Comparing Diatom Paleo-Assemblages to Determine How Different Environments Affect Diversity in the Geological Rock Record

Comparison of Diatom Paleo-Assemblages with Adjacent Limno-Terrestrial Communities on Vega Island, Antarctic Peninsula 

By: Marie Bulínová, Tyler J. Kohler, Jan Kavan, Bart Van de Vijver, Daniel Nývlt, Linda Nedbalová, Silvia H. Coria, Juan M. Lirio, and Kateřina Kopalová

Summarized by: Dani Storms, a senior undergraduate student at the University of South Florida seeking to earn a degree in Geology with a concentration in geophysics. Dani changed her major from English to Geology her sophomore year after taking an Introduction to Earth Science class taught by Dr. Sarah Sheffield. Dr. Sheffield played a significant role in helping her discover a love and curiosity of how geology shapes our everyday lives. She is interested in furthering her education by attending graduate school to earn a master degree in the field of natural hazards, preferably landslides or avalanche control. She hopes to eventually obtain a PhD as well. Dani has loved being in the outdoors her whole life. In her free time, she enjoys hiking, camping, biking, crocheting, and spending quality time with her pup, Zion. 

What data were used? Diatoms are extremely abundant microfossils that are composed of silicon dioxide (SiO2) and can be used to reconstruct different environments through the rock record (i.e., paleoenvironments). This study used statistical analysis to discover if there was a significant difference of diversity within diatom assemblages from core samples derived from two Antarctic lakes, both with varying habitats. Core samples contain sediment that was deposited in paleoenvironments and obtained by drilling into the earth, and these can give insight into how climate has changed over time. The lakes were on Vega Island, in Devil’s Bay (Lake Anónima) and Cape Lamb (Lake Esmeralda). 

The samples were viewed under 100x magnification in order to determine diatom species. The species were then categorized into sub-Antarctic, Maritime Antarctic, and Continental Antarctic groups to determine their biogeographic distribution. Samples were taken from ponds, streams, mosses, and steep habitats to compare the core samples to modern day environments. However, not enough data could be collected from the stream, mosses, and steep habitats for a fair comparison. Therefore, the comparison of habitat differences on different sides of the island was restricted to only ponds.

In order to determine if there was a significant difference between the distributions, the study considered relative abundance, species richness and evenness in relation to diatom counts. Relative abundance refers to the percentage of diatoms found in each sample, richness is the number of species found in the sample, and evenness is comparison of the relative abundance of each individual species. 

Results: Overall, diatom assemblages varied in composition significantly, most likely due to the differences in waterway connections between sites and due to some sites being isolated. Between the categories, Maritime Antarctic Region contained the greatest number of species. Nearly 43% of the taxa found on Vega Island were Antarctic in distribution, while only 6% were found within the Antarctic Continent. Sub-Antarctic accounted for 3% and less than 1% were contributed by the Antarctic Region. The study then addresses the most abundant genus and species within Lake Esmeralda and Lake Anónima. Between the 132 species observed, 100 were found within Lake Esmeralda and only 32 species were found in both lakes. This means that Lake Esmeralda has a greater richness since it contained more species. 

Lake Anónima was found to be most similar to modern environments with the most noteworthy similarities being derived from streams on Devil’s Bay. However, there were several species found only within the core sample containing the paleo-assemblage. The paleo-assemblage consisted primarily of pond and stream species. For Lake Esmeralda, many of the taxa were not found within the modern environment at all. The taxa not found in the modern environment contained both aquatic and terrestrial species of diatoms. 

The authors of the study hypothesize that the connectivity of waterways and habitat type contributed to the difference in diatom assemblage structures. Lake Esmeralda is hydrologically disconnected, meaning it does not have connections to other bodies of water. The disconnect would result in less carbon being funneled into the lake from an outside source, which could alter the chemical makeup of the lake, allowing only certain species to survive as pH levels change. There is also a possibility that Lake Esmeralda might have had a higher preservation rate that allowed for a clearer comparison of paleo-assemblages versus modern, which would explain the higher amounts of diversity between the two. 

However, Lake Anónima is the complete opposite. It is well-connected to a stream that allows for the transportation of diatoms. It also has underground drainage that connects it to other lake-systems and surface streams. The study notes that even if the transport of diatom valves were to not occur, the connection of waterways would result in similar hydrochemistry between the connected water and lakes. This could have led to less viable conditions for preservation that could result in the lower amounts of diversity found. 

Figure 3: These boxplots visualize the comparison of species richness (S), Shannon Diversity (H’), and evenness (J’) between Esmeralda Lake and Anónima Lake core samples. The thicker black lines display median values.

Why is this study important? Looking at the conditions in which modern diatoms are found compared to that of paleo-assemblages can help construct a model, or standard, that can be applied to diatoms in the fossil record. This would allow us to reconstruct paleoclimates and trends associated with how they are affected by waterway connectivity. The differences in diatom-assemblages and species could be used as indicators of climate change. The different modern species that were found to be specific to ponds, mosses, and streams could give insight to what type of habitat fossilized diatoms would have been found in. 

The big picture: As the climate begins to warm and ice melts away, the connection between waterways will more than likely increase, this would cause a more uniform distribution of diatom assemblages and loss of diversity due to the similar chemical compositions of the water. The concept of creating a model that can be applied to the differences of diatom assemblages in modern and paleo-environments could essentially allow for paleoclimate and hydrological connectivity reconstruction. For instance, if we found a more uniform distribution in a general area, we might be able to determine if there was more connectivity between body of waters at some point in the geological record. Another example would be how on average, modern-day dry mosses contain fewer species of diatoms than wet mosses. Knowing this, we could analyze fossilized mosses to give insight into whether they would have been dry or wet. We could also use the findings of this study to determine what bioregion ancient diatoms would have been in based off species type and the diversity of the assemblage. 

Bulínová M, Kohler TJ, Kavan J, Van de Vijver B, Nývlt D, Nedbalová L, Coria SH, Lirio JM, Kopalová K. Comparison of Diatom Paleo-Assemblages with Adjacent Limno-Terrestrial Communities on Vega Island, Antarctic Peninsula. Water. 2020; 12(5):1340. https://doi.org/10.3390/w12051340

Kelsey Jenkins, PhD Candidate

I’m Kels, and I’m a PhD Candidate at Yale University in the Department of Earth and Planetary Sciences. I completed my undergraduate in Geology and Geophysics at Louisiana State University, followed by an M.Sc. in Biological Sciences at Sam Houston State University.

What was your path into science? If you ask any vertebrate paleontologist this question, the majority will say, “Uhh, I was five years old once.” I stopped asking other paleontologists because the answer is so predictable, and it’s my truth as well. 

