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paleoanthropology, genetics and evolution

Photo Credit: Hand remains of Homo naledi. John Hawks CC-BY 2.0

Homo naledi was chipping its teeth amazingly often

I’d like to point everyone to this new article that may give some insight into the diet or behavior of Homo naledi: “Behavioral inferences from the high levels of dental chipping in Homo naledi. Ian Towle from Liverpool John Moores University examined the H. naledi dental sample last year and, with his colleagues Joel Irish and Isabelle De Groote, he has shown something very interesting about Homo naledi in comparison to other primates: They chipped their teeth a lot.

Figure 1 from the paper tells the story:

Dental chipping frequency in H. naledi compared to other hominoid samples
Figure 1 from Towle et al. 2017, showing the dental chipping rates per tooth class in H. naledi and other samples

Compared to chimpanzees and gorillas, extinct hominins like Au. africanus and Paranthropus robustus crunched on things that chipped their teeth a lot more — for mandibular molars, 25% in Au. africanus, versus only 10% for gorillas. For maxillary molars, gorillas crunched a bit more, and P. robustus surprisingly little. So there seems to be a good bit of noise in the data. But H. naledi puts the apes and other hominins to shame, with 50% chipping in maxillary molars and premolars, 60% in mandibular molars, and 40% in mandibular premolars.

Whatever it was eating or doing with its postcanine teeth, H. naledi was chipping them a lot. And those chips are not microscopic things, they are obvious on visual inspection of the teeth:

Figure 2 from Towle et al showing dental chips
From Figure 2 of Towle et al., 2017, showing dental chips on H. naledi specimens.

In other words, these are macroscopic aspects of tooth wear. We have seen on the teeth of H. naledi that there is a very high wear differential between teeth, and they seem to really have distinctive patterns of wear. Towle and colleagues point out that it is not just anything that yields this kind of chipping, it is seen predominantly in populations that incorporate high amounts of grit into their normal diet. For example, baboons:

The extant primate samples may offer more useful comparisons for H. naledi. For example, in a microwear study by Nystrom et al. (2004), baboons in dry environments were reported to consume large amounts of grit. In the present, combined sample of hamadryas and olive baboons, we found similarities to H. naledi, with frequent small chips and a higher rate of chipping among posterior teeth relative to anterior teeth.

And humans that eat things that sometimes contain shell fragments:

A Late Woodland sample from Cape Cod in the U.S.A. has a pattern like H. naledi in terms of frequency and position (McManamon, Bradley, & Magennis, 1986). The overall frequency is 43% and molars are reported as the tooth type most prone to chipping, with interproximal surfaces most affected. Unfortunately, frequencies for tooth types and positions in that study are not reported. McManamon et al. (1986) suggest that the cause of this patterning was the incorporation of sand, gravel, and/or shell fragment contaminants into the food.

Towle and colleagues note also that the Taforalt sample from the Epipaleolithic of Morocco also has high rates of dental chipping, again thought to relate to the incorporation of shells and fruit stones into the diet. These are high quality food sources that have small, hard objects within them.

The fact that there are human samples with frequencies of chipping comparable to that in H. naledi makes this a bit less puzzling. I would suggest we are looking at dietary adaptability within a population that has a relatively high energy density in its foods. That idea is consistent with the fact that H. naledi has relatively small tooth sizes, despite having substantial chipping rates.

What will be interesting is to see what the microwear texture is like in H. naledi. The sampling for microwear has been done, and our team is now working on assessing it. Thus far, microwear studies have given counterintuitive results as applied to robust australopithecines like P. robustus and others like Au. africanus. “Nutcracker man” evidently wasn’t cracking nuts. That result is holding in this study according to chipping—when you look at the most robust dentitions here, in P. robustus, they have among the lowest rates of dental chipping.

Anyway, it is exciting to see these clues emerge. The picture from dental chipping is remarkably consistent across the H. naledi sample, and it is telling us something very interesting about the diet or other uses of the teeth in this species.

Features of the Grecian ape raise questions about early hominins

Today, Jochen Fuss and colleagues have published a new description of the morphology of a mandible of Graecopithecus freybergi, from Pyrgos Vassilissis Amalia, Greece: “Potential hominin affinities of Graecopithecus from the Late Miocene of Europe”. They carried out microCT imaging of the mandible and another fourth premolar attributed to Graecopithecus from Bulgaria.

