And then we came to the end, a few post #MOOC musings

This past semester was…hectic. I could add many other adjectives with differing connotations to that sentence, but needless to say, teaching Wellesley’s first MOOC course, coupled with ordinary professional obligations, coupled with a lot of life, coupled with a few other significant personal and professional happenings, made for a busy semester. Hence my internet silence in this space.

Screen shots from a sampling of the lectures for 207x

Screen shots from a sampling of the lectures for 207x

Not surprisingly, one of the first things I wanted to write about in my return to this space is that MOOC (WellesleyX 207x – Introduction to Human Evolution). I wrote about my expectations going into the course a fair amount over the summer last year (see here), but I wanted to start by looking back at the goals I laid out for the course.

1) Dissemination of knowledge about human evolution

My biggest goal for the class was to make an open-access resource for education about human evolution. Course “certificates” were processed today and more than 1000 students successfully passed the course. The online course, 207x, is not equivalent to my on-campus Introduction to Human Evolution seminar, Anthropology 207. The latter is intended to provide students an introduction in human evolution and evolutionary theory in order to equip them to take that knowledge with them into advanced-level college courses. 207x worked off a lot of shared content, but was never meant to achieve the same ends. Yes, it was still intended to provide students with an introduction to human evolution, but with the goal of giving students an enhanced ability to critically engage with representations of human evolution in the public sphere. I feel pretty good about this goal.

In addition to the 1000-plus students who earned certificates, probably about 3x that number were active in some form by the end of the 12th and final week of the course, either watching lecture videos, reading articles, or completing assignments. By the 12th week, that represented a commitment of ~50-60 hours of work…all geared towards human evolution. A Facebook study group that popped up even prior to the launch of the course remains active even now that the course is over, with nearly 1,300 users. But the numbers only tell a small part of the story.

One student, a volunteer docent at the Smithsonian, is making downloaded copies of the course available for other docents interested in improving their knowledge on the subject in order to make them better at what they do:

In any case, it is clear to me that many of my fellow HHO Resource Docents who were unable to take your course would benefit by an enhanced understanding in many topic areas from being able to watch your video lectures and having access to the course maps and summaries and to the items on your course reading list.

One of my goals was that some of the course content might be usable in high school settings, providing students with evolutionary resources prior to college. Along that line:

Thanks for letting me reactivate ‘my inner fish’. I intend to pickup teaching biology again.

And more…

I’m a high school Biology teacher and I really enjoyed every lecture. I learned so much and can’t wait to share some of my new knowledge with my students. I can’t thank you enough for taking the time to offer all of the content for FREE- wow edx and Professor Van Arsdale- great MOOC!!


2) Pedagogical Improvement

My job is to research human evolution and teach human evolution to Wellesley College students. For the investment in 207x to be worthwhile, it needs to return some value to those students. One of my goals was therefore to use 207x to create more of a flipped classroom environment for my on-campus class, transforming it from a lecture-dominated course to a more seminar-style discussion, with more in-class time dedicated to creative pedagogy.

In its first iteration, I was only partially able to achieve this goal. But even with partial success, this meant that my on-campus 207 class went from being about 80% lecture to about 50% lecture. Next time I teach it, that number will be closer to 20%, with considerable class time freed up to work directly with fossil casts, engage in facilitated but open-ended discussion, and give students more opportunity to bring their own understandings into class. My favorite day of class this past semester was “bipedality day” in which, instead of lecturing on the anatomy and functional morphology of bipedality, I relocated our classroom to the gym and had everyone walk funny. It was great!

So while I did not quite do everything I wanted in this arena (yet), I am optimistic running 207x will continue to improve my teaching of the course at Wellesley.

As an aside, the process of putting together an online course, including the organization, filming, and other production considerations, was itself a valuable experience for me. It is always good to have the opportunity to think about teaching and the different components that go into teaching in a different way.

3) Generate Interest in Evolutionary Studies

Part of my goal of engaging with a public audience was to generate more interest in human evolution and evolutionary studies. 207x offered no credit, in part, because I do not want my teaching to undercut the teaching of my colleagues at peer institutions. One of my final lines from the course was this, “I don’t want 207x to be your last course on this topic, I want it to be your first.”

