#FossilFriday: 2015 Retrospecticus

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Holy crap 2015 was a big year for fossils. And how fortuitous that 2016 begins on a Fossil Friday – let’s recap some of last year’s major discoveries.

Homo naledi

Homo naledi mandibles in order from least to most worn teeth.

Some Homo naledi mandibles in order from least to most worn teeth.

The Homo naledi sample is a paleoanthropologist’s dream – a new member of the genus Homo with a unique combination of traits, countless remains belonging to at least a dozen individuals from infant to old adult, representation of pretty much the entire skeleton, and a remarkable geological context indicative of intentional disposal of the dead (but certainly not homicide, grumble grumble grumble…).  The end of 2015 saw the announcement and uproar (often quite sexist) over this amazing sample. You can expect to see more, positive things about this amazing animal in 2016.

We’ll be presenting a bunch about Homo naledi at this year’s AAPA meeting in Hotlanta. I for one will be discussing dental development at Dinaledi- here’s a teaser:

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As long as we’re talking about the AAPA meetings, my colleague David Pappano and I are organizing a workshop, “Using the R Programming Language for Biological Anthropology.” Details to come!

Lemur graveyard

Homo naledi wasn’t the only miraculously copious primate sample announced in 2015. Early last year scientists also reported the discovery of an “Enormous underwater fossil graveyard,” containing fairly complete remains of probably hundreds of extinct lemurs and other animals. As with Homo naledi, such a large sample will reveal lots of critical information about the biology of these extinct species.

Australopithecus deyiremeda

Extended Figure 1h from the paper, with a Demirjian developmental stages, modifed from Table 2 from Kuykendall et al., 1996. Compare the M2 roots with completed roots of the M1 (to the left).

Extended Figure 1h from Haile-Selassie et al. (2015), compared with Demirjian developmental stages 6-8 . While the M1 roots look like stage 8 (complete), M2 looks like stage 7 (incomplete).

We also got a new species of australopithecus last year. Australopithecus deyiremeda had fat mandibles, a relatively short face (possibly…), and smaller teeth than in contemporaneous A. afarensis. One tantalizing thing about this discovery is that we may finally be able to put a face to the mysterious foot from Burtele, since these fossils come from nearby sites of about the same geological age. Also intriguing is the possible evidence, based on published CT images (above), that A. deyiremeda had relatively advanced canine and delayed molar development, a pattern generally attributed to Homo and not other australopithecines (if this turns out to be the case, you heard it here first!).

Lomekwian stone tool industry

3D scan and geographical location of Lomekwian tools. From africanfossils.org

3D scan and geographical location of Lomekwian tools. From africanfossils.org.

Roughly contemporaneous with A. deyiremeda, Harmand et al. (2015) report the earliest known stone tools from the 3.3 million year old site of Lomekwi 3 in Kenya. These tools are a bit cruder and much older than the erstwhile oldest tools, the Oldowan from 2.6 million years ago. These Lomekwian tools, and possible evidence for animal butchery at the 3.4 million year old Dikika site in Ethiopia (McPherron et al. 2010;  Thompson et al. 2015), point to an earlier origin of lithic technology. Fossils attributed to Kenyanthropus platyops are also found at other sites at Lomekwi. With hints at hominin diversity but no direct associations between fossils and tools at this time, a lingering question is who exactly was making and using the first stone tools.

Earliest Homo

The reconstructed Ledi Geraru mandible (top left), compared with Homo naledi (top right), Australopithecus deyiremeda (bottom left), and the Uraha early Homo mandible from Malawi (bottom right).

The reconstructed Ledi Geraru mandible (top left), compared with Homo naledi (top right), A. deyiremeda (bottom left), and the Uraha early Homo mandible from Malawi (bottom right). Jaws are scaled to roughly the same length from the front to back teeth; the Uraha mandible does not have an erupted third molar whereas the others do and are fully adult.