I am from Houma, Louisiana, a region of the country that is certainly not known for its fossils or for an exceptional educational system. Luckily, I had the support of my parents who encouraged their daughter’s unusual fascination with fossils. But, when college came around, I was clueless on how to get an education in paleontology…it’s not as if there was a paleontology degree. I chose a big state school, LSU, because I thought it would have the most resources available to me, and I could figure it out from there. I initially majored in anthropology, thinking that’s what I needed to work on dinosaurs (wrong!), but by luck I signed up for a historical geology class as an elective. The first class covered the history of the earth and the fossil record. I changed my major shortly after to geology, and I navigated my way through the department until I met my first mentors in paleontology, Judith Schiebout and Suyin Ting. They gave me a job in the museum collections cataloging a huge donation of mammal fossils, and I spent two years getting hands on experience and teaching myself basic anatomy and taxonomy. Following that, Patrick Lewis, my M.Sc. advisor at SHSU, offered me a project on a strange little reptilian creature from the Triassic of South Africa which fueled my current love of fossil reptiles, reptilian evolution, and dentition. I’m still working on reptile evolution and functional morphology now in my PhD with Bhart-Anjan Bhullar.

What is your research about? Imagine every reptile you’ve ever heard of, living and extinct: lizards, snakes, turtles, dinosaurs, alligators, mosasaurs, pterodactyls. Now, imagine the grandpa that unites them all, the original reptile ancestor. I research the creatures that lead up to that original reptile ancestor. Those animals represent some of the first widespread colonization of land by tetrapods (four-legged animals), and they preserve some of the first instances of important adaptations seen in modern reptiles. That part of the reptilian lineage holds clues about how to become an effective land animal following the initial embargo from water onto land by more fish-like creatures.

What are your hobbies and interests outside of science? I’m still figuring that one out. I enjoy cooking, hiking, crochet, writing, and spending time with my friends, but it’s not always easy to separate myself from work and research. When you pursue science, you’re pursuing a passion, and you don’t always want to take a step back. But, it’s important to take breaks and stretch your legs, though telling yourself that is sometimes easier said than done. If I can give students any piece of advice: you definitely need to take breaks. Get a hobby. Get several. Find out what else you might enjoy too.

Happy National Fossil Day 2021!

National Fossil Day poster for 2021 by the National Park Service.

Today is International Fossil Day! 

International Fossil Day  is an initiative by the International Paleontological Association and the National Park Service (National Fossil Day in the U.S.), the idea is to spread the interest in the life of the past and many different organisations and museums around the world host events or activities today. Of course we, the Time Scavengers team, have to participate in this, there can never be too much paleo-related fun! 

We want to celebrate IFD by showing off our team members’ favourite extinct species or individual fossils, some facts about the species or individual and why we picked them as our favourites.

Click here to visit the National Park Service website to learn more about National Fossil Day, and here to visit the International Palaeontological Association to learn more about International Fossil Day!

Linda

A fossil cave bear skeleton. Image credit: Wikipedia.

Most of my paleontology lectures during my undergrad took place in small rooms somewhere deep in the side wings of the institute building, on the edge of the paleontological collection/museum that is located within the institute. Whenever me and my friends were waiting for our professors to show up, we would stare and marvel at the exhibited specimens. I vividly remember walking into that area for the first time, it is dominated by a huge, mounted skeleton of an adult cave bear (Ursus spelaeus) and I was completely blown away by the sheer power it radiates. I didn’t care too much about the T. rex skull cast around the corner that most others found so fascinating. From that first day of paleo classes, having my own mounted cave bear skeleton has been on the top of my bucket list. U. spelaeus lived during the Pleistocene across both northern Asia and Europe and went extinct during the Last Glacial Maximum about 24,000 years ago. They are closely related to brown bears (Ursus arctos), the two species have a last common ancestor about 1.2 million years ago. Even though they were huge, powerful bears that were reaching 3.5m (11.5ft) when standing upright, with large teeth and fearsome claws, it’s currently thought that the majority of the western populations were eating an almost exclusively vegetarian diet! Recently, two very well preserved frozen cave bear carcasses have been discovered in two separate areas of thawing permafrost in Russia, an adult and a cub, both with almost all soft tissue present and intact. I’m already excited and looking forward to reading all the new research that will be done on these specimens!

Maggie 

Cast of U. anceps skull. Image credit: Wikipedia.

I worked at the Field Museum of Natural History during the summer of 2015 and that experience was what solidified my interest in paleontology. I worked with my supervisor on Eocene mammals from the western United States and had some of my first experiences doing large scientific outreach events during that summer. Because of that summer I will always have a soft spot for Uintatheres!

Uintatheres (U. anceps) lived during the Eocene in North America and were large browsers. These animals looked similar to rhinos but male U. anceps had six knob-shaped protrusions coming off of their skulls. Part of my experience working with these fossils was reorganizing the collections space that housed the skulls, they are incredibly heavy! I mentioned that U. anceps were browsers, but they also had long canine teeth that resemble the canines of saber tooth cats. These teeth may have been used as a defense mechanism but also may have played a role in how they plucked leaves from plants. While I don’t work on Eocene mammals now, Uintatheres will always be special to me for the role they played in getting me excited about paleontology and scientific outreach!

Whitney

Whitney next to Asteroceras stellare.

I cannot pick just one fossil to highlight right now, so here are two of my favorites! In 2016, I was studying in England and visited the Natural History Museum in London where I saw an incredible ammonite, Asteroceras stellare. Asteroceras was a large ammonite that lived during the Early Jurassic and whose shell reached nearly three feet in diameter. Asteroceras was a nektonic carnivore who might have fed on fish, crustaceans, and bivalves.

Whitney in front of an ichthyosaur!

My favorite vertebrate fossil is the Ichthyosaur. I loved visiting the Jurassic Coast in England and got to explore Lyme Regis, both the birthplace of Mary Anning and a town that had references to paleontology everywhere you looked. You can see ichthyosaur fossils in both the Lyme Regis Museum and the Natural History Museum in London and at the NHM, you can see some of the specimens that Mary Anning and her family had collected along the Jurassic Coast. Ichthyosaurs (Greek for “fish lizard”), are marine reptiles that lived during much of the Mesozoic and were thought to be one of the top aquatic predators of their time.

Mike

Mike in front of an American mastodon statue!

I have three favorite extinct species: the American mastodon (Mammut americanum), the dinosaur Parasaurolophus, and the chalicothere Moropus elatus. Mastodons are distant relatives of the elephants, and they seem to be overshadowed by the wooly mammoth. However, both lived in North America until the end of the Pleistocene epoch. I’ve always thought that Parasaurolophus was an elegant duck-billed dinosaur, and I’ve seen them featured in several movies in the Jurassic Park series. I think that chalicotheres are so bizarre! Distant relatives to horses, rhinos, and tapirs, imagine a big draft horse with giant claws instead of hooves! I’ve seen several skeletons of these over the years. Moropus elatus went extinct in the Miocene epoch.

