Our paper: The evolution of early Homo

This past Spring I published a paper, together with Milford Wolpoff, on the early evolution of our genus, Homo. The paper had several inspirations, independent of my own research in this arena associated with my work at the Lower Paleolithic site of Dmanisi. First, Suwa, et al. (2007), published a paper several years ago in which they conclude there is no evidence of Homo habilis and Homo erectus co-existing in the deposits of the Turkana Basin. Rather, all of the identified habilis specimens appear to pre-date the erectus remains, making a linear relationship between the two sets of remains possible. This idea is hardly new. Indeed, our other starting point was the original debates between Robinson and Tobias regarding the Olduvai remains from the 1960s. Regarding this earlier material, Robinson said:

…the Bed I [Homo habilis] material may represent an ad- vanced form of Australopithecus and the Bed II specimens an early H. erectus and at the same time the latter may be a lineal descendant of the former (Robinson 1966, p. 123).

Here is where Dmanisi comes into play. Dmanisi sits, chronologically, right in the middle of the rich deposits from Turkana and Olduvai, while providing the best single locality view of early Homo variation. Why not expand the null hypothesis of Suwa (2007) to the larger, more inclusive sample including Dmanisi. So that is what we did.

I don’t want to recapitulate the entire paper, but basically we examine the pattern of variation created by pairwise sampling as much of the fossil record from his time period (~1.9-1.5 MYA) as possible, attempting to reject a single, evolving lineage model. We fail to do so, while demonstrating that our approach can discriminate between even meager samples of Homo/robust Australopithecus. We fail to reject the null hypothesis, suggesting that despite the much expanded fossil record for this time period, the single lineage model remains the parsimonious explanation (based on our approach).

Modified from Van Arsdale & Wolpoff (2013)

Modified from Van Arsdale & Wolpoff (2013)

As it turns out, I am glad I did not blog on this earlier (despite plans to do so), because the paper has generated some response. Jeremiah Scott has a paper in press at Evolution responding to the paper (our reply is also forthcoming), and Adam Gordon & Bernard Wood mention the paper in an in press publication in the Journal of Human Evolution. This response is not surprising. Our argument is a bit heterodox. But more importantly, we published our complete data set with the publication, the largest available cranial data set for early Homo anywhere in publication. We wanted people to respond. How else does science work?

A few other points I wanted to raise about our paper. An important, but easily overlooked, part of our paper is the formulation of our hypothesis as an evolving lineage. This might sound matter of fact, but it is actually a rarely acknowledged approach in paleoanthropology to compare fossil assemblages spanning (hundreds of) thousands do years, with museum collections of primates and humans that span a few decades. This is not necessarily an insurmountable problem, but it is an implicit assumption about how we construct hypothesis tests that makes tests of evolution (i.e. changing patterns of variation) difficult. We are not testing a static model of variation, but rather one that changes across the time period we study.

Finally, we prioritize sample size over sample quality in our analyses. Our approach is multivariate, but not a traditional multivariate approach that utilizes a variance/covariance matrix generated from our sample. The nature of the fossil record from this time period (and most others), means that there are too many missing measurements and too many fossils lacking comparable elements to generate any kind of sample size (either in measurements or in specimens) for a traditional multivariate approach. Were we to take such a view, we would end up comparing only the very few well preserved specimens, utilizing only the very few measurements that are represented on each of them. We think the less preserved fossils matter. They do not preserve as much information as the better preserved specimens, to be sure, but given the data constraints within our field, an effort should be made to include them within the basic evolutionary models we construct. So that is the approach we take.

I am of course biased, but I happen to think the origin of the genus Homo is the most exciting current area of research in paleoanthropology. The evolutionary transitions that characterize the emergence of Homo from Australopithecus set the stage for the pattern of human evolution that develops in the Pleistocene. I hope our paper will continue to generate responses, both pertaining to our conclusions and the approach we take to reach those conclusions.

