4 ms·

There was a book I read in the 1970's about "sociobiology" that explained this. If I remember right: People share exactly 50% of their genes with their parents

by vorg 9y ago

There was a book I read in the 1970's about "sociobiology" that explained this. If I remember right: People share exactly 50% of their genes with their parents and children, but only probably 50% of genes with siblings -- it could be 51%, or could be 48%. To preserve their own genes, people will feel altruistic to give their lives for three of their siblings (about 150% of their own genes saved), but not for one sibling (only about 50% saved). People share between 90% to 110% of their genes with two siblings (I'm guessing the variance here), so will give their lives for two siblings they share 110% of their genes with, but not two they only share 90% with. The feeling of "liking a sibling as a friend" is the same as being willing to give one's live for them, so in today's age of large urban groups where friendship is a proxy for one's siblings in small tribes during the hunter-gatherer era, it follows people choose their friends because they share more than the average genetic material with them.

grzm 9y ago
Could it have been E.O. Wilson's Sociobiology: The New Synthesis? https://en.wikipedia.org/wiki/Sociobiology:_The_New_Synthesis https://en.wikipedia.org/wiki/Sociobiology:_The_New_Synthesi... The two brothers/eight cousins idea goes back as far as Haldane regarding kin selection: > No, but I would to save two brothers or eight cousins. https://en.wikiquote.org/wiki/J._B._S._Haldane https://en.wikiquote.org/wiki/J._B._S._Haldane Wikiquote has that as quoted in 2007, but I'm not sure how far back he originally stated it.
- cgag 9y ago
  The version I heard was "I would gladly give up my life for two brothers or eight cousins.". I much prefer it.
  - grzm 9y ago
    It's more succinct and stands alone (as opposed to the actual quote, which requires additional context), I agree. It's just not quote attributed to anyone in particular, as far as I know.
Ultimatt 9y ago
It doesn't follow at all because the vast majority of genetic diversity is not tangibly self evident from just being friends with someone. We all share the same number of genes with each other. The common differences are tiny single base changes. The vast majority of these are not phenotypic but neutral chamges that dont impact the products produced by your genes.
tzs 9y ago
> People share exactly 50% of their genes with their parents and children, but only probably 50% of genes with siblings -- it could be 51%, or could be 48%. I don't see why the percent shared could not be higher than 50% with your parents or children. You can share a gene with someone that you did not get it from or give it to. For example, suppose some particular gene has three variants, V1, V2, and V3. If your mother has V1/V2, and your father has V2/V3, the possible cases for you are V1/V2, V1/V3, V2/V2, and V2/V3. In two of those cases you share 50% of that gene with each parent. In the other two cases you share 50% with one parent and 100% with the other parent.
- vorg 9y ago
  What I wrote is what I got from reading the book a long time ago. Of course biology has advanced since the 1970's -- and of course my memory or understanding of it could be faulty because I read it as a teenager. What you wrote might explain why parents have "favorite" children they're more likely to give their life for.

by vorg 9y ago

grzm 9y ago

Could it have been E.O. Wilson's Sociobiology: The New Synthesis? https://en.wikipedia.org/wiki/Sociobiology:_The_New_Synthesis https://en.wikipedia.org/wiki/Sociobiology:_The_New_Synthesi... The two brothers/eight cousins idea goes back as far as Haldane regarding kin selection: > No, but I would to save two brothers or eight cousins. https://en.wikiquote.org/wiki/J._B._S._Haldane https://en.wikiquote.org/wiki/J._B._S._Haldane Wikiquote has that as quoted in 2007, but I'm not sure how far back he originally stated it.

cgag 9y ago
The version I heard was "I would gladly give up my life for two brothers or eight cousins.". I much prefer it.
- grzm 9y ago
  It's more succinct and stands alone (as opposed to the actual quote, which requires additional context), I agree. It's just not quote attributed to anyone in particular, as far as I know.

Ultimatt 9y ago

It doesn't follow at all because the vast majority of genetic diversity is not tangibly self evident from just being friends with someone. We all share the same number of genes with each other. The common differences are tiny single base changes. The vast majority of these are not phenotypic but neutral chamges that dont impact the products produced by your genes.

tzs 9y ago

> People share exactly 50% of their genes with their parents and children, but only probably 50% of genes with siblings -- it could be 51%, or could be 48%. I don't see why the percent shared could not be higher than 50% with your parents or children. You can share a gene with someone that you did not get it from or give it to. For example, suppose some particular gene has three variants, V1, V2, and V3. If your mother has V1/V2, and your father has V2/V3, the possible cases for you are V1/V2, V1/V3, V2/V2, and V2/V3. In two of those cases you share 50% of that gene with each parent. In the other two cases you share 50% with one parent and 100% with the other parent.

vorg 9y ago
What I wrote is what I got from reading the book a long time ago. Of course biology has advanced since the 1970's -- and of course my memory or understanding of it could be faulty because I read it as a teenager. What you wrote might explain why parents have "favorite" children they're more likely to give their life for.