Posted by: Dan | February 15, 2008

Evolution as a Heuristic, and Evidence for it

Various questions about life abound that are best explained by evolution, and not at all explained by creationism, design, or its permutations. How well do you understand evolution and its implications?

Some questions to think about - first, the abstract questions:

Does evolutionary theory explain how life began? Is evolution a random process? Can organisms sense a need to evolve? Do individuals evolve? Does evolution result in perfection? Are biologists split on evolution? The answer to these questions (No) often surprises people. This project aims to clear up these and other common misconceptions, and present a coherent explanation of the many facets of evolutionary theory.

And then, some specific questions:

Why does giving mineral supplements to undernourished, anemic individuals cause many of them to die of bacterial infections? Why did Dr. Heimlich need to develop a maneuver to dislodge food from peoples’ windpipes? Why does each of your eyes have a blind spot and a significant tendency for retinal detachment, but a squid’s eyes, which provide equally sharp vision, do not have either problem? Why are depression and obesity at epidemic levels in the U.S.? When Europeans came to the Americas, why did 90% of the Native Americans die of European diseases, but few Europeans died of American diseases? Why do pregnant women get “morning sickness?” Why do people in industrialized countries have higher incidence of Crohn’s disease (related to irritable bowel syndrome) and asthma than people in undeveloped countries? Why does malaria still kill over one million people each year? Why is so much of the product, Depend® or Poise® (for incontinence), sold each year? Why do people given anti-diarrheal medication take twice as long to recover from dysentery as untreated ones? Why do people of European descent have a fairly high frequency of an allele, which, in the homozygous condition, confers resistance to HIV infection? Why do older men often develop urinary problems? Why do so many people in Austin suffer from “cedar fever?”

Useful educational websites:
This View of Life
Action BioScience
Talk Origins
Evolution at PBS
Understanding Evolution

Books:
Ernst Mayr’s What Evolution Is
Sean B. Carroll’s Endless Forms Most Beautiful

Links:
Neurotopia and the Austin-American Statesman

Categories:

« Evolution Sunday 2008
Leatherbacks on Migratory Odyssey Across Pacific »

Responses

Lynn Margulis spoke Thursday evening, Feb 14 at Cornell as part of Darwin Days 2008. She spoke about endosymbiosis, and about the Gaia hypothesis.

Will Provine introduced Margulis by mentioning the recent Warda and Han preprint which questions endosymbiosis, and suggests the “Might Creator hypothesis” to replace it. Provine framed this as progress for endosymbiosis, as it is now considered part of the evolutionary mainstream which is under attack from Creationists.

Margulis’ talk was rather unfocused, with lots of “gee whiz” slides but no clearly formulated argument. She mentioned assorted planetary science stuff, about Venus being to hot, Mars too cold, and Earth just right (the Goldilocks planet) and about how all of life as we know it is only on the surface of this one planet. She mentioned the Gaia hypothesis frequently and prominently, although she said a few things that leave me with the impression that she takes it as a metaphor, rather than as a literal and serious scientific proposal.

In the question and answer period afterwards, someone mentioned Dawkins’ “selfish gene” idea, which she dismissed as being false because organisms are selected, not genes directly. It struck me that Lovelock’s Gaia hypothesis has been criticized on very similar grounds, and yet Margulis gushes over about that. Even if the selfish gene concept is not literally true, why could it not be useful in the same way as the Gaia hypothesis; a novel viewpoint that can lead to new insights?

Margulis spoke about the billions of years of microbial development preceding the Cambrian explosion, and how the “charismatic megafauna” tends to monopolize the attention. She placed the origin of eukaryotes as at least 1.2 billion years ago.

Margulis showed many examples of endosymbiosis: green snails which sequester chloroplasts from their algal diet, microbial communities which digest cellulose in termites, etc. She presented several examples I hadn’t heard of before. Oddly, she presented very little about the genetic data which makes the case for endosymbiotic theory so much stronger.

She mentioned only briefly that she doubts neo-Darwinism, and proposed that all eukaryotic evolution and speciation proceeds through “genome acquisition.” I don’t think she could make a convincing case for this. She said that she had searched diligently, but had never seen examples of speciation through the accumulation of mutations. I have to wonder how diligently she searched.

No one brought up her HIV/AIDS denialism.

By: ivy privy on February 18, 2008
at 6:29 pm

Ivy,
Interesting - wish I were there to have heard that talk myself.

Certainly I agree that Margulis is a bit, shall we say, unorthodox. Gaia is a farce, and I’m glad to hear that she didn’t bring up her HIV/AIDS denialism.

Similarly, the way you describe the discussion on speciation sounds a bit half-baked.

Wish I were there.

By: Dan on February 18, 2008
at 6:56 pm

Choanoflagellate genome

Grandpa!

By: ivy privy on February 22, 2008
at 7:34 pm

That is an interesting paper. I’ve actually been taking a look at it, and tossing around the idea of blogging it (probably at Bitesize Bio though).

By: Dan on February 23, 2008
at 2:58 pm

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