3 ms·
>> would require some kind of selective pressure Not selective pressure, but lack of it. When you take away selective pressure for a specific trait, organisms
by jondubois 8y ago
>> would require some kind of selective pressure
Not selective pressure, but lack of it.
When you take away selective pressure for a specific trait, organisms become weaker on average in respect to that trait; when a trait loses importance, populations divert their resources to different traits.
- Dylan16807 8y agoFor a gene to decay without selective pressure takes a very long time, especially when your population is not on the edge of starvation.
- londons_explore 8y agoA selective pressure going away is as strong as a selective pressure appearing. Eg. 100 years ago, 20% of children would die as infants. Imagine all of those children died of a mutation which causes half the usual sperm count, together with a lack of resistance to polio/cholora. Now that polio/cholora don't exist, all those people survive, and within 3 generations, nearly everyone has at least a grandparent with that 'low sperm count' mutation.
- Dylan16807 8y ago> Eg. 100 years ago, 20% of children would die as infants. Imagine all of those children died of a mutation which causes half the usual sperm count, together with a lack of resistance to polio/cholora That wouldn't be a steady state. A gene that powerfully negative, with no upsides, would decrease in prevalence by a significant amount every generation. > Now that polio/cholora don't exist, all those people survive, and within 3 generations, nearly everyone has at least a grandparent with that 'low sperm count' mutation. Everyone has an ancestor with the gene. But they only have a 1/8, 1/16, 1/32 chance of inheriting it from that specific ancestor. Generation to generation, the percentage of people with the gene will be almost identical. Just like eye and hair color.