- Jun 5, 2003
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Evolution is a change in allele frequencies in a population over time. But it can add information, or remove information. In fact, speciation often happens when an isolated population has less genetic information (Founder Effect) and then becomes reproductively isolated from the rest of the species, effectively forming a new species.
After that, the new species generally goes through a stage of increasing information as new mutations appear. Every new mutation adds information to the population genome. Claude Shannon pioneered the mathematical understanding of information, and his theory (which also allows NASA to communicate with spacecraft over millions of kilometers of space) allows us to look at the way that evolution changes genetic information in a population. The equation describing this process is:
Where H is the information in the population for a given gene, and p is the frequency of each allele in that population. An allele is a different version of the same gene. So if there are two alleles, each with a frequency of 0.5, then the information for that gene in the population is about 0.30. If there's a new mutation for that gene, and it eventually increases so that each allele has a frequency of about 0.333, then the information for that gene would be about 0.48.
Information is basically a measure of uncertainty in a message. So in this case, it would be the uncertainty of which allele exists in a given member of the population. So, because the uncertainty is less if you have only two alleles, there is less information, and when there are three alleles, there is more information. And yes, if the alleles don't all have the same frequency, information will be different.
For example, if the frequencies for two alleles are 0.9 and 0.1, then the information would be about 0.14. Because there is less uncertainty about which allele a particular organism in the population might have. And if there is fixation and only one allele, then the information is 0.0, because there is no uncertainty at all.
After that, the new species generally goes through a stage of increasing information as new mutations appear. Every new mutation adds information to the population genome. Claude Shannon pioneered the mathematical understanding of information, and his theory (which also allows NASA to communicate with spacecraft over millions of kilometers of space) allows us to look at the way that evolution changes genetic information in a population. The equation describing this process is:

Where H is the information in the population for a given gene, and p is the frequency of each allele in that population. An allele is a different version of the same gene. So if there are two alleles, each with a frequency of 0.5, then the information for that gene in the population is about 0.30. If there's a new mutation for that gene, and it eventually increases so that each allele has a frequency of about 0.333, then the information for that gene would be about 0.48.
Information is basically a measure of uncertainty in a message. So in this case, it would be the uncertainty of which allele exists in a given member of the population. So, because the uncertainty is less if you have only two alleles, there is less information, and when there are three alleles, there is more information. And yes, if the alleles don't all have the same frequency, information will be different.
For example, if the frequencies for two alleles are 0.9 and 0.1, then the information would be about 0.14. Because there is less uncertainty about which allele a particular organism in the population might have. And if there is fixation and only one allele, then the information is 0.0, because there is no uncertainty at all.