Mike next to a Moropus elatus skeleton!
A statue of Parasaurolophus.

Alex

Like anyone in paleo would tell you I can’t pick one particular fossil organism as my favorite. Currently my favorite fossil organism is the “bear-dog” known as Amphicyon ingens which would have been a formidable predator during the Mid-Miocene. The cenozoic was a time for innovation in mammals and bear-dogs were the best of both worlds. All the stoic grandeur of a bear and all the cute charm of a dog, what more could you want? The picture shown was taken at the American Museum of Natural History in New York City.

Amphicyon

Jonathan Jordan (Paleo Policy Podcast)

For me, the Mesozoic reigns supreme. However, my recent trip to the La Brea Tar Pits in Los Angeles gave me a greater appreciation for the Cenozoic era and mammalian evolution in general. While it may not be my favorite fossil ever, I was captivated by Panthera atrox’s look and the idea of an American Serengeti 340,000 to 11,000 years ago. Genetic analysis suggests with high likelihood that Panthera atrox is a close relative of the Eurasian Cave Lion (Panthera spelaea). After the Bering Strait land bridge was submerged by rising sea levels, Panthera atrox was isolated from its Eurasian relatives and became a distinct species that has been found as north as Alaska and as south as Mexico. Neat! Check out an image of Panthera atrox’s skull on the Smithsonian Learning Lab site!

Kristina

I’m fortunate to have worked on many different types of animals during my career, starting with dinosaurs, then moving to Devonian brachiopods and their encrusting organisms, and now working on much younger Pleistocene-aged animals that are still alive today. I mostly study biotic interactions, such as predation, so I thought I would share my favourite trace fossil (ichnotaxon), Caedichnus! Trace fossils are different than a body fossil because they show evidence (or traces) of an organism or its behaviour. In the case of Caedichnus, this trace fossil is created by a crab trying to break into the shell of a snail by peeling away at the shell opening (aperture) until it can reach the snail’s soft body. Imagine having a crab try to peel your shell back like an orange – scary! Caedichnus traces are useful for determining how many crabs were in an area, and identifying patterns of crab predation through space and time. I’m now using them to determine the impacts of climate change and human activity on crab fisheries since pre-human times.

Adriane

Like most of my colleagues above, it is incredibly hard for me to say which fossil is my favorite! So instead, I’ll talk about my favorite fossil group, the foraminifera. Foraminifera are single-celled protists that live in the surface ocean (planktic foraminifera) or in/on ocean sediments (benthic foraminifera). Planktic foraminifera are my favorites; they evolved about 175 million years ago, and still live in the global ocean today! One of the ways which we know about past climate states how the ocean behaved to such warming and cooling events of the geologic past is through analyzing the chemistry of fossil foraminifera shells, or tests! Foraminifera are also incredibly useful in studies of evolution, as they have a robust fossil record. Learn more about Foraminifera here!

Various planktic (surface-dwelling) foraminifera (marine plankton) species. Images are 60-100x.

What’s YOUR favourite extinct species? Let us know in the comments, maybe we will feature them in a future post!

A Model of Sea Star Locomotion Using Tube Feet

Sea star inspired crawling and bouncing

by: Sina Heydari, Amy Johnson, Olaf Ellers, Matthew J. McHenry, and Eva Kanso

Summarized by Max Botwin, a geology major at the University of South Florida. He is currently a senior and will be graduating in Summer 2021. He is planning to move to Texas in May and looks forward to learning more about the world of geology as he works in the field. In Max’s free time, he enjoys playing with his dog Nilla and exploring the local trails around USF’s campus.

What data were used? The model was created by the researchers using parameters that were observed and measured from Asterias rubens sea stars, such as tube foot length during extension or contraction, density of water, buoyancy, and others.

Methods: To effectively model the locomotion of sea stars, the researchers adhered to what they called “hierarchical control laws”, which was the idea that the sea star controls the direction of movement for all of its tube feet, but the power and the recovery from a contraction is determined by each tube foot at an individual level. The researchers observed sea star movement and created a mathematical model to encompass as many parameters involved with tube foot locomotion as possible, including buoyancy of the feet, density of water, extension of tube feet, etc. Researchers were also able to quantify the pull of tube feet from extending and push from contracting using length of tube feet. Researchers were able to use their model and the data they collected to run many simulations with varying numbers of tube feet over different terrain to test the speed, stability, coordination, and overall effectiveness of tube feet locomotion. Examples of the simulations run by the researchers can be found in the link here.

Results: From this study, researchers have found that sea stars give a general command to the tube feet to move in a certain direction, but the power and the recovery from a contraction of the tube feet is controlled by the individual tube feet. This allows for a crawling movement from the sea star which allows it to travel across most terrain underwater and even swim. Tube feet are only effective underwater, since they work through jet propulsion where the tube foot will extend and fill a vacuole with water, then contract and squeeze out that water to propel themselves. The tube feet on sea stars are only related to one another by their attachment to the sea star and nothing else; there is no communication between the tube feet. Despite this, tube feet seem to fall into coordinated movements, where some tube feet are angled backwards and push forwards and some are angled forwards to “pull” the sea star forward. This pseudo coordination of movement is not limited to tube feet that are adjacent to one another, which means that tube feet can fall into the same locomotion “group”, even though they are not located near one another. When this occurs, the sea star goes from crawling to a bouncing gait which is much faster, but also requires more energy and was therefore found to only be useful under certain circumstances. Researchers saw that sea stars preferred to “pull” when moving vertically and pushing when moving horizontally.

Figure 2 from Heydari et al. (2020). (a) Common sea star used in the study called Asterias rubens. (b) Image of tube feet on Asterias rubens. (c) Image showing the bouncing gait of Asterias rubens. (d) Cross section of Asterias rubens to show the parts of its nervous system. (e) The anatomy of tube feet for mature sea stars. (f) The different actions that tube feet can undertake to perform locomotion. (g) This is a schematic of the mechanical rendition of a sea star including tube feet to help model sea star movement. (h) A flow chart to describe the hierarchical motor control used to command the tube feet in the mechanical sea star.

Why is this study important? This study is important because of the versatility that sea stars have in their movement across most surfaces underwater. If this locomotion can be accurately modeled, it can be recreated for robots, vehicles, or other such applications. The ability to traverse underwater terrain can have impactful applications in many industries that need to do work on the bottom of a body of water. Imagine a vehicle that is able to remain submerged and move along the ground while underwater to repair a bridge or to clean the bottom of a lake- the possibilities are endless!

