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I think it's because that 3% number is so small, it actually comes down to "outcompeted". A merger of two equally fit sub-species would result in more DNA persi

I think it's because that 3% number is so small, it actually comes down to "outcompeted". A merger of two equally fit sub-species would result in more DNA persisting.

josefx 1y ago
Isn't there already an overlap in the upper 90% between humans and apes? I don't know how much the neanderthal DNA differed back then, but it couldn't be more than that, could it? So wouldn't 3% of the total be at least a third of the parts that did differ?
- pbmonster 1y ago
  It's always confusing how those DNA comparisons are worded. We share almost 99% of our DNA with chimps, for example. But this just means that if you go down the genome, we have 99% of the same types of genes. And that's true even though we don't even have the same number of chromosomes as chimps! (We also share 50% of DNA with bananas - which just shows how incredibly complex basic stuff like cell respiration is.) This is different than the statement that you share 50% of your DNA with your siblings, of course. Because in that case, you actually have the exact identical alleles as your siblings in 50% of your DNA. The 3% neanderthal DNA is the second type of comparison.
  - JohnMakin 1y ago
    When stated this way, 3% seems like quite a lot.
    - pbmonster 1y ago
      Yes! You have 32 great^3-grandparents, 3% DNA is equivalent to one of them being purebred neanderthal.
  - samuell 1y ago
    The 99% identity with chimps is extremely misleading without clear qualification. The fact that it has been used without qualification has a lot to do with the fact that most of our genome was assumed to be junk, which we know today is not the case, per the ENCODE project for example. Thus, the 99% number needs to stop being perpetuated. Today we know that the alignable parts (parts that are similar enough that they can be aligned with each other) are down in the 80s percents between humans and chimps, which can be digged out from e.g. this recent big study (some numbers are in the paper, and some needs to be digged out of the supplementary material): Yoo, D. et. al. (2025). Complete sequencing of ape genomes. Nature, 1-18. https://www.nature.com/articles/s41586-025-08816-3 https://www.nature.com/articles/s41586-025-08816-3 Then remember that a 15%-ish difference with chimps means hundreds of millions of base pairs of difference.
hammock 1y ago
There are a number of ethnic groups (not species or subspecies, I realize) that are less than 3% of the gene pool today (and happened over a much shorter timespan I would suppose) such as Irish, Jewish, Armenian, etc. Would they be considered having been outcompeted at this point?
- andrewflnr 1y ago
  No. There are still 100% individuals of all those groups, and the timescale of recorded history is too small for the same kind of competition as between neanderthals and sapiens anyway.
ricksunny 1y ago
I think that's the crux of the cognitive dissonance we all experience when described the trope for the first time. 3% of group B's genes persisting eons later in the combined genome A+B isn't necessarily reflective of the original relative size of the population of B vs. A. Evolution only countenances which genes conferred a survival benefit edge to persist. Suppose population A was one million individuals, and population B was only one hundred (a 10000X disparity). Assume complete absorption of B into A over an instantaneous period of time. The proportional genetic representation argument, if it were operative, would imply that eons later, only 0.01% of the combined genome is from population B. Only that's not how genetics works - what matters is how much of a survival benefit did population B's genes confer on the inheriting offspring? To put up a concrete example, if population B had a gene conferring immunity to a regionally endemic pathogen, then that pop. B immunity gene is going to quickly saturate representation in the offspring populations as pathogen-vulnerable population members die off from disease.

I think it's because that 3% number is so small, it actually comes down to "outcompeted". A merger of two equally fit sub-species would result in more DNA persisting.

josefx 1y ago

Isn't there already an overlap in the upper 90% between humans and apes? I don't know how much the neanderthal DNA differed back then, but it couldn't be more than that, could it? So wouldn't 3% of the total be at least a third of the parts that did differ?

pbmonster 1y ago
It's always confusing how those DNA comparisons are worded. We share almost 99% of our DNA with chimps, for example. But this just means that if you go down the genome, we have 99% of the same types of genes. And that's true even though we don't even have the same number of chromosomes as chimps! (We also share 50% of DNA with bananas - which just shows how incredibly complex basic stuff like cell respiration is.) This is different than the statement that you share 50% of your DNA with your siblings, of course. Because in that case, you actually have the exact identical alleles as your siblings in 50% of your DNA. The 3% neanderthal DNA is the second type of comparison.
- JohnMakin 1y ago
  When stated this way, 3% seems like quite a lot.
  - pbmonster 1y ago
    Yes! You have 32 great^3-grandparents, 3% DNA is equivalent to one of them being purebred neanderthal.
- samuell 1y ago
  The 99% identity with chimps is extremely misleading without clear qualification. The fact that it has been used without qualification has a lot to do with the fact that most of our genome was assumed to be junk, which we know today is not the case, per the ENCODE project for example. Thus, the 99% number needs to stop being perpetuated. Today we know that the alignable parts (parts that are similar enough that they can be aligned with each other) are down in the 80s percents between humans and chimps, which can be digged out from e.g. this recent big study (some numbers are in the paper, and some needs to be digged out of the supplementary material): Yoo, D. et. al. (2025). Complete sequencing of ape genomes. Nature, 1-18. https://www.nature.com/articles/s41586-025-08816-3 https://www.nature.com/articles/s41586-025-08816-3 Then remember that a 15%-ish difference with chimps means hundreds of millions of base pairs of difference.

hammock 1y ago

There are a number of ethnic groups (not species or subspecies, I realize) that are less than 3% of the gene pool today (and happened over a much shorter timespan I would suppose) such as Irish, Jewish, Armenian, etc. Would they be considered having been outcompeted at this point?

andrewflnr 1y ago
No. There are still 100% individuals of all those groups, and the timescale of recorded history is too small for the same kind of competition as between neanderthals and sapiens anyway.

ricksunny 1y ago

I think that's the crux of the cognitive dissonance we all experience when described the trope for the first time. 3% of group B's genes persisting eons later in the combined genome A+B isn't necessarily reflective of the original relative size of the population of B vs. A. Evolution only countenances which genes conferred a survival benefit edge to persist. Suppose population A was one million individuals, and population B was only one hundred (a 10000X disparity). Assume complete absorption of B into A over an instantaneous period of time. The proportional genetic representation argument, if it were operative, would imply that eons later, only 0.01% of the combined genome is from population B. Only that's not how genetics works - what matters is how much of a survival benefit did population B's genes confer on the inheriting offspring? To put up a concrete example, if population B had a gene conferring immunity to a regionally endemic pathogen, then that pop. B immunity gene is going to quickly saturate representation in the offspring populations as pathogen-vulnerable population members die off from disease.