Homo: What, Who, When, & Where?

Guest speaker: Dr. Bernard Wood (GWU)

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You guessed it, we had another guest speaker this Friday instead of our regularly scheduled BS&M meeting. No complaints here, though. This week’s speaker is a giant in the field of paleoanthropology: Dr. Bernard Wood of the Center for the Advanced Study of Human Paleobiology at George Washington University. Dr. Wood stopped by Rutgers to give us his thoughts on the last ~50 years worth of work on the origins of the genus Homo.

Instead of just writing a summary of his talk, I’m trying my hand at Storifying my tweets from the event. Check out the thread and let me know what you think about this format!

Next week, alas, still no BS&M (!), but check back here for ANOTHER defense update! Stan Kivai will be defending his dissertation on the effects of mechanical and nutritional properties on foraging in juvenile Tana River mangabeys. Fingers crossed that the snake is small!

BS&M Does Dissertation Defenses

Congrats to Dr. Hlubik & Dr. Janiak!

Hey BS&M fans, thanks for sticking around. We’ve had fewer journal club meetings than usual this semester (and thus, fewer papers to blog about) thanks to a host of awesome guest speakers and, now, two successful dissertation defenses in as many months! Major BS&M congrats go out to Dr. Sarah Hlubik and Dr. Mareike Janiak, whose names you might recognize from their guest blog posts on mystery spit and Cretan footprints.

For the readers who aren’t in academia, the dissertation defense is the culmination of a person’s graduate student career. While the format varies from school to school, there tend to be some common elements. After a PhD candidate submits their written dissertation to their committee members (made up of their main advisor[s], department members with complementary areas of expertise, and an “outside” expert or two from another university), they schedule a time and place for a public “defense” of their dissertation (some schools call this a “Final Public Oral Examination”). For us at Rutgers, the defense itself is a 40-50 minute powerpoint presentation on our work, followed by questions from our committee, followed by public questions. The whole thing generally takes between an hour and a half and two and a half hours.

The dissertation defense is a stressful rite of passage that has been likened to a snake fight. It’s also incredibly rewarding for the fellow grad students in the audience, because, while we know generally what our friends are working on, we rarely get into the nitty-gritty details of it with them. The defense is an opportunity to celebrate their hard work and hear them get called “Doctor” for the first time (the novelty of which has yet to wear off for me, personally).

So, here’s a toast to Dr. Hlubik: may you find Prometheus in the Kenyan desert.

Sarah_defense

And to Dr. Janiak: may your exoskeletons be chinitous and your copy numbers variable.

Mareike_defense

BS&M Gets Visitors: the Tapanuli Orangutan and Dr. Sarah Tishkoff

Expanding our understanding of diversity

This week’s BS&M blog takes on two new pieces of anthro news – neither of which we’ve actually had a journal club meeting about!

The first bit of news has been making waves all over the internet (as news tends to do, I guess): a third species of orangutan has been named! The newly designated Pongo tapanuliensis, or the Tapanuli orangutan, comes from the southernmost extent of the previously known Sumatran orangutan (Pongo abelii) range. P. tapanuliensis was named on the basis of morphological and genetic comparisons, which suggested that its skeleton looks subtly different from that of all other living orangutans (for example, in having relative broad upper canines and a relatively shallow face) and that it’s the oldest orangutan lineage (having split from the line leading to the other two species around 3.38 million years ago). Pretty cool!

pongo_tapanuliensis
Welcome to the fam, Pongo tapanuliensis! (From Nater et al. 2017)

While the naming of a “new” mammal species (especially one as large as an orangutan) is always exciting, there are a few potential issues to consider. First, P. tapanuliensis was named on the basis of a single (male) specimen and two genomes. It’s possible that there are other Tapanuli orangutan skeletons in museum collections that were not previously recognized as different from the northern Sumatran populations; this would be a something to look into, in the interest of increasing sample size. I’m also curious about what the skeleton of a female Tapanuli orangutan might look like.  Second, Nater et al. estimate that there are already fewer than 800 Tapanuli individuals left. This (and splitting the Sumatran orangutans into two species) has implications for conservation. Is it worth it to prioritize saving the more endangered Tapanuli orangutan, which may already lack a population of viable size, or is it better to concentrate efforts on the Sumatran orangutan? A more optimistic view might be that this new species will attract attention (and money, which is ultimately what allows conservation efforts to happen) to the plight of orangutans generally. It’s impossible to know. Either way, the “discovery” of the Tapanuli orangutan expands our understanding of the diversity of our closest relatives – again, pretty cool!

