Anthro News

#MeetAlesi

So, the big fossil news that the Leakey Foundation was teasing when last I posted? It was this:

Alesi_anterior view
Anterior view of the cranium of Nyanzapithecus alesi (Nengo et al. 2017)

BS&M Blog readers, meet Nyanzapithecus alesi, a new 13 million-year-old Miocene ape from Kenya. HOW COOL IS THAT?!

I will tell you how cool. VERY COOL. I’m biased (as always – because I pick the things I want to write about for the blog, which are things that I think are very cool), but seriously. There are a bunch of reasons this discovery is awesome, like:

1) You don’t often find complete crania (the skull minus the jaw) of fossil apes. Typically, the bones at the back of the skull (the ones that form the brain case) break sometime before a fossil is found (if it’s found at all, which is a whole different issue). If you want to become a primate fossil, it takes specific circumstances and a lot of luck.

2) You really don’t find fossil ape crania in Africa dated to between 10-14 million years old. Alesi is it. Other fossil ape partial crania are known from this time period in Europe (Pliobates cataloniae at 11.6 mya and Pierolapithecus catalaunicus at 12.5-13 mya from Spain, and Rudapithecus hungaricus at 10 mya from Hungary, to name a few) and Asia (Sivapithecus indicus at 12.3 from Pakistan), which might say something about where fossil apes originated or it might either be the result of less digging having happened in Africa resulting in a deficient fossil record or the difficulty in identifying the earliest apes.

MioceneApe_crania
Pliobates (Alba et al. 2015), Pierolapithecus (Moya-Sola et al. 2004), and Rudapithecus (Begun et al. 2012). (Left to right)

3) You also rarely find infant material in the primate fossil record. (Yes, I know, the Taung Child is an exception to this rule, too.) Infant bones are smaller and more fragile than those of adults, which makes them even less likely to fossilize and be recovered later.

Alesi is also awesome, simply by virtue of being a Miocene ape (my Miocene bias is definitely showing). The Miocene (23-5.3 mya) often gets called a “planet of the apes” because there was a huge diversity of hominoids (the fancy taxonomic group name for apes, including us, is Hominoidea) that lived through Europe, Africa, and Asia at that time. Which is SUPER AWESOME because they were “experimenting” with different types of locomotion at that time (which is totally my jam), but also makes it really hard to tell our potential ancestors from our side-branch cousins. A classic problem for people who work on Miocene apes is that they have ape faces and monkey bodies, and the field disagrees about which is more important (the face or the body) for figuring out who is related to who. Hopefully one of the authors of the Alesi paper (shout out to Kelsey Pugh!) will be able to work some of these relationships out with her dissertation research.

My final thought/question (for now) on Alesi is: the authors suggest that gibbon-like features evolved in parallel several times in different branches of the hominoid lineage – why couldn’t these features be ancestral, rather than derived? If that was the case, it would just require that a different set of facial features evolved in parallel instead. So why the gibbon-like ones and not the other ones?

That’s all for now! Hopefully BS&M will be back on September 8th – catch you then!

References
Alba, D.M., Almécija, S., DeMiguel, D., Fortuny, J., de los Ríos, M.P., Pina, M., Robles, J.M. and Moyà-Solà, S. (2015). Miocene small-bodied ape from Eurasia sheds light on hominoid evolution. Science350(6260), aab2625.

Begun, D. R., Nargolwalla, M. C., & Kordos, L. (2012). European Miocene hominids and the origin of the African ape and human clade. Evolutionary Anthropology: Issues, News, and Reviews21(1), 10-23.

Moyà-Solà, S., Köhler, M., Alba, D. M., Casanovas-Vilar, I., & Galindo, J. (2004). Pierolapithecus catalaunicus, a new Middle Miocene great ape from Spain. Science306(5700), 1339-1344.

Nengo, I., Tafforeau, P., Gilbert, C.C., Fleagle, J.G., Miller, E.R., Feibel, C., Fox, D.L., Feinberg, J., Pugh, K.D., Berruyer, C. and Mana, S. (2017). New infant cranium from the African Miocene sheds light on ape evolution. Nature548(7666), 169.

