Thread by @johnhawks

I'm participating in the "Deciphering Denisovans" symposium at #AAPA2019 this morning. I'll be tweeting fairly intensively as the session unfolds. The session will be livestreaming on FB: facebook.com/events/4743010…

The symposium program is online here: meeting.physanth.org/program/2019/s…

The symposium is now opening with @SerenaTucci and @cegAmorim explaining the livestreaming and opportunities to ask questions online and in person later in the session. #AAPA2019

@SerenaTucci @cegAmorim Bence Viola is presenting his work on the morphology of the fossils of Denisovans. They're fragments that in most situations might have become forgotten in a museum. #DecipheringtheDenisovans #AAPA2019

@SerenaTucci @cegAmorim Viola: Denisova 13 is a newly identified fragment of parietal bone, which is the first specimen with Denisovan mtDNA that shows any aspect of skull form. The bone is thick! #DecipheringtheDenisovans #AAPA2019

Viola reports that from what is visible about its shape and form, the parietal is "intermediate between Neanderthals and H. heidelbergensis and H. erectus" Closest other fossil: Ngawi cranium, Mid-Pleistocene from Java #decipheringthedenisovans #AAPA2019

Next talk is @ChrisStringer65, who is joining the symposium remotely by Skype. He's talking about the broader context of Middle Pleistocene fossils in Eurasia, trying to narrow down what traits are primitive and derived.

How to classify the Denisovans? @ChrisStringer65 rejects the idea that they should be placed with Neanderthals into a species, suggests a new species might be appropriate but more data needed. #decipheringthedenisovans #AAPA2019

Now @MMartinonT is presenting an overview of the Chinese dental record to examine whether Denisovan tooth morphology might give some indication of their relationships. #decipheringthedenisovans #AAPA2019

@MMartinonT is identifying dental traits that are highly associated with H. erectus in Asia. But there are Chinese fossils that lack these traits -- another group! #decipheringthedenisovans #AAPA2019

@MMartinonT is giving a lot of shape data from enamel-dentin junction of incisors (visible only from microCT data) suggest the presence of a population with similarities to Neanderthals and modern humans in later Middle Pleistocene Chinese and Javan fossils. #AAPA2019

This is quite a strong hypothesis from @MMartinonT that there is a non-erectus Asian population, a clear candidate for Denisovans. So far no DNA evidence to test this. #DecipheringtheDenisovans #AAPA2019

@tommyhigham is now reporting on the ways that he, Katarina Douka, and coworkers have established the chronology of hominins and human-modified bone and ornaments in Denisova. #DecipheringTheDenisovans

Now @tommyhigham is presenting a multifactor model for chronology, including mtDNA branch lengths. The possibility arises that Neanderthal specimens may cluster into stage 5e, possibly a climatic explanation for alternating hominins at Denisova #AAPA2019 #DecipheringtheDenisovans

@tommyhigham Looking at C14 dates, ornaments and bone points at Denisova are less than 50,000 years. @tommyhigham says this doesn't settle who made them, maybe Denisovans #AAPA2019 #DecipheringtheDenisovans

How do we identify more remains of Denisovans? @tommyhigham is presenting on behalf of @Katerina__Douka on the large-scale identification of the identity of bone fragments that can't be identified from morphology. #DecipheringtheDenisovans #AAPA2019

ZooMS = mass spectrometry to quantify the amino acid sequence in collagen, which can identify bone to family level. That can help to understand what animals are being eaten by hominins. One in a thousand or fewer are fragments of hominin bone. #DecipheringtheDenisovans #AAPA2019

Five hominin bone fragments have been found by @Katerina__Douka at Denisova, that's 5 out of 13 total hominin fragments. Nearly doubles the record, and identified the exceptional "hybrid" individual, maybe also first modern humans at site #AAPA2019 #DecipheringTheDenisovans

Viviane Slon is describing the sequencing work on Denisova 11. This is the specimen identified as a first-generation mix with a Denisovan father and Neanderthal mother. #DecipheringtheDenisovans #AAPA2019

This story from last year is one of the best pieces of science in human evolution done in recent years. #AAPA2019 #DecipheringtheDenisovans

Slon suggests that admixture was frequent when archaic populations met, but maybe their overlap in space and time was very limited. #DecipheringtheDenisovans #AAPA2019

Will Rendu @RenduW is joining the symposium remotely from Russia. Skype problems with poor connection, so we're going to video fallback. (There's a video fallback!) #DecipheringtheDenisovans #AAPA2019

Rendu's presentation examining the prey animals of hominins and carnivores at Denisova. Red deer were hunted by hominins during spring and summer in most of the chronology, hyenas occupied site during winter. #DecipheringtheDenisovans #AAPA2019

Only in the oldest parts of the site is there evidence that hominins were hunting during the winter, there's horse and rhino hunting there also. #DecipheringTheDenisovans #AAPA2019

@RenduW showing some of the evidence of skinning animals. Marmots very common, majority of cutmarks. Also evidence of skinning carnivores including bears and wolves. #DecipheringTheDenisovans #AAPA2019

#DecipheringTheDenisovans session resuming now after break with @melanoidin talking about what we can learn about ancient populations by looking at traces of their DNA in living people. #AAPA2019

@melanoidin Vernot begins with, "Denisovans show that the Neanderthal introgression was not a unique event, that this was something that happened repeatedly between many pairs of populations." #AAPA2019 #DecipheringtheDenisovans

@melanoidin BV: Population structure in Denisovans explains why we are bad at separating Neanderthal from Denisovan sequences within living Melanesian populations. #DecipheringTheDenisovans #AAPA2019

BV: "There is incredible heterogeneity across the genome in the density of DNA from archaic humans". Areas without introgression are "deserts" of archaic DNA. Are they evidence of mating incompatibility? #DecipheringTheDenisovans #AAPA2019

BV: In four regions of the genome, both Neanderthal and Denisovan DNA have overlaps of "deserts". These areas may help to determine whether these deserts are due to selection against archaic introgression or chance. #DecipheringTheDenisovans #AAPA2019

BV presenting analysis of Denisova 11 low-coverage genome to see evidence of ancestral introgression in either the Neanderthal mother or Denisovan father of this individual. #DecipheringTheDenisovans #AAPA2019

BV: The method showed that the Denisovan father had ancestral Neanderthal introgression. And the Neanderthal segments are pretty different from the mother's autologous segments. Meaning possibly different Neanderthal populations! #DecipheringTheDenisovans #AAPA2019

Murray Cox by video is describing new results from genome sequencing in Indonesians, and also from Papua New Guinea. The PNG samples have two distinct sources of Denisovan ancestry, both different from the Denisova 3 genome sequence. #DecipheringTheDenisovans #AAPA2019

MC: The divergences within Denisovans are equal or greater to the most different living human populations #DecipheringTheDenisovans #AAPA2019

MC: Best estimate suggests that most divergent Denisovan introgression happened earliest, at "first contact". Later Papuans mixed with a less divergent Denisovan group. Last, the Siberian-similar Denisova population mixed with mainland Asians. #DecipheringtheDenisovans #AAPA2019

MC: Modeling shows that Papuans must have had introgression from Denisovans very recently, within 15-30,000 years ago. Last archaic humans on Earth? #DecipheringtheDenisovans #AAPA2019

I need to take a break from tweeting to prepare my discussion which is coming up next after @emiliahsc, who is looking at high altitude adaptations with Denisovan introgression. #AAPA2019 #DecipheringtheDenisovans