Fuss and colleagues show that the fourth premolar root configuration has some similarities with Ardipithecus, Sahelanthropus and Australopithecus. On this basis, they argue that Graecopithecus should be accepted as a member of the human clade, a hominin, closer to humans than chimpanzees and bonobos.

They go further. These Graecopithecus specimens are both older than 7 million years, making them earlier than any known hominin in Africa. So Fuss and colleagues claim that the origin of the hominin clade may itself have been in Europe.

More fossils are needed but at this point it seems likely that the Eastern Mediterranean needs to be considered as just as likely a place of hominine diversification and hominin origins as tropical Africa.

Is it going too far to say that this fossil jaw is the earliest hominin?

Here’s what I think: Paleoanthropology must move past the point where a mandibular fragment is accepted as sufficient evidence.

As blog readers are my witnesses, if I ever describe an unassociated mandibular fragment, I will never claim it is the earliest hominin, the earliest Homo, or the earliest modern human. Again and again, discoveries of relatively complete skeletal evidence have shown that different hominin (and ape) lineages had mosaic morphological patterns across the skeleton. Parallelism and convergence among lineages have been widespread in our evolutionary tree, and no single feature or fragment can accurately indicate relationships.

What’s worse, when we look at the earliest hominins, very few scientists have actually examined the evidence. Ann Gibbons wrote in 2006 that only one scientist at that time had seen all the key fossils, and for all anyone knows that may still be the case – since one of the most important specimens remains unpublished fifteen years after its discovery. Most scientists have been mere spectators, forced to look at cartoon images of skull and pelvis reconstructions that have never to my knowledge been examined by any independent scientist.

I don’t want to take away from the value of the study of Graecopithecus here. It’s pretty cool that Fuss and colleagues were able to find some hidden morphological clues in these very fragmentary specimens. That mandible has only one good tooth in it!

Graecopithecus mandible from Fuss et al. 2017
Figure 1a and 1b from Fuss et al. 2017, showing Graecopithecus specimens. Original caption: a, Type mandible of G. freybergi from Pyrgos, Greece. b, RIM 438/387 –Left P4 of cf. Graecopithecus sp. from Azmaka, Bulgaria. From left to right: distal, mesial, lingual, buccal, occlusal and apical.

With very little to go on, they have done an admirable job of focusing on some interesting dental features that have been seen as important in the early evolution of hominins. I think the study is valuable and I do not question any of the morphological findings.

But consider the example of Ardipithecus. It has a partial skeleton with impressive cranial, dental, and postcranial morphology, and reasonable scientists still cannot decide if it is a hominin. If anyone actually thought we could trust the premolar roots, we wouldn’t be arguing over Ardi.

I think we should take seriously that Graecopithecus premolar root morphology may be yet another demonstration that supposed “hominin” characters actually evolved in other branches of apes during the Miocene. This feature is far from alone. Many other features that supposedly link Ardipithecus or Sahelanthropus with hominins are also found in other Miocene fossils. My colleagues and I documented some of these Miocene ape-like features in Sahelanthropus in 2006.

We need to look with a more critical eye at the fossil evidence for the earliest hominins. They really share very few features with later hominins like Australopithecus. I think we should consider that they might instead be part of a diversity of apes that are continuous across parts of Africa and Europe. Our real ancestry during this earliest phase of our evolution may still be undiscovered.

Reference

Fuss J, Spassov N, Begun DR, Böhme M (2017) Potential hominin affinities of Graecopithecus from the Late Miocene of Europe. PLoS ONE 12(5): e0177127. doi:10.1371/journal.pone.0177127

Wolpoff, M. H., Hawks, J., Senut, B., Pickford, M., & Ahern, J. (2006). An ape or the ape: is the Toumaï cranium TM 266 a hominid. PaleoAnthropology, 2006, 36-50.


Doing some reading on supraorbital torus anatomy today, ran across this snarky passage from Mary Doria Russell’s (1985) paper, “The Supraorbital Torus: A Most Remarkable Peculiarity”.

Browridges have often been interpreted as selectively important eye protection, serving as anatomical sun visors (Boule and Vallois 1957, von Haartman 1974, Kurtén 1979) or bony unbrellas (Davies 1972). It has also been suggested that the Australian Aborigines' well-developed browridges protected their eyes from the venom of Australian spitting snakes (Davies 1972). While the selective advantage of some protection against being blinded by venom is obvious, the fact that the snakes in question are ground-dwelling decreases the usefulness of a barrier above the eyes.