Anthro News

Big-headed babies and manspreading

August has arrived, the summer is winding down, and those anthropologists lucky enough to be off doing fieldwork have started to come home. A new academic year will begin soon and, with it, the official resumption of the Bones, Stones, and Monkeys journal club! I’m looking forward to getting some new, interesting discussion posts going, but for now, two more pieces of anthro news.

This week’s news comes from the world of #scicomm (aka, public science communication). Science communication/outreach is definitely picking up steam as a major movement lately (though it has always been important) and some excellent #scicomm is being done by anthropologists. We’re lucky enough to study something that people always seem to find interesting – themselves!

First up, Dr. Julienne Rutherford (U. Illinois – Chicago) gave a public radio interview about how modern birth practices might affect human evolution. The overarching question this type of research is trying to answer is, essentially, how does culture interact with and shape biological evolution. Humans babies have relatively large heads compared to those of most other primate babies, which tends to make giving birth difficult. We’ve gotten around the complications of this issue culturally via C-section, but before surgical interventions were possible the size of a baby’s head was a serious selective pressure on birth canal size – too large a head could mean death for both mother and infant. With that pressure removed, Dr. Rutherford suggested that we could potentially see even more variation in female pelvis/birth canal size and somewhat bigger-headed (though not super genius) babies as a result. I’d be curious to see estimates of how long it might take for infant head size/female pelvis size and shape to decouple, given that there has been some cool previous research on how these two things are linked.

Next up, Dr. Caroline VanSickle threw down about “manspreading.” Spoiler alert – it’s a cultural phenomenon, not a biological one. Basically, an emeritus kinesiology professor suggested in an interview that manspreading is the result of sexual dimorphism (sex-related differences in appearance/shape/size) between the male and female pelvis. Specifically, the narrow pelvis of men causes their hip joints to pinch when their knees are together – an issue that is allegedly alleviated by manspreading. Dr. VanSickle shoots this down as not being a biological reality. Behavior isn’t determined by one’s skeleton, which changes during life depending on what you do with it. We call this Wolff’s Law (and I’m probably biased in my enthusiasm for her invocation for it – my entire dissertation was on Wolff’s Law and the pelvis). In addition to being able to shape your skeleton with your behavior, she also mentions research showing that manspreading does not occur in all cultures or with the same frequency between cultures. Personal bias aside, Dr. VanSickle’s case against biological determinism as an excuse for rude behavior was nicely made, so let’s all just keep our knees to ourselves on public transportation, okay?

That’s all I’ve got today from the world of anthro news! The Leakey Foundation tweeted today that they have “exciting fossil news to share tomorrow,” so stay tuned!

Disclaimer: I know Caroline (as I’ve said before, the pelvis world is small). She’s still right. 

Further Reading
Fischer, B., & Mitteroecker, P. (2015). Covariation between human pelvis shape, stature, and head size alleviates the obstetric dilemma. Proceedings of the National Academy of Sciences112(18), 5655-5660.

Ghost Lineages Ride Again: the Spit Edition

Guest Blogger: Mareike Janiak

Darcy asked me to write a guest post on “the new spit paper” and it shows that she knows me well. Saliva? Salivary proteins? Functional genetic variation in those proteins? Possible interbreeding with mystery hominins? The microbiome?

Fav_things_gif.gif

The new spit paper” by Duo Xu and her colleagues is titled “Archaic hominin introgression in Africa contributes to functional salivary MUC7 genetic variation” and is going to be published in the journal Molecular Biology and Evolution.

The authors looked at genetic variation in a gene called MUC7, which codes for mucin 7, a protein that is only found in saliva. In an earlier study, they found that the number of times a specific part of the MUC7 gene is repeated varies across different primate species. In gorillas it is repeated only 4-5 times, while vervet monkeys have 11-12 repeats. Humans have 5-6 repeats, but the gene hadn’t been thoroughly investigated in our own species, which is where the current paper comes in.

