Science & Nature Archive

Wednesday, September 23, 2009

If Evolution Isn't Directed, Why Is Life Now More Complex Than in Ancient History?

A common misconception about evolution is that it has a goal, that organisms evolve from lower to higher forms. This is sometimes referred to as the Ladder or Progress, with primitive forms at the bottom and more advanced forms towards the top of the ladder (and commonly, being the self centered species that we are, with humans on the top rung). This isn't true. Evolution has no direction. Organisms adapt to fit their local environment in whatever way works best. But if evolution has no direction, why is it that life now is more complex* than life from billions of years ago?

This really is pretty easy to understand once you give it a little thought. Let's use distance as an analogy. There's an old saying, that the journey of a thousand miles begins with a single step. You can't walk from Los Angeles to New York instantly. It takes many, many small steps (literally in this example) to get there. If we consider Los Angeles to be simple, and New York to be complex, then at any point on your journey, as you've increased your distance from LA, you've increased your complexity. And it's obvious that you can't get to a certain point of complexity until you've already taken all the previous steps leading up to it. You can't just instantly go from simple to complex.

But a journey still implies direction, and I've said evolution doesn't work that way. Evolution is more like a drunkard's stagger. If you have a drunk that starts out in LA, and let him wander aimlessly with no particular destination in mind, he may eventually end up in New York, but it definitely wouldn't be a straight line. He may just as likely never make it to New York, and never even leave LA. To extend the analogy further, he may end up in Seattle. He'd still be a long way from LA, but in a completely different direction. Squids, for example, are remarkably complex, but they took a different path to their complexity than us vertebrates, and their resulting complexity is different from ours.

Below is a graph that roughly illustrates this in an evolutionary context. It starts off at zero, and for every step, it goes up or down by a random amount** between -0.5 and 0.5. After every 10 steps, it splits, and each new 'lineage' then varies in that same manner. This was carried on for 40 steps, resulting in 8 lineages by the end.

Random Distribution Simulating Evolution of Complexity

Remember, this is all random variation from a starting point at zero, going in small steps. After 40 steps, one lineage had varied to more than 3.4 away from zero, while other lineages didn't vary very much away from zero at all. If this was representing complexity, and if the steps were assumed to be thousands or millions of generations, it demonstrates how complexity can evolve slowly from simple beginnings, without any conscious aim toward increased complexity. (As I said, this is only a rough illustration of evolution. Evolution is driven by more than just random variation, and the divergence of lineages isn't as predictable as that.)

Evolution really does sometimes decrease complexity. For an intimate example, consider what you're sitting on - a nice smooth posterior. Some time millions of years ago, our ancestors lost their tails, a complex feature with muscles, bones, and tendons. Their lifestyles were probably such that a tail just didn't really do that much good, so there was no reason for natural selection to maintain it. And now, we have backsides that are less complex than our simian ancestors.


*'Complex' is actually a little hard to define. How exactly do we mean complex? Number of genes? Number of specialized cell types? How do we even differentiate specialized cell types? (more info) This seems like one of those problems where we know it when we see it. I think most people would agree that a mammal is more complex than an earthworm, even without a quantitative definition of that complexity.

**Technically, a pseudo random number generator was used (Visual Basic). For this application, that's close enough to truly random.

Wednesday, June 3, 2009

Bees

I had an interesting experience at work last Friday. Some time in the early afternoon, we started noticing some bees around the entrance to a trailer. We hadn't seen any yet this summer, so I poked around to see where they were coming from. I saw a few going in and out of a hole in the liner under the floor, so I ran home to get some wasp poison, and sprayed around the hole. As the afternoon wore on, more and more bees kept showing up. I kept spraying for a while, but eventually gave up. By the time I left to go home, here's what it looked like (I gave two different resolution options to view these bigger):

Bees View 1
800x600 (92.4 kB)
2816x2112 (504 kB)

Bees View 1
800x600 (104 kB)
2816x2112 (514 kB)

Bees View 1
800x600 (104 kB)
2816x2112 (491 kB)

And here are a couple videos of it that I uploaded to YouTube. The first one's a bit long, but you don't have to watch the whole thing. At the end of the second one, I got scared when I felt something land on my arm, but I didn't get stung.