It is a little difficult for me to directly assess this goal, but again, I have some hints. First, a seemingly large number of my students have enrolled in John Hawks forthcoming course, “Human Evolution: Past and Future” (offered via Coursera).

More than 5000 students with less than a college degree signed up for the course. I have not yet checked the cross-tabs to see what percentage of these students stuck with the course, but that is a large audience, many of them high school students, potentially getting ready to go off to College, hopefully with an enhanced interest in human evolution.

But even beyond these kinds of interactions, my hope is that students from 207x go out into the world as newly critical students of human evolution. To that end:

I’m taking so much away from this class. I can’t wait to go to the nearby museums and caves to not only learn more but to get involved as much as I can.

And more…

I spent the day at the American Museum of Natural History today and spent a little time in the Hall of Human Origins. We were there to see a couple of ticketed events, so I didn’t have too much time, but it was amazing to see so many of the fossils we studied in the course in person…I hope to go back soon to spend more time there. If anyone has plans to go and would like company, let me know.

And more…

Last weekend I happened to visit the Museum of Man in San Diego, where I live, and had forgotten the permanent display there called “Footsteps in Time.” There I saw reproductions of so many of the fossils shown in the course–Lucy, the Taung Child, the Black Skull, samples of Oldowan tools, and best of all, a plaster of the Laetoli steps. It was, wow, these are like old friends–I know about each of them. Then I read the recent article in the New York Times about obtaining DNA from a 300,000 year old hominid and was able to read it intelligently and could place it in the context of the complexity of our evolution that was discussed in class.

Win. Win. Win.

As a academic professionals, I think it is extremely important to be aware of the potentially corrosive aspects of making higher education passive and online. I think these fears can be dealt with responsibly, however, to generate something that produces a net benefit not only to its students, but also to the professional community associated with the study of human evolution.

Take Advantage of the Properties of a Truly Massive Classroom

My final goal was to take advantage of having a truly LARGE classroom. Evolution is all about variation. Human evolution is all about variation in humans. The variation you can sample out of a class of 20 students, even a diverse institution like Wellesley College, is limited. The diversity you can sample out of students logging in from 172 different countries?…that is much larger. And potentially a great tool for teaching evolution! Each week my students had the opportunity to answer questions about themselves. Basic, simple (and at times a bit odd) questions, but questions that represent some of the variability we express as humans in how we look, what we do, and how we interact with the world around us.

This is a goal that will really only be fully realized in the course’s second iteration. The EdX platform is still maturing, and in its present form, did not make it easy for me to quickly and easily access student response data. But I will get to those data eventually. And I think the results will be interesting…


I feel very good about the first iteration of 207x. I will be writing more about it over the coming weeks and months, but my initial response is quite positive (despite the fact that the original production of the course, on an extremely compressed timeframe, was quite stressful). There are a lot of questions higher ed institutions need to face about MOOCs, the most significant being what is the intended goal and do the costs and benefits justify that end. There are also questions for academics (e.g. how can these courses be conducted in an ethical and beneficial way to the profession as a whole?). And while I remain deeply skeptical and critical of the notion that MOOCs might “replace” traditional higher ed teaching, my view that MOOCs can generate positive value has been reinforced.

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The new (wonderful) Dmanisi skull

A new paper on the newest skull from the Lower Paleolithic site of Dmanisi (Georgia) is out in Science this afternoon (Lordkipanidze, et al. 2013)1 (the accompanying Science news story, from Ann Gibbons, is here). This is a spectacular specimen and I am very excited to see the research being published. I had the tremendous privilege of being at the site the day the fossil was first uncovered in 2005, and watched it as it slowly emerged and was eventually removed during that field season.

D4500 at the time of its discovery

D4500 at the time of its discovery

Not only is it a fantastic specimen (meticulously prepared by Gocha Kiladze and Yoel Rak), but it is associated with my favorite fossil in the hominin fossil record, the Dmanisi 2600 mandible. Dmanisi now has produced five relatively complete crania, four of which have associated mandibular remains, in addition to the post-cranial remains of several other individuals. It is not an overstatement to say that Dmanisi may be the most important single locality anywhere in the pre-1 million year hominin fossil record. I will have much more to say about this specimen and the new work in the coming days and weeks, but lets start with a few of the basics.

