Evolution is descent with modification.


I'm specifically talking about biological or organic evolution here. It's necessary to make this distinction because the word itself precedes its biological usage. Anyone who adheres to the traditional sense of the word might be misled into thinking that individual organisms transform themselves from one form to another! We can avoid this by making a second bold declaration:

Populations evolve, not individuals.


Even exceptions to this broad rule can be subsumed when start to see everything as a population; an individual is, after all, a population of cells. Let's skirt around the edges of this issue of levels of evolution (which just begs for a write-up of its own) and stick to the task at hand.

Evolution happens to populations of living things that reproduce. (If there was a population of critters that didn't reproduce, they'd eventually die off. Even immortal critters have to knock off eventually. So, conveniently enough, any living thing that happens to still be walking around is probably reproductive. Even those noding E2.)

It isn't enough to simply reproduce for there to be biological evolution, however. There must also be some system of genetic inheritance. At least some of the generative information contained in the parent must get passed onto the offspring.

Reproduction and genetic inheritance: it so happens that having these two ingredients is enough for biological evolution. How evolution applies strictly to populations may become clearer now: because some individuals may leave more offspring than others (by dumb luck or otherwise -- genetic drift and natural selection) causes the membership of the population to change between generations.

We've had to assume that there are genetic differences between families. One exception to the bare minimum for evolution I gave above is when everyone is genetically identical. The changing makeup of a population that is evolution is strictly genetic change. Pierced noses and dyed hair don't count.

I feel comfortable about making this assumption because genetic variation is virtually guaranteed. Mutations are always being introduced in the genetic code because of mistakes made during replication. Mutation is the fuel of the engine that is evolution.


Where does this leave us? There are two more things that I want to mention about evolution: speciation and evolution's place in society.

Did you notice that the fundamental processes that I mentioned above don't account for the proliferation of species? Heck. Neither did the Origin of Species. Speciation is a special case of evolution.

This write-up is dedicated to the late Stephen Jay Gould, who would have done a much better job of it.


What follows below is the original content of this write-up. Because it has since migrated to the top of the nodeshell, and because it refers to write-ups since deleted, an overall upgrade became necessary.

There is a fundamental and common mistake being made here that cmmike has touched upon; and it is also worth elaborating on. As a biological term, evolution refers to heritable change. This can be caused by selection as pi has described, but also by mutation and sampling error (drift). A good analogy for the latter process comes in the form of black and white beans in an urn. A handful of beans will not necessarily reflect the colour proportions within the urn.

Because these process involve genetic change and because genetic change is heritable, all these processes are components of evolution.

Ever since the development of evolution as a principal biological discipline, other disciplines have drawn analogies from evolutionary processes including history, sociology and the computational sciences. It is an important caveat that transmission and reproduction within these systems will have very different constraints than a genetic (flesh and blood) system. Hence, these analogies are often inaccurate and misleading, succeeding only in generating excitement, misplaced legitimacy and confusion.

The development of cumulative changes in the characteristics of populations of organisms from each generation to the next. Evolution occurs by mutations in the structure of the genetic material, and the passing on of these changes from ancestor to descendant. Evolution is a fact; it is the way in which it occurs that is a theory.

See: Darwinism, neo-Darwinism, natural selection, gradualist evolution, punctuated equilibrium, biochemical evolution, macroevolution, microevolution, convergent evolution, divergent evolution, parallel evolution.

Evolution is as much a fact as the earth turning on its axis and going around the sun. At one time this was called the Copernican theory; but, when evidence for a theory becomes so overwhelming that no informed person can doubt it, it is customary for scientists to call it a fact. That all present life descended from earlier forms, over vast stretches of geologic time, is as firmly established as Copernican cosmology. Biologists differ only with respect to theories about how the process operates. - Martin Gardner

Biological evolution can take place in many ways. Many of the other writeups here describe the process in terms of passing along those traits that allow an organism to survive for longer. In theory, organisms that avoid being eaten will have more opportunities to reproduce. That is how we end up with insects that look just like leaves and zebras whose markings make it difficult to tell them apart when they stampede.