Just as Sonia Harmand and colleagues pushed back the origins of technology, Brian Villmoare et al. pushed back the origins of the genus Homo, with a 2.7 million year old mandible from Ledi Geraru in Ethiopia. This fossil is only a few hundred thousand years younger than Australopithecus afarensis fossils from the nearby site of Hadar. But the overall anatomy of the Ledi Geraru jaw is quite distinct from A. afarensis, and is much more similar to later Homo fossils (see image above).  Hopefully 2016 will reveal other parts of the skeleton of whatever species this jaw belongs to, which will be critical in helping explain how and why our ancestors diverged from the australopithecines. (note that we don’t yet have a date for Homo naledi – maybe these will turn out to be older?)

Early and later Homo

Modified figures X from Maddux et al. (2015) and 13 from Ward et al. (2015).

Left: modified figures 2-3 from Maddux et al. (2015). Right: modified figures 7 & 13 from Ward et al. (2015). Note that in the right plot, ER 5881 femur head diameter is smaller than all other Homo except BSN 49/P27.

The earlier hominin fossil record wasn’t the only part to be shaken up. A small molar (KNM-ER 51261) and a set of associated hip bones (KNM-ER 5881) extended the lower range of size variation in Middle and Early (respectively) Pleistocene Homo. It remains to be seen whether this is due to intraspecific variation, for example sex differences, or taxonomic diversity; my money would be on the former.

Left: Penghu hemi-mandible (Chang et al. 2015: Fig. 3), viewed from the outside (top) and inside (bottom). Right: Manot 1 partial cranium (Hershkovitz et al. 2015: Fig. 2), viewed from the left (top) and back (bottom).

Left: Penghu 1 hemi-mandible (Chang et al. 2015: Fig. 3), viewed from the outside (top) and inside (bottom). Right: Manot 1 partial cranium (Hershkovitz et al. 2015: Fig. 2), viewed from the left (top) and back (bottom).

At the later end of the fossil human spectrum, researchers also announced an archaic looking mandible dredged up from the Taiwan Straits, and a more modern-looking brain case from Israel. The Penghu 1 mandible is likely under 200,000 years old, and suggests a late survival of archaic-looking humans in East Asia. Maybe this is a fossil Denisovan, who knows? What other human fossils are waiting to be discovered from murky depths?

The Manot 1 calvaria looks very similar to Upper Paleolithic European remains, but is about 20,000 years older. At the ESHE meetings, Israel Hershkovitz actually said the brain case compares well with the Shanidar Neandertals. So wait, is it modern or archaic? As is usually the case, with more fossils come more questions.

Crazy dinosaurs

YiQiSkeksis

Yi qi was bringing Skeksi back, and its upper limb had a wing-like shape not seen in any other dinosaur, bird or pterosaur. There were a number of other interesting non-human fossil announcements in 2015 (see here and here), proving yet again that evolution is far more creative than your favorite monster movie makers.

ResearchBlogging.orgWhat a year – new species, new tool industries, new ranges of variation! 2015 was a great year to be a paleoanthropologist, and I’ll bet 2016 has just as much excitement in store.

References (in order of appearance)

Haile-Selassie, Y., Gibert, L., Melillo, S., Ryan, T., Alene, M., Deino, A., Levin, N., Scott, G., & Saylor, B. (2015). New species from Ethiopia further expands Middle Pliocene hominin diversity Nature, 521 (7553), 483-488 DOI: 10.1038/nature14448

Harmand, S., Lewis, J., Feibel, C., Lepre, C., Prat, S., Lenoble, A., Boës, X., Quinn, R., Brenet, M., Arroyo, A., Taylor, N., Clément, S., Daver, G., Brugal, J., Leakey, L., Mortlock, R., Wright, J., Lokorodi, S., Kirwa, C., Kent, D., & Roche, H. (2015). 3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya. Nature, 521 (7552), 310-315. DOI: 10.1038/nature14464

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

Thompson, J., McPherron, S., Bobe, R., Reed, D., Barr, W., Wynn, J., Marean, C., Geraads, D., & Alemseged, Z. (2015). Taphonomy of fossils from the hominin-bearing deposits at Dikika, Ethiopia Journal of Human Evolution, 86, 112-135 DOI: 10.1016/j.jhevol.2015.06.013

