Author Topic: Basic Principles of Evolution  (Read 2934 times)

Offline googlyeyesultra

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Basic Principles of Evolution
« on: January 08, 2008, 06:08:03 PM »
I've compiled a basic (certainly not comprehensive) list of major evolutionary theories and hypothesis. Mostly, this is a quick reference for those interested in evolution; however, I'm curious as to which of these Darwinbots accurately models and which of these need improvement. Feel free to add to or critique this list.

Once one bot in a line develops a poor mutation, all descendants will have no fewer numbers of deleterious mutations (except as the result of a ridiculously unlikely back mutation). This means that unless selective pressures are far higher than mutation rates, deleterious mutations will gradually accumulate in a population. This is called Muller's Ratchet.

In an asexual population, a beneficial mutation can only become fixed if all other lines die out (possibly extinguishing other beneficial mutations they had).

The most accurate unit of selection is the gene. A gene can occasionally evolve to help other organisms with the same gene at the detriment to its host. This is called the selfish gene or the Green Beard effect.

In addition to merely surviving, in a sexually reproducing organism, the organism must possess traits that are favorable to prospective mates in order to reproduce. This is called sexual selection.

On occasion, a deleterious mutation can occur along with a beneficial one. Oftentimes, especially in difficult situations, this poor mutations will spread due to proximity (can't remove it from the organism without removing the beneficial one). The poor mutation is genetically hitchhiking.

Generally, evolution happens slowly most times, and then rapidly works in times of extreme hardship. This is called punctuated equilibrium.

Evolution rarely, if ever, follows a straight path. It wanders about, trying things randomly until it finds something that works.

Evolution does not pick that which is awesome, uber, or efficient. Natural selection favors anything that can reproduce successfully.

There is an evolutionary arms race. Competing organism have to accumulate beneficial mutations in order to compete with every other organism that is doing the same thing. This is called the Red Queen effect.

Most mutations are neutral or deleterious. Very few are beneficial.

Large populations are needed to avoid bottleneck effects, where a few organisms are the only representatives of a genome, and may have less or worse mutations than the majority of that species.

Point mutations are necessary to evolve a first replicator, but from then on, they are usually bad things. Copy mutations power evolution once basic reproduction occurs.

Genetic drift allows some neutral mutations to fix in a population.

Offline Numsgil

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Basic Principles of Evolution
« Reply #1 on: January 09, 2008, 01:40:21 AM »
Good list

Offline shvarz

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Basic Principles of Evolution
« Reply #2 on: January 09, 2008, 12:34:52 PM »
I would not call these "basic principles". They are more like "simple things that follow from basic principles".

Nevertheless, let's go through your list and see what DB can reproduce:

Once one bot in a line develops a poor mutation, all descendants will have no fewer numbers of deleterious mutations (except as the result of a ridiculously unlikely back mutation). This means that unless selective pressures are far higher than mutation rates, deleterious mutations will gradually accumulate in a population. This is called Muller's Ratchet.
CHECK!

In an asexual population, a beneficial mutation can only become fixed if all other lines die out (possibly extinguishing other beneficial mutations they had).
CHECK!

The most accurate unit of selection is the gene. A gene can occasionally evolve to help other organisms with the same gene at the detriment to its host. This is called the selfish gene or the Green Beard effect.
This is a controversial statement, but if we assume its premise, then:
CHECK!

In addition to merely surviving, in a sexually reproducing organism, the organism must possess traits that are favorable to prospective mates in order to reproduce. This is called sexual selection.
MISS. Two problems: a) sexual reproduction is broken in current DB; B) bots are not nearly complex enough to gather information and judge on anything aside from some superficial traits.

On occasion, a deleterious mutation can occur along with a beneficial one. Oftentimes, especially in difficult situations, this poor mutations will spread due to proximity (can't remove it from the organism without removing the beneficial one). The poor mutation is genetically hitchhiking.
CHECK/MISS There are two things mixed in here. One is linkage disequilibrium which only applies to sexual organisms and thus is a MISS for DB, another is hitchhiking in asexual populations and that DB can do, so CHECK!

Generally, evolution happens slowly most times, and then rapidly works in times of extreme hardship. This is called punctuated equilibrium.
MISS. Punctuated equilibrium requires diverse environments and large population sizes. DB is driven in large part by drift.

Evolution rarely, if ever, follows a straight path. It wanders about, trying things randomly until it finds something that works.
CHECK!

Evolution does not pick that which is awesome, uber, or efficient. Natural selection favors anything that can reproduce successfully.
Again, a controversial statement, there is no consensus on this in evolutionary science. But if we assumes that this is true, then it should be true in DB. Thus, CHECK.
 
There is an evolutionary arms race. Competing organism have to accumulate beneficial mutations in order to compete with every other organism that is doing the same thing. This is called the Red Queen effect.
CHECK!

Most mutations are neutral or deleterious. Very few are beneficial.
CHECK!

Large populations are needed to avoid bottleneck effects, where a few organisms are the only representatives of a genome, and may have less or worse mutations than the majority of that species.
This is tautology. By definition bottlenecks are temporary reductions in population size, thus saying "large populations are needed to avoid bottleneck effects" will always be true.

Point mutations are necessary to evolve a first replicator, but from then on, they are usually bad things. Copy mutations power evolution once basic reproduction occurs.
Controversial statement. We don't know how first replicators evolved. Other than that, CHECK!

Genetic drift allows some neutral mutations to fix in a population.
Tautology again. Genetic drift is fixation of neutral mutations. But if you insist: CHECK!
« Last Edit: January 09, 2008, 12:36:32 PM by shvarz »
"Never underestimate the power of stupid things in big numbers" - Serious Sam