Evolution: do YOU GET IT?

PROVE IT!

1. Replication/Reproduction: organisms have offspring.

2. Heredity: offspring inherit characteristics from their parents. Provable by observation, but I suppose if you're determined to deny it then there isn't much hope for you.

3. Fecundity: organisms that can reproduce, intend to reproduce, and survive to reproduce, reproduce. This is a statistical statement, but it is better understood by its tautological opposite: organisms that do not survive to reproduce, do not reproduce.

4. Death. Organisms eventually stop reproducing. (This premise is necessary to ensure less fecund organisms produce fewer offspring - just a quibble).

Accept these premises and we have proved, scientifically and logically, micro-evolution: over time, the descendents of those with the characteristics of 'ability to reproduce' will dominate. Micro-evolution is the shift in the distribution of characteristics within the pool of characteristics of a single species.

Micro-evolution says that a species will lose the characteristics that make it less able to reproduce. Macro-evolution introduces the ability to obtain new characteristics that make a species more able to reproduce. To make the leap to macro-evolution we must introduce mutation[1], the introduction of error in the reproductive process leading to the presence of characteristics in offspring NOT present in the parents. Consequently the distribution of characteristics can then shift outside the pool of those currently present. Mutation can be proven easily but only by science, hence the major problem with getting science-phobic creationists to accept macro-evolution. The only solid requirement for mutation is that it is not always deleterious.

Eventually a species will either be unable to become more able to reproduce, or the environment will change and the characteristics required will therefore change, leading to a steady shift.

With the combination of these premises, replication, heredity, fecundity, death, and mutation, we have established a statistical necessity for macro-evolution. I include statistical because we must accept that there are small odds of adaptation going against the trend.

Evolution applies to anything with these characteristics, not just living organisms.

[1] There are other ways for new characteristics to be introduced, such as via viruses. Mutation is the most dominant method.

Joss Knight

Every living thing on earth contains genes made of the chemical DNA. Like a recipe, the genes have the information needed to construct a living thing from materials available in the environment. The special thing about DNA is that every time an organism reproduces, it passes all or part of its genetic code (as written by DNA) to its offspring. Due to imperfect copying, the offspring's recipe is slightly different from the parents'. Over many generations, the accumulations of these small genetic changes can have a significant effect on the phenotype (the physical body) of the individual.

The best explanation for this accumulation of change is natural selection. For natural selection to occur there must be:

1. Reproduction - Where the traits of the parent(s) are passed down to the offspring,

2. Variation - Not all individuals are genetically the same and,

3. Competition - Due to limited resources, not all individuals survive to reproduce.

This simple algorithm is sufficient to produce the variation and complexity that is observed now, and the changes over time observed in the fossil record. Computer simulations using this algorithm produce similar variation and complexity over time.

In the real world, the change from one species to another occurs most efficiently when breeding populations become isolated. Because the genes don't mix between isolated populations, the accumulated changes stay within each group. During future contacts between groups, the changes can be significant enough so that no fertile offspring are produced. At this point a new species has been formed.

At a point about 5 million years ago a group of apes split up. The descendants of one group became chimpanzees. The descendants of the other group became human. This change occurred because of the accumulation of differences in the genes of the individuals who were successful at reproducing. And by the way-It's not that we evolved from apes: WE ARE APES.

Mark

Do I understand evolution? Yes, I think I do.

In fact it is Very Simple Indeed (VSI), and that's all you need to remember. It's a mnemonic, see:

V-ariation

S-election

I-nheritance

This is how it works. First you need a population of things which reproduce. The kids will either be identically the same as the mums and dads, or else they won't. We find, in practice, that they aren't. That's variation.

As a result, the next generation will all have little, subtle differences. They all live in a place we call an environment. The thing about an environment is that it applies survival pressure. Some of the kids will be a bit better equipped to deal with the environment they find themselves in, and some will be less well equipped, because of the variations they have. So a few more of the better equipped kids will grow up to whatever age they breed at and will breed successfully, than of those that are less well equipped. That's selection.

When reproduction takes place, although the kids may have further variations, they also tend to have the same subtle variations that their parents had. That's inheritance.

So whatever it was that made a subset of one generation better able to survive to reproduce, will be even more prevalent in the next generation. It's a feedback loop. Apply this, over hundreds, thousands, millions of generations, and before you know it, you have a population that has developed all manner of features that are beneficial in helping its members reach the age at which they reproduce.

That's EVOLUTION.

It happens. Its a fact. Get over it.

The theories of evolution -- yes, there are a few -- are another thing entirely. These are the things that explain how and why the variations happen; what, and with what effect, are the selective pressures; and the mechanism by which inheritance takes place. There are a few of these theories, some in conflict with each other, some more accepted than others. But none of these theories deny the fact that VSI occurs. In fact they take it for granted.

Evolution -- making life better for millions of years.

Jeremy Goulstone

The key concepts are replication, variation and selection.

1. Start with something that replicates, that is, makes copies of itself.

2. If there is variation, that is, the copying process is not perfect, so as a population of the replicator is created, the individual members are not absolutely identical then

3. if there is selection, that is the environment applies pressure to the population so that some replicate more than others (because they are not all identical)

- the result has to be that the individuals best suited to the environment replicate more than the rest. Gradually, the characteristics of the population will change, so that the majority of the population will embody the favorable characteristics, even if only a small minority did so when the environmental pressure arose.