The Big Picture: This study has shed light on unknown factors involved in how tube feet are controlled by the sea star and researchers were able to study and simulate sea star locomotion but were not able to match the complexity of real sea star locomotion. Answers beget more questions and that rings true here as well; the researchers were able to answer some of the “how” for sea star locomotion but were unable to explain the “why” behind it. This study can be used as a base for future models of the same type and can go further in detail using new parameters and improve their models to better depict the movement of tube feet on sea stars.

Citation: Heydari S, Johnson A, Ellers O, McHenry MJ, Kanso E. Sea star inspired crawling and bouncing. J R Soc Interface. 2020;17(162):20190700. doi:10.1098/rsif.2019.0700

Comparing humans and dogs: how two species in close communities relate

Trabecular bone in domestic dogs and wolves: Implications for understanding human self-domestication

by: Habiba Chirchir

Summarized by Maraley Santos. Maraley is an undergrad geology major at the University of South Florida. After graduating high school at the turn of the century, Maraley did what any student with an aptitude in science does when listening to others’ advice. She went to business school! After discovering a dislike of markets and business she put her college career on pause and reassessed life. Understanding her distaste of business but a love for data and science she decided to go back to school and major in her passion, earth science. Maraley believes it is never too late to learn, and this is the mantra she repeats to herself during all those restless nights of studying. She is supported by her wonderful partner in life Jeremy, their awesome daughter Leia, and her loyal pup Charlie. In her free time, she is an aquarist, hiker, rock collector, bassist, and is learning to build things that will work.

What data were usedSamples of the adult femoral head, highest point of the thigh bone, and distal bones, the ankles, of Canis lupus (gray wolf) and the largest Canis familiaris (domestic dog) breeds were acquired from the American Museum of Natural History (AMNH) in New York City, the Field Museum of Natural History (FMNH) in Chicago, and the National Museum of Natural History (NMNH) Smithsonian Institute in Washington D.C.. The 3D image results obtained from CT scans of these samples were analyzed and the qualitative results were summarized using numerous statistical methods. 

Methods: The robustness of bone, or trabecular bone fraction (TBF), was examined in this study to test the difference, if any, between grey wolves and their relatives, the domestic dog. The femora of both species were scanned using an X-ray CT at two separate facilities at the University of Texas (UT) and the University of Chicago (UC) while the distal tibiae (lower leg bone) were scanned using another type of CT scanner. The researchers hypothesized that domestic dogs have a more gracile, or delicate, bone structure their grey wolf relatives and they  scans hypothesized that the scans would show this. 

Results: TBF analyzation in the proximal (top part) femora and the distal tibiae of the domestic dog (C. familiaris)and the wolf  (C. lupus) revealed that the average TBF of these bones in wolves is greater than in domesticated dogs. Statistical analysis showed minimal error and boxplots helped visually assess the significant differences between the robustness of the bones in wolves and dogs, with wolves showing significantly thicker bones. Wilcoxon rank-sum tests (which essentially show if two populations show differences between them or not) showed the proximal femora (figure 1) and the distal tibia (figure 2) of the wolves showed greater TBF than of those in domesticated dogs. 

Figure 1 – proximal femora trabecular bone fraction

Why is this important? The analysis done in this study was used to test the hypothesis that domestic dogs have lower TBF (a more gracile or delicate bone structure) than their wolf ancestors due to self-domestication. In other studies, we see this pattern of gracility in human bodies when comparing it to our ancestors- our bones have also seen a trend of lower TBF through time. The ability of a dog to self-domesticate was due to their propensity of pro-sociality, or friendliness, with humans. This pro-sociality was reciprocated by humans, and the close relationship we see today between these two species is evident. As two species that domesticated alongside each other and live in close communities, we can study the effects of domestication in both species and make comparisons that can help us understand that process in humans. Unlike dogs, humans do not have such close living ancestors, so using relevant examples can help build that understanding.

Figure 2 – distal tibia trabecular bone fraction

The big picture: This study adds to the literature understanding self-domestication, a process that is not only behavioral, but also biological. Research has shown that self-domestication among most species lends to smaller body sizes, decrease in skeletal robusticity and possibly a decrease in bone density. Another hypothesis that is being studied is the effect domestication has on sedentism, the reduction of the need for a species to move long distances for survival (hunting for food and water resources), staying in one place. Studying domestication and understanding humans as being domesticated animals will help identify the long-term effects of sedentary lifestyle on our bodies, diseases that may arise of a lifestyle that isn’t compatible to our biology, and help expose the effects of extreme selection pressures among our best friend, the dog.

Citation: Chirchir, H. (2021). Trabecular bone in domestic dogs and wolves: Implications for understanding human self‐domestication. The Anatomical Record304(1), 31-41.

Matthew Inabinett, Appalachia CARES/AmeriCorps service member; assistant collections manager at the Gray Fossil Site & Museum

Tell us a bit about yourself

I’m a vertebrate paleontologist currently living in Johnson City, Tennessee. I graduated from East Tennessee State University (ETSU) with my master’s degree in paleontology in May 2020. While I was a student at ETSU, I had a graduate assistantship position in the fossil collections at the Gray Fossil Site & Museum (GFS), which I’ve fortunately been able to continue since November 2020 thanks to a position serving at GFS through AmeriCorps. Prior to coming to ETSU for graduate school, I earned my bachelor’s degree in geology from Amherst College in Amherst, Massachusetts, in 2018. As a student at Amherst, I worked all four years as a docent in the Beneski Museum of Natural History — as you can probably tell, I really love natural history museums and want museum work to be a core component of my future. 

Image 1: Me in collections at the Gray Fossil Site & Museum. I am holding the 19th thoracic vertebrae of the Gray Fossil Site’s mastodon, which is very likely a new species. The left and right hindlimb bones (femora, tibiae, and fibulae) are on the cabinet behind me. (August 2021)

How did you get interested in science?

For as long as I can remember, I’ve been very interested in animals, and from about the age of four that interest grew to include fossil animals. Through reading lots of books and watching science shows as a little kid, I became increasingly fascinated by animals, in particular dinosaurs. Even as a young kid, I was always pretty interested not just in the animals themselves (e.g., which dinosaur was the biggest or coolest-looking) but in how they lived and what their world was like, and how they evolved with changing ecosystems, which are definitely interests that have only continued to grow as I’ve studied paleontology professionally. 

I should also point out that in addition to reading books and watching television programs about nature and paleontology, some of the most critical sources for fueling my interest in science were family trips to zoos, aquariums, and museums. There really isn’t anything as fascinating as getting to see live animals or real fossils in person — now just as much as when I was an elementary schooler — and these places gave me a real-life look at research and conservation in action. If I can hop on a little soapbox for a moment, I just want to say that over the past year with the COVID-19 pandemic, places like these — which are generally operating on tight budgets anyway — took a serious financial hit, and if you’re in a position where you are able to support zoos, aquariums, museums, or similar science education venues in your area, please do! These are the places that not only push forward our knowledge of life on Earth and our ability to conserve it, but also can inspire people to become scientists themselves or to be more supportive of science-based causes and issues, and as such represent something really valuable in our society.

