1) Natural Selection: is the process whereby organisms better adapted to their environment tend to survive and produce more offspring.
2) This can be seen in a modern example of natural selection where:
Resistance to antibiotics is increased through the survival of individuals that are:
o immune to the effects of the antibiotic o whose offspring then inherit the resistance, creating a new population of resistant bacteria.
Thus, natural selection constantly removes those genetic alleles that even slightly decrease average reproductive success.
3) That being said, the human population still has many deleterious alleles that are still prevalent given the high heritabilities and prevalence rates of severe mental disorders.
So today we’re …show more content…
8) Mutation-selection is unlikely to be the only explanation for heritability of severe mental disorders. So another explanation that can be particularly important is evolutionary time lags.
When environments change quickly, this can cause mismatches such that ancestral alleles are poorly adapted to current environments. So alleles that were once neutral or adaptive may be today’s at-risk alleles.
Di Rienzo and Hudson proposed the ancestral-susceptibility model where the current at-risk alleles are ancestral and are being driven to extinction due to rapid changes in human environments. Consistent with this, rates of allelic substitution (reflecting natural selection) are over 100 times higher in the last 10,000 years than they were during most of human …show more content…
This might suggest that low doses of risk alleles (which are typically found in relatives) have positive effects that counterbalance their high-dose negative effects.
In support of this claim, studies showed that Schizotypy (a personality disorder characterized by a group of symptoms similar to but less severe than schizophrenia) is higher among highly creative individuals according to Nettle and Clegg. And one interpretation is that low doses of schizophrenia risk alleles increased creativity and fitness in ancestral environments.
10) Why do the alleles that predispose to severe mental disorders exist? To conclude, the search for the genetic causes of mental illness has been following the direction taken by medical research for quite some time. However, we don’t know yet but it is fair to say that mutation selection, time lags, and balancing selection probably all play roles to different degrees. Of the 3, the mutation-selection explanation has the strongest support to date, but the weight of evidence may shift as new data become available. Given the rapidity with which the genetic code is being deciphered and the increasing ability to test evolutionary hypotheses using genetic data, it is likely that, within the next 10 to 20 years, we will have a good understanding of why the alleles that increase
2) This can be seen in a modern example of natural selection where:
Resistance to antibiotics is increased through the survival of individuals that are:
o immune to the effects of the antibiotic o whose offspring then inherit the resistance, creating a new population of resistant bacteria.
Thus, natural selection constantly removes those genetic alleles that even slightly decrease average reproductive success.
3) That being said, the human population still has many deleterious alleles that are still prevalent given the high heritabilities and prevalence rates of severe mental disorders.
So today we’re …show more content…
8) Mutation-selection is unlikely to be the only explanation for heritability of severe mental disorders. So another explanation that can be particularly important is evolutionary time lags.
When environments change quickly, this can cause mismatches such that ancestral alleles are poorly adapted to current environments. So alleles that were once neutral or adaptive may be today’s at-risk alleles.
Di Rienzo and Hudson proposed the ancestral-susceptibility model where the current at-risk alleles are ancestral and are being driven to extinction due to rapid changes in human environments. Consistent with this, rates of allelic substitution (reflecting natural selection) are over 100 times higher in the last 10,000 years than they were during most of human …show more content…
This might suggest that low doses of risk alleles (which are typically found in relatives) have positive effects that counterbalance their high-dose negative effects.
In support of this claim, studies showed that Schizotypy (a personality disorder characterized by a group of symptoms similar to but less severe than schizophrenia) is higher among highly creative individuals according to Nettle and Clegg. And one interpretation is that low doses of schizophrenia risk alleles increased creativity and fitness in ancestral environments.
10) Why do the alleles that predispose to severe mental disorders exist? To conclude, the search for the genetic causes of mental illness has been following the direction taken by medical research for quite some time. However, we don’t know yet but it is fair to say that mutation selection, time lags, and balancing selection probably all play roles to different degrees. Of the 3, the mutation-selection explanation has the strongest support to date, but the weight of evidence may shift as new data become available. Given the rapidity with which the genetic code is being deciphered and the increasing ability to test evolutionary hypotheses using genetic data, it is likely that, within the next 10 to 20 years, we will have a good understanding of why the alleles that increase