William. W. Howells (1980), writing on the way that new discoveries have affected the interpretation of Homo erectus:

The pattern of discovery to a degree continues that of the past. Java has gone on producing material at a familiar pace, while in Europe fossils have been sparse and fragmentary, with two spectacular exceptions (Petralona, Arago), India continues a blank; China has just begun to produce significant finds again. Africa has taken more of its rightful place. However, if one were to take Weidenreich or Boule as a standard, description has been rather slow, and even preparation, especially in the case of delicate specimens, has delayed up full appreciation of some finds.

Reference

Howells, W. W. (1980). Homo erectus—who, when and where: a survey. American Journal of Physical Anthropology, 23(S1), 1-23.

Funding must make room for exploration

Scientists often say that you already need to have a result in hand to have a chance at being funded for research. Applications where the results are truly unknown are almost never funded.

Instead, applications succeed when they include slick “pilot data” showing the likely outcome, frame the research in terms of well-known earlier results, and seem certain to lead to a positive result. Failure to reject a null hypothesis is not an option. Replication of other research is almost never funded.

This system is wonderful if the goal is to add one brick at a time to the foundation of what we already think we know. But in many areas of science, what we think we know is wrong. And as many others have noted, the bias against negative results and replication has led some fields to a crisis of false published results.

If we want to get at the nature of things, we need scientists who explore new ideas, even if they don’t come pre-packaged with pilot data.

Times Higher Education has a conversation with Nobel Prize-winning scientist Saul Perlmutter, who “Nobel laureate says scientific breakthrough ‘would not be possible’ today”.

“People forget that what you’re looking for is gigantic surprises and transformations that allow us to do things that we never thought were possible,” he said.
“The only thing we know of that seems to work is to create an environment where people are thoughtful, they’re hopeful and they’re trying many ideas.”
He said that this approach can even be seen among venture capitalists, who only expect a “small fraction” of their investments to be successful.
“You’re looking for those rare, special investments and you have to spread the resources in order to get them,” he said.
Saul Perlmutter. Photo: Wikimedia Commons

Over Twitter in the last few weeks, I’ve seen disappointment from several professional colleagues after the rejections of their latest grant applications. The most heartbreaking had reviewers who wrote that their labs “did not have the necessary expertise to carry out the research.” Of course, I know the people, and I know that in each of these cases, these researchers have already published previous work close to their new proposals. They not only have the expertise, I would consider them among the world’s experts.

Think about this kind of comment. I’ve gotten the same thing on my own applications for funding in the past. This is why researchers are driven to include pilot data in their applications, to show that they have already produced results. It’s why researchers apply for funding to do nearly-completed research, so that they can redirect a fraction of the funds to the next project.

Maybe in an environment where the probability of funding were higher, these kinds of comments would be ignored. But take that idea seriously for a moment. Doesn’t it mean that with less funding, we are being even more conservative in what we fund? Doesn’t that make us even less likely to learn something new?

I don’t want to look at the same questions, the same experimental models, again and again. I want to work on new ideas, with a great team of people who have a wide range of backgrounds. It’s what Perlmutter is saying, “create an environment where people are thoughtful, they’re hopeful, and they’re trying many ideas.”

Exploration may not always lead to discovery, but it’s the only thing that does.


Essential reading on the effects of sexual harassment and assault in field paleoanthropology: “In case this helps you: This happened to me while I was trying to become a paleoanthropologist.”

UPDATE (2017-05-28): This post was removed from the linked website by its author, so the link is dead.


Notable: O’Malley, R. C., Stanton, M. A., Gilby, I. C., Lonsdorf, E. V., Pusey, A., Markham, A. C., & Murray, C. M. (2016). Reproductive state and rank influence patterns of meat consumption in wild female chimpanzees (Pan troglodytes schweinfurthii). Journal of human evolution, 90, 16-28. doi:10.1016/j.jhevol.2015.09.009

Synopsis: Looking at long-term data on diet and reproductive status in wild chimpanzees at Gombe, Tanzania, O’Malley and colleagues found that pregnant females ate more meat than lactating or non-pregnant, non-lactating females. This effect was concentrated in low-ranking females, who have less access to meat than high-ranking females, so social rank and pregnancy both interact as factors influencing female meat consumption.

Interesting because: Pregnancy and lactation have high energy costs and protein costs for females. Meat is a relatively high-energy and high-protein food source. A supply of meat in the diet of pregnant or lactating females would seem to be useful or adaptive, even though meat makes up a fairly small fraction of the chimpanzee diet and can easily be dominated by high-ranking females and males. These data show that female chimpanzees do compete effectively for meat despite low social rank, when they are pregnant.

