PSY 544 Lecture Notes - Lecture 8: Diminishing Returns
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What are some of the implications of the similarity b/w family members and what that
might lead us to predict: first thing is the:
• The theory of parent-offspring conflict
The theory plays out like this: each child is guaranteed shares 50% of the parents genes as
children get their genes from their parents (half from more half from dad) - for any father
or mother it's guaranteed that each child shares 50% of their genes and this should incline
parents to treat their children roughly equally - but now consider this: you as yourself
share 100% of your genes but your siblings only share 50% of your genes on avg so there is
a clash here genetically - parents should be inclined to treat children relatively equally,
their genes will spread more effectively if they treat their children relatively equal as each
child is equally genetically related - but the genes that are in you will spread more
effectively if they incline you to prioritize yourself over your siblings because you're
related a 100% to yourself and only 50% with your siblings
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• For parents, each child shares 50% of their genes. This should incline parents to treat their
children roughly equally.
• For children, they share 100% of their own genes (obviously), but their siblings only share
50% of their genes.
• So, genes would spread more effectively if they led you to prioritize yourself more than
your sibling.
• If your parents have resources (ex. Food), your parents will have some investment in your
upbringing, they will have resources that they will split in the family - now imagine that
they have 2 meals and they give 1 meal to you and it increases your chance of surviving by
4 survival units and any additional resource that they give you is likely to have diminishing
returns for ex. If they give you the second meal, now it's probably not worth as much to
your survival because you've already had a bunch of food and it will increase your chance
of survival by some amount but less than 4 because you've met your basic need and it will
now store this food for later on. So it's likely to benefit you by 3% now. Because you and
your siblings are equally genetically related to your parents, if we take the perspective of
genes lurking (so this is not your parents perspective but rather the perspective of the
genes) - so if there are genes in your parents that incline them to show favouritism to you
- they give you both the meals and that increases your survival by 7 survival units total
(3+4) but there is only 50% chance that the gene prompting them to show favouritism is
also present in you so that means the chance if we multiple it by 7x0.5=3.5 now on avg
they have added 3.5 survival units to that gene in the future as sometimes the gene will be
present in which case it will be 7, sometimes it will be absent in which case it will be 0, so
on avg they have added a 3.5 survival unit - for ex you're the oldest child and their gene
prompts them to favour the oldest child, that gene will increase the survival of itself by 3.5
in the next generation - now imagine what happens if the genes that are lurking in your
parents incline your parents to treat you and your sibling equally and not show
favouritism. So now you get 1 meal, i.e. 4 survival units to you and your sibling gets one
meal which is 4 survival units, now if we multiple the likelihood by which that gene is in
you and your sibling so - 4x.5=2 ---- 2x.5=2 (8x0.5=8) so genes that prompted equal
distribution of resources essentially in this abstract case increases the survival of the gene
compared to the gene that inclined them to be selfish so when we look at this way we
would see that the pressure for genes to evolve and predispose parents to treat their
children relatively equally and this will cause this gene to profilatrate in the next
generation
• The theory of parent-offspring conflict
• Let’s eplore soe siplified ases.
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•
• Genes in parents, promoting favouritism
• Because you and your sibling are equally genetically-related to your parents, genes in your
parents will spread more rapidly if they incline parents to treat children
equally.
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Document Summary
What are some of the implications of the similarity b/w family members and what that might lead us to predict: first thing is the: the theory of parent-offspring conflict. This should incline parents to treat their children roughly equally: for children, they share 100% of their own genes (obviously), but their siblings only share. 50% of their genes: so, genes would spread more effectively if they led you to prioritize yourself more than your sibling. 4 survival units and any additional resource that they give you is likely to have diminishing returns for ex. So it"s likely to benefit you by 3% now. If first (cid:373)eal (cid:272)o(cid:373)es to (cid:455)ou (cid:894)(cid:449)orth (cid:1008) u(cid:374)its (cid:895) a(cid:374)d se(cid:272)o(cid:374)d (cid:373)eals goes to (cid:455)our si(cid:271)li(cid:374)g (cid:894)that"s worth 4 units to them) - this increases my survival by 4x1=4. So the total survival devoted to the gene in the next generation is 4+2=6.
