3 ms·

I am reading about this story for a while now and still do not get what is so surprising about it. While people of caucasian descent all share about 2% of their

by patall 11y ago

I am reading about this story for a while now and still do not get what is so surprising about it. While people of caucasian descent all share about 2% of their DNA with the Neanderthals, thats all random bits and not a single larger fragment or even chromosome. The latter would need to happen for the Y Chromosome. All Chromosomes but Y (and Mitochondria) can exchange fragments with their homologs but as there is always just one Y chromosome in any given cell, thats is not going to happen there. Therefore, if we should find it, we would find a whole Y Chromosome. But that is not going to happen. And that is honestly not very surprising...

sokoloff 11y ago
> While people of caucasian descent all share about 2% of their DNA with the Neanderthals That number is shockingly low to me, which probably means I misunderstand some subtlety of what you're saying. Could you expand/explain? (I'd have expected a figure starting with at least two 9s [99+%])
- meric 11y ago
  The context of the comment is - Humans share 40% of DNA with a lot of plants.
- loudmax 11y ago
  Modern Europeans share about 2% of their alleles with Neanderthals might be a more correct way to put it. But to understand that sentence, you have to understand what's an allele (and I'm not completely sure I'm using the term correctly).
  - danieltillett 11y ago
    This is pretty close. A simpler way of describing this is 2% of the average genetic heritage of a European is able to be traced back to Neanderthals. This is a lower bound and it may be higher. The more interesting observation is that the 2% is not the same 2% in everyone of a European genetic background. Overall at least 25% of the Neanderthal genome is present across the whole population.
- jessaustin 11y ago
  Perhaps GP means that 2% of the "DNA" can't be traced to recent African ancestors, so it "must have" come from Neanderthals? Ah, nice, that meets my steelmanning quota for this week.
- bryondowd 11y ago
  Perhaps it's only counting 2% of the DNA that we didn't already share with Neanderthals prior to cross-breeding. As in, 2% of what had diverged from a common ancestor. So, you could look at DNA of neanderthals and humans prior to cross-breeding events, and then eliminate everything in common, which would probably be the 99+% you would expect. Then take what's left and look at how much we picked up after cross breeding.
cauterized 11y ago
IIRC from some long-ago bio courses, the Y chromosome also shares fragments via copying mistakes, but what tends to happen over time is that they "migrate" off the Y chromosome entirely, further shrinking it.
- pygy_ 11y ago
  Form my own memories of long-ago courses, the Y chromosome is partially homologous to X and exchanges alleles with it during meiosis. It has its own, non-homologous region too that doesn't trade DNA.

by patall 11y ago

sokoloff 11y ago

> While people of caucasian descent all share about 2% of their DNA with the Neanderthals That number is shockingly low to me, which probably means I misunderstand some subtlety of what you're saying. Could you expand/explain? (I'd have expected a figure starting with at least two 9s [99+%])

meric 11y ago
The context of the comment is - Humans share 40% of DNA with a lot of plants.
loudmax 11y ago
Modern Europeans share about 2% of their alleles with Neanderthals might be a more correct way to put it. But to understand that sentence, you have to understand what's an allele (and I'm not completely sure I'm using the term correctly).
- danieltillett 11y ago
  This is pretty close. A simpler way of describing this is 2% of the average genetic heritage of a European is able to be traced back to Neanderthals. This is a lower bound and it may be higher. The more interesting observation is that the 2% is not the same 2% in everyone of a European genetic background. Overall at least 25% of the Neanderthal genome is present across the whole population.
jessaustin 11y ago
Perhaps GP means that 2% of the "DNA" can't be traced to recent African ancestors, so it "must have" come from Neanderthals? Ah, nice, that meets my steelmanning quota for this week.
bryondowd 11y ago
Perhaps it's only counting 2% of the DNA that we didn't already share with Neanderthals prior to cross-breeding. As in, 2% of what had diverged from a common ancestor. So, you could look at DNA of neanderthals and humans prior to cross-breeding events, and then eliminate everything in common, which would probably be the 99+% you would expect. Then take what's left and look at how much we picked up after cross breeding.

cauterized 11y ago

IIRC from some long-ago bio courses, the Y chromosome also shares fragments via copying mistakes, but what tends to happen over time is that they "migrate" off the Y chromosome entirely, further shrinking it.

pygy_ 11y ago
Form my own memories of long-ago courses, the Y chromosome is partially homologous to X and exchanges alleles with it during meiosis. It has its own, non-homologous region too that doesn't trade DNA.