Useful insight: Females did not significantly change insect consumption, even though it is another significant source of protein and energy, more reliable than meat. They seem to be eating insects at near a maximum, limited by the high time involved in foraging insects and insect defenses. Meat has a higher degree of variability.

Should we move to a system where every scientist gives grant money away?

Worth a read: “With this new system, scientists never have to write a grant application again”.

In Bollen’s system, scientists no longer have to apply; instead, they all receive an equal share of the funding budget annually—some €30,000 in the Netherlands, and $100,000 in the United States—but they have to donate a fixed percentage to other scientists whose work they respect and find important. “Our system is not based on committees’ judgments, but on the wisdom of the crowd,” Scheffer told the meeting.
Bollen and his colleagues have tested their idea in computer simulations. If scientists allocated 50% of their money to colleagues they cite in their papers, research funds would roughly be distributed the way funding agencies currently do, they showed in a paper last year—but at much lower overhead costs.

The incredible costs in time and money just to apply for grants and allocate grant funding are approaching insanity levels. With success rates spiraling down below 15%, researchers are spending more and more of their time writing grant applications and less and less doing research, teaching students, or sharing with the public. The average successful grant applicant sinks months of work into grant applications each year that could have been spent doing science, in a fairer system.

I’ve thought a lot about the kind of “self-organized fund allocation” described in the linked article. Allocating money on the condition that some must be given to other researchers would create several downstream benefits. Scientists who maximize the ability of other scientists to produce their own new and useful results would have a big advantage in this system. Jerks would be punished appropriately. Once they have a role in the system, scientists could make rational decisions about how to collaborate with other researchers to build a larger program, instead of trying to centralize into their own little kingdoms.

The article mentions that Bollen’s scheme includes a condition that you can’t just give money to coauthors. The supposed problem is that people will choose to allocate funding to their friends.

Personally, I think that kind of condition decreases the appeal. Maybe there should be a barrier to allocating within an individual’s institution, to prevent administrators from pressuring researchers to keep the money at home. But I think the ability to allocate money to friends will encourage the development of stable research collaborations across institutions (and internationally). Besides, giving other scientists the means to reward friendly behavior will create a lot more friendly environments for science in the future. I think people allocating money within “friend” networks is a feature of a system, not a bug.

But one thing that I think this model wouldn’t address is the risk-averseness of today’s scientists. Today’s funding model disincentivizes taking true intellectual risks. The funded applications are those for which outcomes can be predicted. As a result, some of the most talented researchers are aiming low, instead of trying to swing for the fences. But giving people money to allocate to others is not likely to address what I see as a big problem. To be sure, having a more stable funding, at a low level, will enable some people to try radical new ideas. But any system where a winner-take-all effects kick in is one where it’s hard to fund contrarian or risky research.

Of course, as applied to human evolution research, or even biological anthropology more broadly, this kind of system wouldn’t have quite the impact as biomedical science. If we divided all the NSF funding for Biological Anthropology among the bona fide researchers in this field working in the U.S., it would average less than $3000 per scientist. Still, I’m pretty sure that amount would generate a lot more research distributed across hundreds of working scientists instead of clumped into the overhead budgets of a few big winners.


Notable: Bocherens, Hervé, Martin Cotte, Ricardo A. Bonini, Pablo Straccia, Daniel Scian, Leopoldo Soibelzon, Francisco J. Prevosti. 2017. Isotopic insight on paleodiet of extinct Pleistocene megafaunal Xenarthrans from Argentina. Gondwana Research (in press). doi:10.1016/j.gr.2017.04.003

Synopsis: Bocherens and colleagues did stable isotopic sampling of bones and teeth from extinct sabertooths, horses, and various extinct xenarthrans including glyptodonts and giant ground sloths. The sabertooths obviously turned out like modern carnivores in their stable isotopes. The extinct megafaunal xenarthrans looked just like modern herbivores, with no sign of the in-between diet of some modern species that rely on insect-eating or occasional scavening, like armadillos.

Interesting because: Some paleoecologists had suggested that these weird-looking extinct species might, in addition to eating plants, have been part-time scavengers, or have relied on insect consumption. That is, they might have been a bit more like bears than elephants. That proves not to be the case in any significant way, at least for the South American extinct species sampled.

Best line: “Therefore Megatherium is not the cryptic flesh-eater suggested by some authors that could have accounted for the supposed imbalance of carnivores in the South American megafauna.”