What kind of work do you do?

My research as a graduate student and since has focused on prehistoric elephants, in particular on mastodons — an extinct family similar to but only distantly related to the living elephants, and characterized most recognizably by the conical cusps on their teeth. Mastodons evolved in Africa and spread to Eurasia and eventually, about 16 million years ago, to North America where they survived until about 12,600 years ago and were an important part of large mammal communities across the continent. I am interested in the taxonomy, evolution, and lifestyles of mastodons in North America, particularly in the southeastern US. My thesis focused on (re)describing five mastodons from the Pleistocene (ice age) of coastal South Carolina, including the two individuals used to make the skeletal mount on display at the Beneski Museum. These mastodons showed some features like relatively large tusks in their lower jaws and really broad molars that are toward the extreme end of the spectrum for their species. I’m currently involved in some other projects along similar lines, looking to quantify variability in mastodon molars and particularly in the presence/absence of tusks in the lower jaw. 

Image 2: The American mastodon mount (along with other creatures!) at the Beneski Museum of Natural History at Amherst College. The skeleton and upper teeth are from one individual, the lower jaw with its teeth and tusks are from a second; the skull, upper tusks, and pelvis are reconstructed. These specimens were found in South Carolina in the 1860s. Notice the tusks in the lower jaw — they are the largest I’ve tracked down in any American mastodon. (February 2020)

My position at the GFS is in collections, which I think is a really wonderful way to experience the museum world. Basically, this is a position that involves the storage, cataloguing, accessioning, and upkeep of fossils once they’ve been excavated and prepared, and assisting researchers and students with access to the specimens. I’ve had to learn a lot about archival materials and practices to ensure long-term stability of specimens, as well as how to document specimen information, loans, research access requests, and other important information. I find it an especially exciting career path because of the opportunity to look at all the fossils in the collection up close (it’s done wonders for my osteological knowledge), and the fact that the Gray Fossil Site, which unsurprisingly dominates our collection, is both incredibly rich and the only site of its age (Early Pliocene, about 4.8 million years ago) in Appalachia means that many of the fossils I get to handle and house represent species new to science! 

How does your research contribute to understanding paleontology?

Mastodons were a long-lived group that entered North America about 16 million years ago and survived here until about 12,600 years ago at the end of the last ice age; in that time they were found across the whole continent and were important parts of large mammal communities, so understanding their natural history helps paleontologists form a better picture of what was going on in North America more broadly. Even though mastodons are really common ice age fossils in most of North America, the first 15 million years or so of their history on the continent is not well-understood, and even comparatively well-studied ice age mastodons have lots of unanswered questions. I’ve focused especially on mastodons in the Southeast because it’s an area where they are common but generally not as well-studied as other places like the Midwest and Great Lakes region, and only by describing and studying more specimens from comparatively understudied time intervals and places can paleontologists begin to piece together what variation exists in mastodons and what it might mean. It’s important to tease apart what kinds of variability indicate differences between mastodon species (and when and how different species might’ve separated from each other), versus adaptations to particular environmental conditions over time, versus the individual variation present in any species. The environmental aspect is interesting given the ongoing investigation into the (probably very substantial) role rapid climate change at the end of the ice age had in the extinction of mastodons and other large mammals; understanding how mastodons themselves changed in response to earlier climate changes might help us better understand why they went extinct at the end of the ice age, and perhaps what that might mean for their modern elephant relatives. 

Compared to research, working in natural history collections might not seem like it contributes as much to answering questions or spreading knowledge about paleontology, but I think that it is actually a great way to do both of those. Without well-maintained collections, conducting research becomes much more difficult, so by making sure that materials in collections at GFS are well-housed and well-maintained, catalogued, accessioned, properly labelled and documented, and accessible to researchers (who have filled out their research access request paperwork beforehand!) I’m playing my part to further scientific progress at this remarkable site and in the field as a whole. The institution outlives the individual, and so I hope that by always adhering to best practices in collections and treating the tasks with care, our specimens will have a better chance of surviving in perpetuity. Additionally, it’s not only research that is benefitted by a well-maintained fossil collection; public outreach can be as well. When it comes to choosing fossils for display and interpretation, collections staff are often going to be indispensable resources when it comes to considerations both aesthetic (e.g., what specimens are the most striking?) and functional (e.g., how stable will this fossil be out of collections in a display case, and is predisposed to fragility due to its curation history?). As I got my start in museums as an educator, I try to keep things like this in mind at GFS, which may be coming in handy soon as we begin the process of revamping our exhibits.

What are your data and what do you study?

Image 3: Measuring the jaw of the Gray Fossil Site mastodon. The long symphysis (chin) and lower tusks differ from the American mastodon and other species. (February 2019)

My research is on mastodons, and there are a few areas I’m particularly interested in: mastodon from the Southeastern US, the variability in the form and presence of lower tusks in some mastodons, and patterns in variability in tooth form as a proxy for species differences in mastodons. Despite being one of the most common, charismatic, and well-known groups of fossil animals in North America, there are a lot of things about mastodon evolution we don’t really understand. While there’s a lot of exciting research going on in the genetics of ice age mammals, including mastodons, my own research uses the good ol’ dry bones approach of looking at morphology: not all fossils preserve good genetic material, even if they’re geologically recent enough to (this seems like it’s a particular problem in the Southeast), and a lot of the areas where we have the biggest questions about mastodon history (when did certain lineages/species split from each other and how? what might have driven certain adaptations?) involve fossils too old for genetic work to be done. Documenting, measuring, and describing specimens — especially teeth, the most durable part of the vertebrate skeleton and (in most mammals) among the most taxonomically informative, and especially especially the 3rd molars (in elephants and their relatives, the largest, longest-lasting, and most distinctive tooth) — provides a basis for large-scale studies of patterns and gives us a morphological framework on which we can place the results of isotopic and genetic studies. I also have a great fondness for “historic paleontology,” investigating and revisiting work done many decades ago to see how older scholarship can fit in with newer interpretations, and to try and solve long-standing questions where information may have slipped through the cracks of history. This kind of investigation laid the groundwork for my master’s thesis, which was anchored on the redescription of the mastodon skeleton on display at Amherst College, collected in 1868, published on briefly in 1918, and little remarked-upon since — which is a shame, because some of that material is really remarkable; the lower tusks on that mount, for example, are the largest I’ve come across for this species of mastodon, and the teeth are proportionally wider than in any other specimen yet measured.

Image 4: Measuring a baby tooth from an early mastodon, Zygolophodon proavus, at the Beneski Museum of Natural History. (February 2020)

What methods do you use to communicate science?

