Life is an entropy exchange

Just one more word about this evolution thing.
Naysayers often point to the Second Law of Thermodynamics to support their view that evolution can't be true because entropy (chaos, disorder, randomness...) increases.

quick review of the laws:
0 = definition of temperature
1 = conservation of energy
2 = entropy of an isolated macroscopic system never decreases
3 = as temperature goes to absolute zero, entropy approaches a constant minimum

The laws do not at all forbid evolution of complex organisms. They just tell us this added complexity has to be paid for.

OK. A complex organism has less entropy than a simple one. So it's going against the grain to go from simple to complex, and in the case of the magnificent human brain it's just unreasonable.
But hey, we appear to go against the Second Law all the time. Meerly by growing, the simplest bug decreases its own personal entropy.
How can that be?
Well, you have to consider the "isolated macroscopic system". An individual is not an isolated system. It eats. It breathes. It metabolizes. It shits. It has an impact on its environment. To draw a circle around the 'system' here, you have to include the entire planet, plus the moon because its pull provides us with the energy that moves the oceans around, plus the sun because of the energy it send us.
And now there's plenty of room to mess with the conservation of energy and increasing entropy. Living organisms are constantly involved in converting one form of energy to another, and in increasing entropy here to decrease it there. Many developments in body form cost energy (it takes an effort to make an eye, it takes energy to make thick bark), but if that development is more advantageous than costly (finding food more easily, resisting beetles) it will be retained. A development no longer advantageous (like dewclaws) will fade away as its parts degenerate or are co-opted for new uses.
We humans cannot always think of what advantage is being gained, so we cannot explain everything. Sometimes the advantage no longer is one. It can take a long time to adapt to a given circumstance, and when that circumstance changes, the old adaptation may persist for many generations.

The Laws of Thermodynamics have nothing to say against evolution. They just tell us to look at the whole system, and that local differences in entropy even out in the system as a whole.

Change for the better

I was having a discussion the other day about how species change over time. It's interesting how ingrained is the idea that evolution has to 'go' somewhere, that evolution equals progress toward a predetermined goal or an ideal.

Evolution is actually a neutral term. Evolution responds to the environmental pressures of the moment, pressure that can change direction or be reversed. New strains or species are 'better' than the old in the limited sense of being better adapted to succeed in the conditions they've been selected for. To say a species is 'more evolved' literally means it has gone through more reproductive cycles under the influence of selective pressure.

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So to people who stand aghast to think humans descended from apes (apes, eww)(whaddya mean eww? we're still apes!), think of this: our closest relatives the chimpanzees are more evolved than we are. Yes, really. From the point at which our branches diverged, they have gone through more generations (because humans become sexually mature later in life), and to show for it they have more changes in their DNA than we do. We have gone a different route, and we have different lives as a result, but don't say we're more evolved.

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Bacteria: now those suckers are evolved!

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All around us, all the time

Ok, one more on the subject, and then I'll move on.

One of the interesting points in discussing evolution is that people tend to think of it as something that happened long ago. Evolution 'set' living things the way they are and that's it. And thus any evidence for evolution is to be found in the fossil record, and only in the fossil record.

Not so, not so!

Plenty of evidence is found in the fossil record, but that's not the only place to find it. Even back in my own university days, there was the classic story of moths in London. Used to be they had light-colored wings. As pollution turned the tree trunks on which the moths rested all black, the moths stood out and were easy prey. Over time, darker moths survived and eventually matched the tree trunks. Then people started coming out of the industrial revolution with a wish for clean air, the pollution was cleaned up, and London tree trunks are no longer black as coal. Dark moths, finding themselves easy prey like their light predecessors, disappeared, while lighter ones survived. Today moths in London have light coloring again.

It's easy to see how an animal or plant that is better at surviving and reproducing than its brethren gradually comes to dominate its ecological niche. This is true in the wild, and it's true for domesticated species. Just take dogs. Dogs we like the look of get special opportunities to breed. We force their evolution into various strange forms by selecting individuals. It's the very same thing as frogs evolving in a pond, only speeded up by the heavy hand of human dog-breeders and with endpoints that apply (naturally) only to the special case of domesticated dogs.

Thing is, selective pressure applies to humans too. We might like to think of ourselves as exempt, but not at all! There's a lot of time involved in natural selection. You have to pass your genes on to children, who grow up and have children of their own, so for people it takes 15-40 years for a single round of selection. In the modern age, we change our environment much faster than that.

