Today’s guest is Professor Shara Bailey, Professor and Associate Chair of the Department of Anthropology at New York University and Director of the Center for the Study of Human Origins. Shara is a biological anthropologist whose research focuses on using dental morphology to understand human evolution. She was awarded her undergraduate degree in Psychology and Anthropology from Temple University, and then went on to receive her masters and PhD degrees in Anthropology from Arizona State University. Following her PhD, Shara worked as a postdoctoral researcher at the Center for the Advanced Study of Human Paleobiology at The George Washington University, before moving to the The Max Planck Institute Department of Human Evolution in Germany as a Research Scientist. Shara joined the faculty at NYU in 2005.
What are your research interests, and your particular area or method of expertise?
I study human evolution from a dental perspective. I do this by examining dental morphology, which refers to the bumps and grooves that are on the tooth surface. I use dental morphology to reconstruct evolutionary relationships and identify human species from the fossil record. We find that even in living people there are differences in the configuration of these bumps and grooves on the teeth, with areas of the world like Europe, Northeast Asia and sub-Saharan Africa having identifiable patterns of trait frequencies. These patterns make tooth morphology really useful for investigating ancestry of modern populations. There are also dental traits and trait patterns that are particular to certain human groups (like Neanderthals) in the past. This fact allows us to identify species and reconstruct relationships among species going back 4 million years.
How did you first become interested in human evolution and specifically dental anthropology?
Well, I actually became interested in human evolution by accident! I was majoring in psychology at the time, and I decided to take an introduction to biological anthropology class to satisfy my final science requirement. I was so excited by the class that in the end I decided to double major in Anthropology. In my senior year, I knew I wanted to go to graduate school but I was still on the fence regarding Psychology vs. Anthropology. I was (and still am) very interested in neuroscience, cognition and memory but I could also see myself as an anthropologist. So I took a career test which clearly pointed me in the direction of anthropology. One thing that stood out was that I realized I’d be much happier working outside and/or traveling around the world then I would be decapitating rats and dissecting their brains in a laboratory!
In an archaeology class, I had learned about Christy Turner’s research at Arizona State University (ASU), which used dental morphology to reconstruct Native American origins. Being very interested in this topic and also inexplicably drawn to the American West, I decided to apply to ASU, and ASU only, for graduate school. In hindsight it wasn’t the best idea to put all my eggs in one basket, but luckily ASU accepted me – thank goodness! In my first semester at ASU, Christy Turner’s Dental Anthropology class introduced me to the fascinating world of teeth. I first did my master’s degree studying the distribution and inheritance of a rare dental trait that appeared in relatively high frequencies in the Pima and Papago populations. I had planned to do a PhD on the dental morphology of South American aboriginal people. At about the same time, my friend was organizing a conference on the nature of modern human origins, because that (replacement vs. continuity) was the big debate in the early-mid 1990’s. It was there that I realised that nobody was using a dental perspective of the fossils to answer this question. I decided to shift my dissertation topic to examining Neanderthals and the subject of dental continuity in Europe. A year later quite fortuitously, the Institute of Human Origins came to ASU bringing with them leading figures in human evolutionary studies – Bill Kimbel and Don Johanson. Bill eventually became my PhD mentor. He encouraged me to look at teeth with “new eyes”, which led me to investigate ways to quantify dental morphology using new methods, specifically morphometrics.
How was your PhD experience and would you change anything about it?
My PhD experience was wonderful. I still consider those years some of the best years of my life – I don’t think I would change anything about it. Many of my best friends today are those that I met during graduate school. PhDs programs have changed a lot since I went to school; nowadays tuition is nearly always free and the best schools, including NYU where I am now, provide a very generous stipend with no teaching requirements attached to it. Back in the 90s, that model was the exception rather than the rule. I did receive an out-of-state tuition waiver as ASU, my first year and free tuition in subsequent years. This was certainly helpful, but I wasn’t paid to do my PhD. I had to compete with many other students for teaching and research assistantships; as soon as I got my master’s degree, I started teaching at local community colleges. I enjoyed it and even though it didn’t pay much, I got a lot of valuable teaching experience. One of the arguments of providing PhD students with a stipend is to reduce time to degree by eliminating distractions such as having a job.. But in my 20+ years of experience, this approach has not led to a reduction in the time to degree – people are not finishing any earlier than they did before stipends became the norm!
After your PhD, what projects have you worked on?
Bernard Wood, at The George Washington University, recruited me to come do a postdoc there after hearing me present my dissertation results at our associations annual meetings. During this time with Bernard, I expanded my research back into the more distant fossil record and started looking at comparative samples from the great apes. This was a fantastic opportunity that provided a broader context to what I do, and it also allowed me to look first-hand at fossils that are millions of years old, rather than just Neanderthals and Homo sapiens as I had done for my PhD.
Actually, at the same conference that Bernard offered me a postdoctoral role, Jean-Jacques Hublin at the Max Planck Institute, offered me a position there as well. So after my postdoc at George Washington University, I moved to Germany. There, I dove more fully into the period of overlap between Neanderthals and Homo sapiens. Jean-Jacques has a great deal of expertise in archaeology and the Middle to Upper Palaeolithic transition, which is an important context for the fossils. Jean-Jacques was particularly interested in whether or not we could differentiate Neanderthals from Homo sapiens from teeth alone, given that many sites with so-called “transitional” tool kits preserved only fragmentary remains. The Department of Human Evolution at the Max Planck Institute was multidisciplinary: people on our floor worked on isotopes, dating, archaeology, 3D geometric morphometrics and microstructure. Working in Germany was also great for networking, and I went to European conferences and I met new colleagues that I otherwise might not have met.
