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Wednesday, August 31, 2011

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.

ResearchBlogging.org
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)


References
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

Tuesday, August 30, 2011

And I thought I had it bad (or, "Toad terrors")


The world can be a terrible place. Sure, there are the finer things that make life worth living - puppies, spooning, hoppy beer, etc. - but there are also things that make you wonder, 'Now why should anyone ever have to endure this?' I recall being a child, growing up on the mean streets of Kansas City, MO, it was a struggle just to get an education. There were bandits that set up a 'toll' to cross the bridge to get to the school, and if we didn't have any pence to put in their pouches, well we'd have to fight our way into the classroom (see map below, of Lincoln College Prep middle school). Getting home in the afternoon was even worse. There was an Iron Maiden. And this thing.
I thought my midwest urban childhood was tough, until today when I read about "cane toads" (Rhinella marina) (below, right). Now, toads in general are odd animals. They're vertebrates, with a sweet bony spine and skeleton, like us humans and wicked-pisser mammals. But they're also not like us ("NLU," as my sweet, politely diabolical grandma would say). Not like us at all. When a human is a baby, she or he looks more or less like an adult, albeit much smaller and cutely misproportioned. But a toad - well, amphibians just have a totally different life plan. Toad babies are these "tadpoles" (or "pollywogs" if you're feeling especially cavalier and sassy) that don't have a body with a head and four limbs that can be used for being awesome. Instead, pollywogs are these fat embryo-ish bodies trailing along a slithering tail. Limbs eventually form from tiny buds and the tail is lost. But superficially, the panning out of toad ontogeny looks like giant sperm deciding to become frog-like abomination unto something. So toads are already not quite right from the get go.

But this one species, the cane toad, has tadpoles that EAT THEIR EGG SIBLINGS and EMIT A CHEMICAL THAT STUNTS THE DEVELOPMENT OF THEIR BROTHERS and SISTERS. In the history of human society there have been a number of stories of family eating family, but there is nothing quite like this. It's a mix between the child-eating Kronos (or Roman "Saturn") or Thyestes (though his was accidental), and Cain and Abel from the Bible that's such a smash with the Judeo-Christians, or Romulus and Remus from the mythic founding of Rome. [Hey I guess my Classics BA has come in handy after all!]

So next time you're feeling down and out, upset with the hand the great Dealer has dealt you, just be glad you weren't a cane toad. Because then you'd've either been eaten/murdered by your older sib, or you'd've eaten/murdered your siblings. Yikes.

Feelings aside, this toad presents a very interesting case study. It will be interesting to uncover the biochemistry and genetics behind how the older pollywogs stunt the development of their little brothers and sisters. I can see this really helping with an understanding of how growth and development are controlled and inhibited, and possibly even how they can be manipulated. It would also be interesting to see if in the evolution of these species, there arose any biochemical defenses expressed in eggs and young larvae against older sibs' fratricidal fragrances, or if it was simply a 1-sided battle.

Life is a funny, funny thing.
Works Ci-toad [sorry for the terrible pun :( ]

PS

Wednesday, August 24, 2011

Dmanisi homs hit the town

Proof that paleoanthropology is cool: the Dmanisi hominids (Mzia is the girl on the left and Zezva the dude on the right), tagged onto a storefront in downtown Tbilisi.


Back to the backbone of Homo erectus

Of course the title is referring to all of the back bones. An alternate title may be "The backbone's connected to the - what bone?" but that's also kinda lame. I'll do better next time.

Martin Hausler and colleagues (in press) report on newly identified vertebral fragments of the WT 15000 Homo erectus skeleton, perhaps the most complete of an early hominid (this one ~1.5 million years ago). This skeleton, and other early hominids (i.e. Australopithecus africanus), were described as having six lumbar (lower back) vertebrae; the modal number in humans is 5, and 3-4 in the great apes. The issue of vertebral formula (the number of cervical, thoracic, lumbar, and sacral verts) in hominids is interesting because it is unclear what the ancestral condition is: was ancestral pattern to have more lumbars (like australopiths) from which humans and apes lost verts, or is ape pattern is ancestral, and lumbars were gained then lost over the course of human evolution?

The fragments found by Hausler and team establish that the WT 15000 individual - and presumably all H. erectus - possessed only 5 lumbar vertebrae. In the past, the only evidence of the 6th-to-last pre-sacral vertebra was the vertebral body. It was unclear whether this vertebra would have had articular facets for ribs (like a thoracic vertebra) or not (like a lumbar vertebra). The pedicle fragments identified by Hausler and colleagues (figure to the right) have a rib facet, and so indicate that the 6th-to-last vertebra of this skeleton was thoracic. Thus, WT 15000 - and again presumably all Homo erectus - had a modern-human-like vertebral formula.

The evo-devo of the spinal column is interesting because it seems to me that it may not be so outlandish to try to identify and test hypotheses about how spinal column development (segmentation) changed over the course of hominid and ape evolution. In trying to determine how development of vertebral segments evolved it is important to know how ancient the human pattern is, and so the identification of 5 lumbars in WT 15000 at 1.5 million years ago is an important finding. I need to think on this a bit, I'll hafta get back to you . . .
ResearchBlogging.org
* figures are from Hausler et al. in press

Reference
Martin Haeusler, Regula Schiess, Thomas Boeni (2011). New vertebral and rib material point to modern bauplan of the Nariokotome Homo erectus skeleton Journal of Human Evolution : 10.1016/j.jhevol.2011.07.004

Sunday, August 21, 2011

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.

Reference
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

Tuesday, August 2, 2011

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!