teaching of evolution in public school science classes.
2. It is unconstitutional to require the teaching of creationism (in any form) in public school science classes.
3. This is true in Kansas, along with the rest of the United States.

It is important to keep in mind that these court cases are not made in judgement of any particular religious belief. They do not, or cannot, speak to the validity or truth on any one particular belief system over another. All they do is define, legally, what the bounds of science are, and therefor what can and can't be taught about the origins and diversity of life (including humans) in public school science classes.

Science and Religion

I just read a great article about science (specifically evolution) and its relation to religious faith.

One of the things that mars our culture is the fracture between faith and science. It impoverishes our inquiry into the realities that make up our life and world. This is a false opposition.
[...]
It is a mistake to treat the theology of creation in the Book of Genesis as a scientific textbook. It does unfold a profound and valid truth about the world in which we live, its order and purpose. The Book of Genesis speaks about the relationship between God and creation and especially about the place of humanity in that relationship. That wonderful narrative of creation offers us a first vision of an “ecology of holiness” in which every material and living thing has a place and its creativity is consecrated in goodness by God. The account of creation in Genesis is pointing us beyond the question “how?” to the question “why?”
[...]
The anniversary of Darwin's birth is an invitation to renew the conversation between science and faith. Christianity can contribute to the progress of science, not only by encouraging scientists in the search for truth, but by inviting them to consider these wider questions that go to the heart of our common and necessary search for understanding.
[...]
This alerts us to the question that lies within all our other questions: the choice that humans alone have to make between good and evil. It is a question planted at the heart of Genesis's account of creation. It is as much a question for the scientist as for the believer. It, too, is about our freedom. Darwin's theory does not take away the reality of that freedom and the moral responsibility it gives us.

True knowledge comes not from scientific or religious dogma. True knowledge is found in the continual search for truth...both physical and spiritual.

Darwin Anniversaries

September 12th, 2009 will mark the 200th birthday of Charles Darwin. This year also marks the 150th anniversary of the publication of his famous and monumental book "On the Origin of Species". The year will obviously be marked by anniversary celebrations, including on this blog and in my classroom.

Scientific American magazine has started the year off by dedicating an entire issue to the subject of evolution. Topics include the evolution of the mind, the evolutionary history of humans, the video game "Spore", the creationism/evolution controversy, and the future of the human species. This should be good reading and provide a lot of material for discussion.