A SINGLE LINEAGE IN EARLY PLEISTOCENE HOMO: SIZE VARIATION CONTINUITY IN EARLY PLEISTOCENE HOMO CRANIA FROM EAST AFRICA AND GEORGIA

Adam P. Van Arsdale and Milford H. Wolpoff

ABSTRACT: The relationship between Homo habilis and early African Homo erectus has been contentious because H. habilis was hypothesized to be an evolutionary stage between Australopithecus and H. erectus, more than a half-century ago. Recent work re-dating key African early Homo localities and the discovery of new fossils in East Africa and Georgia provide the opportunity for a productive re-evaluation of this topic. Here, we test the hypothesis that the cranial sample from East Africa and Georgia represents a single evolutionary lineage of Homo spanning the approximately 1.9–1.5 Mya time period, consisting of specimens attributed to H. habilis and H. erectus. To address issues of small sample sizes in each time period, and uneven representation of cranial data, we developed a novel nonparametric randomization technique based on the variance in an index of pairwise difference from a broad set of fossil comparisons. We fail to reject the hypothesis of a single lineage this period by identifying a strong, time-dependent pattern of variation throughout the sequence. These results suggest the need for a reappraisal of fossil evidence from other regions within this time period and highlight the critical nature of the Plio-Pleistocene boundary for understanding the early evolution of the genus Homo.

*****

1. Van Arsdale, A. & M. Wolpoff (2012) A single lineage in early Pleistocene Homo: Size variation continuity in early Pleistocene Homo crania from East Africa and Georgia. Evolution 67-3: 841–850 DOI: 10.1111/j.1558-5646.2012.01824.x

2. Suwa, G., B. Asfaw, Y. Haile-Selassie, T. D. White, S. Katoh, G. Wolde Gabriel, W. K. Hart, H. Nakaya, and Y. Beyene (2007). Early Pleistocene Homo erectus fossils from Konso, southern Ethiopia. Anthropol. Sci. 133–151. DOI :10.1537/ase.061203

3. Robinson, J. (1966) The distinctiveness of Homo habilis. Nature 209:957–960.

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The minimum evidence necessary to demonstrate evolution

Each week in Wellesley 207x I will be providing my students with a “thought question for the weekend” related to that week’s course content. Students are invited to provide their responses on the discussion forums. These responses are not graded, but they can be viewed and commented on by others in the class. I have been very happy to see that the first question has prompted responses numbering in the hundreds (maybe thousands), with lots of back and forth comments.

The first question was: What is the minimum evidence necessary to demonstrate evolution?

I have to admit, the question is intentionally vague. I want my students to think about each word in that question (i.e. “minimum,” “demonstrate,” “evolution”) and respond according to their own interpretation of the question. Again, I have been happy to see a variety of responses reflecting a variety of readings of my question.

From my view, there are a number of ways this question can be approached, much of it hinging on how the word “evolution” is interpreted. The definition I provided for evolution in Week 1 is:

Evolution is heritable change in a population through time (or across generations)

How would you demonstrate that? That depends, in part, on what you already know.

If you know that DNA is the primary mechanism of inheritance, it makes sense to start with DNA. And indeed, we have a convenient theoretical model for looking at genetic observations and determining if evolutionary forces are responsible for the pattern of variation we see: Hardy-Weinberg equilibrium. H-W lessons are foundational to understanding evolution and are nearly ubiquitous in introductory textbooks…but seldom is the principle’s significance adequately conveyed to students. H-W is based on our understanding of how genetic variants (alleles) are transferred from one generation to the next, in a particulate fashion (discovered first by Gregor Mendel). A typical H-W equation assumes the simplest scenario of two alleles, represented in frequency by p and q, and provides us with an expectation for their relative frequency in a population. The reason H-W works is because it is a model that assumes no evolution is taking place. Therefore, since there is no heritable genetic change, underlying allelic frequencies should not change. So the H-W equation gives us an expectation of the frequency of variation in a population. In other words, the H-W equation gives us a null model we can test, the rejection of which tells us evolution has happened. A set of genetic observations that are not at H-W equilibrium must have undergone some kind of evolutionary change (mutation, selection, drift, gene flow, etc…).

