Woman's DNA discovered in 20k year old deer-tooth pendant

They didn't sequence the whole human genome (~3 billion bases) for multiple reasons. I am not an expert on ancient DNA but I will try to explain the paper as best I can:

1. Contamination with other flora and fauna DNA 2. Relative low proportions of human DNA 3. The DNA is usually highly degraded, which limits the analyses to short read sequencing (in this case they used 76 bp reads). The halflife of human DNA is ~521 years.

To mitigate these problems they used multiple targeted approaches including one to isolate mitochondrial DNA, where they managed to sequence the whole ~16kb human mtDNA, where each base was covered by 62 sequencing reads on average (62x coverage).

They used another to isolate specific regions containing single nucleotide polymorphisms (SNPs), which are DNA mismatches known to be related to ancient human DNA and humans. They targeted 470,724 single nucleotide polymorphisms of which 70% (336,429) were recovered.

They did perform shotgun sequencing on all of the DNA isolated, but due to species assignment issues they again focused on fragments that contain diagnostic SNPs in these cases they only recovered a small number of SNPs per sample, again due to the relatively low proportion of human DNA and its degradation (20,526, 3,734, 124,862, 85,901, 34,756, 41,632, 34,677 and 72,992) as per the legend in figure 3.

Keep in mind that this is survivorship bias. The vast majority of DNA from this period has lots. Sure, there is tons that exists but we haven't found but without a doubt almost all of it has been lost.

This is DNA that happened to be the right conditions to survive. It isn't so much that the medium is resilient but that if stored in the correct conditions it can survive.

It’s even more impressive when you compare it to rna, which “lives” minutes. Take away the pair strand, add a hydroxyl group and a uracil, and it’s a totally different thing.

So this is how I should be storing family photos.

When can I start storing passwords in mine?

It's basically everyone!

Denisova cave has been known for about 150 years or so. Back in the 1970s, the Soviet Union sent some archaeologists out to see what was in the cave. They found some upper paleolithic stuff (e.g. like what the article is about), as well as some mousterian stuff (very weird this far north and east). They did excavations over the next couple of decades and eventually, some of the dating/sequencing technology improved to the point where it could actually be used on the cave artifacts. That's when they discovered denisovans and immediately made the cave one of the most important archaeological sites on the planet. There's been no lack of funding since.

Two reasons:

- Elk is ambiguous. There's an Elk/Wapiti in North America, Central Asia, and East Asia, and another species of deer referred to as an "Elk" by people in Eurasia, but which is known as a "Moose" in North America.

- Because journalists these days don't have time to look these kinds of things up. The original paper only refers to it as wapiti/cervus canadensis/deer. If the whoever wrote that article knew it refers to an elk, they'd have pointed that out for the reader.

Elk is pretty ambiguous — it refers to different species depending on the context (in Europe, ‘elk’ refers to what in north America is called a moose. Wapiti is a name for what ‘elk’ refers to in North America). You get a similar problem with the words ‘hawk’ and ‘buzzard’

It says a lot about the state of discourse and gender science that I can't tell if you genuinely don't understand or if you are being facetious.

But assuming you are being genuine: your sex (faka gender) is encoded in your DNA on the 23rd chromosomal pair. If you have two X chromosomes (XX), you are a female human (woman). If you have one X and one Y (XY), you are male human (man). These chromosomes dictate your sexual development (organs/hormones/etc). There are some people (estimated at 1-2% of the human population) who are "intersex", in that they don't have an XX or XY pair, but some variation thereof (XXY, XYY, etc). However even these variations generally fall under one or the other umbrella of male or female. e.g. Klinefelter syndrome (XXY) is generally going to present as male (albeit frequently with poorly developed testicles and other complications). Genes are complicated so this is a bit of an oversimplification.

To make this more about sex itself (since humans are a sexually reproducing species and that is why we are having this conversation at all), there are effectively three options for all humans: you produce small gametes (sperm / male) or you produce large gametes (eggs / female), or you produce neither due to some complication and therefore cannot participate in procreation. This is dictated almost wholly by your DNA.

So, back to the article: they know the DNA in the deer tooth was from a woman because (presumably) the 23rd chromosome was an XX pair.

DNA has a very strong signal for man, woman, and everyone in between.

There actually was human DNA in it so I don't know why we're scoffing as successful methods as if they're unreasonable.