# Thread: How Evolution Increases Chances?

1. Do you think the following is an accurate description?

Let's take a series of 10 mutations, each with a probability of 1/10. They come together to form a single complex system the chances of this is 1/(10^10).

Now let's suppose there are only ten organisms per generation. It's unlikely any one of them will develop this complex system.

However we'll use natural selection, not random chance:

1) As the chances are 1/10 the first mutation arises (square brackets isolate individual organisms):
[*][*][*] [*%][*][*][*][*][*][*]

2) This doesn't help us, as the second mutation relies on the first, and there is only one organism (so 1/10 isn't that good). Unless that mutant spreads to dominate the entire population (natural selection):

[*%] [*%] [*%] [*%] [*%] [*%] [*%] [*%] [*%] [*%]

3) Now 1/10 isn't so hard anymore (as there are 10 organisms with the mutation):

[*%] [*%] [*%] [*%] [*%] [*%] [*%] [*%!] [*%] [*%]

4) This continues:

[*%!] [*%!] [*%!] [*%!] [*%!] [*%!] [*%!] [*%!] [*%!] [*%!]

[*%!] [*%!] [*%!] [*%!] [*%!] [*%!/] [*%!] [*%!] [*%!] [*%!]
[*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/]

[*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/] [*%!/{] [*%!/] [*%!/]
[*%!/{] [*%!/{] [*%!/{] [*%!/{] [*%!/{] [*%!/{] [*%!/{] [*%!/{] [*%!/{] [*%!/{]

etc. etc. until you have an individual with:

[*%!/{.@?+"]

Essentially reducing the odds from 1/(10^10) to inevitable (when we don't consider other pathways to adaptation).

2.

3. First of all, 1/(10^10) does not equal 1/100, it equals 1/10,000,000,000.

You are kind of thinking along the right track. The chances of the 10 mutations accumulating in a single organism would be 1/(10^10) provided that the 9 intermediate steps along the way provide no advantage over the wild-type organisms.

However, if the intermediate mutations lead to a reproductive advantage, then their frequency in the population will increase*. This improves the odds that the 2nd mutation will occur in a gene which has already acquired the 1st mutation.

In this manner a seemingly unlikely event, such as the 10 mutations occuringly sequentially in the absence of selection, is arrived at through a series of reasonably likely intermediates acted upon by natural selection. Climbing mount improbable!

* it is also worth pointing out that neutral or even deleterious mutations can increase in frequency within a population simply by chance (genetic drift). Especially, if you are dealing with small population groups as in this example.

4. It actually does happen, the emergence of complexity that requires independent mutations.

Recent example was the guy that kept bacteria under glucose conditions followed by starvation for 20 years.

One colony evolved the ability to process citrate which required at least two independent mutations to happen.

They could actually track back to generation 20.000 or so and find a population that was prone to evolve the last mutation needed for citrate use again. But the populations from the generations before generation 20.000 or so didn't.

So you can calculate yourself silly in your mind, but the fact is it happens, happened and will happen.

5. Originally Posted by electricant
First of all, 1/(10^10) does not equal 1/100, it equals 1/10,000,000,000.
K, I fixed that.

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