Osteology Everywhere: Bacon or first rib?

I went to a cafe today to eat breakfast and get some work done. Write, write, write. It’s important to be properly nourished to ensure maximal productivity.

The Ron Swanson diet.

The Ron Swanson diet.

But I was aghast to behold the food they placed before me:

More bacon, please.

What on earth is this?

First of all, this is not a sufficient amount of bacon.


Secondably, this bacon is a spitting image of a first rib:

First ribs, from left to right: Human, chimpanzee, bacon. First two images from eSkeletons.org.

First ribs from the right side of the body, viewed from the top. From left to right: Human, chimpanzee, bacon. First two images from eSkeletons.org.

At the top of the ribcage, just beneath the clavicle and subclavian artery and vein, the first rib is much shorter and flatter than the rest of the ribs. As Jess Beck at Bone Broke points out, “The first and second rib give something of an awkward ‘slow song at a middle-school dance’ kind of a hug, while the lower ribs provide a more comfortable and self-assured embrace.” I mean, just lookit how sheepishly the bacon dances with the eggs in the first picture, it has ‘middle-school dance’ written all over it.

But the bacon is not totally identical to the human and chimpanzee counterparts. It’s missing their anteromedially sweeping arc, and the distal portion reaching out to the egg is fairly straight. This suggests we’re probably missing much of the original distal end. Posteriorly or dorsally (toward the bottom in the pic), it also appears to be missing much of the lateral portion including the vertebral facet. In this regard, this bacon rib looks a lot like the first rib of Homo naledi:

Full stack of ribs. From left to right: Human, bacon, Homo naledi, Dmanisi Homo erectus, Australopithecus sediba (x2), Australopithecus afarensis specimen "Lucy," Ardipithecus ramidus, and chimpanzee. Images not to scale except Lucy and Ardi.

Full stack of ribs. Left to right: Human, bacon, Homo naledi, Dmanisi Homo erectus, Australopithecus sediba (x2), Australopithecus afarensis specimen “Lucy,” Ardipithecus ramidus, and chimpanzee. Images not to scale except Lucy and Ardi. Image credits given below.

It is hard to make good homologous comparisons among these fossils and bacon, since so many are so incomplete. But it looks like the hominins are relatively longer (front to back, or dorsoventrally) compared to the chimpanzee. That is, oriented along the rib “neck,” the ventral/distal end projects far more medially beyond the proximal vertebral facet in the chimp, while in the hominins the two ends are more flush.  Ardi is really incomplete and so very hard to orient, but it may be more like the chimp (I think it needs to be rotated to the right more, to make the lateral edge more vertical like all the other specimens).

It will be interesting to see what my colleagues working on the Homo naledi thorax have to say about rib shapes and their functional importance, hopefully not too long from now.

Anyway, I really wish I had more bacon.

Fossil rib sources
ResearchBlogging.orgDmanisi Homo erectus: Lordkipanidze D, Jashashvili T, Vekua A, Ponce de León MS, Zollikofer CP, Rightmire GP, Pontzer H, Ferring R, Oms O, Tappen M, Bukhsianidze M, Agusti J, Kahlke R, Kiladze G, Martinez-Navarro B, Mouskhelishvili A, Nioradze M, & Rook L (2007). Postcranial evidence from early Homo from Dmanisi, Georgia. Nature, 449 (7160), 305-10 PMID: 17882214

Australopithecus sediba: Schmid P, Churchill SE, Nalla S, Weissen E, Carlson KJ, de Ruiter DJ, & Berger LR (2013). Mosaic morphology in the thorax of Australopithecus sediba. Science, 340 (6129) PMID: 23580537

Homo naledi: Morphosource.

Australopithecus afarensis and Ardipithecus ramidus: White TD, Asfaw B, Beyene Y, Haile-Selassie Y, Lovejoy CO, Suwa G, & WoldeGabriel G (2009). Ardipithecus ramidus and the paleobiology of early hominids. Science, 326 (5949), 75-86 PMID: 19810190

The small, big new Dmanisi skull

The 5th skull early Homo skull from the site of Dmanisi was announced last week. The skull was discovered nearly 10 years ago, but is finally (and very comprehensively) published in Science (Lordkipanidze et al. 2013). The ‘new’ D4500 cranium goes with the massive D2600 mandible, making this the earliest and most complete skull of Homo that I know of. It’s really a remarkable specimen, for a number of reasons beyond its age and completeness. I’ve been busy traveling, teaching and writing lately, so I haven’t yet gotten to pore over the details as much as I’d like. So I hope to sporadically post thoughts on this badass new skull as they come to me. In the mean time, several of what I’d consider the top biology/anthropology blogs*** have discussed the skull, so do check those out if you haven’t already.