Villmoare, B., Kimbel, W., Seyoum, C., Campisano, C., DiMaggio, E., Rowan, J., Braun, D., Arrowsmith, J., & Reed, K. (2015). Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia Science, 347 (6228), 1352-1355 DOI: 10.1126/science.aaa1343

Maddux, S., Ward, C., Brown, F., Plavcan, J., & Manthi, F. (2015). A 750,000 year old hominin molar from the site of Nadung’a, West Turkana, Kenya Journal of Human Evolution, 80, 179-183 DOI: 10.1016/j.jhevol.2014.11.004

Ward, C., Feibel, C., Hammond, A., Leakey, L., Moffett, E., Plavcan, J., Skinner, M., Spoor, F., & Leakey, M. (2015). Associated ilium and femur from Koobi Fora, Kenya, and postcranial diversity in early Homo Journal of Human Evolution, 81, 48-67 DOI: 10.1016/j.jhevol.2015.01.005

Chang, C., Kaifu, Y., Takai, M., Kono, R., Grün, R., Matsu’ura, S., Kinsley, L., & Lin, L. (2015). The first archaic Homo from Taiwan Nature Communications, 6 DOI: 10.1038/ncomms7037

Hershkovitz, I., Marder, O., Ayalon, A., Bar-Matthews, M., Yasur, G., Boaretto, E., Caracuta, V., Alex, B., Frumkin, A., Goder-Goldberger, M., Gunz, P., Holloway, R., Latimer, B., Lavi, R., Matthews, A., Slon, V., Mayer, D., Berna, F., Bar-Oz, G., Yeshurun, R., May, H., Hans, M., Weber, G., & Barzilai, O. (2015). Levantine cranium from Manot Cave (Israel) foreshadows the first European modern humans Nature, 520 (7546), 216-219 DOI: 10.1038/nature14134

Yi qi: Another fossil from The Dark Crystal

It was a good week for weird dinosaurs. On Monday scientists published Chilesaurus, “an enigmatic plant-eating [dino] from the Late Jurassic period of Chile” (from the paper title). Even more curious, Xing Xu and colleagues announced Yi qi, a Skeksis-like nightmare from the Jurassic of what is now China.

Yi qi on its deathbed, refusing to go quietly.

Here’s the fossil itself:

The Yi qi partial skeleton (Figure 1 from Xu et al.). Inset c is a closeup of the skull, and e a closeup of the elongated finger bones on the right side. Lookit that majestic mane of feathers flowing from the back of its head and down its neck.

The Yi qi partial skeleton (Figure 1 from Xu et al.). Inset c is a closeup of the skull, and e a closeup of the elongated finger bones. Lookit that majestic mane of feathers flowing from the back of its head and down its neck.

Yi qi is Mandarin for “strange wing.” Why “strange”? Here’s the cleaned up schematic of the fossil above:

The rest of Figure 1 from Xu et al. Important for flight are the structures labeled "ldm4/rdm4" and "lse/rse."

The rest of Figure 1 from Xu et al. Key wing structures are labeled “ldm4/rdm4” and “lse/rse.” Light gray shading represents feathers in the fossil, while dark gray appears to be some sort of membrane.

The right side of the figure, depicting the left side of this monster, shows the wing anatomy nicely. Bones with “md,” for “manual digit,” in the label are the homologues (or anatomical equivalents) of your fingers. Notice that the fourth one (“ldm4”) is drastically longer than other digits. This alone suggests some special function for this digit. Emanating from the wrist is another structure, “lse,” for “left styliform element.” In anatomy, “styl-” refers to a structure that sticks out; your skeleton is littered with “styloid processes.” Unlike digits, which are a line of several bones (“phalanges”), this styliform element is a single, rod-like structure made of bone. If you look at the “rse” above, beneath it you’ll see a dark patch running its length, which the researchers identified as “sheet-like soft tissue,” or membrane. These membranes are also found by the elongated md4s.

