Monday, February 07, 2005

Evolution and Ernst Mayr

The theory of evolution has been in the news quite a bit lately. This past week marked the passing of evolutionary biologist Ernst Mayr who has been described as one of the most influential scientists of the 20th century. Mayr is most noted for his 1942 book - Systematics and the Origin of Species, where he outlined his theory of allopatric speciation. This view, which was actually rejected by Darwin, held that speciation could only take place if populations were geographically separated. It was Mayr that introduced the currently accepted definition of a species as a population of interbreeding organisms. It is only through spatial separation that evolution would lead to enough alterations that would prevent interbreeding.

I don't think the general public realizes how important evolution is to modern biology and medicine. The reason why experiments on bacteria, yeast, worms, flies, and mice have any impact on human physiology is that we share a large portion of the same genetic material. For example, 50% of the genome of the tiny nematode worm C. elegans can be found in humans. Evolution gives us a framework for understanding why this is so and where to look next.

November's issue of National Geographic has an illuminating article on Darwin. A sobering statistic is that in polls taken in 1982, 1993, 1997, and 1999, the creationist stance - that God alone and not evolution produced humans - had never drawn less than 44 percent of the US population. Only 37 percent of Americans were satisfied with allowing room for both God and Darwin (a view that is compatible with Roman Catholic dogma).

I think we have a public relations problem here. Perhaps, instead of battling directly with the creationist movement, we need to point out how useful the concept of evolution can be. We can show them how biologists use ideas from natural selection to develop the therapies that could save their lives. Maybe I'm treading on dangerous ground but maybe we should argue that evolution may not be in contradiction with the bible. Evolution is about dynamics and not necessarily initial conditions. Who knows, the world could have been set in motion 4000 years ago with the entire cosmological, fossil and historical record in place for us to discover. Creationists cannot argue that we do manipulate domestic animal breeds and that antibiotic resistance is a real thing implying that evolution is currently taking place. Surely, a beneficent God would have given us the means to help ourselves. Organizing life around evolution would be one of God's gifts.


11 comments:

steve said...

The process of evolution has been experimentally verified without question. But has anyone shown that humans could have evolved from complex molecules in the time allowed? (e.g., age of the universe = 10 Gyr?) I think the best claim a creationist (or "intelligent design" enthusiast or whatever) could make is that, sure, evolution works, but without a hidden push every now and then there has not been enough time to achieve the observed complexity of the biological world. Since we can't really estimate the necessary timescales from what we currently know, we can't rule out this possibility.

I once asked a well-known evolutionary biologist at Harvard about this, and was stunned to realize he didn't understand my question. He gave me a BS answer about the observed mutation rate being fast enough to explain the observed complexity of life, but I don't how anyone could justify that.

Of course Occam's razor suggests that evolution alone is capable of producing humans in the allotted time, but that is not yet verifiable scientifically.

Carson Chow said...

Hi Steve,

I don't think we've even shown that bacteria could have evolved in the time allotted. I think it is reasonably safe to say that diffusion through species space alone is probably not sufficient. There must be layers of meta-level dynamics that we just don't understand. I'm not an expert but I don't think we even have a clue as to how to model the global process mathematically.

My point was that there are two issues here. The first is whether or not evolution is soley responsible for all life on earth. The second is whether or not it plays an important role in biology. It seems like the debate is focused on the first question but maybe we should shift it to the second. If we can separate theology from biology we might do ourselves a favor. Somehow the cosmologists seem to have escaped the attacks. The big bang theory is not nearly as controversial as evolution. One of the reasons might be that cosmologists have gone out of their way to say science cannot say anything about what happened before the big bang or why it even happened. They've left room for God. Maybe we should do the same in the life sciences. However, I think we're kind of stuck in an NRA-like dilemna. We're worried that if we give up our hand held howitzers, they'll take away our beebee guns. We can't concede that we don't fully understand evolution because we're afraid creationists will ban it in schools and biology as we know it will end.

cc

Anonymous said...

Another wonderful blog, now to read and think. Thank you, Carson.

Anne

Anonymous said...

http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/07/05/MNGFV7GBAS1.DTL

A giant in biology has evolved to 100
He helped modernize Darwinism
By Keay Davidson - San Francisco Chronicle

"I'm the last survivor of the golden age of the (neo-Darwinian) Evolutionary Synthesis," Mayr says in an essay published in Friday's issue of Science. The synthesis became, and remains, the basis for evolutionary teaching in high schools and colleges.