So one answer to my question, pointed out by several students, is simply a demonstration that a population is not at H-W equilibrium. And indeed, this relationship is foundational to modern population genetics. But as an answer to my question, it assumes we know the mechanism of inheritance, how that mechanism functions (broadly), and that we are looking at genetic variation to demonstrate evolution.

What if instead we are looking at living organisms and their distribution and variation in the natural world (much like Darwin, himself)? What if, additionally, we don’t have a solid understanding of the mechanism of inheritance (again, like Darwin)?

In this case, we really only need to demonstrate that things vary across time and space, and that some of this variation is passed on from parents to offspring. That is it, really. This is a very preliminary demonstration of evolution, however. Darwin was interested not only in demonstrating that things change over time, but that this process of change over time can lead to the formation of new kinds of things (i.e. species). In other words, that the natural processes of change over time give rise, gradually, to new kinds of species and therefore the diversity of life on the planet. In this case, we need to add a few steps to our required evidence.

Now we need to not only demonstrate that organisms vary across time and space, but that the inherited variation is associated with greater reproductive and/or survival benefits, or in other words, higher evolutionary fitness. This is harder to demonstrate, because it requires working across multiple generations of an organism (though in organisms with short life cycles, like bacteria or fruit flies, this is not nearly as onerous). Alternatively, we might bypass the need to observe organisms across multiple generations by observing that across a whole host of environments, organisms seem to “fit,” or are “adapted” to their environments. A logical interpretation of this observation is the process of natural selection, an interpretation realized by both Darwin and Alfred Russell Wallace. Note that in this case we have expanded upon our understanding of evolution to not only include heritable change over time, but also the origin of species. We have also focused our interest in adaptive change, or change brought about by the actions of natural selection (not mutation, drift, or gene flow).

It is harder to observe, because it does not lend itself to a logical explanation as readily, but we could also demonstrate evolution in natural populations by simply observing random change over time via genetic drift. Say we have a flock of 100 sheep that we maintain at exactly that size, allowing every female and male to reproduce equally. In this case, there is no (or almost no) selection occurring, but genetic drift will lead to changes in our population over time. This might seem minor, but it is in fact evolution, and it is possible to imagine this scenario leading to the potential development of new species (particularly if my neighbor’s flock is isolated from mine). I say that drift would be harder to observe because it is random with respect to outcome, and therefore is not as readily observable as a pattern. Traits that are adaptations, traits that “fit” their environment, often are striking to us because of the patterns they depict.

Finally, we might try to demonstrate evolution via the fossil record. Here, the presence of a continuous lineage over time, or perhaps even bifurcating into two lineages, gets us a long way to demonstrating evolution. We have thousands of examples of fossil lineages showing change over time, with intermediate or “transitional” specimens. This observation, however, still requires a theoretical explanation of how evolution takes place. So the theoretical process, again our gift from Darwin and Wallace (built on the backbone of numerous earlier work by 19th, 18th, and even earlier naturalists) is still necessary in this case.

In short, there are a lot of potential ways to demonstrate evolution, even minimally. Depending on how broad a definition of evolution you would like to encompass and the kind of observational data you have available to you, you answer my question in a host of different ways.

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A worldwide audience

I promise to not write solely about my EdX course, but…it is live as of this morning. And in the first three hours of being live, we have had students posting in the discussion forum from every continent outside of Antarctica. Students from Brazil, Chile, Colombia, Estonia, Spain, UK, Belgium, Netherlands, India, East Timor, Morocco, South Africa, and on and on. I admit to being somewhat blown away by this, even though I expected it and intentionally structured the course in anticipation of this kind of audience.

