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Author Topic:   What mutations are needed for a particular trait (e.g. wings) to arise?
Codegate
Member (Idle past 144 days)
Posts: 84
From: The Great White North
Joined: 03-15-2006


Message 35 of 111 (345467)
08-31-2006 2:13 PM
Reply to: Message 24 by skepticfaith
08-30-2006 6:53 PM


Re: Finite possibilities - not infinite..
Others have said this, but the path that evolution follows is far from random. It's all based on the capabilities of a given individual to survive.

Here's a simple example that shows how quickly a positive trait can take over a localized group of creatures.

Let's assume that we have a small group of 1000 critters, that live in a stable environment that only supports a population of 1000. Because it is a stable population each member of the group has on average 1 child that survives to procreate.

These 1000 critters have some variation of course do to random mutations. Some have longer hair, some have darker coloring, whatever. Nothing major though.

Now along comes some event that slightly changes the environement over a long term. Perhaps it's an ice age. Perhaps it's a switch in the ocean currents. Perhaps its a new predator. It doesn't matter what it is, just that it changes their living environement over a significant time.

Suddenly our 1000 critters are not all equal. Let's say of the 1000 in the population now there are 50 that are slightly better suited to the new environment. Perhaps they had a slightly darker colouring and can hide from the new predator easier.

What does this advantage mean? For the purpose of this example I am going to say that it means that the 50 'better suited' critters now give birth to 1.01 offspring on average that survive to procreate, and that those offspring themselves have the better trait also.

Doesn't sound like much, does it?

Let's run the math. Assuming that the environment can still only support 1000 critters due to food constraints, space, whatever, how long would it take for this new trait to completely dominate the population?

Additional assumptions to simplify the math. Critters live 1 year and in that time they procreate once.

(initial better population)*(increase rate (number of gens)) = (population of better individuals)

50 * ( 1.01 x ) = 1000

x = log(1000/50) / log(1.01)

x = 301 or so

So after a mere 300 years, the new trait will completely dominate the population. There was no 'great plan' to make this change happen, it was just selection.

Looking at wings, as per the topic, and using Archers outline of the changes required it's not that unreasonable, I believe, to see how it happened. The points he brings up are all concerned with selection.

It's not at all like winning the lottery 1000 times in a row. It's like winning the lottery once and having 1000 kids that you teach how to win. So they change the rules of the lottery. 1 of those 1000 kids figures it out, has 1000 more kids and teaches them how to win the new lottery and so on.

We are talking about millions and millions of iterations in evolutionary time. It really hard to visuallize these vast breadths of time and the changes that they can cause.


This message is a reply to:
 Message 24 by skepticfaith, posted 08-30-2006 6:53 PM skepticfaith has responded

Replies to this message:
 Message 36 by skepticfaith, posted 08-31-2006 2:52 PM Codegate has responded

  
Codegate
Member (Idle past 144 days)
Posts: 84
From: The Great White North
Joined: 03-15-2006


Message 41 of 111 (345494)
08-31-2006 4:49 PM
Reply to: Message 36 by skepticfaith
08-31-2006 2:52 PM


Re: Finite possibilities - not infinite..
skepticfaith writes:

I see your point about selection but what you mention is not a mutation! There were alredy slightly darker critters in the population!

But it is a mutation. If the genome was 'pure' there would be no variation. It is these tiny little mutations that cause slight physical differences that drive everything. A little section of your DNA doesn't copy quite perfectly (mutates) and suddenly you have slightly longer hair then your counterparts.

Typically, these changes have no effect on your effectiveness as a living creature. Because of this, in a given population you have all sorts of little 'neutral' mutations that cause variability with no meaningful effect.

However, if an environemental change comes along, suddenly one or more of these mutations may become benificial as per my example. Also, some of them will become detrimental and that subset of the population would die off much faster then the others.


This message is a reply to:
 Message 36 by skepticfaith, posted 08-31-2006 2:52 PM skepticfaith has not yet responded

  
Codegate
Member (Idle past 144 days)
Posts: 84
From: The Great White North
Joined: 03-15-2006


Message 43 of 111 (345503)
08-31-2006 5:11 PM
Reply to: Message 39 by skepticfaith
08-31-2006 4:01 PM


Re: Summary ..
skepticfaith writes:

This new challenge can be overcome with a new trait - which appears by chance again - about the odds of winning the lottery. the process is repeated and we have a creature that again looks a little different.

Now I regret using the word lottery :)

This whole lottery analogue is only applicable if you are aiming for a particular end goal (winning the lottery). This however is not how evolution works.

Every living creature (I believe this to be correct - somebody please correct me if it isn't) has mutations. I've heard 200-500 mutations are present in every human.

Going back to my little mythical population, every single one of the critters potentially won the lottery. The are all sitting there with the little mutations waiting for the environment shift that would make them the 'alpha' critter. Unfortunately, 950 of the 1000 in my example were given the wrong mutation.

Evolution doesn't care where it's going - it has no idea. This is also why we can't easily point at hundreds of mutations and say "Hey look! Benefitial mutations!". Mutations are just copying errors that typically cause no meaningful effect in the current environment.

It's not until there is a change in the living contidions when some of these mutations become 'better' then others.


This message is a reply to:
 Message 39 by skepticfaith, posted 08-31-2006 4:01 PM skepticfaith has not yet responded

  
Codegate
Member (Idle past 144 days)
Posts: 84
From: The Great White North
Joined: 03-15-2006


Message 111 of 111 (347576)
09-08-2006 2:38 PM
Reply to: Message 100 by Someone who cares
09-07-2006 11:38 PM


Re: Is it possible mathematically?
I really love arguments like this because they actually make it easier for evolution to occur. Unfortunately, the numbers are not correct.

Someone who cares writes:

99.9% of mutations are harmful!

You do realize that you have several mutations yourself, right? Based on some poking around I've done the actual number ranges somewhere between 3 and 500 depending on what you read. I'm pretty sure 99.9% or those are not harmful. In fact I'm betting that 99.9% of them are neutral.

I really wish I knew where you got that percentage from. I've heard numbers like it mentioned before by creationists and it has absolutely no basis in reality.

Regardless of that issue, lets move on. Let us assume that 99.9% of mutations in a given population are harmful. For simplicities sake, lets assume that every member of the population has 1 mutation. I'd like to show you how that would actually benefit the population.

In evolutionary terms, harmful equates to less likely to reproduce.

So, if 99.9% of a population are less likely to reproduce then the others in their population then that 1% will very quickly become the majority population.

Alternatively, if 99.9% of mutations are neutral (as they appear to be in reality) then it takes much longer for the beneficial mutations to express themselves in quantity because there are so many neutrals still in the population.

I hope that once you think about this, you'll see that this is how it would work. I can put together the actual math that proves this if you want. Post 35 in this thread goes over the basic math.


This message is a reply to:
 Message 100 by Someone who cares, posted 09-07-2006 11:38 PM Someone who cares has not yet responded

  
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