The first thing I noted about D4500 is its small brain size, estimated at a mere 546 cubic centimeters. For perspective, D4500 is the green point in the following plot showing brain size in early human evolution:

Endocranial volume for various fossil hominin fossils. 1: Australopithecus afarensis, africanus & boisei; 2: Dmanisi specimens; 3: "habilines" 4: early African Homo erectus; 5: Indonesian and Chinese Homo erectus

Endocranial volume for various fossil hominin fossils. 1: Australopithecus afarensis, africanus & boisei; 2: Dmanisi specimens; 3: “habilines” 4: early African Homo erectus; 5: Indonesian and Chinese Homo erectus. D4500 is green with envy.

I got to see (but not study) the cranium a few years ago when I was helping with the Dmanisi Paleoanthropology field school, and I remember noting just how “robust” the specimen was – big mastoid processes, prominent and thick brow ridge, huge attachments for the neck muscles. In humans, and presumably our fossil forebears, these features are more developed in males than females, and so presumably D4500 was a male (consistent with the huge, associated D2600 mandible). In many primates, and 4 to ~1 mya hominins so far as we can tell, males are larger than females. So it is surprising that a robust probable male cranium is in fact not only the smallest in the Dmanisi sample, but also at the low end of early African Homo (i.e. habilis or rudolfensis), comparable to the largest australopiths. Of course, the only other faces known from Dmanisi are either not fully grown (D2700 and D2282) or old and decrepit (D3444), so perhaps the larger-brained specimens would have been at least as robust as D4500. An untestable hypothesis!

The new skull really highlights the overlap, or continuous variation between later australopiths and early Homo known also from eastern Africa. In association with the postcranial remains known from Dmanisi, the authors the paper posit that early Homo may have been distinguished from Australopithecus not so much in brain size as in body size. We could probably add body shape (limb proportions) and tool use to that list of distinguishing features, and to be sure there are Oldowan tools and small but human-like body size and shape indicated by postcrania at Dmanisi. But then, evidence for body proportions and for/against tool use in Australopithecus, especially later in the record, is somewhat equivocal…

More thoughts to follow.

*** https://blogs.wellesley.edu/vanarsdale/2013/10/17/uncategorized/the-new-wonderful-dmanisi-skull/; http://johnhawks.net/weblog/fossils/lower/dmanisi/d4500-lordkipanidze-2013.html; http://ecodevoevo.blogspot.com/2013/10/how-many-human-species-are-there-is-it.html

Reference: David Lordkipanidze, Marcia S. Ponce de León, Ann Margvelashvili, Yoel Rak, G. Philip Rightmire, Abesalom Vekua, and Christoph P. E. Zollikofer. 2013. A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo. Science: 342 (6156), 326-331.

Dmanisi Homo erectus: I’ll have what she’s having

Speaking of diet in fossil humans … Herman Pontzer and buddies just published a brief analysis of fine-scale tooth wear in the Dmanisi Homo erectus specimens.

Source: http://bit.ly/uD1LWo

Teeth are useful as hell in life. Humans’ teeth are critical not only for eating, sporting a sexy smile, and biting people (right), but also for speech and song (“f,” “th” and “v” sounds). Some parents even harvest their childrens’ exfoliated baby teeth. The things we do with teeth.

Teeth are also really useful for studying long-dead people and animals – teeth may preserve pretty well for millions of years, they can be used to estimate an individual’s age-at-death, and their shape and composition can be used to learn about diet. In a vile act of revenge, the food that sustains us also scrawls its Nom Hancock into the surfaces of our teeth. So, scientists can study the microscopic marks (= “microwear”) on tooth surfaces to see what kinds of foods were eaten shortly before death. Peter Ungar, an author of the current paper, has done a lot of work here, and his website is worth checking out if you’re interested in learning more. Microwear can’t really tell you exactly what an animal was eating, but can tell you whether the animal mostly ate grasses, leaves, hard objects like nuts, and so forth.

So Pontzer and colleagues (in press) examined the microwear on some of the lower molars of the youngest members of the nearly 1.8 million year old (Ferring et al. 2011) Homo erectus group from Dmanisi in the Republic of Georgia. To the left is a picture of the jaws, from the paper (from another paper. How meta of me). The microwear patterns of these badass early humans fit cozily within the variation exhibited by other Homo erectus specimens.