By Sunday, the bees were no longer on the step, but had taken up residence under the trailer. We had to call in a bee keeper to get rid of them. He came in after dark on Sunday (so that the bees would be in the hive) and worked until midnight. He said that there must have been at least 20,000 bees. He didn't think they'd been there very long, that they'd probably just arrived.

That is, by far, the most bees I've ever seen in my life.

Friday, February 27, 2009

Investigating a Few Claims from Global Warming Doubters

Global WarmingThis past weekend, I got into a discussion with a couple friends about global warming. This was a different group than the one that inspired this blog entry, Global Warming - It's Real, And We're Causing It. These two had several arguments against global warming, not just a general distrust of the science. Like I wrote in that other entry, I'm far from being an expert in climate science. I've kept up with it a bit, but I've mostly trusted that the actual experts know what they're talking about, and when they said that there's a very, very high probability that global warming is human caused, I believed them. Well, arguments from authority don't carry much weight when people are giving you specific reasons why they doubt a theory. So, I had to do a little deeper research into their claims.

Below is the response I sent to them via e-mail. Since it's so long, I'm not going to put it in blockquotes. Also, since I'm posting this on my blog, I'm not going to use their real names. But rather than calling them John Doe I and John Doe II, I'll go with the first names from Comedy Central's news hour, John and Stephen.

[start of e-mail]

John & Stephen,

John, I know you're used to these e-mails. Stephen, this is just what I do after discussing something controversial - backing up what I said with a few references and doing a little more research. It looks like you do about the same - [my wife] gave me the articles you found.

Okay, first I guess I'll try to cover a few of the things we discussed over the weekend. There were a few points brought up that stuck out to me: 1) CO2 is not a greenhouse gas, 2) 30 years ago climatologists were predicting an ice age, while now they're predicting global warming, so how can we trust what they're saying, 3) Current data indicates that we're actually headed into a cooling period, 4) Mars ice caps are melting, indicating that increased solar activity is responsible for the recent warming trend, and 5) Sensors used to take measurements of polar ice were flawed, so we can't trust those measurements. I probably got a few of those wrong, mixed up a few with claims I've read on the Internet, and there are probably a few that I forgot, but that's mostly what I remember. So, I tried looking up those claims and here's what I came up with.

1) CO2 is not a greenhouse gas.

I guess you already looked this up, Stephen, since you wrote on the printouts you gave [my wife] that CO2 actually is a greenhouse gas. Just to give a little information for John, though, here's some more info, mostly summarized from Wikipedia (http://en.wikipedia.org/wiki/Greenhouse_effect). Most of the electromagnetic radiation the sun emits is in the visible spectrum. Greenhouse gases, pretty much by definition, don't absorb light in the visible spectrum, so most of the radiation from the sun makes it all the way to the surface of the Earth. There, it does get absorbed by numerous objects. As these heat up, they will radiate some of that energy back out in the infrared spectrum. Now, greenhouse gases, again pretty much by definition, do absorb light in that spectrum. So, the gases absorb that infrared radiation and heat up. Some of that heat will be transferred to surrounding gases, with some of it eventually making it back down to the ground. Some of it will be radiated back out in all directions - some back towards the ground, and some out into space. So, the net result of having greenhouse gases in an atmosphere is that the temperature of the planet will be higher.

The main greenhouse gas in our atmosphere is water. It provides around 36% of the heating. Next comes carbon dioxide, at around 9%. It's a little difficult to calculate how much heating each gas provides, since they interact with each other. For example, if you remove all the CO2 and water from the atmosphere, we would lose more than 45% of the greenhouse heating.