As I noted above, I started out as a museum docent, and I still think talking to people face-to-face at a museum is the finest, most engaging way to share the excitement of paleontology. That’s not really something I’ve gotten to do with a lot of regularity since I came to ETSU, but through collections I’ve gotten opportunities to be involved with another really great branch of museum education and outreach: exhibits! There is a lot of work that goes into making a museum exhibit — even a temporary one. Specimens have to be assessed and have condition reports filled out, and adequate supports have to be made for them; theme, tone, and content have to be decided on for the text, and illustrations and graphics have to be made; and the exhibit has to be prepared with visibility and accessibility for as many museum-goers as possible in mind. Earlier this year, I was able to complete a small temporary fossil exhibit that my colleagues and I began back in early 2020, before the pandemic, and I found the whole process fascinating. There are so many things that I just hadn’t considered about the process beforehand, and I think getting to have that experience is really informative. It’s certainly a different feeling to chatting with visitors and educating on the fly out on the museum floor.

What is your favorite part of being a scientist?

One of the things I find most exciting about being a scientist — and particularly a paleontologist — is just the connection you get to have with the natural world. In doing paleontology, in any capacity, you’re connecting yourself with everything that came before you in some small way. A lot of people like to approach paleontological research with the idea that it should be striving to answer Big Questions with major, serious implications for the modern world (often with particular emphasis, on climate change and its ecological effects), and that research is wonderful and critically important, but I personally don’t agree with the notion that it should necessarily be a driving factor in all paleontological research. Sorry to expound my own weird philosophy on the subject, but… humans are the only species we know of that has ever had the capability to look back and to study what the world was like in own past and before we even existed; I think that we almost owe it to the organisms that came before us to study and understand them and their lives and their worlds. There’s something primal and fascinating about getting to hold in your hands, to see and seek to understand, some part of a living thing that has been hidden away for millions of years. I don’t think it’ll ever stop being an amazing thrill.

Image alt 5: The lower jaw of an American mastodon from South Carolina, at the Mace Brown Museum of Natural History at the College of Charleston. Note how this mastodon lacks tusks in its lower jaw. (May 2019)

What advice would you give to aspiring scientists?

For someone who wants to be a scientist, I’d say it’s good practice to get into to learn to change your mind about things with new information, and try not to make knee-jerk decisions or reactions — which are not things that come naturally to (probably) anyone, but learning to adapt your interpretations and opinions with more data and more reflection is critical in science. Also, though this is cliché, you should definitely always have an excitement for the natural world and an inquiring mind about it. For someone interested in paleontology particularly, I would say (though I expect most people who are seriously interested about paleontology would already be doing this) to take a real interest in living fauna and flora for their own sake, because you’ll learn a lot about how organisms work and it really will help you think about what fossil organisms and ecosystems must have been like, and of course because the species we share the planet with now are totally fascinating in their own right. Another paleontology topic I feel is important to clarify is that to be a paleontologist, you don’t have to be good at all aspects of paleontology: fieldwork is NOT a requirement to be a good paleontologist; being skilled at preparing fossils is NOT a requirement to be a good paleontologist; having the often-methodical skills for collections or curation is NOT a requirement to be a good paleontologist; teaching classes is NOT a requirement to be a good paleontologist; having a doctorate is NOT a requirement to be a good paleontologist. Knowing and respecting the value of — and potential stumbling blocks in — each of these areas will serve you well, and help you carve out a niche for yourself where you feel you fit in, and have a job that matches your skills. Don’t be afraid to realize that you maybe aren’t cut out for some parts of paleontology — maybe you hate being out in the dirt, or dread the idea of spending years working toward a PhD. There’s still room for you to contribute great, important work to the field.

First signs of bird extinction from 40,000-1,700 years ago on Timor-Leste

First record of avian extinctions from the Late Pleistocene and Holocene of Timor Leste 

Summarized by Julie Sanchez, a senior at the University of South Florida who is majoring in Geology. She plans to graduate with her Bachelors of Science in summer of 2021 and wishes to continue her studies in graduate school, focused in petroleum geology. Outside of her academics, she loves to embrace her crafting side by painting or designing ceramic pieces. She also loves to walk trails and observe the beautiful rocks around her. 

What data were used? The researchers collected fossil birds from excavated sites in Timor Leste and then used collections of bird skeletons from the Smithsonian Institution’s National Museum of Natural History in Washington D.C. and Bergen University Museum in Norway to identify the newly found fossils. Here, the researchers were able to obtain information on what kinds of bird skeletons were resided in Timor, as well as bird skeletons that may have migrated to Timor. Research from a previous study of these skeletons provided useful information on the taphonomy of birds in Timor that added to the understanding of the results in this article.  

Methods: Researchers set up two locations of excavation in Timor: one in Jerimalaj and the second in Matja Kuru, both of which are located on the northeast part of Timor Leste (Figure 1).  Using mesh screens, the researchers were able to wet the screens and expose the bone/fragments found. As the fossils began to appear, they were measured with a digital caliper. The texture and porosity levels of the fossilized skeletons were also noted, to  help differentiate and categorize the juvenile bird bones from the mature bird bones. Radiocarbon dating was used to determine the ages of the bones/fragments found. 

This image shows the location of Matja Kuru and Jerimalai in Timor-Leste, where the fossils were excavated.

Results: The researchers recovered 416 bird bones from Jerimalai and Mataja Kuru. Throughout the excavation, there were more species found in Jerimalai than in Matia Kuru. Unfortunately, 65% of the fossils were not distinguishable. The reason for this was because most of bones were fragments, which only allowed them to narrow it down to being just a bird fossil. With the residual 147 identifiable fossilized specimens, it was determined that there were 29 bird species across 16 families. It was found that quails and buttonquail birds were more prominent at Maja Kuru, though they are considered rare in the city of Jerimalai today. There was also a crane species found that is extinct today. This represents the first known extinction event of birds in Timor. Their research also determined that although quails and buttonquails are morphologically similar, 29 different specimens were distinguished because of differences in bone structure. The results featured only a single fragment of Blue-breasted quail, S. chinensis, which was found in Jerimalai. Six specimens found in Jerimalai were determined as Metallic Pigeons. All of this information helps researchers better understand the modern day bird populations in this area/ 

Why is this study important? For about two hundred years, researchers have been studying the birds in this area. In spite of their research, the is still a big gap in regard to what kind of birds lived in Timor. This study allows the public to observe another perspective that was once “not there.” With the addition newly discovered bird species, it allows researchers to use this information in future studies of bird biodiversity, as well as understand what bird species coexisted during the Late Pleistocene and Holocene. 

The big picture: Knowing what types of birds existed on Timor can gives us insight about the environments the birds lived in, as well as climate change, and the relationships these animals could have had with other organisms. By understanding what bird species were once there, we can better understand what Timor was like during the Late Pleistocene and Holocene. We can also use this information to better understand global sampling, as many areas of southeast Asia are still underexplored for fossils. 