Microwear in Homo erectus is pretty variable, but still rather distinct from other fossil groups like robust Australopithecus, and a little less distinct from their putative ancestor H. habilis. This suggests that something special about Homo erectus was the species’ great dietary breadth – Homo erectus‘ key to colonial and evolutionary success might not have been the adoption of a key dietary resource, but rather the ability to utilize a wide range of food resources. Atkins diet be damned. What’s neat is that the Dmanisi hominids, though kind of primitive (Australopithecus-like) in terms of brain size and some aspects of skull shape, nevertheless demonstrated key behaviors of H. erectus, namely colonization (Dmanisi is the oldest reliably-dated hominid site outside Africa), and dietary flexibility. This really suggests the success of our ancestors was due to some behavioral innovation, aside from advances in stone tool technology.

Source: http://bit.ly/vCTfeR

Now, these Dmanisi H. erectus kids’ teeth wore like other H. erectus, and it would be reasonable to infer that this is because they ate similar foods. This makes it all the more mysterious that the other Dmanisi jaws, from older adults, have teeth completely worn to shit (sorry to swear). D3444/3900 (left) are the cranium/mandible of an individual who was missing all their teeth, except maybe a lower canine – the earliest example of edentulism in the human fossil record (Lordkipanidze et al. 2005). D2600 (below) is a very large mandible with teeth so worn that the pearly-white first-molar crowns were gone and the internal pulp cavity (and nerve) were exposed. (Interestingly, D2600 is so large that some researchers initially argued it represented a different species from the other jaws – yet Adam Van Arsdale presented evidence that this extreme tooth wear may actually be responsible for making jaws relatively taller in early humans).

Source: http://bit.ly/u6bk6h
So what’s curious is why the older Dmanisi hominids should show such an extreme amount of tooth wear compared to other H. erectus, but microwear on the young suggests their diet was the same (that is, just as diverse in texture) as others in the species. Was Dmanisi-level tooth wear (and tooth loss) comparable to other H. erectus, and we just happen not to have found them at other sites? (KNM-ER 730 from Kenya is the next-most worn early Homo that next comes to mind) Is there another aspect of diet we don’t know about, that caused the Dmanisi teeth to wear especially quickly? Or were these early Homo from Dmanisi actually living longer than other H. erectus? I suspect the second is more likely, but that’s a hypothesis that remains to be tested.
Read more, dammit!
Ferring, R., Oms, O., Agusti, J., Berna, F., Nioradze, M., Shelia, T., Tappen, M., Vekua, A., Zhvania, D., & Lordkipanidze, D. (2011). From the Cover: Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma Proceedings of the National Academy of Sciences, 108 (26), 10432-10436 DOI: 10.1073/pnas.1106638108
Lordkipanidze, D., Vekua, A., Ferring, R., Rightmire, G., Agusti, J., Kiladze, G., Mouskhelishvili, A., Nioradze, M., de León, M., Tappen, M., & Zollikofer, C. (2005). Anthropology:  The earliest toothless hominin skull Nature, 434 (7034), 717-718 DOI: 10.1038/434717b
Pontzer H, Scott JR, Lordkipanidze D, Ungar PS. In press. Dental microwear texture analysis and diet in the Dmanisi hominins, Journal of Human Evolution (2011). DOI:10.1016/j.jhevol.2011.08.006

How old is the Acheulian tool industry and why does it matter?

Two views of an Acheulian handaxe adorn the cover of this week’s Nature (right). Always happy to see paleoanthropology stuff be classy, front-page news. The cover highlights Christopher Lepre’s and colleagues’ announcement of what may be the oldest Acheulian tools known.

To recap stone tools: The first good evidence of tool use by humans’ ancestors are the Oldowan lithics from the 2.6 million year old site of Gona in Ethiopia (Semaw et al. 2003). McPherron and others (2010) reported 2 possibly-cut-marked animal bones from the 3.4 million-year old site of Dikika; but this latter evidence is a bit too scant for us to really be sure our ancestors had adopted technology this early. Anyway, the Oldowan was a very basic tool industry, consisting largely of crude flakes taken off cobbles. It may sound lame, but even the most basic stone-tool-making requires some skills, trust me, it’s kinda hard. So stone tools appear roughly 2.5 million years ago, which is also about the time that we have fossils that might document the earliest members of our genus Homo. Sweet.