Here's another link, showing the actual absorption spectrum of CO2, and giving a more detailed explanation of how the absorption works on a molecular level:
http://www.wag.caltech.edu/home/jang/genchem/infrared.htm

There are other greenhouse gases, as well. Some are more effective on a pound for pound basis (such as methane). However, because their concentrations are so much lower, their total effect isn't as great.

One argument I have heard, is that carbon dioxide may be a result of warming - that some mechanism causes more CO2 to enter the atmosphere as the temperature increases. This argument is usually in response to the historical trend of global temperature vs. CO2. However, we can be pretty darn sure that much of the reason CO2 levels are rising right now is because of people burning fossil fuels. All that carbon was sequestered underground, and we're releasing it faster than it can be sequestered again. So, knowing that CO2 is definitely a greenhouse gas, if there's a mechanism that causes CO2 levels to rise with temperature, it's a feedback that's going to make the current situation worse.

2) 30 years ago climatologists were predicting an ice age, while now they're predicting global warming, so how can we trust what they're saying.

I wasn't paying much attention to climate science 30 years ago, so I can't speak to this directly. I do know that the way the media currently presents science is pretty bad. Look how much the media hyped the recent announcement of finding methane on Mars and how it could be indicative of life. The reality is that the current scientific consensus is much more conservative - it may be life, but there are many other possibilities it could be, and we just won't know until we get more data. So, if science reporting 30 years ago was anything like it is today, I could easily see the media playing up reports far more than what was the actual scientific consensus.

I found a fairly recent paper in the journal of the American Meteorological Society doing a literature search on climate research during the 60s and 70s. They found that a small minority of papers predicted global cooling, but that the majority actually were predicting global warming even then. So, it appears that the scientific consensus on global warming hasn't changed in the past 30 years, and has just gotten stronger. Here's a short blog entry describing the paper, which also has a link to the full paper:
http://www.realclimate.org/index.php/archives/2008/03/the-global-cooling-mole/

3) Current data indicates that we're actually headed into a cooling period.

For your reference, John, here's one of the articles Stephen printed out for me:
http://www.dailytech.com/Temperature+Monitors+Report+Widescale+Global+Cooling/article10866.htm

My main take of that article is that there's not enough information in it to predict that we've actually started a cooling trend. Average global temperature is influenced by quite a few factors, and thus fluctuates quite a bit from year to year. Global warming doesn't predict that every year will be warmer than the last, only that the trend is to higher temperatures. Just look closely at the graph they've provided. Several other periods show similar valleys, quickly rebounding to higher temperatures. Maybe this recent drop was the biggest, but not by a lot. Unless these temperatures stay low for a longer period than previous valleys, there's no reason to believe that this is a long term trend.

The only mechanism the article gives for why temperature might be decreasing is "reduced solar activity." Looking at the article linked to in the original article, the mechanism claimed seems to be the Sun's magnetosphere shielding Earth from cosmic rays, and the effect that has on cloud formation. The solar activity being described is not the solar irradiance. If solar irradiance were decreasing, I would fully expect that would decrease the Earth's temperature. How could it not? But actual measurements of solar irradiance show it to be pretty darn constant. It does vary slightly over an 11 year cycle (same as sun spots), but that variance is only ±0.65 W/m² about a 1366 W/m² average, or about 0.1% total variance.
http://en.wikipedia.org/wiki/Solar_variation

Hmm, I just found another record of solar irradiance in the NASA link a few paragraphs below. It looks like the current valley in solar irradiance is a little lower than the previous two valleys, but still not very far off from the average - maybe abut 0.15% total variation. It looks like we're right about at the minimum, and getting ready to start receiving more energy from the Sun again.