As quincyfree described earlier, a species can also evolve as a result of genetic drift and mutation. A salient example of this is the lack of genetic variability between harbor seals. This species was hunted almost to extinction; recently, the number of harbor seals has increased a great deal, but because the current population was derived from a very small population, the genetic difference between individual harbor seals is very small. Genetic drift and mutation are the main causes of evolution in species that reproduce asexually.

One additional force that drives species evolution (at least of sexually reproducing organisms) is sexual selection. Sexual selection works independently of what has so far been referred to as "natural selection," and favors those organisms that have traits that allow them to reproduce more often. Basically, sexual selection acts to preserve the heritable traits that make a particular organism sexy. The classic example of this is the peacock's tail. If you have ever been around a peacock, you know that the big fancy tail is little more than a convenient handle. However, peahens find that same elaborate peacock tail practically irresistable. It is possible that sexual selection is responsible for the entire population of people that are cute, but stupid.

So, in the end, there are basically three traits any individual organism can have that increase the chances that its genes will make it into the next generation. It can be smart (natural selection), it can be lucky (mutation, genetic drift), or it can be attractive (sexual selection).

Good luck transmitting those genes!

The Evolution of Evolution:

What amounts for the similarity among many species?

Creationist-
The divine plan of creation (purpose unknown) produced the basic "kinds" of organisms.

Lamarckian-
Decent from a common ancestor.

Darwin-
Descent from a common ancestor.

Modern Biology-
Descent from a common ancestor.

What accounts for the origin of variations among members of a species?

Creationist-
Although they can be environmentally caused, they are part of the divine plan of creation.

Lamarckian-
Environmentally caused.

Darwin-
At times: Unknown causation.
At times: environmental changes cause new variations, although the variations may be in any direction.

Modern Biology-
Heritable differences are caused by random changes (mutation) in the genetic material.
Noninheritable differences are caused by the environment.

What accounts for the presence of particular organs and structures through time?

Creationist-
They were initially designed so by the creator.
Many present creationists believe that organ defects, diseases, etc., are caused by the fall of humans from divine grace and/or intervention by the devil.

Lamarckian-
Use enhances the development of adaptive variations, and disuse eliminates nonadaptive ones.

Darwin-
Natural Selection perpetuates only adaptive traits and eliminates nonadaptive traits.
At times: use and disuse.

Modern Biology-
Primarily natural selection but other forces may be involved. (such as mutation)

What accounts for the variation among species?

Creationist-
The seperate creation of each species.
Many present creationists believe that the original "kinds" of organisms were perfect, and variations leading to species have been degenerative.

Lamarckian-
Each species has responded to different environmental needs by developing new organs or discarding old ones.

Darwin-
At times: Selective differences among species account for their changed inheritance.
At times: Differences in the use and disuse of particular organs has changed inheritance.

Modern Biology-
Changes occur in the genetic material of each species through the process of mutation and the various forces that change gene frequencies.

What accounts for the resemblance of organisms to their parents?

Creationist-
Mechanisms unknown, but acquired characters are inherited as part of the divine plan.

Lamarckian-
Those characters acquired through use and disuse are inherited through a pangenesislike process.

Darwin-
At times: unknown
At times: pangenesis

Modern Biology-
Transmission of genetic material through the germ plasm.

- From Strickenberger's "Evolution, 3rd Edition"

bedrick has correctly pointed out that there is widespread confusion between evolution and natural selection. It is also confused with Darwinism.

'Evolution' is an old word, and a plain English word meaning development, unrolling, or increasing complexity. The Webster definitions hint at some of this as much as Webster ever reveals any meaning mutter.

Darwin's theory of evolution is so familiar now, and has been applied so widely, that it seems natural to think of evolution as Darwinian evolution. But really all it means is 'change' in some expanding way. So the solar system has evolved. The English language has evolved. These do not imply that any natural selection, or any analogous process such as artificial selection, has taken place.

The evolution of organisms is an old idea; it might well go back to the Greeks, though I can't think of specific instances: it would be a characteristically Epicurean idea, for one. In modern times Erasmus Darwin and Lamarck put forward theories of evolution. A lot of people before (Charles) Darwin believed that species evolved from other species. They just didn't know how.