A diverse classroom can be wonderful for any topic, but I will reiterate that it is especially wonderful for a class focused on human evolution and the human fossil record. Evolution is a process focused on sorting, creating, and changing patterns of variation through time. And yet variation, even the variation in ourselves and those around us, is an inherently tricky topic to wrap your mind around. Our words, and the concepts we use to give meaning to the world around us, are not particularly flexible when it comes to variation (as an example, write a 5-second definition of “tree” on whatever scrap of paper is nearby, and then look outside and see how adequately your definition accounts for the diversity of trees you see before you…probably not very well). We even have developed an entire discipline, statistics, to help us describe and manipulate variation in a way that is translatable and coherent. Variation is a challenge, and yet it is central to how evolution operates.

HamletContrast this with the fossil record, where our entryway into understanding variation comes from individual fossil specimens, scattered across time and space. As it turns out, the human fossil record is quite well represented and well-studied, but it still poses a significant scientific challenge to move from looking at isolated fossils to reconstructing patterns of biological variation in the past.

The bridge that lets us do this is typically comparisons with living patterns and the variation present in contemporary biological systems. And yet, the world is a big place, and our view of it is fairly limited to a particular time and place. But that is where this global classroom comes into play. Within our class, we have an audience coming from all over the world, of all ages, with a host of backgrounds. We represent an abundant spectrum of living human biological variation. And throughout this class, we will take advantage of that fact to better understand, interpret, and develop scientific knowledge from the human fossil record.

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Set to go live, Wellesley 207x and questions of scale…

In two days, Wellesley 207x – Introduction to Human Evolution, will go live. The course is the culmination of a fairly frenzied amount of work over the past three months, and I am excited to see that work actually reach an audience. With the course on the verge of that threshold though, I find myself thinking all the more about the scale of my audience. The course currently has approximately 18,000 students registered. Is that a big number or a small number?

From the “big” ledger:

  • In my 7+ years of teaching (two at the University of Michigan, five+ here at Wellesley College), I estimate that I have taught approximately 1000 students. So this class, in one semester, gives me a chance to increase my student audience by nearly a factor of 20. That seems big.
  • If I remain at Wellesley College for the remainder of my career (~30 years) and continue to teach a student load roughly equivalent to what I have so far, that would give me access to about 3,500 students. So in one semester, I might teach five times as many students as I will have the opportunity to teach in my entire career here at Wellesley College. Again, that seems big.
  • Wellesley 207x is running in conjunction with my on-campus seminar, Anthropology 207, with the two courses integrated in several ways. The ratio of students in the on-campus seminar to the on-line course is approximately 1:1275. Yet again, that seems huge.

From the “not so big” ledger:

  • I am a rabid baseball fan, with my allegiance falling with Cleveland (having grown up on both the East and West-sides of Cleveland). Cleveland has one of the worst attendance records in the league, averaging a paltry 19,252 paid attendance. In other words, more people pay to see one of the least supported baseball teams in the country, each game (and MLB teams play 81 home games!), than are registered for my course. That makes the enrollment seem small. Ubaldo Jimenez, in his 15 home starts, will have “reached” an audience vastly larger than my course.
  • My graduate alma mater, the University of Michigan, has an undergraduate enrollment of about 25,000 students. So my course will reach fewer people than the number of undergraduate students housed at just one public University in the country. Again, that seems small.
  • A 2005/2006 Pew survey of views on evolution in the United States founds that 42% of Americans think that living things on the planet have always existed in their current form. Assuming the survey is accurate and only adults (age 18+) are considered, this means that approximately 100,000,000 people in this country don’t acknowledge the reality of evolution. That number really makes my course enrollment seem small.

Regardless of whether it is big or small, 18,000 students are 18,000 students. It is a larger classroom to talk about issues of human diversity and evolution than I have ever had before, and hopefully one that will generate rich discussion. If even 1,000 students exit the course with an improved understanding of and greater interest in human evolution, I will consider it a massive success. It is also not too late to sign-up if you want to add to that number.

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Laetoli, Boston-style

How do you film a class segment about the Laetoli footprint trail without going to Tanzania to film? By going to the beach, of course!