The legend goes that the next technological revolution doesn’t come until about 1 million years later – until around 1.5 million years ago, stone tools were quite basic. But after a while we start seeing these “handaxes” or “bifaces” (cuz flakes are removed from both of the core’s faces; see above) that have become kind of the hallmark of what’s termed the Acheulian industry. I’m sure there are other key indicators but what do I know, I’m not an archaeologist. Arguably, the rise of the Acheulian from its humble Oldowan beginnings is a milestone in human cognitive evolution – a more complex tool should require a more complex brain, right? Lepre and team announced today that they have some Acheulian handaxes from the Kenyan site of Kokiselei-4, dating to 1.76 million years ago. The authors draw two conclusions: 1) the Acheulian (and thereby more advanced cognition) is a few hundred thousand years older than previously thought, and 2) the co-occurrence of Acheulian and Oldowan tools at this time indicates the presence of contemporaneous human species with different cognitive capabilities.
Now what’s a bit odd here is that the presence of handaxes among otherwise Oldowan assemblages is not a new or unique thing. In her archaeological research at Olduvai Gorge in Tanzania, Mary D Leakey distinguished some assemblages as “Developed Oldowan.” Here’s a relevant blurb from a study by Y. Kimura (2002: 292-293):
“Leakey recognized two distinctive industries, Oldowan and Acheulian, from Bed I through Bed III at Olduvai. The former was characterized by the presence of various choppers and attributed to Homo habilis sensu lato, whereas the latter was traditionally defined to contain bifaces more than 40-60% of the tools, and attributed to H. erectus sensu lato.
The Oldowan was then classified into Oldowan (1.87-1.65 mya) and Developed Oldowan (1.65-0.6 mya) based on the increased light-duty tools, spheroids and bifaces in the latter. The Developed Oldowan coexisted with Acheulian” (emphasis mine)
So the co-occurrence of Oldowan (i.e. choppers) and Acheulian (some handaxes) is known from other sites, albeit not until around 1.5 million years ago. Too bad I’m not an archaeologist nor know more about lithics, because I wish I could put the new Kokiselei-4 assemblage into this context – just how is it different from “Developed Oldowan”? As John Hawks pointed out before I did, “developed Oldowan” doesn’t appear in the Lepre et al. discussion. Hrm. Then they make this statement:

Homo erectus is traditionally thought to be the first hominin to disperse from Africa, yet the oldest known out-of-Africa fossil hominin sites lack stone tools or preserve only Oldowan-style artefacts. … Our data indicate that the earliest development of the Acheulian occurred in Africa at 1.76 [million years] ago and was contemporaneous with or perhaps pre-dated the earliest hominin dispersals into Eurasia (Lepre et al. 2011: 84).

They then go on to suggest that two contemporaneous species lived in Africa in the early Pleistocene – one of these species invented the Acheulian and stayed in Africa, while the other species was too dumb to make anything beyond Oldowan, and instead these dullards left Africa to colonize the rest of the world. This silly scenario seems to stem from an under-appreciation of what Dmanisi demonstrates (possibly since the recent dating paper by Reed Ferring and others only came out a few months ago, probably after the Lepre et al. paper was in press). The Dmanisi fossils establish that hominins more primitive than later Homo erectus (Rightmire et al. 2006) had dispersed into Eurasia by around 1.85 million years ago (if not earlier), with mere Oldowan technology (Mgeladze et al. 2010, Ferring et al. 2011). So Lepre et al.’s claim that the earliest Acheulian “was contemporaneous or perhaps pre-dated” the first out-of-Africa dispersals just isn’t true. And without that, there’s no support for the silly scenario of a smart, techno-savvy but stationary species being contemporaneous with a colonizing but less crafty-and-cunning species.
It’s really cool if the Kokiselei-4 tools truly represent the earliest record of the Acheulian. But, it should be clear by now that we can’t simply equate technology and taxonomy. So how old is the Acheulian and why does it matter? I’m fine with a 1.76 million year date, but I also don’t think it matters too much. (sorry to be so Dmanisi-centric)
Ferring, R., Oms, O., Agusti, J., Berna, F., Nioradze, M., Shelia, T., Tappen, M., Vekua, A., Zhvania, D., & Lordkipanidze, D. (2011). From the Cover: Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85-1.78 Ma Proceedings of the National Academy of Sciences, 108 (26), 10432-10436 DOI: 10.1073/pnas.1106638108
Kimura, Y. (2002). Examining time trends in the Oldowan technology at Beds I and II, Olduvai Gorge Journal of Human Evolution, 43 (3), 291-321 DOI: 10.1006/jhev.2002.0576
Lepre, C., Roche, H., Kent, D., Harmand, S., Quinn, R., Brugal, J., Texier, P., Lenoble, A., & Feibel, C. (2011). An earlier origin for the Acheulian Nature, 477 (7362), 82-85 DOI: 10.1038/nature10372
McPherron, S., Alemseged, Z., Marean, C., Wynn, J., Reed, D., Geraads, D., Bobe, R., & Béarat, H. (2010). Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia Nature, 466 (7308), 857-860 DOI: 10.1038/nature09248
Mgeladze, A., Lordkipanidze, D., Moncel, M., Despriee, J., Chagelishvili, R., Nioradze, M., & Nioradze, G. (2011). Hominin occupations at the Dmanisi site, Georgia, Southern Caucasus: Raw materials and technical behaviours of Europe’s first hominins Journal of Human Evolution, 60 (5), 571-596 DOI: 10.1016/j.jhevol.2010.10.008
Rightmire, G., Lordkipanidze, D., & Vekua, A. (2006). Anatomical descriptions, comparative studies and evolutionary significance of the hominin skulls from Dmanisi, Republic of Georgia Journal of Human Evolution, 50 (2), 115-141 DOI: 10.1016/j.jhevol.2005.07.009
Semaw, S., Rogers, M., Quade, J., Renne, P., Butler, R., Dominguez-Rodrigo, M., Stout, D., Hart, W., Pickering, T., & Simpson, S. (2003). 2.6-Million-year-old stone tools and associated bones from OGS-6 and OGS-7, Gona, Afar, Ethiopia Journal of Human Evolution, 45 (2), 169-177 DOI: 10.1016/S0047-2484(03)00093-9

