Elephants are extraordinary creatures, known for their intelligence and social complexity. We are not really sure how their brains evolved, but we do know that extant elephant brains are about three times heavier and contain about three times more neurons than our own.
And while Suzana Herculano-Houzel et al determined that the human brain may have more cognitive abilities than an elephant, this particular human never would have guessed that its trunk may have had anything to do with its brain evolution.
This line of thought has occurred, however, to Mpilo Nxumalo, Msc Candidate at the Evolutionary Studies Institute, University of Witwatersrand, who is pursuing this research now for his Masters degree, thanks to funding from the National Research Foundation (NRF) and the Centre of Excellence in Palaeosciences.
It was thanks to that same Centre of Excellence in Palaeosciences that I learned of Mpilo (please see tweet below). Paleoanthropologist Kimberleigh Tommy very kindly put me in touch with him, and Mpilo generously agreed to tell me more about how his research began, what initially drew him to paleontology, and what he hopes to learn.
Jeanne: Reading about your work on Twitter, I became very excited: not only had I never drawn a connection between the trunk and the corresponding size of the brain, but because–as you say–the trunk is ‘their most defining feature’! To my knowledge, this work has not been researched before.
What led you to pursue this path?
Mpilo Nxumalo: I have always loved mammals, especially elephants. In my honors year I worked on cynodonts, which are mammal-like reptiles and ancestors of mammals. For my master’s project, I wanted to work on something younger and recent. When my supervisor Dr. Julien Benoit told me about this project on elephants, I jumped on it immediately. After reviewing the literature on this subject, I realized how important this work is, what it could mean for science, and I get to contribute to the unveiling of the origins story of my most favorite animals in the world. This is a rare opportunity.
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Image of elephants, courtesy of Getty Images
Jeanne: The Twitter post from the Centre of Excellence in Palaeosciences (@CoE_Palaeo) states: “Since soft tissue material does not readily preserve in the fossil record, paleontologists have been using other osteological correlates to estimate the dimensions of soft tissue structures such as the dimensions (volume) of the infraorbital foramen and retraction of the naris, and thus deduce morphological and palaeoecological functions.”
Can you help me understand this? How would this help you in your work?
Mpilo Nxumalo: The end goal of this research is to recreate the character state or the biology of ancient elephants, and see how they have evolved through time, to their current state. Researchers working on living elephants discovered that there is a strong correlation between the size of the nerve that controls and power the trunk, to the size or dimensions of the trunk. This means that if we know the size of the nerve we can work out the size of the trunk. In addition, this nerve passes through a bony tunnel inside the skull called the infraorbital canal, from the brain to the trunk. Since soft tissue structures such as nerves and trunks do not preserve, we use the volume (dimensions) of this tunnel (osteological proxy) to work out the size of this nerve. Once we have the size of the nerve for any fossil we can work out the dimensions of their trunks. Part of my job is to measure these correlations on living animals and make them quantifiable instead of qualitative. On fossils, we measure the volume of this canal and use these regression models or correlation curves to work the volume of the trunk.
Jeanne: That same Twitter post states: “I aim to identify quantifiable metrics to address the evolution of the trunk such as the dimension of the infraorbital canal for the infraorbital nerve that innervates the trunk and the retraction of the nares (for the nostrils) using CT scans. My second objective is to test how these metrics correlate with the dimensions of the trunk in modern ‘ungulate’ taxa (elephants, tapirs and sagas) based on a data set of photographs and literature.”
Are you using CT scans on fossils? If so, upon what types of ancient elephantids are you working? Are these fossils local?
Mpilo Nxumalo: Yes, I use CT scanned data provided by my supervisors, in the Virtual Imaging Lab in my institution. I am working on the lineage of Proboscidea as a whole, from the basal most ones such as Moeritherium to the extant elephants. We are trying to sample this lineage as much as we possibly can; the problem is most of the older ones are preserved as fragments and teeth. There are collections in Nairobi and London national museums which I wish to visit; there, they have a wide variety of well-preserved specimens in large numbers.
Jeanne: Do you have any expectations regarding what the trunk metrics for elephants, tapirs and saigas will tell you? (Do tapirs and saigas also have big brains?)