(An added confusion is that before Charles Darwin the word was also used for an entirely different theory, Webster's 6.(b), which no-one believes in any more.)

The radically new theory, discovered independently first by Patrick Matthew, then by Charles Darwin, then by Alfred Russel Wallace, was a theory of how evolution occurred. They came up with the idea of natural selection. Their idea is now known to be true, and Lamarck's idea of how evolution occurs is known to be false.

And to round off, Darwinism is this combination: that evolution occurs by means of natural selection; what we may also call "Darwinian evolution".

Gorgonzola has pointed out that in modern scientific discussion the word Darwinism is sometimes used more narrowly, with the added sense of gradualism. This is particularly the case with the Stephen Jay Gould camp who attack more orthodox Neo-Darwinism. But Darwin himself was not committed to gradualism, which was a term in nineteenth-century geology opposed to catastrophism. He phrased his arguments in gradualist terms to emphasize how slight the change needed to explain evolution was.

  Evolution is the brainchild of a man named Charles Darwin. It was originally conceived by him on the ship HMS Beagle from 1831 - 1836.

  While in the island chain Galapagos Archipelago Mr. Darwin observed interesting discrepancies between finch species. Some finches had curved beaks for probing flowers, while other had long straight beaks, which appeared to have been designed for drilling holes in wood for insect food.

  Previously any scientist observing this discrepancy would have assumed that God had simply designed the finches differently, so they would not have to share the same food source. Darwin postulated something different. He suggested that perhaps once in a while a finch would be born with a slightly different beak than its parents. This beak may have been better designed for acquiring food than that of the other finches in the area. Now let’s say during the lifetime of this finch the food supply became scarce for some reason or another. While the other finches may starve, the finch with the special beak would have an alternate source of food. This finch would survive and reproduce.

  Now although genetics had not really been introduced to the world at that time, it had been observed that offspring often inherited traits from their parents. Mr. Darwin hypothesized that some of the offspring would be likely to share this (no longer quite) unique feature. Should the period of low food supply continue into their lifetime, or should another one occur, the offspring with the trait would be more likely to survive and produce another generation. This time however the offspring produced are more likely to have the specialized beak, especially since chances are higher that both parents will have the desirable trait. The chance of this happening increases over time, so eventually an entire new race of finches will appear, all with the specialized beak. What happened to the original species? The food shortage probably did not kill them all off, and once the problem is resolved it is more than likely their population climbed back to it’s previous level. Perhaps they migrated to another island, one more abundant in the resources they require for life.

  While this theory is sound, it doesn’t account for finches turning into a completely different species. Mr. Darwin theorized that perhaps, over many, many generations, changes like this would “pile up”. One resource shortage might cause a change in the race’s predatory weapons, allowing them to hunt different types of prey. But this new prey might be harder to digest, leading some time later to the development of different digestive and eating organs. Perhaps this prey is fast so new legs need to be developed. And enhanced intellect certainly has no considerable disadvantages. So these changes keep on piling up, until one day, you have something so wildly different from the original species that it can be classified as an entirely different creature.

  This, the theory of macroevolution, is the most widely accepted explanation for the diversity of life on Earth. However debate continues to this day about its accuracy, and recent discoveries in numerous fields cast serious doubt on macroevolution’s future as a serious theory, therefore this author shall certainly not attempt to reach any conclusion in the bounds of this document. The goal of this document was merely to overview the theory of evolution from an objective point of view, and that being accomplished, is now concluded.

A scifi/comedy film released in June of 2001. Directed by Ivan Reitman and starring David Duchovny, Julianne Moore, Orlando Jones and Seann William Scott. Also features Dan Aykroyd.

The idea is that a meteor containing single celled organisms lands on Earth. The cells evolve at a breakneck pace, and our heroes (a gang of college teachers, various losers and government dropouts) learn this could lead to trouble. Of course the government then takes over research of the aliens and our heroes are kicked out of the loop. The gang then does all the thinking and figuring out while we never really see what the government does (doing field maneuvers or something, I guess) and then they ultimately triumph over the aliens, The Man, and shoddy dialog to save the day.