One known function of mucin 7 is to bind with bacteria in the mouth, so one question the authors asked is whether genetic variation in MUC7 correlates with the type of bacteria found in a person’s mouth. Using data from the Human Microbiome Project the authors found that people that have more similarity in the MUC7 gene also have more similar bacterial profiles (microbiomes) – but only around the mouth. While this is an interesting result, it creates more questions than it answers! Do these different bacterial profiles provide an adaptive benefit? And if so, for what? In what context is it better to have one over the other? Is it dependent on pathogens in the environment or maybe on diet? Lots of great avenues for future research!

But the authors also found something else when they were looking at MUC7 variation across people, something very curious. As expected, they found a number of different patterns of MUC7. These patterns are called haplotypes and they appear as time goes by and (mostly benign) mutations accumulate along the gene. Generally these haplotypes were pretty similar to each other, but (and this is the weird part!) one of them, haplotype E, was totally different.

Most of the MUC7 haplotypes were like these poodles, small differences but all clearly poodles:

regular_poodles

And then there’s haplotype E:

special_poodle

Yes, still a poodle, but also kind of…out there and unexpected.

So what’s the deal with haplotype E?

Continue reading “Ghost Lineages Ride Again: the Spit Edition”

Anthro on TV

I’ll take paleoanthropology for $400.

So this happened on last night’s episode of Jeopardy:

ancient relatives_jeopardy
Photo credit: Zach Throckmorton (@throckman)

Clues included info on bipedalism, fire at Wonderwerk Cave in South Africa, and Homo erectus, among other things (and the full text should be up at j-archive.com in the next few days).

This amused me for a couple of reasons. First, “exam review Jeopardy” is a classic recitation section technique for TAs and it’s not often that we can use a real Jeopardy set of clues for it. And second, this was from Thursday night’s episode of Jeopardy and I was a contestant on Tuesday night’s episode. SO CLOSE and yet so far.

I’ll be keeping my eye peeled for more anthro in pop culture; maybe it will become a recurring blog theme!

Who Were the Oldest Homo sapiens?

Guest Blogger: Rene Studer-Halbach

Jebel Irhoud 1
The cranium of Jebel Irhoud 1, the original specimen discovered by miners in 1961. Modified from Bruner & Pearson (2012)

On June 8 a team of researchers headed by Jean-Jacques Hublin published a pair of papers describing a new set of fossils excavated from Jebel Irhoud, Morocco. The authors argue that these new discoveries are the earliest known Homo sapiens found anywhere in the world. This leads naturally to two simple questions: was this individual a human, and did it really live roughly 315,000 years ago?

To answer the first question, Hublin et al. used digitized 3D landmarks (or, a consistent set of points on all of the skulls) to statistically analyze the shape of the Jebel Irhoud specimens and compare them to a set of other hominin fossils. This allows you to compare shape differences independent of size differences. This analysis suggests that these specimens are more similar to Homo sapiens than any other species. That being said, this method is far from conclusive. Several of the major features that we use to identify Homo sapiens in the fossil record, including a vertical forehead, globular braincase, and protruding chin, are absent from the Moroccan fossils. Are these Homo sapiens because they are more similar to us than anything else, or do we need to rely on the presence of those specific traits to define the species? If they are humans, then we need to update our definition of what it means to be a human, morphologically. Even if not, it’s clearly something extremely human-like living in a time and place where we never expected to find one.

The second question has its own set of complications. The team (Richter et al.) used thermoluminescence dating of artifacts and electron spin resonance (ESR) dating of teeth to arrive at the date of the fossils. Thermoluminescence and ESR dating both measure radiation exposure (or accumulated dose) to determine the age of an artifact or fossil. The ESR dating suggested a date of 252 – 318 ka, but with a p-value that was not low enough to be statistically significant. In and of itself, that would be a tenuous basis for such an extraordinary claim, but the thermoluminescence dating of burned artifacts found in association with those fossils revealed a date of roughly 315 ka for the geological layer as a whole. This was repeated many times over. It’s not perfect, but the date seems reasonably secure.

What does this all mean? Why has this been reported everywhere, from social media to TV news? Most of the coverage has focused on the date. These may be the earliest members of our species ever discovered. That’s cool, and especially since it pushed back the first appearance date so far, from ~200,000 to ~315,000 years ago. But I think that misses the most interesting aspect of this discovery. It makes us reconsider what it means to be human in an evolutionary sense.