Laetoli, if you are not aware, is the ~3.5-3.6 million year old site in Tanzania, where, in 1976, researchers uncovered a series of footprints, including a set made by a few hominins. The site is important in that it provides a flip-side to fossil-based evidence for bipedality in Australopithecines. Whereas fossil evidence (such as A.L. 129-1, or “Lucy” A.L. 288-1) gives us morphology and tasks us with reconstructing function (i.e. movement), the footprints at Laetoli give us evidence of function and task us with reconstructing the morphology necessary to produce such evidence.

So this morning I filmed a few sections for 207x (Introduction to Human Evolution) on Revere Beach in Boston, making footprints and talking about them. As you can see, it was a pretty time and location for some human evolution video production.

Revere1

Revere2

Not from an Australopithecine…

Revere3

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The importance of 300,000 year old cave bear mtDNA

A just released paper in PNAS that reconstructs the mitochondrial DNA of a >300,000 year old cave bear lineage is getting some attention…and for good reason (Dabney, et al., 2013). You might wonder who cares about ancient cave bear lineages outside of ancient cave bear experts. But when those cave bear remains come from the site of Sima De Los Huesos, part of the Atapuerca archaeological complex, and home to the densest concentration of Middle Pleistocene hominin fossil remains anywhere in the world….well, then it gets more interesting.

To step back a bit…we know that DNA tends to preserve better in colder environments, particularly permafrost environments, where the rate of DNA degradation is diminished. Slower degradation means larger fragments of DNA persist for longer periods of time, making it easier to extract and read that DNA. The successful reconstruction of mtDNA from this more than 300,000 year old cave bear specimen at Atapuerca potentially triples the available time frame for looking at ancient human DNA, and was the product not of improved extraction or amplification methods, but instead of better utilization of genomic reference library techniques. Amplifying very small fragments of DNA using PCR requires primers to identify specific fragments, which limits the length at which you can effectively read. The genomic library methods outlined by Dabney, et al. try to circumvent this problem.

the possibility remains that not all sequence information residing in ancient specimens is optimally recovered with these methods. This possibility becomes apparent when inspecting the size distributions of sequences reported from ancient DNA (e.g., refs. 3, 8, and 15), which consistently show a mode of ∼40 bp or larger. It is unclear whether the deficit of shorter molecules is due to poor preservation in ancient biological specimens or their exclusion during sample preparation. This question is of importance because it is expected that the number of DNA fragments in an ancient sample increases exponentially as length decreases and, hence, that most information resides in very short molecules (3, 8). (emphasis added)

If we can properly identify the information available in short sequence reads, we are likely to get access to vastly more ancient genetic information than is currently available.

And obviously if the authors can achieve this with the Sima cave bears, maybe they can do it with the Sima hominins…

mtDNA tree, Figure 3, Krause, et al. (2010) Nature 464, 894-897

mtDNA tree, Figure 3, Krause, et al. (2010) Nature 464, 894-897

Which raises the question of why this is important and what we might expect to find. We already know that mtDNA is only a small part of the evolutionary and biogeographic story of ancient populations, with nuclear DNA presenting a more significant technical challenge to read (because you have vastly more copies of mtDNA than nuclear DNA in your cells, and mtDNA is structurally simpler and much smaller), but also much more valuable information. Current understandings of ancient mtDNA place Neandertals as a side branch relative to contemporary humans, with the mtDNA from Denisova Cave in Sibera a further outgroup (Reich, et al., 2010). Where mtDNA from Sima would fit in (if it is available), particularly relative to the relationship between Neandertals and Denisovans would be a fascinating, if not complete look at the phylogeography of these lineages.

Figure 1, from Reich, et al. (2010) Nature 468, 1053–1060.

autosomal DNA tree, Figure 1, from Reich, et al. (2010) Nature 468, 1053–1060.

John Hawks picks up on a further interesting aspect of the cave bear mtDNA itself:

Personally, I can’t wait until we have a thicker sampling of the Middle Paleolithic time slice for a number of species, because that will enable us to understand the population dynamics in response to at least two and possibly more glacial cycles in Europe.