Subtle spoilers ahead
The movie looked good, but wasn’t written very well. There are too many dud scenes and poorly developed character traits. Several scenes just left you thinking, “ok, thanks for showing us that, but…?”. Like when the heroes are riding around in a jeep singing “Play that funky music” while the world is getting ready to end. Or how the weapon against the aliens is discovered on the back of a t-shirt (?) and without even trying it on any of the many available aliens, the whole team arms up to combat the largest alien by shooting the poison up it’s ass (??). Out of all the junk scenes they did include, they never really did show how they destroyed all the aliens in the end! Instead they concentrated on scenes with Julianne Moore falling down and Sean Scott bumbling into most of the major discoveries. And for some awkward reason they found it necessary for Duchovny and Moore to have a quick hump in a fire truck then add some unfunny blatant, shameless product placement at the end.

I’ll give it a break though. It is a product of modern Hollywood. It did have a few good “gotcha” scenes that made the whole theatre jump. A huge alien fart at the end was kinda funny. The seemingly few visuals it had were very cool, the dragon flying through the mall was great (too bad they killed it). Some of the science was even good. The aliens have twenty base pairs in their DNA while earth animals only have four, hence raising the chance of genetic mutation and evolution (in theory). The slowly evolving aliens wound up becoming elaborate dragons, bugs, amphibious critters and such, while quickly evolving aliens, having no specialization, just turned into blob type things. And Orlando Jones did manage to take a break from comic relief in the end to actually lend some scientific advice. And the door plainly is left open for Evolution Two, with the dragon flying away at the end.

In short, you might want to rent it. Maybe. They did have cool looking dragons and farting aliens.

An album by Geoff Moore and the Distance. Forefront, 1993. Song titles are as follows:

  1. Evolution...Redefined
  2. I can see clearly now
  3. Life Together
  4. Live to Tell
  5. If You Could See What I see
  6. GodGottaHoldOnMe
  7. That's When I'll Know I'm Home
  8. Heart to God, Hand to Man
  9. Why Should the Devil Have All the Good Music
  10. When All is Said and Done


The lyrics for the intro to the first track are as follows, by Geoff Moore and Phil Madiera:

Intro:

There are sounds of a 'typical' (high-)school environment, including locker doors opening and shutting, casual conversation, lots of background noise... these begin to fade as the sound of a creaky door opening takes the lead. The creaky door swings creakily shut and silence ensues for a moment. Then the teacher begins...

Darwin first did the eminent service of arousing attention to the probability of all change in organic, as well as in the inorganic world, being the result of law and not of miraculous interposition. For all life is a continuum. All living things, despite their awesome diversity, are related to each other. And evolution is the term we give to that process by which the structure of plants and animals changes with the passage of time, thus accounting for the continuum.

As the intro is drawing to its conclusion, 'forest' sounds begin emerging around the voice of the speaker, and just as the music begins, a howler monkey gives a call...


As controversial as evolution has been since its introduction as a potential explanation for "the way things are," only the first song of this album really touches on it. It's (probably) obvious that the band is Christian, so it's also obvious that the "teacher's" remarks will be torn apart in the rest of the song. Well... not so much of the 'tearing apart' happens... only a few disparaging remarks about the "teacher" and his words flit by: "Maybe my teacher, he's the missing link...," "Big bang fiction we factualize...". The song is quite a bit more about how much a person can be changed by Jesus Christ.

Personally, I enjoy listening to that particular song and album, but the disparaging remarks without any arguments are rather frustrating. There are Christians and non-Christians on both sides of the evolutionary fence, and either one groundlessly mocking the other is pointless.

Evolution is a movie dirrected by Ivan Reitman released on June 8, 2001. It stars David Duchovny, Julianne Moore, Orlando Jones, Seann William Scott, and Sarah Silverman.

The gist of the movie is that a meteor, carrying alien organisms hits the New Mexico desert. The aliens multiply and evolve at an alarmingly fast rate threatening to take over the world. A community college science professor (Duchovny), his eccentric geologist buddy (Jones), a wannabe fireman (Scott) and a government scientist (Moore) are brought together to deal with the invasion.