The second bit of anthro news is also about expanding our understanding of diversity, but this time of our own genome.

Continue reading “BS&M Gets Visitors: the Tapanuli Orangutan and Dr. Sarah Tishkoff”

BS&M Gets Around to the Monkeys Part of Bones, Stones, and Monkeys

Guest Blogger: Alex Pritchard

Hello BS&M fans! Sorry for the long delay between posts; we’ve had a very busy fall in BS&M land so far with lots of guest speakers and a dissertation defense (congrats to the new Dr. Sarah Hlubik!) interfering with your regularly scheduled programming. Today’s post actually comes out of a paper that we read several weeks ago and is brought to you by a member of the “Monkeys” contingent of BS&M, Alex Pritchard. Without further ado, here it is:

Bab (1)

This week I picked an article that I really like, but, I admit, I found it difficult to convey why I like it when I presented it at our weekly journal club. The authors modeled a behavioral game using ‘savannah baboon’ energetic, reproductive, and social system parameters to test assumptions of Kirkwood’s (1977) disposable soma theory, specifically how each sex (male versus female) may have different evolutionary stable strategies for energy allocation. The disposable soma theory posits that individuals can only allocate limited energy between one of three pathways: growth, maintenance, and reproduction.

In primates, females invest considerable energy into their offspring (the reproduction pathway) and the authors use baboons, broadly, as a case study to test sexual differences in strategies. The benefits of baboons is that there is a large body of literature to use in generating a model, which factors in mortality risk, distribution of males, number of receptive females, and foraging yield. On the basis of this information, individuals then allocate energy to essential functions, growth, maintenance, and reproduction. Importantly, the individuals were informed regarding other modeled individual’s strategies. The optimal reproductive strategy (highest fitness gains) for each sex is of primary interest for the authors.

Overall, I found myself dwelling on a desire for the authors to have taken the model further and, unfortunately, to complicate it further. I think it is mostly owing to their generalization of a ‘savannah baboon,’ which combines elements of several baboon allotaxa (closely related species or subspecies). This eliminates the diversity of baboon allotaxa social systems, behaviors, mating systems, and ecologies. Behavioral distinctions are nuanced between the baboon allotaxa, and as a baboon researcher, I couldn’t help but feel that the model is compromised without at least modelling other variables; for example, male-female friendships or alternative forms of reproductive success (like consortship follows leading to sneak copulations). Broadly, this does not matter for their purposes and it is hard to find fault in this approach for the purposes of this paper. Again, they are modelling a complex system, which inherently means simplifying it to test their hypothesis regarding sexually distinct evolutionary strategies. Their model is compelling to test a wide variety of other hypotheses, however, and they suggest the model could be applied to other species living in different social systems after making some species-specific adjustments.

The required data to model such a system is fairly comprehensive, making this model only applicable to organisms that are already fairly well studied. The results, however, were impressive and their life-history outputs were, for the most part, very similar to the observed patterns. There were some exceptions to this concordance that we (the journal club) wish they had resolved. For example, the rate of aging in males and the maximum reproductive rates for both sexes.

Continue reading “BS&M Gets Around to the Monkeys Part of Bones, Stones, and Monkeys”

BS&M Gets Fancy with Metacommunity Ecology

Guest Blogger: Shauhin Alavi

Last week, I instigated my fellow BS&Mers into veering a little off the beaten path, and convinced everyone to discuss a recent Ecography paper that took a metacommunity approach to studying shape variation in rodents. Metacommunities are sets of communities linked by the dispersal of more than one species. Community scale studies are largely lacking across evolutionary anthropology, and given that many extant primates (and probably fossil hominins) fit nicely in the metacommunity framework, this seemed like a good opportunity to explore the potential applications of this approach to anthropological questions.