eFfing Fossil Friday (another late edition)

ResearchBlogging.orgI’m sitting at a cafe in Tbilisi, departing at 4:00 am tomorrow for America. Readers will notice that I’ve been MIA while working with the second annual Dmanisi Paleoanthropology Field School. I hate to say it but I’m glad I was too busy to blog all the goings-on (though sorry if it disappointed anyone). All in all it was another great year, and we found some great fossils (about which I don’t think I have permission to say anything at all). Here’s this year’s class with their certification of badassery at the site on the last day:
But Dmanisi won’t be the subject of this belated eFfing Fossil Friday. I’d like instead to turn to the question of just what fossils are good for. I’m told that in China, fossil teeth were once interpreted as dragons’ teeth, and so pulverized and sold as medicine. But what good are they to non-medical science? My recent research interests have come to focus on the relationship between evolution and development. Evolutionary developmental biology (“evo-devo”) research has been dominated by studies of genes, gene expression, and model organisms like fruit flies and mice. In such an environment, the question of the relevance of fossils is especially poignant.
But this morning, while planning a human evo-devo course I hope to teach next summer, I stumbled upon a review paper by Rudolf Raff, titled “Written in Stone: Fossils, genes and evo-devo” (2007). I think the abstract sums things up pretty well:

Fossils give evo-devo a past. They inform phylogenetic trees to show the direction of evolution of developmental features, and they can reveal ancient body plans. Fossils also provide the primary data that are used to date past events, including divergence times needed to estimate molecular clocks, which provide rates of developmental evolution. Fossils can set boundaries for hypotheses that are generated from living developmental systems, and for predictions of ancestral development and morphologies. Finally, although fossils rarely yield data on developmental processes directly, informative examples occur of extraordinary preservation of soft body parts, embryos and genomic information.