Mpilo Nxumalo: I expect the basal elephants to have small appendages on their faces similar to the movable lips of rhinos. This small trunk then evolves to become larger through time. Other researchers have qualitatively predicted the size of the trunk for most elephantids, based on the size of the infraorbital foramen and other qualitative proxies. Based on the literature, a true trunk is defined as the fusion of the upper-lip and the nose musculature. Saigas and tapirs, and other animals such as elephant shrews, do not have this configuration, also these features are not functionally used as the elephant trunk. The elephant uses the trunk for navigation, tactile functions, breathing, and detecting pressure and temperature changes in the environment, and many other cool functions. This requires the brain to focus so much of its resources and attention to the trunk, and the large information it receives from it. As the trunk evolved from the basal elephantids to become more complex, we expect the brain-size and the corresponding number of neurons to increase.
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Image of baby tapir, courtesy of Getty Images
As an outgroup for this research I have segmented the infraorbital nerves of many ungulates such as tapirs, saigas, rhinos and other bovids, for comparison and also to create a regression model or quantifiable metrics that we can apply on to the fossil record. I plan to expand this project for my PhD by adding carnivores on to this data set (I.e. elephant seals and cats). It’s about documenting the evolution of the infraorbital nerve in mammals, and improving these correlation models.
Jeanne: Although the soft tissue and trunks of ancient elephantids are not preserved in the fossil record, trunks from mammoths in Siberia have been known to survive. Do you hope to incorporate this into your work at some point?
Mpilo Nxumalo: Yes I do. It would give us a rare insight on this matter, to study soft tissue structures directly rather than inferring from other indirect proxies such as bones and teeth. The problem would be funding, for me to travel to all places where these remains are stored, also to CT scan them. Overall, it is all doable and it would really benefit our research and the science community. Above all, these methods are non-distructive to the fossils and the collected data will be available digitally for everyone to use.
Jeanne: Have you been on any fossil digs? Is there any particular type of fossil you would love to find?
Mpilo Nxumalo: Yes, I have been on a number of fossil sites and excavations for school projects and field camps for training with my supervisors. In my honors project I worked on a missing-link fossil Lumkuia fuzzi (a first step on becoming a true mammal, from mammal-like reptiles), it is the only fossil we have in the world of its kind. I would love find more of its taxa is so we have a more complete picture and data set to work with when addressing the origins of mammals.
Jeanne: What are some of the challenges you encounter?
Mpilo Nxumalo: Funding is my biggest challenge. I wish to visit more collections, create a huge data set that everyone can have access to. I also want to learn more about synchrotrons and the CT scanned data and methods I work with. All these skills are transferable and can be taught to others.
Jeanne: What do you love about elephants and what drew you to paleontology?
Mpilo Nxumalo: I love elephants because of their size, complex social structures and cool biology, their personality and behavior. Even though they are the biggest land animals, they are very humble. In addition, they are one of the emblematic animals of Africa. I chose paleontology because I am searching for answers about myself, where did I come from, this world and the life on it. More importantly I want to know how all this applies to my future, the future of the world and the life on it.
Jeanne: What is your biggest hope regarding your research?
Mpilo Nxumalo: I want people to stop thinking of paleontology as just dinosaurs and hominids, but to know that it is broad, and very much relevant to all of us. In addition, I want people to know that we have vast collections of fossils in the South and across all Africa that the public is unaware of. This is a huge part of our heritage resources, and could be used for tourism and job creation.
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Image of Langebaanweg Fossil Park,Namaqualand, South Africa; courtesy of Getty Images
Thank you so much to the Centre of Excellence in Palaeosciences (@CoE_Palaeo) for tweeting about Mpilo Nxumalo and his work!
Thank you so much to Kimberleigh Tommy, for connecting me with Mpilo!
Mpilo: What a great honor and pleasure connecting with you! Thank you for your time, your responses, and your help with this post! I am so excited about your work!! I look forward to reading your future papers and research!
- Benoit, Julien; Manger, Paul. How did elephants evolve such a large brain? Climate change is part of the answer. The Conversation. July 2019.
- Benoit, J., Legendre, L.J., Tabuce, R. et al. Brain evolution in Proboscidea (Mammalia, Afrotheria) across the Cenozoic. Sci Rep 9, 9323 (2019). https://doi.org/10.1038/s41598-019-45888-4
- Herculano-Houzel, Suzana. The Paradox of the Elephant Brain. Nautilus. April 7, 2016.
- What’s Inside an Elephant Trunk? Science Insider, Youtube