[mmmrtl]

The popular factoid is correct, but the confusion here is that these are different measurements. Humans and chimps' genomes are similar in that if you align all the bases [A,C,T,G] that can be unambiguously aligned between the two genomes, 98.8% of the bases are identical. For modern humans to Neanderthals, that number is 99.7%, and between two random modern humans, it would be ~99.9% on average.

This paper is asking a subtly different question - how much of the modern human genome is strictly human, not by simply lining up bases and running a diff, but looking at the inheritance of chunks of DNA ("haplotype blocks", size determined by processes of recombination, etc.) to try to understand how much and which regions of the modern human genome came from interbreeding with Neanderthals or Denisovans. There was variation in the pre-human population before the human/Neanderthal split, which means that if you compare just a single human to a single neanderthal, you'll find unique variants to each. However, most of those variants will have existed in both the human and neanderthal populations, so they should count neither as uniquely human nor neanderthal (knows as Incomplete Lineage Sorting, or ILS).

The chunks in modern humans that derive from Neanderthals or Denisovans are different in different people and broadly across population groups (e.g. highest percent introgressed in Melanesians, lowest in Africans). But across all the modern humans in the study, there are regions where Neanderthal/Denisovan inheritance or shared variation (ILS) was never seen - that's 7% of the genome ("deserts"). And just 1.5% of the genome was in chunks where moderns human commonly have a unique mutation compared to Denisovans/Neanderthals.

[eloff]

This comment is better quality content than the article. I just wish I understood more of it.

[dekhn]

human genetics/genomics papers assume you understand an enormous amount of details of human genetics, the knowledge of which has been hard-won over a century. I worked in this field for decades, know a ton, and still have to read every sentence in this paper carefully, multiple ttimes, and check various sources to remind myself of technical concepts. There's a reason I switched to working on computing full time- a lot of these state of the art arguments can only be contributed to by people who are, well, state of the art, thick-skinned, and well-funded.

[bigmattystyles]

If you’re a layperson wrt genetics, check out ‘The Gene’ by Siddartha Mukherjee - it’s not too dense, interspersed with personal stories he relates to genetics and a great read. His book on cancer is also amazing, ‘Emperor of all maladies’

[nindalf]

In my limited experience, these are two of the best non fiction books I’ve read. The author makes these subjects utterly fascinating. If he released a book about watching paint dry, I’d buy it in a heart beat and read it.

[GoblinSlayer]

1.5% of the genome sounds like a crazy big number. If that much of genome went the wrong way, we could be dragons.

[chiefalchemist]

Would it be safe to say it's not the percentage of difference that matters, but the role of DNA that's different?

The point being, not all DNA is equal so to speak. That a couple of changes can have massive impact?

[haihaibye]

Yes, a single base change can give you a disease, cause intellectual disability or make you never be born.. There are mutations we never see in adults, as they are embryonically lethal.

Generally, you can tell what matters by seeing if it's been under selection - ie the frequency of that version in the population changes more than randomly.

[qyph]

Thanks, your comment makes the basic differences clear to me.

[thaumasiotes]

> However, most of those variants will have existed in both the human and neanderthal populations, so they should count neither as uniquely human nor neanderthal (known as Incomplete Lineage Sorting, or ILS)

This makes a hash of the headline "Thanks to interbreeding, just 7% of our DNA is unique to modern humans" -- this would be just as true if there had never been any interbreeding between "modern humans" and their various sister lineages.