The movie is pretty stupid and I had recieved it as a joke from my brother, since I'm obsessed with the X-files (which costars Duchovny).

However, I did enjoy it. It is one of those movies that is so stupid, it's just worth watching. And they do make it funny without being annoying about it, which I'm impressed with. The dialogue is lacking a lot, but there are some great moments stuck in there.

I am a freshman bio major at Cornell University and am taking the typical intro bio class. So the evolutionary talk in the movie was familiar and I was impressed with the interesting facts they stuck in. For example, following the evolutionary trends of the alien, they talked about unicellular to multicellular organisms, even evolving to flatworms (platyhelmenthes).

So, go ahead and watch it. You'll come away saying what a stupid movie, but with a smile on your face. And at the end, isn't that the most important part?
Let's take a look at a few ways people use the word "evolution". There are undoubtedly many many more, but they usually fall under the general definiton "Change with respect to time". You might even say that evolution merely means "change".
  • Change with respect to time. It does not have to do with whether that change is for better or for worse, and does not say what the cause for the change is.

    For example, see stellar evolution.

  • In a more restricted sense, we might just say "evolution" when we are really talking about specific type of evolution. Often this omitted type is biology.

    For example, the biological evolution of a human: as you age your body does indeed become different.

  • Related to biological evolution is the fossil record. Sometimes people say "evolution" when they mean the change of lifeforms over the entire history of our planet.
  • Finally, there is a notion that is sometimes assumed: "Natural". This can be applied to either the broad biological evolution (our bodies age naturally), or the evolution in fossil record. The connotation of this naturality is that the change is caused by natural processes.
  • As Gritchka noted above, sometimes people mean "Darwinian evolution".
  • Other times, people say "evolution" in reference to abiogenesis, the creation of the very first life. This is in fact a correct use of the word evolution, but often is not appropriate to a discussion on "Evolution".
I'm not saying that you should always say "progressive naturally-induced change in existing life-forms over the history of life" instead of "evolution", but please remember to be careful when throwing around terms, especially if you switch definitions half-way through. This is so that whoever is listening to you knows what you're talking about, and it also helps to avoid accidental logical errors.

I have heard some people in the Evolution vs. Creation debate give plenty of evidence for progression in the fossil record -- something both sides will agree on -- yet never explain why it must be caused by (super)natural processes. This strikes me as odd because it is exactly what is being debated over. (Although they have demonstrated evolution, it is not in the appropriate sense) Fortunately, the debate usually goes back on topic.

Ev`o*lu"tion (?), n. [L. evolutio an unrolling: cf. F. évolution evolution. See Evolve.]

1.

The act of unfolding or unrolling; hence, in the process of growth; development; as, the evolution of a flower from a bud, or an animal from the egg.

2.

A series of things unrolled or unfolded.

"The whole evolution of ages."

Dr. H. More.

3. Geom.

The formation of an involute by unwrapping a thread from a curve as an evolute.

Hutton.

4. Arith. & Alg.

The extraction of roots; -- the reverse of involution.

5. Mil. & Naval

A prescribed movement of a body of troops, or a vessel or fleet; any movement designed to effect a new arrangement or disposition; a maneuver.

Those evolutions are best which can be executed with the greatest celerity, compatible with regularity.
Campbell.

6. Biol.

  1. A general name for the history of the steps by which any living organism has acquired the morphological and physiological characters which distinguish it; a gradual unfolding of successive phases of growth or development.
  2. That theory of generation which supposes the germ to preexist in the parent, and its parts to be developed, but not actually formed, by the procreative act; -- opposed to epigenesis.

7. Metaph.

That series of changes under natural law which involves continuous progress from the homogeneous to the heterogeneous in structure, and from the single and simple to the diverse and manifold in quality or function. The pocess is by some limited to organic beings; by others it is applied to the inorganic and the psychical. It is also applied to explain the existence and growth of institutions, manners, language, civilization, and every product of human activity. The agencies and laws of the process are variously explained by different philosophers.

Evolution is to me series with development.
Gladstone.

 

© Webster 1913.

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