# Genetics: How similar are my cousin's children to me
**URL:** https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563
**Category:** In My Humble Opinion
**Created:** [December 7, 2014, 11:04am UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563 "2014-12-07T11:04:44Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@Namkcalb](https://boards.straightdope.com/u/Namkcalb)
#### Post date: [December 7, 2014, 11:04am UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/1 "2014-12-07T11:04:44Z")
Genetically speaking, if I wanted to maximise the spread of my genes, how many of my (1st) cousins’ children are worth one of my children?
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### Author:  [@Reply](https://boards.straightdope.com/u/Reply)
#### Post date: [December 7, 2014, 11:47am UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/2 "2014-12-07T11:47:47Z")
According to this [consanguinity table](http://fabpedigree.com/consang.htm), eight. Your first cousin’s child should share 1/16 of your genes, whereas your child would have 1/2.
Edit: This page has an easier to understand graphic:
> **[Consanguinity and the coefficient of relationship](http://wordpress.mrreid.org/2012/03/29/consanguinity-and-the-coefficient-of-relationship/)**
>
> Or What percentage of your genetic code do you share with your second cousin?
>
> Two people who share some of their genetic code (their DNA) are said to be consanguineous ("co" meaning shared and "sanguis" being Latin for blood) and the extent to which...
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### Author:  [@jtur88](https://boards.straightdope.com/u/jtur88)
#### Post date: [December 7, 2014, 2:45pm UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/3 "2014-12-07T14:45:06Z")
You and your cousins share one of two sets of grandparents, so a cousin has half your ancestry in common. The children of your cousins each have half of that, or 1/4.
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### Author:  [@John\_Mace](https://boards.straightdope.com/u/John_Mace)
#### Post date: [December 7, 2014, 2:53pm UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/4 "2014-12-07T14:53:13Z")
> [@jtur88](#):
>
> You and your cousins share one of two sets of grandparents, so a cousin has half your ancestry in common. The children of your cousins each have half of that, or 1/4.
Go back and draw out the family tree and you’ll see that your math is wrong. The correct answer has already been given.
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### Author:  [@ftg](https://boards.straightdope.com/u/ftg)
#### Post date: [December 7, 2014, 5:47pm UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/5 "2014-12-07T17:47:34Z")
Now for the nitpick:
A person and a chimp have 98% of their genes in common. For any two random humans it’s well over 99%.
The numbers given above are an over-idealized simplification. You have to throw out somehow nearly all the genes that are really widespread and that two people could easily have just by chance. Actual attempts to quantify how many such genes would have to be ignored is beyond our current abilities.
If you want to maximize the spread of your genes, help any person, related or not.
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### Author:  [@Smeghead](https://boards.straightdope.com/u/Smeghead)
#### Post date: [December 7, 2014, 7:18pm UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/6 "2014-12-07T19:18:13Z")
> [@ftg](#):
>
> Now for the nitpick:
>
> A person and a chimp have 98% of their genes in common. For any two random humans it’s well over 99%.
>
> The numbers given above are an over-idealized simplification. You have to throw out somehow nearly all the genes that are really widespread and that two people could easily have just by chance. Actual attempts to quantify how many such genes would have to be ignored is beyond our current abilities.
>
> If you want to maximize the spread of your genes, help any person, related or not.
There are two different kinds of genetic “identity”: identity by state and identity by descent. By state is what you’re referring to - if a specific chunk of DNA has the same sequence in me and in you, then they’re the same. All humans have lots of DNA that is identical in this sense from person to person.
What the OP is talking about is identity by descent. That is, we consider my DNA to be different from my wife’s DNA, even if the sequences are exactly the same. This is the kind of thing you see in a lot of diagrams, where one chromosome is blue and one red, representing maternal and paternal inheritance. This is what people mean when they talk about how closely related two people are, or what percentage of their ancestry is from the home country, or whatever.
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### Author:  [@septimus](https://boards.straightdope.com/u/septimus)
#### Post date: [December 7, 2014, 7:54pm UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/7 "2014-12-07T19:54:21Z")
If an animal helps an arbitrary member of its species to survive, that might increase the _species_’ population, but there is likely to be some mechanism, in the present or future, which limits the total population anyway. The “Darwininan Imperative” (to coin a term) is to propagate _one’s own genes_, with their possible advantages _relative to other individuals in the same species_, and increasing the relative portion of such genes in the population. In this sense, OP’s arithmetic formulation may be correct.
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### Author:  [@Namkcalb](https://boards.straightdope.com/u/Namkcalb)
#### Post date: [December 7, 2014, 9:12pm UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/8 "2014-12-07T21:12:04Z")
> [@ftg](#):
>
> Now for the nitpick:
>
> A person and a chimp have 98% of their genes in common. For any two random humans it’s well over 99%.
> The numbers given above are an over-idealized simplification.
Agreed, afterall, we share[50% of our DNA with a banana.](http://qjmed.oxfordjournals.org/content/95/3/195)
> [@Reply](#):
>
> According to this [consanguinity table](http://fabpedigree.com/consang.htm), eight. Your first cousin’s child should share 1/16 of your genes, whereas your child would have 1/2.
Ah! So if I could convince 8 of my cousins to have an extra child, it’d mean one less baby I need to wake up in the middle of the night for
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### Author:  [@Andy\_L](https://boards.straightdope.com/u/Andy_L)
#### Post date: [December 7, 2014, 9:19pm UTC](https://boards.straightdope.com/t/genetics-how-similar-are-my-cousins-children-to-me/706563/9 "2014-12-07T21:19:44Z")
When asked if he would give his life to rescue his hypothetical drowning brother, JBS Haldane replied “No, but I would to save two brothers or eight cousins.” - he’d done the math, you see.