It seems often that fossils are falling by the wayside. There’s a sentiment that there’s not much information to be gotten from fossils – they’re too incomplete, too few, too inconvenient, at least as compared with extremely high-output data such as that coming from genomics. But Raff is right – we need fossils. Beyond the excellent points Raff raises in the review, I’m working on getting the most out of these seemingly data-poor fossil samples. Because modern computers are so powerful nowadays, I’m using their sheer processing power to test hypotheses about growth and development in fossil samples. These battered bunches of bones are too tiny to be analyzed by traditional methods. But one thing I think is important to take away from this computer-crazy Information Age, is that we now have machines that can handle almost any kind of question one can think to ask, and it’s really inspiring. The sequencing and analyses of ancient Neandertal and Denisova genomes (Green et al. 2010, Reich et al. 2010) are excellent examples of the amazing research that can be done with computers and creativity (and probably also a horde of hard-working math majors).
So this eFFF (or Sunday) is not dedicated to any specific fossil or set of fossils, but rather to all fossils, even the crappy fragments. Gaumarjos, fossils: your secrets are not safe from us.
Green, R., Krause, J., Briggs, A., Maricic, T., Stenzel, U., Kircher, M., Patterson, N., Li, H., Zhai, W., Fritz, M., Hansen, N., Durand, E., Malaspinas, A., Jensen, J., Marques-Bonet, T., Alkan, C., Prufer, K., Meyer, M., Burbano, H., Good, J., Schultz, R., Aximu-Petri, A., Butthof, A., Hober, B., Hoffner, B., Siegemund, M., Weihmann, A., Nusbaum, C., Lander, E., Russ, C., Novod, N., Affourtit, J., Egholm, M., Verna, C., Rudan, P., Brajkovic, D., Kucan, Z., Gusic, I., Doronichev, V., Golovanova, L., Lalueza-Fox, C., de la Rasilla, M., Fortea, J., Rosas, A., Schmitz, R., Johnson, P., Eichler, E., Falush, D., Birney, E., Mullikin, J., Slatkin, M., Nielsen, R., Kelso, J., Lachmann, M., Reich, D., & Paabo, S. (2010). A Draft Sequence of the Neandertal Genome Science, 328 (5979), 710-722 DOI: 10.1126/science.1188021

Raff, R. (2007). Written in stone: fossils, genes and evo–devo Nature Reviews Genetics, 8 (12), 911-920 DOI: 10.1038/nrg2225
Reich D, Green RE, Kircher M, Krause J, Patterson N, Durand EY, Viola B, Briggs AW, Stenzel U, Johnson PL, Maricic T, Good JM, Marques-Bonet T, Alkan C, Fu Q, Mallick S, Li H, Meyer M, Eichler EE, Stoneking M, Richards M, Talamo S, Shunkov MV, Derevianko AP, Hublin JJ, Kelso J, Slatkin M, & Pääbo S (2010). Genetic history of an archaic hominin group from Denisova Cave in Siberia. Nature, 468 (7327), 1053-60 PMID: 21179161

Gamarjoba from Dmanisi!

It’s been a bit harder to keep things updated as I journey across latitudes this summer. My last post was from Nairobi, and a few days later I arrived in Tbilisi in the Republic of Georgia (lamazi Sakartvelo). I’ve been involved with the 2nd annual Dmanisi Paleoanthropology Field School, which has been going on for about a week now. Things have been going fast and we’ve been having a lot of fun, so it’s a bit too difficult to recap everything so far. But we’ve had a series of lectures from great people in various fields. Here are some highlights:

Our first lecture was by Dr. Bernard Wood, at the site of Dmanisi itself. He discussed some of the progress and pitfalls in the field of Paleoanthropology. Next was Dr. G. Philip Rightmire, who discussed some aspects of hominid morphology and taxonomy. Then Dr. Reid Ferring discussed the geology of the site. As someone who focuses more on the fossils themselves, Ferring’s lecture was refreshingly fascinating for me. In brief, Argon-Argon dating was used to establish that the Mashavera basalt underlying the hominid (and other!) fossils is around 1.85 million years old. Then there were a series of ash falls that led to the soil formation of the site. A little (stratigraphically) above the fossil deposits is a layer dated by paleomagnetism to correspond to the Olduvai polarity reversal, around 1.76(?) million years ago. So the hominid fossils themselves are pretty well constrained to somewhere between 1.85-1.75 million years ago.

Then Dr. Martha Tappan gave a lecture about the taphonomy (site formation and burial processes) of the site; the neighbors invited me in for some delicious ch’ach’a shortly before the lecture, so I’m afraid my memory of this one is a bit foggy. 😦

Last night Dr. Jordi Agusti lectured about the micromammals at Dmanisi, and at some Spanish Pleistocene sites. Micromammals have large litters and short generation times, so they are good indicators for relative dating. Tonight Dr. Adam Van Arsdale will be lecturing about early Homo from Dmanisi and other sites. It’s been a great lecture series so far, and there are sure to be many great more lectures in the next few fast-paced, fun-filled weeks.

We’ve also been excavating the site, working mostly so far on taking down some of the layers stratigraphically above the hominids to hopefully more fossiliferous layers. I injured my hand on some monkeybars at the park yesterday (they seriously ripped off a big layer of skin, so I’m partially mummified), so I was down for the count today, doing lab work in lieu of excavating. I should be ready to go by tomorrow though.

I know I owe the world a few Effing Fossil Friday posts, so I’ll hopefully have those up soon, too. Nakhvamdis!