Notable: van Leeuwen, Edwin J. C., Katherine A. Cronin, and Daniel B. M. Haun. 2017. Tool use for corpse cleaning in chimpanzees. Scientific Reports 7:44091. doi:10.1038/srep44091

Synopsis: van Leeuwen and colleagues watched as a female chimpanzee used a grass stem to clean the teeth of a male who had died, at a sanctuary for orphaned chimpanzees. Other group members all inspected or interacted with the body, but the female who cleaned the teeth was a close “adoptive” mother to this dead male.

Interesting because: It is the first recorded example of tool use upon a dead body of a conspecific by a non-human animal.

Best quote: “Like humans, chimpanzees may not treat deceased conspecifics carelessly, but instead handle corpses in a socially meaningful way – i.e. as social beings instead of inanimate objects”


A neat article in The Conversation by Justin Bradfield discusses new chemical approaches for identifying traces of poison in the archaeological record: “We’re closer to learning when humans first daubed arrows with poison”.

A recent archaeological discovery at Border Cave (on South Africa’s border with Swaziland), revealed trace amounts of a substance still adhering to a 24 000 year-old wooden poison applicator. This substance was identified as by-products of the poison ricin. Ricin is produced by the castor bean plant, from which castor oil originates. This discovery, though not without its detractors, sparked renewed interest in identifying poison ingredients on archaeological artefacts in various parts of the world.

It has been interesting to see these aspects of modern technical kits extending far back into the LSA. The development of a hunting tradition using poisons may have had enormous influence on the entire LSA tool repertoire. It may also have established a niche in which human body size and robusticity markedly declined. Yet the basis for the change was archaeologically invisible until very recently.


Agustín Fuentes has a short essay in New York magazine’s “Science of Us”: “Creative Collaboration Is What Humans Do Best.”

But in order to best deploy this capacity we need to remove the set of blinders most of us wear. Many humans have become convinced that we are individually powerless, and have forgotten what creativity is and how its spark resides in all of us.
Creativity is not a private endeavor vested in a single person or a select group of people. It is not solely about genius in the arts or sciences, or actions by prominent artists, celebrities, or politicians. It is not even limited to the work of particularly original thinkers. Creativity emerges from the interconnections of ideas, experiences, and imagination.

Fuentes’ new book is called The Creative Spark: How Imagination Made Humans Exceptional.


My University of Wisconsin–Madison colleague, Karen Strier, has studied the muriqui monkeys of Brazil for her entire career. Now, the in small patch of forest where she works, howler monkeys have become victims of the yellow fever epidemic spreading across the country.

The university has done an informative story on how the epidemic is affecting both the prospects for conservation of these wild primates and the scientific study of their behavior: “Yellow fever killing thousands of monkeys in Brazil”.

When she first arrived at her study forest, known as RPPN Feliciano Miguel Abdala, there were just 50 muriquis. By September 2016, there were nearly 340, representing one-third of the species’ total known population. The animals reside in just 10 forests in southeastern Brazil and nowhere else in the world. Strier’s efforts and those of her colleagues have helped restore their numbers.
She is relieved that, so far, the muriquis appear to be less susceptible to yellow fever. “It was really tense – scary – to go into the forest, knowing the howlers were gone but not knowing how bad things might also be for the muriquis,” Strier recalls.

Here’s a nice article about two archaeologists, Gayle Fritz and David Freidel, and their efforts to better educate the public and their students about critical thinking. “Archaeological Fantasies and Hoaxes” presents a list of five big myths and why they are so pervasive in American culture.

The article touches on many valuable points. Here’s something I didn’t know:

“Incidentally, the opening scene shows Indiana Jones grabbing a golden idol off the altar,” Freidel says. “That’s actually a real jade artifact in the Dumbarton Oaks research library in Washington D.C., and it’s an image of the Aztec goddess Tlazolteotl. It’s a real piece of work, but it’s also an unprovenanced piece of work that was not found in good archaeological context. It was looted.”

When it comes to big public misconceptions, I’m not saying the biggest is aliens, but…


Ottoline Leyser, “chairwoman of the Royal Society Science Policy Advisory Group,” has published a brief essay on science assessment in the U.K.: “No researchers should be submitted to the REF”.

I wanted to share this paragraph from the essay, which was brought to my attention by Jennifer Rohn.

A high-quality research portfolio doesn’t consist only of groundbreaking discoveries. It contains work that cements initial findings, integrates existing work, develops tools and resources such as databases, engages diverse groups and nurtures the next generation of researchers.

I live by this principle in all my projects and scientific work.