May 5, 2011

Genetic reason...

This is today's thoughtful cartoon by Zach Weiner on the relevance of genetics in our motivations:




The main fallacy is that inbreeding, at least some inbreeding, does happen.

The other fallacy is that some 99.5% (exact figure anyone?) of the base pairs are identical among all humans and highly conservative (they won't change on risk of death or otherwise extreme crippling), so the time to your total genetic dilution (notwithstanding inbreeding) is a lot shorter that Weiner assumes.

Actually I estimate 150,000 variable base pairs, so following the cartoon's logic, only 18 generations would be needed to total dilution, so only 450 years are needed for (theoretical) total dilution. 

I was going to illustrate this talking about some random person from Columbus' times... but in that time Earth's human population was low enough to allow some of that almost necessary inbreeding of the sort suggested in the cartoon. But now? Now there's more people on Earth than all the base pairs in our genome! Now such necessary inbreeding cannot be taken for granted and will probably not happen in most cases.

Carpe diem (live the day) or just discuss?

5 comments:

  1. Memory is even more weak. I guess a person only "lives" in a memory of a few relatives of him/her, once he/she dies, perhaps 100 years or even less. I don't know what were the names of any of my four great-grandmothers/fathers.

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  2. "I don't know what were the names of any of my four great-grandmothers/fathers".

    I actually know all four of each, but that's because I've had realtions on each side research their own family tree.

    "Actually I estimate 150,000 variable base pairs, so following the cartoon's logic, only 18 generations would be needed to total dilution, so only 450 years are needed for (theoretical) total dilution".

    I used that fact to explain the fixation of mtDNA and Y-haps in this essay:

    http://humanevolutionontrial.blogspot.com/2009/06/human-evolution-on-trial-pedigrees.html

    And the names of my great grand parents are listed there.

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  3. "Now such necessary inbreeding cannot be taken for granted and will probably not happen in most cases."

    Or, alternatively, we are all so inbred that inbreeding has become mainstay.

    More seriously, people with a lot of children (who are also economically advantaged) still seem to have a good chance of transmitting large chunks of their (distinctive) genes into the future. People like Genghis Khan, or August der Starke, perhaps.

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  4. I understand that the Chingis Khan myth is pretty much another modern myth built on legitimate genetic findings but worthless in itself. The alleged Chingis Khan haplotype should be in fact a Turkic lineage from the time of the Turkic expansion, at least a thousand years before Chingis ever lived.

    Whatever the case, haplotypes and haplogroups, which are indivisible but functionally almost irrelevant, are not what is being debated here. The cartoon obviously means autosomal DNA.

    The case is that today's DNA of any living human should be diluted to insignificance (with the possible exception of haploid elements like mitochondrial DNA) in few centuries, as much as your molecules dissolve into generic "dust" upon death.

    Chaos wins, order loses again. Order, even at a biological level ends up being trivial, misleading...

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  5. Why care about yourself 30 years from now ?

    That 'you' will be very different to the current one.

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