Why is Dmanisi important, and what does this new specimen add?

Dmanisi provides the best window we have as to what normal variation looks like in the early Homo fossil record. Dated to between 1.81-1.76 million years, the site sits in the midst of some of the most important fossil sequences in the human fossil record (i.e. Koobi Fora and the Turkana Basin, Olduvai Gorge). But unlike those African sites, the fossils from Dmanisi come from a single locality, with all of the fossil hominins coming from a narrow slice of time within that horizon.

In addition to everything coming from the same deposits, the fossils themselves represent multiple skeletal elements of multiple individuals. Recovering multiple elements from single individuals gives you a much richer window into the biology of these extinct specimens. This is why “Lucy” (i.e. A.L. 288-1), the partial skeleton of an adult, female Australopithecus afarensis, found in Ethiopia in 1974, was such a significant find. Dmanisi has the potential to produce a set of five Lucys (or more).

So Dmanisi has yielded a remarkable set of fossils from the same time and place. Adding to the bonanza, the fossils represent a set of individuals ranging in age (from middle/late adolescence to advanced adult) and encompassing males and females (though some might disagree about the specific designations). In other words, we have young and old individuals, male and female individuals, well-preserved, from the same time and place. Go out onto the street and look around at the people you see. Most of what distinguishes them in terms of their anatomy is their age and sex. If you wanted to construct a window on what kind of variation exists in fossil populations of early Homo, you would be hard pressed to engineer a better site.

And what does that window show?….variation. Lots of it. The existence of the extraordinarily large D2600 mandible was a pretty good preview of what to expect, but even it undersells the true picture of variation at the site. I will save the details for another post, but the new skull means we no longer have to guess as to the face that might accompany that large (presumably male) D2600 jaw.

So what does all this variation mean?

In a paleoanthropological context, we study variation in order to understand how evolution has acted in our past. The first step in this process, when possible, is to try and determine what exactly you are analyzing. And in this, there are different approaches. Some prefer to identify species differences first, so as to have a control over taxonomy first and foremost. This makes sense. Species are a real biological entity, so using them as the basis for future analyses seems like a good starting point.

However, the variation encompassed by any given species can be divided into different components. The two most significant components of variation within a population, as outlined above, are who happens to individuals as they develop throughout life and, at least in humans and many other sexually dimorphic primates, what differences typically exist between males and females. The challenge with starting out by identifying species, is that in order to do so, you must assume some kind of pattern of development and sexual dimorphism. An alternative approach is to begin by asking questions about intraspecific variation (i.e. age, sex, geography). Trying to understand what normal variation looks like within a species by testing hypotheses about the processes (development, sexual differentiation) that give rise to that variation allows us to construct a hypothesis about taxonomy based on more basal aspects of variation. This approach is not necessarily possible with every fossil sample, but a site like Dmanisi, with multiple individuals from the same time and place, is ideal for such an analysis. Indeed, this is the approach I have taken to the Dmanisi hominins since my dissertation (.pdf)2.

The authors of this new study make the argument that the Dmanisi variation is consistent with variation from a single “paleodeme,” or fossil population, from a single species1. The Dmanisi sample comes from one species of early Homo. This is consistent with previous work by the team, including my own work focused on the mandibles. The support for this view is the pattern of preserved morphology in the specimens as well as the geoarchaeological data that place these specimens in the same place and time. Despite the large range of variation encompassed by Dmanisi, it would require special pleading to argue for multiple species at this point.

One of the authors of the new Dmanisi study, Dr. Ani Margvelashvili, was also the lead author of a paper last week that appeared in PNAS on the Dmanisi mandibles (Margvelashvili, et al. 2013)3. Her approach was to examine the seemingly large amount of variation in the Dmanisi mandibles–a topic I have also examined from a different perspective (Van Arsdale & Lordkipanidze, 2012)4–from the perspective of normal dental development and wear. Again, the results highlight the important ways in which normal processes that shape variation at the population level play out within the Dmanisi sample.