As the authors note in the title of their article, this find makes the case for a pan-African evolution of Homo sapiens. Whatever these individuals were, they were different from us, that much is clear, but they were more similar than anything else we’ve found outside of Homo sapiens. Did the traits that we use to define ourselves evolve piecemeal, across Africa? The discoverers of these new fossils suggest as much, arguing that the clear delineations between archaic and modern Homo sapiens no longer apply. It might be that these specimens represent a bridge between those two groups. If so, what we call them is largely a question of what definition you like to use for a species. That’s a question for another time, and maybe one that’s best to answer by looking at other species, where the stakes don’t seem so high.

One way you could characterize the last several decades of research in human evolution is to say that our understanding has changed from a linear evolution to a bushy one. We’ve filled out the tree a little more, and we see more of the branches and evolutionary dead-ends in our lineage. These finds are doing the same thing, but for the evolution of our own species, regardless of what they’re called. Hopefully this will inspire a new set of excavations across Africa, looking for more fossils to confound us and upend our expectations.

References
Hublin, J. J., Ben-Ncer, A., Bailey, S. E., Freidline, S. E., Neubauer, S., Skinner, M. M., Bergmann, I., Le Cabec, A., Benazzi, S., Harvati, K. & Gunz, P. (2017). New fossils from Jebel Irhoud, Morocco and the pan-African origin of Homo sapiens. Nature, 546(7657), 289-292.

Richter, D., Grün, R., Joannes-Boyau, R., Steele, T.E., Amani, F., Rué, M., Fernandes, P., Raynal, J.P., Geraads, D., Ben-Ncer, A. & Hublin, J.J. (2017). The age of the hominin fossils from Jebel Irhoud, Morocco, and the origins of the Middle Stone Age. Nature, 546(7657), 293-296.

Rene Studer-Halbach is a PhD candidate in the Department of Anthropology at Rutgers University. He works on ecological niche modeling and community structure in South African Plio-Pleistocene primates.  

A Mini-Post & Anthro News

Hominin herpes, European apes, and a fossilized spine

Sometimes a lot of cool stuff happens between BS&M meetings. In an effort to keep up with the constant flow of science and to tide you over until our next discussion, we’re going to try to post mid-week mini-blogs and links to what we’re reading during the week.

This week, Google alerted me to another instance of possible between-species hanky-panky in the fossil record. In a new analysis, Underdown and colleagues attempted to figure out the most likely pathway through which humans got genital herpes (HSV2) from the ancestors of chimpanzees. Yes, you read that right. The closest relative of human HSV2 is not HSV1 (oral herpes), but ChHV1 (the chimpanzee version of herpes). The authors suggest that these two viral lineages split from one another between 1.4 and 3 million years ago, and that either Homo habilis got “proto-HSV2” from the ancestor of modern chimps and gave it to Paranthropus boisei, who then passed it on to Homo erectus, or P. boisei got it directly from the ancestor of modern chimps and transmitted it to H. erectus. (H. erectus is generally considered directly ancestral to Homo sapiens, which is why the virus only has to make it to that species to end up in us.)

Before things get too weird, I want to point out that the authors don’t think that the interspecific hanky-panky went down between either H. habilis or P. boisei and a member of the population of ancestral chimps. They suggest that hunting or scavenging meat from infected chimpanzees would have likely been enough to pass the virus on to one of the hominins, probably via chimp blood coming into contact with an open wound during the butchery process. Once “proto-HSV2” made it into H. habilis or P. boisei, however…

anigif_enhanced-17713-1438816389-2

Anyway. HSV2 now joins HPV (from Neanderthals) and body lice (from some archaic form of Homo) as evidence of ~close~ contact between humans and our hominin cousins (Reed et al. 2004, Pimenoff et al. 2017). The coolest thing about all of this research is that it’s not based directly on fossils or on ancient DNA; you can use things like the evolution of viruses to tell us about our own evolution. Awesome.

Read on for links to what we’ve been nerding out over this week and the references for the herpes paper.
Note: the featured photo is the OH5 cranium of Paranthropus boisei (credit: efossils.org)

Continue reading “A Mini-Post & Anthro News”