This all indicates an animal with a thin membrane (kind of like skin, I suppose?) between elongated fourth digits, styliform elements, and probably other parts of the body. Researchers then use the comparative anatomy to reconstruct and interpret the function of this unique wing. Here’s what homologous structures look like in flying animals:

Extended Data Figure 8 from Xu et al. Comparison of the wing structure of different flying/gliding animals.

Extended Data Figure 8 from Xu et al. Comparison of the wing structure of different flying/gliding animals. The yellow segment is the styliform element. Note it comes from the wrist in Yi qi and the Japanese giant flying squirrel, but from the ankle in the bat. Birds and pterosaurs apparently lacked such an accessory structure.

Although media generally report this animal’s wings were like bats’, the authors point out that the placement of this styliform element, at the base of the wrist, is actually most comparable to the Japanese giant flying squirrel (Petaurista leucogenys). Nevertheless, the the construction of the wing, with a membrane between long finger elements, is unlike the wings that other dinosaurs and later birds evolved for flight. This highlights the many ways that flight has evolved – independently – in different kinds of vertebrates over the past 200 million years.

Now, even though these were not giant animals, I think they still would have been terrifying. Not scary in the same way as building-sized theropods like T. rex, 

or Spinosaurus.

No, there is just something a bit creepy about a creature like this. Here is the skeletal reconstruction from the paper:

The dinosaur version of Edward Scissorhands.

Like a dinosaur Edward Scissorhands.

If Yi qi Scissorhands doesn’t drive home just how nightmarish this dinosaur was to behold, check out this uncanny resemblance:

YiQiSkeksis

Yi qi (top) and an Skeksis (bottom). Not the first time The Dark Crystal has predicted important fossils.

Yet again, paleontology shows that fact can be stranger than fiction.

Old bones, new methods

A paper has come out that examines dinosaurs’ sense of smell by using computed tomography (CT) to measure the size of the relative size of dinosaurs’ olfactory bulbs, part of the brain that deals with the sense of smell. This is one example of the really interesting paleontological questions that can be addressed with modern imaging techniques (hint into my NSF proposal…).

The olfactory bulb is a part of the brain that deals with smell. Quite simply, the larger the olfactory bulb, the greater an organism’s reliance upon smelling. As a group, primates rely less on scent than many other mammals, and so their olfactory bulbs are relatively small. Humans have a greatly reduced bulb compared to other primates. Prosimians, the most primitive primates, have much larger bulbs than other primates. Thus, scent plays a larger role for their ecology, possibly due to the fact that many are nocturnal (there’s less light at night, but smells always abound).

This dinosaur study used this logic to infer that Tyrannosaurus rex (probably the ‘sexiest,’ most over hyped dinosaur ever) had a very strong sense of smell. This has important implications about T. rex–was it nocturnal (like all those scenes in Jurassic Park…)? Did scent play an important social role (like modern scent-marking mammals including prosimians)?

Also cool was how the team examined olfactory bulb and brain size. The importance of an scent can be inferred based on an animal’s olfactory bulb size relative to the size of the entire brain. The study used endocasts (naturally preserved impressions of surfaces) of brains and CT scans of skulls to estimate these sizes. This illustrates the usefulness of computed tomography in paleontology. It can be difficult to study certain aspects of fossils non-invasively. By CT scanning a fossil, a digital 3D image of it is created, and this allows researchers to examine all the surfaces (including interior) of the bone, with much better accuracy and resolution than X-rays. In this way, researchers can create ‘virtual’ endocasts, among other things. CT scanning also makes bone (and other material) of different densities distinguishable, so that fossil teeth and the insides of bones can be examined without having to damage them.

CT data are becoming very important not just in medical imaging, but also biological anthropology (Dana knows lots!). Many anthropologists, including the team I met in Vienna this summer, are using CT data to reconstruct fragmentary fossils, uncover tooth shapes in fossil hominins, study brain evolution with ‘virtual’ endocasts, and many other things. This is a very exciting time for anthropology and paleontology, as modern medical imaging techniques have made it possible to address (and ask) research questions that were not possible in the past. In fact, my current NSF graduate research fellowship proposal is seeks to develop a new method for studying cranial variation using CT scans. If I get it (fingers crossed), I’ll keep you all updated with how the research goes. Here’s hoping!