Organisms are replicators, because they procreate, characteristics are inherited, and yet there is variation (children are not identical to their parents). In addition, there is obvious pressure from the environment in terms of ability to survive climate changes, eat, attract mates, etc. So it is clear that organisms (plants, animals, whatever) will evolve over time.

While many people had thought of this before, Darwin was the one who pointed out that this simple mechanism is enough to explain a host of observations. As David Deutsch points out in his book The Fabric Of Reality, the power of a scientific theory lies in its explanatory power. He selects evolution as one of the central theories of our time, because it explains so much. In fact, there is no other theory that attempts to explain speciation and extinction, to name a couple of major topics. The only other approach offered is a shrug and the phrase "god did it".

Richard09

Evolution requires three things:

-replication (which implies inheritance)

- random mutation

- non-random selection

I think it's the non-random selection bit that people have the biggest difficulty understanding. What it means is that for certain reasons - sometimes environmental reasons, sometimes reasons of competitive advantage within the population, sometimes other reasons - some mutations survive to replicate in larger numbers than others. Over time this causes a change in the relative population densities of different mutations. In the extreme case, some mutations don't survive to replicate at all.

It's important to understand that "non-random" doesn't mean "goal-directed". The selection processes at work in one generation are blind to any future conditions or to any future effects of cumulative mutation. In each generation, those best suited to survive the current conditions are the ones that survive best. This is what is meant by "survival of the fittest" - a woefully misunderstood phrase because of the ambiguity of the word "fit".

This is also why Martin's analogy of a river is a good one. Evolution cannot flow "uphill" because it has no knowledge of what lies beyond the hill.

Sgt Dudfoot

Certain chemicals can replicate, making copies of themselves by the very nature of the bonds they form, and there can be variation in this replication. Since there is a limited supply of atoms floating around for them to bond to, the ones that replicate the most often and form the most stable bonds will tend to be the ones there or more of. This is evolution. Just by the fact that not all replicators are equally good at making copies of themselves, some will make more copies at the expense of others that don't replicate as well.

This basic process means that any change for any reason in the replicator that allows it to make more copies will be contained in those copies, which will be more succesful than their "competitors." If the precursor of DNA made copies of itself, and not all copies were equal in terms of making new copies, then those that accomplished it best (by building protein shells around them for protection, or by giving that shell a method or propulsion so they could move to areas with new resources) passed on their configurations and the traits they produced. Since the process of replication isn't perfect, however, not all of these "offspring" had equal chances of survival. Most changes did not especially enhance the ability to reproduce, and so they reproduced less until they were gone, while other did enhance this ability, and they reproduced more until they were the most prevalant.

Small changes add up over eons. There is no force behind it, it is just a mathmatical inevitability.

Replication + variation + unequal survival = evolution.

Jason Manning

Lonely Misanthrope

It can be seen that there are random mutations in nature, as DNA is not perfect (it would be if god created it, but he didn't :P). Now, every once in a while (a long long while), these mutations will have a positive effect. The affected body will then mate, and perhaps pass along this mutation. The new creatures will have a tiny advantage over the rest of their species. Perhaps a little quicker, or better at finding food. When the species fell on hard times, became overpopulated, or perhaps just violent, the new creatures would have an advantage over the rest of the species, so chances are the disadvantaged creatures would die first. The new species would consist of the strongest of the old, and of course, this cycle would continue, with more and more mutations, until the species end is unrecognizable from when it started. Of course, tribes of the species could break apart. Each tribe would evolve differently, such as one evolving into humans, and another evolving into monkies. Evolution really isn't that hard to understand, as it can be easily seen in germs and cockroaches. When a cockroach family is sprayed with chemicals, those with certain mutations may survive, breed and pass these mutations on, eventually making the entire group/tribe/whatever immune to the chemical. So that's it, I've always thought I understood it, hopefully I do.

Drahzar

Evolution consists of certain observed facts and a body of theory that attempts to explain those.

Some observed facts:

The fossil record displays a changing flora and fauna over a series of successive ecologies over a period, if we include bacteria traces, of nearly 4 billion years. It is generally ordered, too, in a phylogenetic manner, with anatomical features appearing and then branching into many fossil species.

The offspring of living creatures display genetic differences from their parents' genomes. These mutations cause phenotypic differences. Some differences enhance the reproductive success of the mutations' bearer, others are detrimental to that success. Thus those mutations that enhance reproductive success tend to accumulate. When sub-populations are isolated genetically from one another, DIFFERENT mutations accumulate in them, causing the sub-populations to diverge. Sufficient divergence results in speciation, that is to say, the two subpopulations diverge genetically to the point where they cannot any longer interbreed.

Note that all of the above has been observed. The THEORY is that these observed genetic processes (random mutation, natural selection, genetic isolation) account for pretty much all of what we see in the fossil record.

(Note that while I am a Christian, I am not a fundamentalist).

Dave Oldridge

An interesting description. It reads a little like a gay man describing a beautiful woman, the facts may be correct but I get the impression there's no passion there. I also strongly disagree with the use of the word "creature".