I think the importance of networking for early career researchers should be stressed more. When I was collecting data for my PhD, I went from one museum to the next and I never really factored in any extra time to have coffee or a bite to eat with colleagues.. It may seem like a small thing but it has consequences – there are fossils I studied, which other people have ended up publishing on, and I think that it is largely due to the relationships they built. I found that working at Max Planck Institute helped me bridge some of those gaps.
What are you currently working on?
I’m currently working on several projects, most of which focus on new fossil finds from eastern and Southern Africa dating from the Pliocene to the Late Pleistocene. I have been using dental morphology to identifying to what species they belong and to help to put them into context.
I’m also just starting a project on dental integration, which is something that has interested me for several years. Teeth need to come together (occlude) in a very specific and precise way to be efficient. I noticed two years ago that in recent humans the lower first deciduous molar (baby tooth) is much more variable in size and shape than is the upper first deciduous molar. This strikes me as odd. You would predict that they would be similar since they need to come together in an exact way in order to function properly. I found much less variation in this tooth in fossil humans (Neanderthals and H. sapiens) than recent humans. And the variation in recent humans did not track onto geography. So something else is at work. What is it? It may be that with the switch to agriculture and/or modern diets selection pressure for proper occlusion has been reduced leaving more wiggle room for variation. Or maybe there is some other reason entirely! I don’t know yet but I’m working to find out. Stay tuned…
What projects or publication, are you most proud of?
I think the paper I’m most proud of is one I did with Tim Weaver when I was at the Max Planck Institute. A lot of times when you find fossils, you find only one or two teeth – but many people would dismiss them, claiming “you can’t tell anything from just a few teeth”. I felt like that wasn’t true and I wanted to figure out how to test it. So, one day I walked down the hallway to Tim Weaver and asked him if there was a way that we could predict the probability of being a Neanderthal based on 1 to 32 teeth. I had all the data and he developed the Bayesian statistics to do it. I really liked that paper because I felt that I had come up with an original idea, I reached out to somebody who could help me, we were able to do it and it was useful; hypothetically a researcher can enter tooth data into our program and it will provide the probability that it is Neanderthal or Homo sapiens. I also liked the paper that I did recently on Denisovan and Homo sapiens introgression events. We knew that these events happened from DNA; however we didn’t have any corresponding morphological evidence because there are so few Denisovan fossils. However, we analysed a Denisovan tooth and found that this second molar has three roots, which had long been considered to be a unique character of modern northeast Asians. This was very exciting as we were able to suggest that this unique trait in modern humans likely came from introgression events with Middle Palaeolithic Asian hominins.
What do you hope we discover or find out about human evolution in the next five years?
I would really like us to be able to develop methods to extract DNA from hominins in areas where it degrades quickly, like Flores where we find Homo floresiensis and in southern Africa where we see Homo naledi. I still have a lot of questions about their place in the human family tree, even after working with that material, and I think that the DNA might be really surprising. I would really like for us to try to figure out what those are based on DNA. I think it would provide some clarity and quite possibly make us completely rethink our assumptions about human evolution, which is always exciting.
Why do you think studying human origins is important?
I think people are curious about where we come from and so the more information we can provide the better. I also think that if we can do this in a creative and approachable way, we can get people generally interested in science. Teaching human evolution in schools is so important because I think it’s vital for people to understand both our history and prehistory, as it affects how we see each other, how we see our place in the world and how we fit into the web of life. Also, when you study human origins, you’re not just looking at fossils but also examining things like climate change and extinction events, so it can give more context as to what we are going through right now.
What advice do you have the students hoping to have a similar career to you?
I have a little sign in my office that says: “If you don’t ask, the answer is always no”. That is because this is my mantra and all my student have heard it at one time or another. I had an undergraduate who wanted to do an honours thesis, but she was meant to graduate in December. She really wanted to do this honours thesis, which was a two-semester class, and I told her to ask the university whether they would be able to give her money so that she could do another semester (NYU is quite expensive). So, she did, and they said yes. When we assume that the answer is no, the answer is always no. It is always worth asking – what have you got to lose?
I also advise students to say yes to opportunities whenever they can. True, you have to be judicious and only say yes to things that interest you – but do not be afraid. Listen to your gut. I was terrified getting off the plane in Germany, not knowing how to speak German or knowing anyone, but it was the best thing I could have done for my career. So, actively look for opportunities and when they come up – dive in!
If you were not a scientist, what career would you choose?
Well, I don’t think it’s an ‘either or’ thing; I have another career as an artist, which is something I’ve done my whole life. I love science and I also love being creative. Painting is a form of mediation for me. But let’s say, for argument sake, that I could no longer be an anthropologist – then I would probably be doing art or writing in some capacity. I’ve been working on a book for some time and I am taking classes to help me convey my message in a humerus and approachable (read here non-sciencey) way.
Conversations in Human Evolution 