The value and significance of Dmanisi extends far beyond Georgia. The window on variation at Dmanisi can be applied to the rich fossil samples from East Africa and elsewhere. When the authors of this study make that step, they determine that we have likely be over-taxonomizing, or relying too much on species identification and diversity to explain the variation we observe in fossils of this time period. All the fossil variation that in East Africa gets divided by some into Homo habilis, Homo rudolfensis, Homo ergaster, and Homo erectus, because the specimens are too variable to represent a single species, viewed from Dmanisi, suddenly look like a single evolving lineage. Or at least, make it harder to reject that idea as a starting hypothesis. Indeed, this is the exact conclusion I reached in a paper published earlier this year, again utilizing a different approach (Van Arsdale & Wolpoff, 2013)5.

The main Dmanisi excavation area and site museum director, Gocha Kiladze

The main Dmanisi excavation area and site museum director, Gocha Kiladze

I will have much more to say about this paper, and these fossils, and the specific details of my own view of these remains. It will be interesting to see how much the current paper shifts the thinking on issues related to early Homo. In the meantime, enjoy this fantastic new fossil and the hard work that went into this paper by a large group of researchers!


1. Lordkipanidze, D., Ponce de León, M., Margvelashvili, A., et al. (2013) “A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early HomoScience 342:326-331.

2. Van Arsdale, A. (2006). “Mandibular variation in early Homo from Dmanisi, Georgia”
Department of Anthropology, Ph.D. dissertation. University of Michigan

3. Margvelashvili, A., Zollikofer, C., Lordkipanidze, D., et al. (2013). “Tooth wear and dentoalveolar remodeling are key factors of morphological variation in the Dmanisi mandibles” PNAS October 7, 2013, doi: 10.1073/pnas.1316052110

4. Van Arsdale, A. and D. Lordkipanidze (2012). “A quantitative assessment of mandibular variation in the Dmanisi hominins” Paleoanthropology 134-144.

5. Van Arsdale, A. and M. Wolpoff (2013). “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.

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The privilege of moving past

The past weekend brought a flurry of activity in the science blogging community, much of it having to do with the assumption of power and authority (and their abuse) associated with gendered roles.

To recap, an editor at made reference to Dr. Danielle Lee as a “whore” when she refused an offer to make a (unpaid) contribution to their online publication. Dr. Lee, a woman of color, responded to the reference by posting a response on her blog, the Urban Scientist, at SciAm. That post was very quickly deleted by the editors, initially without explanation. Why should Dr. Lee not be allowed to respond (and her response is great) when called a whore? The response from Scientific American as to why they deleted the post was slow in coming and awkward in production.

The story got a lot of attention, however, and one of the people who saw it was Monica Byrne (Wellesley ’03), a writer and playwright. Ms. Byrne, it turns out, has had her own unwanted and unwarranted encounter with the coordinating editor of SciAm’s blogs, Bora Zivkovic. While she had previously described her experience of sexual harassment with Zivkovic without naming him, Dr. Lee’s story prompted her to name him. And sure enough, in the comments to her post, she is not the only one who describes this kind of behavior from Zivkovic (despite his apology which describes the encounter with Ms. Byrne as an isolated incident).

So in the span of a few days the science blogging community witnessed two events unfold, both predicated on the power dynamics that permeate the seemingly open and friendly community of online science bloggers, writers, and professionals. I had no prior connections with any of the people involved in these events, but I am a fellow science blogger and as such I think it is right to reflect on these incidents.

The point I would like to bring up now is the problem with the desire, particularly in this case expressed by those in positions of power, to “move past” these issues. A desire to move past unpleasant (and at times criminal) events like these is not ok. “Moving past” is simply another expression of privilege, the same kind of privilege that makes the actions directed at Dr. Lee and Ms. Byrne far too frequent. A woman subject to repeated acts of harassment because she is a woman cannot “move past” that reality. A person of color regularly subject to the assumption of inferiority cannot “move past” that reality. A person whose sexual orientation does not match your own preference and is therefore discriminated against, legally and illegally, cannot “move past” that reality.