Citation: Meijer, Hanneke J. M., et al. “First Record of Avian Extinctions from the Late Pleistocene and Holocene of Timor Leste.” Quaternary Science Reviews, vol. 203, Jan. 2019, pp. 170–184. EBSCOhost, doi:10.1016/j.quascirev.2018.11.005.

Devra Hock, Paleontologist, Ph.D. Candidate

Tell us a little bit about yourself.
Hi! My name is Devra Hock and I am currently working on my PhD on mammalian paleoecology. Outside of my research, I love dance and musical theater. I’ve danced and performed my whole life and recently that interest has shifted towards aerial dance (think Cirque du Soleil, but much less fancy). I teach aerial hoop and pole fitness classes, as well as perform with my aerial studio in Lincoln, NE. Having something else to focus on with non-academic goals and challenges allows me time to have fun and accomplish personal goals. I also have a love of vintage-inspired fashion, and want to help re-define what scientists look like.

What kind of scientist are you and what do you do?
Right now, I am a PhD candidate at the University of Nebraska-Lincoln, which is very similar to a research scientist. I conduct my own research for my dissertation, as well as teach in my department and assist my advisor with his research. I’m studying mammalian paleo-ecology, and specifically looking at how the distribution of mammalian traits can be used to predict environments. To do that, I use historical mammalian distributions and their associated traits and environments as proxies to build a model that can be applied to the fossil data. Currently, I am comparing both North American and African mammal data to determine which is the best proxy to use for Miocene North American fossil localities. Another part of my research is examining the change in North American mammalian distributions from historical to modern times and discussing possible causes. In addition to my research, I am on the board of the Association for Women Geoscientists and currently transitioning from a region delegate to the Communications Coordinator after participating on the communications committee being in charge of the AWG Twitter and part of the team that keeps the website updated.

What is your favorite part about being a scientist, and how did you get interested in science?
I grew up loving going to museums and science centers, but that did not translate into an interest into science as a career field until middle school, with a 6th grade field trip focusing on earth sciences. That was my first exposure of geology as a scientific field. From there, the following year I researched what radiocarbon dating was for a research fair at school and used woolly mammoths as my example in that project. While working on that project, I found myself going down the paleontology documentary rabbit hole and got more and more interested in paleontology itself. In high school, I was lucky to have a science teacher that had a background as a paleo-anthropologist, and I was able to really develop my interest in paleontology throughout high school.

As a scientist, I appreciate the skill to look for questions that don’t have answers and to think critically about data and facts presented to me. I’ve also learned how to be collaborative with a variety of people from different disciplines. Additionally, one of my favorite parts about being a paleontologist is our ability to essentially time travel through our research. Especially when we’re out in the field, we’re standing in rocks that formed millions of years ago and finding fossils that haven’t seen the light of day since they were buried. As a geologist and paleontologist, we’re able to look at the rocks and interpret what environment created each rock layer, and travel through different environments as they changed through time. In my specific field of paleo-ecology, we try to understand what the interactions of animals and their environments looked like throughout time.

How does your work contribute to the betterment of society in general?
My research has two broad contributions to society. First, my research of historical versus modern mammalian distributions will add to our knowledge of the changes occurring in the natural world around us and what the potential causes might be. These discussions contribute to the work of ecologists and conservationists as they work to maintain our natural spaces for future generations. Second, my research into paleo-ecology will add to our knowledge of the evolution of environments and animals throughout time, which also contributes to our understanding of why and how environments change and what the animals’ response has been in the past.

My work with the Association of Women Geoscientists and local outreach events creates discussions about equity and equality in the geosciences for women and other underrepresented groups. Currently both with AWG and in my own department, I have been working with others to find sustainable and achievable methods to increase diversity and inclusivity in the geosciences and to dismantle systemic and institutional barriers.

 

What advice do you have for up and coming scientists?
My biggest piece of advice is to find a way to try out things you’re interested in to see if you really like doing them. I started doing field work in high school as a gauge if I really did like paleontology in practice and not just from TV documentaries. It’s also a great way of building experience and connections. My second biggest piece of advice follows that, which is networking. Just like any other field, your path is what you make of it, but knowing other people in your field can change the shape of your path. Don’t be hesitant to reach out to professors or researchers in the field that you’re interested in. With emails, the worst that can happen is they never respond! Science is filled with opportunities, but unfortunately opportunities aren’t always equal. You may have to seek out experiences that will help you later on. There are a lot of unspoken rules and expectations, and sometimes you won’t get opportunities you are qualified for, and that’s not your fault. You just have to keep pushing and your time will come. However, with everything I just said, don’t lose yourself to your science. We are all multi-faceted human beings with lots of different interests. Make sure to take time for yourself and your other hobbies. Time away from school or research is just as important as time spent working. While school and research are important parts in your life, they aren’t your entire life. Remember, you can’t do science if you’re burned out!

To learn more about Devra and her research, visit her website here!

A call for unifying methods within taxonomy of Tardigrada (the water bears)

Systematics of Tardigrada: A reanalysis of tardigrade taxonomy with specific reference to Guil et al. (2019)

by: James F. Fleming and Kazuharu Arakawa

Summarized by Joshua Golub, a senior at the University of South Florida in the department of geosciences. His specific interests in geology are geophysics and the use of near surface geophysics to gain a better understanding the physical aspects of observing earth processes. While attending the University of South Florida, Joshua has worked full time in the geotechnical engineering industry. Working in the geotechnical engineering industry in soil analysis has given him a perspective on soil properties, as well as utilizing these skills for government projects.  

What data were used? The data that was used came from several sources including from the recently published paper Guil et al. (2019), which was partially criticized by the authors of this paper for having incomplete data to determine taxonomic orders within tardigrades (Figure 1). Authors used the data from all of these sources to re-analyze and understand tardigrade taxonomy. Authors used a type of analysis called BUSCO to uncover the genetic patterns of highly conserved genes (i.e., genes that don’t change for a long period of time) of the species used in this study; BUSCO is a type of analysis that helps determine the full completeness of genes within groups of tardigrades. 

Figure 1: A picture of a Tardigrade (water bear). These organisms are generally 1mm long. Image: Schokraie et al., 2012.

