Oldest Human DNA Contains Clues To Mysterious Species

sciencehabit writes "Analysis of the oldest known genetic material ever to be recovered from an early human reveals an unexpected chapter in the story of human evolution. Researchers extracted mitochondrial DNA from the femur of a 400,000-year-old hominin found in the Sima de los Huesos ('pit of bones'), an underground cave in the Sierra de Atapuerca in northern Spain. Because the early hominins looked a little like Neanderthals, researchers expected their mitochondrial DNA to share a common ancestor. However, mitochondrial DNA from the Spanish hominin was found to share a common ancestor with an enigmatic eastern Eurasian sister group to the Neanderthals, the Denisovans."

Comments

Very interesting, but

[ColdWetDog]

1. They had problems with modern human DNA contamination (not sure why they couldn't get everything clean but since they're the leading edge lab in this sort of thing, it must be a real issue).
2. They had to limit analysis to fragment lengths around 45 base pairs to avoid this contamination. That's tiny compared to what one normally uses.
3. They only had enough to sequence the mitochondrial DNA.
4. It's only one person.

So, it's confusing but it seems from the outside to be due to a limited data set. Now, this sort of thing is at the limit of our current technology and the lab is working to replicate and amplify the data (and work on the somatic genome). So stay confused and stay tuned.

Re:Very interesting, but

[ColdWetDog]

And one other thing, if anybody out there knows:

They eliminated modern contaminating DNA by analyzing only DNA segments with uracil, a base usually found in RNA and a signature of older, degraded DNA.

Uracil is a modified Thymine, in vivo DNA where uracil is incorporated into the chain is repaired by a specific enzyme. Does the Thymine naturally degrade to Uracil over time?

Re:Very interesting, but

[HiChris!]

No, but Cytosine does - the amine group gets hydrolyzed, leaving a Uracil nucleobase. (Also Thymine is a modified Uracil, it's also know as 5-methyl uracil)

Re:underground cave...

[Nkwe]

"underground cave" is there another kind?

Man Cave

Re:Hominin?

[a_n_d_e_r_s]

Hominin a subtribe of homonids

Homonids is great apes thus humans gorillas chimpanzea orangutans

Homonin are all those related closer to humans than chimpanzees thus neantherthals etc

Re:underground cave...

[M. Baranczak]

Nick Cave. Does he still count as "underground"?

Re:science writer knows nothing of science

[wonkey_monkey]

So what exactly is the "clues" that have been gained?

are

Sorry.

So what exactly is the "clues" that are been gained?

Re:Hominin?

[Nerdfest]

... because hominem is a homonym of hominim.

Re:Happy Wednesday from The Golden Girls!

[jc42]

We were human 100000 years ago? Weren't we human-LIKE way back then? I mean, denisovians and Neanderthals weren't human, were they?

Well, if you're talking about the conventional usage of "human" in scientific circles, the answer is: Yes, they were; they just weren't modern humans.

But "human" really isn't a technical term; For that you want something like "Homo" or "hominin", depending on how far back in the tree you want to describe. The term "human" is used informally to mean just about any critters later than the split from the Pan (chimpanzee) branch. It's used when you don't want to be too precise about such things.

OTOH, "human" is widely used in common speech to refer to anyone "not like us". Sometimes it means "white people", especially in writings from before the 20th century. But you don't much hear such usages in scientific settings. You do see it a lot in media coverage of science, but then it means whatever the journalist thinks it means.