Rather than “move past,” we, especially those of us in power or gifted with the privilege of the “proper” gender, skin color, or set of attractions, should seek to linger. Linger in the moments of doubt and uncertainty we have about our own actions (or inactions) and our own culpability in the past. All of us in that position have certainly had many moments when we have actively or passively assumed a position of power and authority because of who we are and the privilege, benefit of the doubt, and assumption of innocence/correctness granted to us. Spend a little time lingering and you will no doubt uncover things you have done (or not done) that facilitated the bad behavior of those around you. And probably you have done some bad things, too. I have.

I haven’t called anyone a whore. I haven’t improperly propositioned someone I have professional power over. But you don’t have to be that obvious to be a part of the problem. Think about your behavior at conferences. Think about your behavior in faculty meetings. Think about your behavior in the field. Think about what you tolerate in others and what you do yourself. Think about the papers you think are “seminal” and look at the authors. How many of them are women? How many of them are researchers of color? Think about how you treat international collaborators and colleagues. Linger in these questions for awhile and probably, like me, you will feel a lot of things float to the surface that are not “the best version of yourself” if not worse. Linger in that feeling and you will likely realize it sucks. But don’t move past it. If you, if I, want to create a better community, better scientists, and better science, that discomfort associated with the realization of your active use of privilege is one of the keys. It needs to be our guide. And no, don’t expect a cookie for the effort.

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207x snapshot #2 : Education level

Another quick snapshot of the student body in 207x. Again, these data are not quite complete, as they are missing ~2000 “late” enrollees. Nevertheless it is an interesting portrait. This is a chart showing the highest level of education achieved by the students enrolled in 207x.


I did not expect to be teaching 800+ Ph.D.s this semester. But neither did I expect to be teaching 800 students not yet out of high school (or junior high in a few cases!).

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MOOCs: Teaching as social action

Teaching is a social action. The interaction within a class between students, the connection between teacher and students, the context in which such conversations take place…all of these are part of the social reality that reflects teaching. One of the (legitimate) criticisms of online education is that the inherently social aspect of teaching and learning is removed. Instead of occupying the same physical space, students and instructors interact virtually, and typically passively, on-demand. From my viewpoint, this is a dramatically inferior learning environment.

And yet, online teaching does not need to be solely passive and solely individual and virtual. During the first week of 207x, students began to introduce themselves on the discussion forum. I was amazed at how, within the first few hours of the course being live, students began to materialize on the virtual world of the discussion forum from seemingly ever corner of the Globe. A facebook group had already been put together with 1000+ members, a discussion group at Nature sprung up, and a twitter hashtag (#207x) began to appear.

This week, I provided the students with a discussion forum specifically intended to enable and encourage in-person meet-ups for students in the course. I don’t know how many of these will actually happen, but again, the students have responded in dramatic fashion. Just looking down the first page of entries, I have students trying to arrange meetups in Oslo, Lima, St. Petersburg, Lahore, Sofia, Singapore, Manchester, Oman, and Mexicali. And these are all from just the first page of about 140 total entries.

While the passive and virtual aspects of online teaching are certainly limited, the distributed nature of the experience, properly socialized, is potentially incredibly powerful. The thought that groups of learners might congregate at coffee shops, bars, and homes over the next 10 weeks to discuss human evolution…simply for the enjoyment of it…gives me goose bumps. I remain highly skeptical of the notion that MOOCs provide an alternative to traditional higher education. But that they might allow for academic resources to be leveraged in the production of something complementary and valuable…that is an idea that I am increasingly in support of.

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Me talking about MOOCs, liberal arts education, and 207x

I gave a talk last week on campus about my course, the new WellesleyX initiative, and the relationship between MOOCs and a traditional liberal arts education.


You can watch a complete cut of the video here.

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207x snapshot: Year of birth

I will be doing a series of quick snapshots of my MOOC, 207x (Introduction to Human Evolution), throughout the semester. I wanted to begin with one showing the self-reported year of birth of the enrolled students. This is actually missing ~3000 late registrants or people who left this question blank, but a pretty fascinating snapshot nevertheless.

As a fun curiosity point, the average age of the students in my class is…my age. Birth year 1979.


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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.


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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