The paper was met with mixed reviews within our group. Part of the problem was that not everyone was familiar with some of the metrics and analyses (and jargon) utilized in the metacommunity framework. Namely, community weighted means (CWM), principal coordinates of neighborhood matrices (PCNM), principal coordinates of phylogenetic structure (PCPS), and redundancy analysis (RDA). Admittedly, the paper was not written in the most accessible way. For anyone that might be interested in reading this paper, see the table at the end of this post for my best attempts at explaining these (at least for our group) commonly unfamiliar concepts.

One talking point amongst the BS&Mers was whether we actually learn anything new by zooming out to the metacommunity level. A few people (mostly from the B&S contingent of our group) argued that we don’t necessarily need the added complexity of communities to study how environment influences shape variation, and that this is easily done at the species level. I personally believe that looking at variation in community level indices (like CWM) allows us to look at very large scale evolutionary relationships that we might miss at the species level. By scaling up to metacommunities, we are acknowledging (after accounting for phylogeny) that all members of the ecological community are subject to the same environmental variables, and therefore the same selection pressures. Understanding how the mean trait value for the entire community varies with the environment gives us a starting point when trying to understand function.

Another interesting talking point amongst the BS&M crowd was whether or not the paper should have been rooted in some hypotheses. Some of us expressed dissatisfaction at how function was implied throughout the paper, yet there were no hypotheses given for how shape should vary with respect to environmental variables. I actually think that in this case, not having explicit expectations was a bit refreshing. I certainly wouldn’t have considered some of the traits that the authors found to vary significantly with environment.

One thought I was left with after reading this paper was that I wish the authors had included community weighted variance (CWV) in their analysis. Having a measure of variance would at least tell us if a particular trait is worth considering in the first place. It would have also been nice to have incorporated a model averaged phylogeny (sensu 10ktrees).

BS&M ended with a very productive brainstorming session about how to extend this framework to primatological and anthropological questions. I think it would be interesting to use remotely sensed measures of canopy structure to see how morphology varies across primate metacommunities. I also think it would be important to use this framework to uncover how neutral and niche processes shape primate communities. Others proposed extending this framework to studying how various measures of social organization may affect primate trait evolution at the metacommunity level. And of course, we couldn’t resist discussing how we might extend this framework to studying trait evolution across fossil hominin communities. A fair bit of the hominin discussion was how to surmount the palimpsest nature of the hominin record.

Overall the BS&M crew seemed receptive to the approach presented in the paper and acknowledged the importance of the complexity inherent at the metacommunity level.

Click through for the table of jargon and references!  Continue reading “BS&M Gets Fancy with Metacommunity Ecology”

BS&M Does Bears?

A brief follow-up on the Cretan footprints

BS&M returned this past Friday and, alas, I couldn’t attend. Luckily, the discussion centered on the Cretan footprints paper that guest blogger Sarah Hlubik covered in our last post, so you guys aren’t missing out on sweet, sweet new paper coverage.

What apparently went down on Friday was a lot of talk about bears. Were there bears in the area during the Miocene? Yep and yep. Can bears walk upright? Yep! What do bear tracks look like? Like this (according to one site, anyway). Does this mean we need to change our name to Bears, Stones, and Monkeys?

It seems the BS&M crowd is fairly skeptical about the claim of bipedal primate footprints in the Miocene, but loves them some possible bearpedality (thanks for that one, Fred). Personally, I’d love to see the authors find some body fossils of any potential candidate track-maker – and if it’s a primate, even better!

Until next time, I leave you with this (credit to Alex Pritchard):

Sunbear
Exhibit A (left): a sun bear foot. Exhibit B (right): a sun bear after it was recorded saying, “it was ME, it was ME ALL ALONG. Even my family – even my IMMEDIATE family bought it!”