Methods: Evolutionary trees can be constructed with two types of data; morphological data and molecular data. Morphological data comes from the specific external shape of the organism, whereas the molecular data is collected using the DNA of the organism. Often, researchers do not have both the molecular and morphological data to construct these evolutionary trees, but when researchers do have both, it can lead to much more accurate results. This paper tries to determine if the evolutionary relationships of tardigrades are better uncovered by using both molecular and morphological data. Recent articles used primarily morphological means to determine tardigrade taxonomy, so this article set out to see how adding molecular data would change the results. Authors in this paper tested to see if using only morphological data could negatively affect the branch lengths of an evolutionary tree, which explains when certain species diverge and become independent of one another (Figure 2). One specific hypothesis that the authors tested was from a previous paper, which used morphological evidence to elevate a group within Tardigrada to Apotardigrada. This paper included an analysis of genes to determine if the findings in Guil et al. (2019), the previous paper in question, had merit to make these major changes to the taxonomy of Tardigrada. They went about this by including several additional methods to the study, including genome sequencing (uncovering the patterns of DNA in each species tested), BUSCO, and a topology analysis, which is used to determine the branch lengths and when the common ancestors of certain tardigrade groups diverged (i.e., became separate populations). 

Figure 2: This figure shows the taxonomic tree for the four tardigrade orders, the branch lengths are inserted with each branch showing the results from each particular part of the data. Each color represents a particular method of data collection that was used. These numbers determine branch length, which helps determine when specific groups of tardigrades split and became distinct species.

Results: The authors had some parts of their assessments that agreed with Guil et al., the paper that used only morphological data, but the authors determined that their analyses don’t support establishing Apotardigrada as a formal taxonomic grouping. The assessment of this paper is that a consensus has not been met when approaching the organization of Tardigrada. Among all the additional analyses that the authors introduced into the discussion of Tardigrada taxonomy, what they make abundantly clear is that there needs to be a reanalysis in how we classify and name subdivisions of Tardigrada and unite a consensus of nomenclature (the names and terms that we use to discuss the group) that can avoid leading to further confusion into the research of these organisms. 

Why is this study important? There is a vast lack of consensus on how to properly organize the taxon of Tardigrada. The proposals that the authors make is for a unification of terms and research to further advance the research of a fairly mysterious organism, but in a way that will be the most accurate. 

The big picture: This call for action, to standardize nomenclature and research methods, is one that can be utilized in all fields of science. Depending on the region of the world, research can get stuck in echo chambers, creating their own terms that are not properly shared with the rest of the scientific community so that anyone who wants to study a particular subject, like Tardigrades, can do so effectively. The authors of this paper state that these holes that sometimes lie within research creates a hindrance on the study of the subject and calling for a consensus in any field of science is always a better route than tackling a topic on your own and exempting others’ research. 

Citation: Fleming, James F., and Kazuharu Arakawa. “Systematics of tardigrada: A reanalysis of tardigrade taxonomy with specific reference to Guil et al.(2019).” Zoologica Scripta (2021).

Dogs, humans, and wolves, oh my! The evolution of prehistoric dogs

Origins and genetic legacy of prehistoric dogs: the evolution of prehistoric dogs

Summarized by Jon Belcher, a fourth-year geology major at the University of South Florida. He plans to become a hydrogeologist after graduation or become a sailor in the US Navy, whichever happens first. He is an avid backpacker and enjoys cooking.

What data were used?: Bergström and others compiled and analyzed genetic data to better understand the population history of dogs. To do so, Bergström and others sequenced 27 ancient dog genomes (i.e., the complete set of genes in an organism), and compared them against both ancient human genomes and modern-day wolf genomes. The data was obtained from using other studies, and the sequencing was performed by the researchers themselves.

Methods: The ancient dog genomes were matched to the ancient human genomes in both time and space, providing a map for how and when dogs and humans spread across the globe. To compare dogs and wolves, the aforementioned prehistoric dog genomes and modern-day wolf genomes were both sequenced, and the similarities analyzed. 

Results: It was found that the population history of dogs mirrored human lineages, suggesting that when humans expanded their ranges and moved into new areas, they took their dogs with them. Dogs largely moved with humans and evolved alongside them. However, there are some instances where the pattern of humans and dogs moving together doesn’t appear to be the case; it is believed that dogs were occasionally traded or otherwise moved between groups of humans, or that humans moved without dogs. One example given in the article is that there were clear genetic similarities between human and dog populations in East Asia and Europe. Humans and dogs in East Asia and Europe were both more closely related to each other than other populations groups that were geographically closer, such as those in the Near East (which is synonymous with the Middle East).

The distribution of domesticated dog breeds and their genetic legacies. The chart on the left side of the figure color codes the ancestry sources of these various breeds and can be used to determine the relative genetic legacy of each breed.

The researchers found that the genomic data, both ancient and modern, were consistent with the idea that there was a single point in the evolutionary transition of wolves from dogs. Furthermore, gene flow between these two species has been mainly unidirectional since that point. The concept of gene flow can best be summarized as the mixing and mingling of genes between two populations through individuals from both populations interbreeding. It was found that the wolves studied were equally related to all dog breeds analyzed, as shown in Figure 2 in the paper. The researchers used this information to further support the idea that the gene flow was unidirectional.

Modern breeds, as seen in the figure below, are mainly composites of the ancient groups studied. There are not many modern breeds that are descended only from one dog lineage. Dogs such as the Alaskan Malamute descend from the Baikal, America, and Modern European lineages. This information is useful in trying to decipher the origin of dog breeds and tracking how different lineages have interacted over time. 

Why is this study important?: This information helped to reveal how dogs have changed over time, including how they have spread over the globe and how modern breeds formed. This relationship between the movement of humans and dogs is a complex one and can have varying outcomes on the actual genetic makeup of populations. 

The geographic origin of dogs remains unclear, as the researchers could not narrow down a singular location from the data. To further their research, the authors of this paper suggest collecting data from even older populations of wolves and dogs, and utilizing other disciplines such as archaeology, anthropology and ethology (i.e., the science of animal behavior) to help pinpoint that precise moment where the first modern dogs originated. 

The big picture: While earlier studies have suggested bidirectional flow of genes between dogs and wolves, this study found that gene flow was mainly from dogs to wolves. Thus, the study helped to overturn incorrect thinking.

The study also raised multiple new questions. One from the article is “how did dogs spread across Eurasia and the Americas by the Holocene”? This question is raised because there is no currently known major human movements that are concordant with this proliferation of dogs. Another question is why, if gene flow can be bidirectional between dogs and wolves, is it only observed as unidirectional. Do dogs that have a higher amount of wolf genes tend to become wilder and thus are either killed or set free and do not survive? Or do wolves generally not have the chance to spread genes to dogs? The data presented in the article mostly talks about no gene flow for “some wolves”, so does this mean that there are other wolf populations that do receive dog gene flow? Further studies may shed light on these questions. 

Citation: Bergström, A., Frantz, L., Schmidt, R., Ersmark, E., Lebrasseur, O., Girdland-Flink, L., Lin, A.T., Storå, J., Sjögren, K.G., Anthony, D. and Antipina, E., 2020. Origins and genetic legacy of prehistoric dogs. Science370(6516), pp.557-564.