The links between other properties of the Sun and Earth's climate are more tenuous. I've seen a few studies claiming such links, but none that seem to hold up to scrutiny from other scientists. If either of you could send something showing a strong link, I'd be interested in reading it. That same Wikipedia article linked above discusses some of these proposed correlations:
http://en.wikipedia.org/wiki/Solar_variation#Global_warming

This article also addresses proposed correlations:
http://www.realclimate.org/index.php?p=180

As far as what could have caused the cooling, it looks like it my be due mainly to La Niña. NASA's Goddard Institute has a good discussion of this:
http://data.giss.nasa.gov/gistemp/2008/

I also found a report from June of last year that predicted this cooling. According to the link below, most climate models ignore short term effects such as El Niño and La Niña. For long term forecasts, they're not that important. For short term forecasts, however, they can have big impacts. The authors incorporated ocean currents into their model to give more short term predictions, and as I already said, they predicted the recent cooling.
http://www.ifm-geomar.de/index.php?id=4192&L=1

4) Mars ice caps are melting, indicating that increased solar radiation output is responsible for the recent warming trend.

The solar irradiance trends linked above show that the melting of Mars ice caps definitely isn't due to solar radiation, since solar irradiance hasn't changed by more than a fraction of a percent, and has actually been on the downward side of the cycle for the past few years. I'm not sure what other properties of the Sun would influence the ice caps on Mars.

A National Geographic news clip on this mentions that a Russian scientist, Habibullo Abdussamatov, thinks increased solar irradiance is heating both planets (again - see the actual measured solar irradiance in the Wikipedia link), but other scientists offer explanations for other factors that drive Mars' climate, including that the wobble of it's tilt axis is more pronounced than Earth's.
http://news.nationalgeographic.com/news/2007/02/070228-mars-warming.html

Wikipedia also has a section on this. The consensus seems to be that no one's exactly sure what's causing the Martian ice caps to melt, but it seems to be a local climate phenomenon, not a global one. With Mars' thin atmosphere and lack of oceans, it doesn't have the same thermal buffers as Earth, so smaller phenomena can have a larger effect. It mentions that dust storms could have darkened the ice caps, increasing the amount of solar energy they absorb, causing them to melt faster.
http://en.wikipedia.org/wiki/Climate_of_Mars#Evidence_for_recent_climatic_change

Here's another article discussing the southern Martian ice cap:
http://www.realclimate.org/index.php?p=192

I guess the short of it is, although people have hypotheses, no one's exactly sure what's causing Mars' ice caps to melt, because it's another planet that we haven't been able to study in enough detail to know the intricacies of what drives its climate. Although the solar irradiance argument put forth by Abdussamatov is almost certainly wrong.

5) Sensors used to take measurements of polar ice were flawed, so we can't trust those measurements.

To be honest, I'm not sure exactly which measurements you were talking about. I did see a mention of something in a recent entry on Carl Zimmer's blog (he happens to be one of my favorite science writers). Was this what you were referring to?
http://blogs.discovermagazine.com/loom/2009/02/22/a-wrinkle-in-ice-or-not/



I still don't know as much about global warming as I do about other fields, but the more research I do, the more confidence I have in the science. But, I could still be wrong. Keep sending me articles you think show global warming to be wrong. If it is, I'll change my view eventually. If the scientists are right, though, then the next thing to discuss is what to do about it. Do we even try to reduce our carbon output, or do we just adapt to any changes global warming causes? Personally, I think it will be somewhere in between. Trying to eliminate carbon output cold turkey would be more costly than adapting to the changes from global warming. But not doing anything about carbon output and focusing solely on adaptation would probably be more expensive than a little up front cost on energy research right now.

-Jeff

[end of e-mail]

If I get any responses from them that show anything I wrote to be wrong, I'll be sure to add it here. I also let both of them know that I was putting a copy of this here on my blog, so maybe they'll post their comments here.

Thursday, February 12, 2009

Book Review - Evolution: What the Fossils Say and Why It Matters

In honor of Darwin Day, I figured that I'd post an entry related to evolution. Here is my review of Evolution: What the Fossils Say and Why It Matters, written by Donald Prothero, Ph.D. Let me say right at the beginning that the book was very good, and that I recommend it.

