In bacteria, they produce a lot more mutations in stressful environments because it is evolutionarily advantageous. In other words, if your situation is killing you playing Russian roulette with your genes is a better bet than accepting certain doom. Maybe you produce a deadly mutation that kills you and maybe you produce a mutation that helps you survive certain doom.
My recollection is that snails can reproduce either sexually or asexually and they preferentially reproduce sexually in stressful environments and asexually in environments that make staying the same more advantageous.
Sickle Cell is protective against malaria. Sickle Cell trait is protective without causing Sickle Cell Anemia, which is a horrible condition. So one copy of the mutation and you are more likely to survive in an area where malaria is prevalent and two copies and you are jacked up, but maybe less jacked up than with malaria.
Some studies suggest that Cystic Fibrosis is a predominantly Caucasian disorder because having one copy of the gene is protective against certain disease that were sweeping through Europe at one time. Two copies tends to kill people gruesomely at young ages.
So I think generally speaking the answer is that species seem to seek mutations when what they are doing currently isn't working and seek stability when what they are doing currently is working.
Also I have read that it is believed that half or more of all human pregnancies probably end in the first two weeks and result in a heavier-than-normal period without the woman even realizing she was ever pregnant in most cases because those fetuses are simply not viable. Laying bets on "Will this novel mutation or novel combination work?" tends to get a result of "Nope. It so doesn't work, it's not worth investing precious resources in to bring the baby to term and let it be born."
We mutate more when it is "mutate or die" and less when mutating is the thing more likely to kill you.
My recollection is that snails can reproduce either sexually or asexually and they preferentially reproduce sexually in stressful environments and asexually in environments that make staying the same more advantageous.
Sickle Cell is protective against malaria. Sickle Cell trait is protective without causing Sickle Cell Anemia, which is a horrible condition. So one copy of the mutation and you are more likely to survive in an area where malaria is prevalent and two copies and you are jacked up, but maybe less jacked up than with malaria.
Some studies suggest that Cystic Fibrosis is a predominantly Caucasian disorder because having one copy of the gene is protective against certain disease that were sweeping through Europe at one time. Two copies tends to kill people gruesomely at young ages.
So I think generally speaking the answer is that species seem to seek mutations when what they are doing currently isn't working and seek stability when what they are doing currently is working.
Also I have read that it is believed that half or more of all human pregnancies probably end in the first two weeks and result in a heavier-than-normal period without the woman even realizing she was ever pregnant in most cases because those fetuses are simply not viable. Laying bets on "Will this novel mutation or novel combination work?" tends to get a result of "Nope. It so doesn't work, it's not worth investing precious resources in to bring the baby to term and let it be born."
We mutate more when it is "mutate or die" and less when mutating is the thing more likely to kill you.