Reference
Zelinitsky D, Therrien T and Koboyashi Y. Olfactory acuity in theropods: paleobiological and evolutionary implications. Proceedings of the Royal Academy B. Corrected proof, in press.

"Spring" Break TV

Spring break, even if it takes place in February, is not a time for being productive. I took this to heart last week as I caught up on zoning out in front of the TV. But it wasn’t all Sabrina the Teenage Witch reruns for this girl: I also caught bits and pieces of two fairly interesting Nova episodes on PBS, “The Four-Winged Dinosaur” and “Ape Genius”.

“The Four-Winged Dinosaur”
I’ll admit, I’m not as fascinated by dinosaurs as some in this lab, so this episode did not hold my interest for the entire hour. However, I came in toward the end and was fascinated to discover that amidst scenes from “Jurassic Park”, they were interviewing a real scientist who actually is trying to breed dinosaurs! The entire episode (or so I gathered) looked at how birds evolved from dinosaurs. They took a bird embryo, and injected it with a virus that would attack the DNA and turn on previously turned off genes, including one that apparently coded for the bird to grow teeth in its beak. But the bird embryo with a beak-full of teeth was not the coolest part. Next they tried to create an emu-asaurus! They didn’t actually manage this, but the Nova voice-over talked us through the technique of how it could be possible to turn an emu egg into an emu-like dinosaur. To quote a friend, “haven’t they seen Jurassic Park? Don’t they know how that turns out??” All I know, is that if they ever manage to recreate dinosaurs, they should avoid breeding raptors – those guys in the movie are SCARY!

“Ape Genius”
This episode aired a while ago, but unfortunately I missed it the first time around. Thank god for reruns! This episode, which I actually watched most of, looked at what apes were and were not capable of doing in terms of communicating, learning, and working together (all those traits people try to describe as culture). I don’t have any profound conclusions about this episode, but I found a number of the experiments they did interesting and will describe a few of them here.

  • Will two chimps work together to get and then share food? The animals had to both pull a string at the same time to get a long plate of food close enough to their cages to eat. Results: if the food was split already, the chimps would work together and each take their share. If the food was not split up, the chimps would usually start fighting and not get the food close enough to reach. If the apes were bonobos, they worked together and shared their food without problems.
  • Do chimps understand the value of an M&M? A trainer puts 7 M&Ms in one bowl and 2 in another, and whichever bowl the chimp points to, a second chimp gets those M&Ms. The first chimp gets the bowl he doesn’t point to. Results: Even after multiple trials, the chimp still points first to the bowl with the most M&Ms, and thus does not get them.
  • Do human children understand the value of a gummy bear? Similar to the above test, in this one an adult explains to a 4-year-old that the one gummy bear in front of them is theirs to eat, but if they wait until the adult leaves and comes back, then they get the entire package of gummy bears. In most cases, the child ate the one gummy bear and did not get the package (these tapes were adorable to watch, by the way).
  • Do chimps understand numbers? A chimp is taught, using dots, the numbers 1-9. Then the previous chimp experiment (the one with the M&Ms) is repeated using numbers instead of M&Ms (introducing a symbolic element). In this case, the chimp learns to point to the lower number, and thus receives more M&Ms. However, the voice-over points out that chimps in the wild do not develop symbols on their own, they are just able to understand some of them when humans teach them.
  • Will bonobos protect or share outside of their own family group? A dead bonobo that is a stranger to a group of live bonobos is placed in the live bonobos’ habitat. Humans with long poles use the sticks to “attack” the dead bonobo. Result: the live bonobos shriek and try to protect the dead bonobo from the offending poles, even though they did not know the bonobo in life.

These were just a few of the interesting experiments compiled in this episode. If you ever catch the rerun of either of these, they might be worth checking out! Next up, a post about all the crappy TV I also watched over break… or maybe I’ll just keep that to myself.