 

Hominin Trackways in the Cretan Miocene?

Guest Blogger: Sarah Hlubik

An in-press paper, available in the Proceedings of the Geologists’ Association on Aug. 31, describes trackways dating to 5.7 mya on Crete (shown in this post’s lead image, from Gierlinski et al. [2017]). This places them just before the Messinian Salinity Crisis, when the Mediterranean dried up, global climates were nice and warm, and the planet really did belong to the apes. A potential hominin trackway (let’s be real, any trackway at all) from this time period is WAY COOL for a couple of reasons:

1. Tracks do not preserve very well. Ever go walking along the beach and look behind you to see your footprints washed away by the next wave? Yeah, me too. Most footprints made in the dirt, sand, or mud, are going to be washed away or destroyed by other individuals, or simply smoothed over because there is so much water in the sediment. For tracks to preserve, they have to dry out a bit, and then be covered pretty quickly by sediment that is a little different in texture or that won’t end up squishing together with the underlying layer. So tracks at all are always really cool, and offer a glimpse into environments and animal communities that we generally don’t see.

2. The Miocene gets called the Planet of the Apes because of the intense radiation of apes that happened during that time period (23-5.3 mya). We know some about the vast array of species that must have occupied the Old World at that time, but there is a lot we don’t know (again, see how to become a fossil), and what we don’t know may have been living on ancient Crete and walking, at least some of the time. Suspensory locomotion evolved sometime during this period (see Pierolapithecus, Dendropithecus, and Dryopithecus), and many later Miocene apes were highly orthograde (which just means they sat upright). Today, suspensory locomotors include gibbons and orangutans, and these (also orthograde) apes are able to walk on two legs over the ground, so it isn’t outside the realm of possibility that a highly orthograde ape had to move across a relatively open, albeit somewhat gooey, landscape and did so on two legs.

Cheezburger animals monkey trees jungle GIF

3. Footprints can tell us a lot about who made them, even if they can’t tell us definitively who made them. Footprints can give us clues about how many toes, or digits, are on a foot, whether the toes had nails, hooves, or claws, and the overall shape of the foot. We can determine the direction individuals were walking, and get a general idea of a minimum number of individuals within a group (to an extent –preserved footprints should represent individuals who are walking over the landscape at roughly the same time, but who can say if they were there together). In this case, the authors claim that the footprints show a foot that resembles ours with all the toes, even the big toe, together, but without claws or a defined arch. Because of this, the authors claim that an original (basal) member of the Hominini clade (our own branch of the family tree) made these tracks, and suggest that whatever it was eventually gave rise to whatever we are now.

I’m not convinced, but I am certainly intrigued. At 5.7 mya, it post-dates early potential basal members of our lineage (Sahelanthropus and Orrorin) residing in Central and Eastern Africa, where current evidence overwhelmingly supports hominin evolution in savannah environments. Crete is a long way from any of these places, even if the Mediterranean Sea wasn’t a factor, and there are no Miocene ape fossils found particularly close to the trackways site. That doesn’t mean these footprints don’t belong to Miocene apes, but it makes it harder to argue that it was definitely an ape and not, say, a bear. Especially given the vast array of apes inhabiting the Planet of the Apes, I don’t have a problem with the possibility that more than one Miocene ape stood up to get across a flat surface, but it would be nice to point to a fossil close by in time and space and say, ‘Hey, it’s probably that guy!’.

Reference
Gierliński, G.D., Niedźwiedzki, G., Lockley, M.G., Athanassiou, A., Fassoulas, C., Dubicka, Z., Boczarowski, A., Bennett, M.R. and Ahlberg, P.E. (2017). Possible hominin footprints from the late Miocene (c. 5.7 Ma) of Crete?. Proceedings of the Geologists’ Association.

Sarah Hlubik is a PhD candidate in the Department of Anthropology at Rutgers University. She works on early hominin control of fire at Koobi Fora, Kenya.