Still, no scientific paradigm is ever complete. There are always unresolved puzzles, which provide grist for the mills of dissenters.

For example, critics still insist that the neo-Darwinian synthesis can't explain obvious cases of rapid species evolution. Since the 1970s, the best- known of these skeptics have been Niles Eldredge and the late Stephen Jay Gould.

One of the most baffling case examples of rapid speciation -- the formation of new species -- is found in African lakes, such as Lake Malawi and Lake Victoria, which formed 12,500 years ago. Since then Lake Victoria's original population of cichlid fish has evolved into "hundreds of different species. ... If you look at their jaw shapes, they're vastly different," says a leading historian of biology, William B. Provine of Cornell University.

"And some eat fish, while some eat shellfish, and some others eat little microorganisms in the water. Some are adapted to deep water, while some are adapted to shallow water," Provine adds. In short, the African cichlids offer an astonishing portrait of biological diversity -- "and it all happened in 12,500 years!"

Even Mayr has been impressed by the amazing story of the cichlids. Previously, from 1942 until the 1980s or 1990s, he insisted that new species form when creatures become geographically isolated -- say, on an island -- from their genetic peers.

But the geographic speciation theory has trouble explaining the cichlids. How, skeptics ask, could so many varieties of a single type of fish emerge so fast in a single lake, where they all swim in the same body of water?

Hence, in recent years, Mayr has mellowed in his thinking about speciation. While he still regards geographic speciation as the main engine of species formation, he acknowledges that other processes might also be involved....

Anne

Anonymous said...

Toward a New Philosophy of Biology
Ernst Mayr [1988]

The complexity of living systems.

Living systems are characterized by a remarkably complex organization which endows them with the capacity to respond to external stimuli, to bind or release energy (metabolism), to grow, to differentiate, and to replicate. Biological systems have the further remarkable property that they are open systems, which maintain a steady-state balance in spite of much input and output. This homeostasis is made possible by the elaborate feedback mechanisms, unknown in their precision in any inanimate system.

On the average...organic systems are more complex by several orders of magnitude than those of inanimate objects. Even at the molecular level, the macromolecules that characterize living beings do not differ in principle from the lower-molecular-weight molecules that are the regular constituents of inanimate nature, but they are much larger and more complex. This complexity endows them with extraordinary properties not found in inert matter.

Systems at each hierarchical level have two properties. They act as wholes (as though they were a homogenous entity), and their characteristics cannot be deduced (even in theory) from the most complete knowledge of the components, taken separately or in other combinations. In other words, when such a system is assembled from its components, new characteristics of the whole emerge that could not have been predicted from a knowledge of the constituents. Such emergence of new properties occurs also throughout the inanimate world, but only organisms show such dramatic emergence of new characteristics at every hierarchical level of the system.

Anne

Anonymous said...

Carson

My eyes are not the best though corrected. The dark background swallows light making your lovely blog harder to read.

Anne

sjfromm said...

Steve wrote, Since we can't really estimate the necessary timescales from what we currently know...Funny...I've thought exactly the same thing for over a decade now.

sjfromm said...

Carson wrote, I think it is reasonably safe to say that diffusion through species space alone is probably not sufficient.But natural selection is precisely diffusion through species/genome space acted upon by selective pressures.

There's no other explanation of complex design out there.

Carson Chow said...

I should say, diffusion on a static background is insufficient. Natural selection is only a local dynamical rule. If you isolate one species and assume it diffuses in the static background of its environment, then there may not be enough time to evolve. What you're missing is the interactions between multiply co-evolving systems. Hence, you may have to take the entire ecosystem in toto if you want to understand evolution.

Anonymous said...

"What you're missing is the interactions between multiply co-evolving systems. Hence, you may have to take the entire ecosystem in toto if you want to understand evolution."

Organisms evolve rather than parts of organisms, and they evolve in an ecosystem.

Anne

Carson Chow said...

I think it is still under debate as to what is evolving. Dawkins for example believes that genes are the prime entity. Genes within an organism may be battling with themselves. Also, most mutations are probably neutral and have no phenotypic effect but may come into play at a later time. Bacteria, phages and viruses exchange genetic material horizontally. Phages evolve so quickly that you may not even be able to separate them into separate species. As I put in my post on What is Life?, I don't think one can separate organisms from their constituents or environment. I think everything is evolving at all scales all at once.