The more comparative models we have for ancient DNA in other species, the better understanding we can have about how to interpret aDNA in humans from the climatically volatile Late Pleistocene. Indications of widespread regional extinction in other large-bodied mammals, for example, might provide good reason to refine the expectations and thereby test hypotheses about such phenomena in human prehistory. I will add, such data might also allow us to potentially begin to get around issues of equifinality by providing independent lines of evidence. For example, maybe aDNA evidence might support parallel reconstructions of population history in Neandertals and other large-bodied European mammals during the Riss glaciation period (~140-200 kbp), but contrasting models in the Würm period (~20-90 kbp). A differential response between humans and other species during this latter glacial period could allow a more direct test of whether or not archaeological changes in the latter Neandertal record are a result of environmental forcing or biocultural innovation and adaptation.

The greatest obstacle for hypothesis testing in the paleo-record is equifinality. Lots of possible answers seem equally likely (or at least indistinguishably likely) for a given question. Was it environment? Was it culture? Was it demography? Single lines of evidence–archaeological samples, fossil remains, aDNA–are insufficient to get around this problem. But coupling different lines of evidence, particularly when the predictions for such lines of evidence diverge, is, in my view, the most valuable aspect of the continuing emergence of ancient DNA Studies.

*****

1. Dabney, et al. (2013) “Complete mitochondrial genome sequence of a Middle Pleistocene cave bear reconstructed from ultrashort DNA fragments” PNAS www.pnas.org/cgi/doi/10.1073/pnas.1314445110

2. Krause, et al. (2010) “The complete mitochondrial DNA genome of an unknown hominin from southern Siberia” Nature 464, 894-897. doi:10.1038/nature08976

3. Reich, et al. (2010) “Genetic history of an archaic hominin group from Denisova Cave in Siberia” Nature 468, 1053–1060. doi:10.1038/nature09710

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Six degrees of Earnest Hooton

In my “Race and Human Variation” (Anth 214) I try to use race as a guide to teach some of the history of physical anthropology. One of the lessons I present, using myself as the example, is “six degrees of Earnest Hooton.” Hooton, originally trained as a classicist from Wisconsin, helped train, and thereby populate, much of the first generation of American physical anthropologists. Hooton’s students and their subsequent academic progeny on down the line represent a diverse group–in background, experience, training, and perspective–and yet it is worth considering the impact of this academic founding event.

The Academic Phylogeny of Physical Anthropology project that I linked to last week gives us a tool to look at this in more detail. There are still many additions that could be made to the tree, but at the moment, the tree has nearly 1100 people with no user submissions waiting to be added. Here is a cut-away of Hooton’s section of the overall picture:

HootonTree

As you can see, it is rather large. I admit to having lost count, but it appears to represent ~40% of the total entries into the phylogeny. Hooton’s personal relationship to the field remains remarkably under-studied (Giles, 2012), despite being controversial. Hooton’s legacy, however, largely is American Physical Anthropology, for better and for worse.

One of the other interesting things the above tree clearly demonstrates is the complexity brought about by over-lapping generations. For example, I am an academic “cousin” to one of my undergraduate advisors (George Armelagos), being an equal number of steps removed from Hooton, despite a 38-year gap (1968 vs. 2006) in our Ph.D. dates.

*****

1. Giles, E. (2012) “Two faces of earnest A. Hooton” Yearbook of Physical Anthropology 149(55):105-113. DOI: 10.1002/ajpa.22162

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Forensic osteology resource

The good people at forensicosteology.org have put together a large number of resources related to the field. I see today that they have a wonderful metabase of searchable osteology trauma specimens, including catalog/institution reference information as well as photographic (and in some cases radiographic) images. I can’t wait to pass this along to students when I teach forensic anthropology in the Spring. (h/t Kristina Killgrove @DrKillgrove, University of West Florida).