You can see the effects of being poorly adapted to 21st century life in the type 2 diabetes that is rampant in many first-world countries, notably America. But this doesn't affect all groups equally. People who come from places that were more recently similar to an older way of life, where periods of feast and famine were regular and severe are harder hit by diabetes today. Their metabolism hasn't had as much time to adapt. It used to be advantageous to be able to eat huge amounts of food and store that energy as fat that would be consumed metabolically during times of famine. The fatties could survive, for example, the harsh Arctic winter, whereas thinner people could not. Eventually developing diabetes wasn't much of an issue compared with a serious annual risk of starvation. Now that food is abundant all the time, the craving to eat is still there, the ability to store fat is still there, but the crisis never comes and the diabetes does.*

So evolution goes on all over the world, every day, for every species. The selective pressures may be different, and often man-made, but there will always be pressure from somewhere, and living organisms will always respond to it.**

*the selective pressure against people vulnerable to type 2 diabetes may seem irrelevant to reproduction, because it generally occurs after childbearing is finished. However, it is probably not irrelevant. First, it has been shown that women who live withing 30km of their mothers have more children than their sisters who live farther away, an effect likely explained by the help that grandparents, and grandmothers in particular, give in raising the families of their offspring. If grandmothers are not available, through distance or death, women appear to hesitate more in having larger families. Also, having a parent of either sex die young hinders families economically and socially. Remember, in reproductive success, it's the number of fertile children you have that counts, not the proximal reasons why you have number of children you do - whether you conciously choose to limit your family or not.

**there is some argument that modern medical care is putting humans beyond the reach of evolution, since people who would otherwise not survive do now go on to have families. This is certainly true in some respects, but overall evolution still has its say in our future.

Half an eye IS better than none

Alright, Ginger, here you go. I'm going to do this off the top of my head because my references are at home (or on line, but if I start calling up this stuff I'll never take a break to get any work done).

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Evolution works in small steps. Lots of creatures are born with small genetic variations that did not exist in their parents (replicating our 3,000,000,000 base pairs of DNA is bound to make a mistake somewhere eventually). Sometimes that means you're born with Muscular Dystrophy; usually it means nothing at all: now and then it means you're a little bit better at something.

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One of the creationist arguments that evolution cannot be right is that this kind of small incrementation cannot possibly result in complex structures that don't work until all the parts are there. Having just some of the parts would be useless and not advantageous, so you couldn't get them all together by chance. An oft-taken example is the eye.

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But it simply isn't true that the modern human eye must be complete and perfectly functional for it to be advantageous. Certainly, when competing one human against another, being myopic is not as good as having clear vision. And being color-blind is not as good as being able to see the usual spectrum of colors. And having macular degeneration is disadvantageous too. But that's comparing partial vision to good vision, when you should be comparing partial vision to even less vision or none at all.

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Early in the course of animal life on earth, imagine that no creature can see. Then one creature happens to have a patch of cells that are somewhat sensitive to light. This may indeed be advantageous because it gives the creature an edge in knowing where to find shelter, or which direction to go to find food plants that grow in the light. Then one of this creature's descendents had a light-sensitive patch that was bigger, and so could start to detect the movement of something dark against the sky. This creature might avoid predators better than its peers and thus survive to reproduce more. Then in one of its descendants the light-sensitive patch developed in a sort of indentation, and this concentrated the light in one area, resulting in better resolution. And so on. The indentation deepens to a globe, an eye. The light-sensitive cells become sensitive to different wavelengths, giving color vision. The globe is capped with a lens of very stable, clear, flexible proteins (the crystallins, a family of enzymes used for completely different purposes, just happen to fulfil these critera, and now make our lenses) that helps focus light into sharp images. Every step of building an eye is more useful to some animals than the eye without that step. Examples of different eyes, down to simple light-sensitive patches, abound in the animal kingdom (and that's where I need my references to cite them for you).

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The very definition of what's a good eye varies with different animals. Cats' eyes are well developed for gathering all the light they can in the semi-dark, but that night-vision sacrifices daytime detail. Predators tend to have front-facing eyes with excellent acuity in a narrow zone in front where their prey is, with a concurrent sacrifice in peripheral vision. Prey animals, in contrast, have their eyes on the sides of their heads, making for excellent peripheral vision to spot that stalking lion but poor depth perception in front. Deep-living animals, if not completely blind, are often content with light-sensitive patches signalling 'up'.

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So in the course of evolution, changes that head toward something more useful than the previous version tend to let their animals live more successfully. What is better depends on what you need - whether you're prey or predator, living in bright light or shadows. Changes that don't help, or that hinder, either go unnoticed, or disappear from the gene pool, or are known to us as birth defects or genetic illnesses, or contribute to the diversity of the species. Just think of the color of your iris: living in most places, this color doesn't impact your physical fitness but it well may impact your sexual fitness by making you more desirable to the opposite sex (notably if your eyes are blue); in other places, like an equatorial desert where the sun is harsh, having a dark iris may protect your eye from too much light and thus have a real impact on your ability to function outdoors. Usually eye color is placed in the basket of normal variation without impact, but is it really...

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Anyway, the point is that the complex and magnificent thing that is an eye can indeed be developed through evolution, and there is plenty of evidence that it did so. Every part of the eye is explained, from its existence, position, color, eyelashes, tear ducts, even the awkward inside-out design (with the light-sensing retina behind other structures, and a central blind spot where the optic nerve enters - if one were to design an eye from scratch, surely this organisation would be avoided! but it's a leftover from earlier versions). A person denying evolution may then say, 'well, that's just a bad example, let me take another one.' But that one too will be argued and we'll just go on and on and on.

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I'll give you more if you ask for it, but it's time to prepare today's oncogenetics class. (cancer - now there's evolution gone wild!)

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