Download Chapter 8 Summary

Chapter 8 Summary
Battle of the Generations
Genetically speaking, a mother should never favor one of her children. All of her children
have ½ of her genetic makeup and this makes them all equally as important. This does
not mean that in all instances she will equally divide her resources between her children.
Dawkins defines Parental Investment (PI) as “any investment by the parent in an
individual offspring that increases the offspring’s chance of survival (and hence
reproductive success) at the cost of the parent’s ability to invest in other offspring”. He
clarifies that PI can be measured in the decrease in life expectancy of other children that
are born or may be born in the future. It is difficult to say how a female should invest her
life’s resources but one thing is clear, if she spreads them too thin she will reduce the
optimal outcome of her genes success. So what happens if a female’s children are two
different ages and she needs to split up he resources unevenly. If she gives her resources
the older son her younger son will die. If she gives her resources to the younger child,
there is a good chance that the older child will be able to fend for himself. At the same
time, if it is a life or death situation she is probably best saving the older son because she
has already invested more time into him and she would have to invest more of her
resources to get the younger child to the same age.
Dawkins looks at menopause and speculates about why this phenomenon evolved.
His reasoning is that at some age, it became more beneficial to a female’s genes to stop
bearing children of her own and start investing resources in her grandchildren. At some
point, the chance of an older female’s child reaching adulthood is lower than the chance
of her grandchild reaching adulthood and therefore it is more beneficial for her to invest
her resources into the grandchild. Overall, if females do invest unequally it should be
based on expectation of life and age.
What about selfish children? Dawkins says that children should grab as much of
the cake until they start to lower the survival of their siblings. Each sibling shares ½ of
the genes which is the same relationship from a child to a mother. An older brother at
some point has to give his younger brother the pint of milk because if he does not his
brother will be weak. In addition, one pint of milk no longer sustains the appetite of the
older brother so taking the pint of milk is overly selfish and the copies of his genes would
benefit more. If the cost to the other children is less than double the benefit to the older
brother than he will continue to be selfish. However, when the cost is over double it is in
his genes benefit to give up the resources.
Sometimes, females will give birth to one extra offspring and according to
available resources will care for the child or not. If she meticulously feeds the children in
order of size and age than she will be able to cut her losses and let the youngest/weakest
child die. Sometimes children blackmail parents into giving them more than their fare
share of resources. Birds will chirp loudly which attracts predators so parents need to shut
the chick up so they don’t all get eaten. It seems odd that this blackmailing behavior
would evolve as the child would have way to much to loose if a predator actually came.
Overall, a selfish child is likely to grow up and have selfish children himself. It seems as
a though a compromise must be met between the child and his parents in order to
optimize the success of the selfish gene.