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Exciting news! Our paper out today in @Nature shows how we recovered ancient human DNA from the surface of a pierced elk tooth pendant found in Denisova Cave. We were able to use this DNA to learn about the actual person who wore and/or made this artefact! www.nature.com/articles/s41586-023-06035-2(1/22) 
Before working with real artefacts, we needed to make sure that we would not alter their surface structure. We teamed up with @EllenSchulzK to perform 3D surface measurements of archaeological bones and teeth before and after DNA extraction using different chemicals. (2/22) 
We identified a phosphate-based temperature controlled extraction as the best non-destructive method. Incubating the specimen in a phosphate buffer and sequentially increasing the temperature from 21 - 90°C, gradually released DNA from the artefact.Illustration by @merszym (3/22) 
Together with @MarieSoressi, we started applying our method to a set of artefacts from Quinçay Cave (France), excavated in the 1970-90s. We were excited to find ancient mammalian DNA from the animal the artefact was made of in some of the samples. (4/22) 
However, we encountered an enormous problem with modern (human) contamination. This contamination was most likely introduced during excavations or while studying the artefacts and made it challenging to find any traces of ancient human DNA. (5/22) 
To address the contamination issue, we focused our efforts on artefacts which were excavated with precautions to prevent the introduction of modern DNA, such as wearing gloves and a face mask, as demonstrated by @MarieSoressi in the image below. (6/22) 
The samples from Bacho Kiro Cave(Bulgaria) and Denisova cave(Russia), excavated with these measures, showed substantially lower levels of modern contamination. In future excavations we hope to continue using these basic techniques to prevent the introduction of modern DNA!(7/22) 
The elk tooth pendant from Denisova cave did not only yield ancient DNA from the animal it was made from but also substantial amounts of ancient human DNA - presumably from the person handling the pendant in the deep past! Illustration by @AnnetteGunzel (8/22) 
Our analysis of the human and elk mitochondrial DNA, done by @ElenaIreneZ and @MatejaHajdi, revealed an age estimate between 19,000 and 25,000 years old. (9/22) 
Recovery of ancient human nuclear DNA allowed @melanoidin to determine that the pendant was made, used, or worn by a woman, based on the relative amount of X chromosome DNA. (10/22) 
Moreover, @ElenaIreneZ and @MatejaHajdi found that this woman was genetically closely related to the contemporaneous ancient individuals from further east in Siberia, the so-called ‘Ancient North Eurasians’ whose skeletal remains have previously been analyzed. (11/22) 
For the first time ever, we were able to directly link the genetic traces of an ancient individual to an object handled by that person. (12/22) 
With more specimens excavated with contamination prevention measures – that is wearing gloves and a face mask - it could become possible to systematically study the DNA of the makers or users of ancient artefacts. Illustration by @AnnetteGunzel (13/22) 
So much about what we know about our past comes from the studies of artefacts. The people who used these ornaments and tools left their DNA behind with every touch – and for the first time, we have used this DNA to connect an ancient pendant to the person who handled it. (14/22) 
As I wrap up this thread, I want to take a moment to express my gratitude to everyone who contributed time, expertise and hard work. Your invaluable contributions were essential to the success of this project, and I am deeply appreciative of each and every one of you. (15/22)
I want to give a big shoutout to Matthias Meyer and @MarieSoressi for their exceptional co-supervision of this project. Your support and guidance have been invaluable throughout this journey. Thank you both for being a scientific inspiration. (16/22)
Also I would like to express my deep appreciation to my shared first authors @ElenaIreneZ&@EllenSchulzK. Thank you both for being such great team members. And apologies to all collaborators for having the most confusing author list ever with 3 Elenas, 1 Ellen and 1 Helen. (17/22)
A big thanks to the whole team who has dedicated time and effort to excavating, studying and investigating exciting finds both on site and in the labs. Without your hard work and dedication, it would not be possible to explore these fascinating questions of human history. (18/22)
Thank you for your confidence in this project, and for all the efforts you have made to bring it to fruition: Maxim Kozlikin, @HelsFewlass, @melanoidin, Michael V. Shunkov, Anatoly P. Derevianko, @Katerina__Douka, @drianbarnes, @MarieCSoulier, Anna Schmidt, @merszym (19/22)
@TsanovaTsenka, Nikolay Sirakov, Elena Endarova, @spmcpherron, @jjhublin, @jfkelso and Svante Pääbo and also the whole Methods group at the MPI @louisajauregui, @JuliaRi08615797, @le_kohli and many more not being on Twitter. You are the greatest team one could wish for!(20/22)
Finally my heartfelt gratitude goes to @MatejaHajdi for being a catalyst to my scientific journey. Without your support, I would not have had the courage to take this path. You are a constant source of inspiration, an exceptional scientist, role model and a true friend. (21/22) 
If you made it until here and still want to read more about how we got ancient human DNA from the pendant found in Denisova cave you can continue reading in the Behind the paper blogpost here: ecoevocommunity.nature.com/posts/tracing-touch-through-time-recovery-of-an-ancient-woman-s-dna-from-a... (22/22) 