The title of the book is a bit misleading, in that it leaves out a major theme that was covered. A good portion in the beginning of the book is spent debunking creationism. Perhaps some readers are aware of Duane Gish's Evolution? the Fossils Say No!, and so notice the play on words and realize that Prothero's book was partly in response to Gish. For others (such as me before I read the book), the allusion isn't so obvious. In any case, Prothero devoted a good bit of space to pointing out the errors in many creationist arguments, including a detailed explanation on how the Grand Canyon was formed through slow geological processes and not through a catastrophic flood, along with the evidence on how we know this.

Also in the beginning of the book, Prothero spent some time explaining science & paleontology, which is what you'd expect for a book intended for a lay audience. His explanation of cladistics was very good.

Finally, on page 145, Prothero started Part II, which presented the evidence and explanations of the history of life on this planet. He started right from the beginning, with a few theories on abiogenesis. Consequently, his first chapter from Part II didn't really have any fossil evidence. As soon as he progressed in time to when organsims developed hard parts that could fossilize, the book finally lived up to its name. He tried to cover a little bit of everything, from pre-cambrian single celled organsims, on up to very recent mammalian evolution. Obviously, with a 400 page book trying to cover that much territory, he couldn't go in depth into any particular topic, but he did give a very good overview. He did tend to cover vertebrates in more detail than any other lineage, but I suppose that's because that's what most readers would be most interested in.

Since the book was about fossil evidence, it included a great deal of photos and drawings of fossils. To give a sense on what was in the book, below is one of my favorite figures, illustrating the transition from seal-like mammals to walruses. (I apologize for the poor quality of these images, especially along the edges, but I wasn't about to ruin the binding on my book just to make it lay flat in the scanner.)

Walrus Transitional Fossils

Another good example of the way fossils were presented is the figure below, showing the homology between non-avian dinosaurs and birds.

Non-avian Dinosaur & Bird Homology

As would be expected in a book about evolution, there were many cladograms (family trees). They were almost all well illustrated with representative members of each lineage, such as the one below.

Rhipidistian Cladogram

The center of the book contained several pages of color plates. These included some nice color photos of fossils, as well as some artistic renderings of what the animals might have looked like in life.

Tiktaalik Fossil & Reconstruction

I did have a few reservations. For one, I would have liked to have seen even more photos & illustrations of fossils. In some sections, Prothero mentioned fossils in the text, but had no illustrations to show the reader what they actually looked like. In several sections, Prothero made statements to the effect of, a highly trained paleontologist can see that... I realize that expertise is important, but Prothero came off as a bit condescending in several places. I would have preferred to have seen wording like careful observation shows that...

Overall, it was a very good book, and very informative. I'd already read a few books on evolution prior to this, but they had dealt with much more specific topics, such as the transition from sea to land, or human evolution. This was the first book I'd read that covered such a wide range of transitions, with so many photos and illustrations to support it. If you're already familiar with the creationist arguments, or have a good lay understanding of how evolution works, Part I can be a bit of a slog, although I can see how those chapters would be very informative to people without that background. But once you get to Part II, it's a very informative, fun to read book.

Thursday, February 12, 2009

Happy Darwin Day

Darwin's BirthdayToday is the 200th birthday of Charles Darwin, the man who presented evolution in such a way and with sufficient evidence that it became obvious that it was the explanation for how life developed on this planet. Others had ideas of transmutation before Darwin, and Alfred Russel Wallace even came up with a theory of natural selection very similar to Darwin's at around the same time, so it's apparent that humanity would have eventually recognized how evolution works. But Darwin's genius in presenting all the evidence for evolution in the way he did certainly gave the field a huge head start.

If you're looking for a way to celebrate Darwin Day, DarwinDay.org has a list of events from around the world. If you're in the DFW area, the Dallas Museum of Nature & Science is having Drinks with Darwin from 6:30 to 8:00. If I was just a little closer, or if this was the weekend, I'd probably go. However, I think I'm just going to have to content myself with watching the lineup of evolution documentaries on The Science Channel (and maybe the episode of Walking with Dinosaurs on Animal Planet).

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