Science & Nature Archive

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).

Friday, January 16, 2009

Life on Mars

My Favorite MartianThis news has already made it around practically all of the science blogosphere, and I even saw it mentioned in a special breaking news type segment on the Science Channel last night, but it's so cool that I can't resist commenting on it.

NASA just announced that they've definitively found methane on Mars. This is the first time they've been positive - previous announcements of methane were tentative, requiring more examination of the evidence. Since methane gets broken down very quickly in the Martian atmosphere (through as yet unknown mechanisms), finding methane means it must have been released into the atmosphere fairly recently. From what I've been able to gather, there are three likely sources for this methane:

  1. Biology This is most exciting possibility, that living organisms beneath the Martian permafrost are creating the methane as waste.
  2. Geochemical While I don't find this quite as exciting as life, it would mean that Mars is still geologically active. There are several processes that this could be.
  3. Reservoir In other words, there's no current process producing new methane. It was previously generated either biologically or geochemically (or both), and became trapped, and all we're witnessing now are periodic leaks.

I'm trying to be reserved about this, since NASA got my hopes up before with the announcement of probable fossil microbes in a Martian meteorite, which turned out to be not as probable as they'd initially thought. It still could be microbe fossils, but it could also be from non-biological sources along with Earthly contamination. So, I'm trying not to get too excited about this announcement.

But, if the methane does turn out to be from biological origin, it means we've found aliens! Granted, life on Mars may be little green slime instead of little green men, but it would still be extraterrestrial life. From Carl Zimmer's blog coverage of the news conference, there were a few statements that do seem to indicate that biology is the most likely source of this methane.

2:18 Mumma points out that if volcanoes were making the methane, you’d expect other gases too, which they don’t see. NASA will look for other things that would be consistent with biology.
2:21 Mumma is explaining some of the backstory–first reports of observations were in 2003. We knew we had methane since late 2003, he says. But they’ve been working to make the data “unassailable.” We’ll see…
2:35 Back to the science: Lisa Pratt says methane from rock (serpentinization) is rare on Earth and actually plugs up active sites. This is why she takes biology seriously as “slightly more plausible.”

There are two possibilities I can think of for this life (if it does indeed turn out to be life):

  1. uses DNA or RNA
  2. uses something else

If the microbes use DNA or RNA, then it would seem extremely likely that they have a common ancestor with life here on Earth. From what I've read, scientists think it's more likely that life would have originated here on Earth, and then got transferred somehow to Mars. Though it's still possible that it went in the other direction - life originating on Mars and then seeding Earth.

If the microbes don't use DNA or RNA, then it would seem most likely that they originated independently from the life here on Earth. Now that would be super exciting. For one, it would mean that life probably is fairly common in the universe, and that we're not all alone. Heck, if so many solar systems have life, then other multicellular and intelligent life out there seems much more likely, maybe even other technologically inclined organisms capable of producing civilizations. However, it will be a long time before we can look into those possibilities. But, the possibility of independent life on Mars is exciting for another reason - it would show us another strategy for life to take. It would start to show what types of things common to life on Earth are that way because they're needed for life, or simply because of historical contingency.

This really is some of the most exciting news I've heard in a while. Now we just have to wait to see what the actual source turns out to be.

Further Reading:

Added 2009-01-19 Phil Plait of the Bad Astronomy Blog has finally weighed in on this topic. He's very reserved about the whole thing, stressing that we don't know exactly what's creating the methane, and that we just need to wait for more data. He also criticizes much of the media for over hyping the biology aspect of the story.

Revised 2009-02-13 to added the statement "(if it does indeed turn out to be life)." That section's been bugging me ever since I first posted this - I should have edited that a while ago.

Thursday, January 15, 2009

Darwin Year Events in Dallas

Charles Darwin as a Young ManI wrote an e-mail to the Dallas Museum of Nature & Science asking them about Darwin Year events. Since the events don't seem to be advertised very prominently on the museum's site, I'll post their response here:

Hi Jeff. We are going to host two events. Cocktails with Charles on his actual birthday 2/12 and cupcakes with Charles on Saturday 2/14. The Thursday event is for adults only and the Saturday event is for families.

I don't think I'll make the two hour drive to to Dallas just for cocktails or cupcakes, but if I just happen to be visiting my wife's family that weekend...

Friday, January 2, 2009

Happy Darwin Year

Charles Darwin as a Young ManSince 2009 marks the bicentennial of Charles Darwin's birth, as well as the 150th anniversary (sesquicentennial) of the publication of On the Origin of Species, many groups have decided that 2009 should be Darwin Year. So, to kick off the year, here are a couple links to good sites dealing with Darwin.

  • Nature's Darwin 200 The prestigious journal has put together a collection of articles, editorials, news stories, and various other essays and features that have to do with evolution in general or Darwin in particular.
  • The Darwin 200 Consortium Hosted by London's Natural History Museum, this site also has a collection of info on evolution, as well as info about upcoming events to celebrate Darwin Year.
  • DarwinDay.org Another good site with evolutionary info. The events on this site are mostly on or around Darwin Day, February 12th.
  • American Museum of Natural History's Darwin page Yet another good collection of information. This is from the exhibit that ran in the museum from 2005 to 2006.

To give a short taste of the Nature site, they've made freely available, and even encouraged dissemination of (so sharing it here is perfectly legal), an article on 15 Evolutionary Gems, collecting information from articles published in the journal "over the past decade or so to illustrate the breadth, depth and power of evolutionary thinking."

Don't forget to check with your own local museums. Even if they don't have any special events scheduled for Darwin Year, they're always fun to visit, anyway.

Added 2009-01-02 Well, I figure that for the kick off to Darwin Year I might as well post links to the previous posts I've made on evolution or Darwin. If I happen to post anything else on the subject during this year, I'll try to remember to update this list.

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