A “through and through” gunshot wound from the Hamann-Todd collection at the Cleveland Musuem of Natural History, found via the FOROST metabase

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Creating scientific knowledge within an evolutionary framework

In my class today, we are talking about how you create knowledge regarding human evolution. We will discuss, in brief, how we know what we know about the world around us. In that context, we will talk about how scientific knowledge, based on a specific perspective and methodological approach, differs from other kinds of knowledge production. I am not a science purist…I think there are other ways of creating knowledge about the world that have value. But when it comes to understanding the natural world (not necessarily our experience of the natural world, but rather the world itself), science is best.

Applying a scientific perspective to the world of the past, for example the ~5-7 million years of hominin evolution, requires an awareness that we are one or two steps removed from direct observation. Instead of observing how the world works within the controlled setting of a lab, we instead rely on observations of how the natural world has changed throughout time and across space, using our understanding of active forces to infer how such forces operated in the past.

There are pros and cons to such a diachronic perspective. On the positive side, there are no artificial constraints on what has actually happened. The world is what it is, it is not what we have set up on a lab bench (leaving aside the Hitchhiker’s Guide to the Galaxy view…). However, this also means that the observations available to us–fossils, geological formations, traces of past atmospheric conditions, etc…–require their own interpretation. They are not matter of fact things. That they exist is matter of fact, but understanding why they are the way they are and what they mean for the world of the past is a scientific question which demands a scientific answer. That the paleo-sciences require an additional inferential step does not in any way diminish their science bona fides, it just puts them within a particular epistemological framework.

I therefore take the perspective that evolution (and science, in general) is not something that asks for your belief. It only asks for your acknowledgement. And that acknowledgement does not close the door on skepticism. Indeed, the scientific practice is fundamentally based on skepticism, the idea that our current understanding of the observations available to us is subject to revision given new observations.

Applied to paleoanthropology, this provides a valuable perspective for understanding why new fossil discoveries overturn old theories. It is not, as some critics of evolution like to point to, evidence of the failure of our field, but rather evidence of its success. Ideas should change as our observations of the world change.

All of which is a nice excuse for me to link to Holly Dunsworth’s (Anthropology Dept., University of Rhode Island) segment for NPR’s “This I believe” series, titled, “I am evolution.”

Of course I believe evolution.

But that is different from believing in evolution.

To believe in something takes faith, trust, effort, strength. I need none of these things to believe evolution. It just is. My health is better because of medical research based on evolution. My genetic code is practically the same as a chimpanzee’s. My bipedal feet walk on an earth full of fossil missing links. And when my feet tire, those fossils fuel my car.

And to add a little bit at the end, we are also talking this week in my course about how biological anthropology (and paleoanthropology in particular) fit within the broader field of anthropology. I think the same perspective outlined above can be invoked here. Biological anthropology is well-equipped to answer a specific set of questions based on observations of human variability, past and present. Some of these questions overlap with the interests of the other sub-fields of anthropology in dynamic ways, and in some instances, the evolutionary perspective provided by biological anthropology is clearly superior. But not in all cases, and not without leaving the door open for critique and skepticism.

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Paleoanthropology pic(s) of the day

I have not posted a paleoanthropology pic of the day recently, so in honor of a forthcoming JHE paper on a new partial temporal bone from the site of Kromdraai, South Africa (Braga, et al.), here are a few pics of Kromdraai (circa 2005).

Kromdraai entered the paleoanthropological world when fossil hominin teeth from the site were brought to Robert Broom, in 1938. These teeth helped form the holotype of Australopithecus (Paranthropus) robustus. Since that time a variety of research groups have worked at the site, yielding thousands of fossil remains and numerous hominin specimens.

The site itself:

OLYMPUS DIGITAL CAMERA

A close-up of some of the existing breccia:

OLYMPUS DIGITAL CAMERA

The site is located within a region filled with fossil hominin sites, known as the Cradle of Humankind, a designated UNESCO World Heritage Site. Here is the surrounding scenery from a rainy January day:

OLYMPUS DIGITAL CAMERA

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