Beckett Sterner, Arizona State University, and Scott Lidgard, Field Museum of Natural History, have written a new interpretation of a critical period in evolutionary biology leading to how scientists classify organisms: the “Systematics Wars” of the late 1960’s through the 1980’s.
This was a time when prominent biological systematists fought bitterly along partisan lines. They critique philosopher David Hull’s historical account in Science as a Process, which began what later became the common view that one camp, cladistics, straightforwardly “won” over another camp, phenetics.
Hull prioritized theory over practice and the conflicts of a few leading theorists over the less polarized interactions of systematists at large. He treated cultural evolution and biological evolution as forms of the same general process; cladistics and phenetics as holistically opposed theories can only interact by competition to the death.
Sterner and Lidgard instead analyze what systematists actually did in this period, the workflow that they followed, the methods they used, and the common problems that arose and were solved to the benefit of both camps.
They hope this opens a new window of different perspectives on how we classify organisms—the mathematization of systematics.
Nature human behavior has just published a research highlight written John Carson about work at the Sibilo School Road Site in Kenya done by Nick Blegen, Harvard University, that has recovered large quantities of obsidian along with Middle Stone Age (MSA) tools . The finds are thought to date back at least ∼200 kyr.
As Carson summarizes: “Geochemical analyses demonstrated that the majority of obsidian pieces had their provenance at a source site >160 km away, indicating long-distance transport of raw materials during the MSA.” Previously, East African sites evidencing long-distance resource transport have all be less than <50 kyr old.
Evidently known MSA sites of this age are rare in East Africa. If more sites can be found and excavated, the “big story” usually told about the evolution of human social behavior may need updating: far-reaching resource networks and/or intergroup trade in raw materials could have developed earlier than generally believed in the history of our species. If so, then in Carson’s words: “we may gain greater insight into the timeline of social evolution that eventually led to our modern group behaviours.”
Blegen’s report was just published (unfortunately behind a paywall) in the Journal of Human Evolution. Here is the abstract you will find available there for free:
This study presents the earliest evidence of long-distance obsidian transport at the ∼200 ka Sibilo School Road Site (SSRS), an early Middle Stone Age site in the Kapthurin Formation, Kenya. The later Middle Pleistocene of East Africa (130–400 ka) spans significant and interrelated behavioral and biological changes in human evolution including the first appearance of Homo sapiens. Despite the importance of the later Middle Pleistocene, there are relatively few archaeological sites in well-dated contexts (n < 10) that document hominin behavior from this time period. In particular, geochemically informed evidence of long-distance obsidian transport, important for investigating expansion of intergroup interactions in hominin evolution, is rare from the Middle Pleistocene record of Africa. The SSRS offers a unique contribution to this small but growing dataset. Tephrostratigraphic analysis of tuffs encasing the SSRS provides a minimum age of ∼200 ka for the site. Levallois points and methods of core preparation demonstrate characteristic Middle Stone Age lithic technologies present at the SSRS. A significant portion (43%) of the lithic assemblage is obsidian. The SSRS obsidian comes from three different sources located at distances of 25 km, 140 km and 166 km from the site. The majority of obsidian derives from the farthest source, 166 km to the south of the site. The SSRS thus provides important new evidence that long-distance raw material transport, and the expansion of hominin intergroup interactions that this entails, was a significant feature of hominin behavior ∼200 ka, the time of the first appearance of H. sapiens, and ∼150,000 years before similar behaviors were previously documented in the region.
Please note: this news story, recovered on 28-Jan-2017, was originally published in Science Dialogues on 27-August-2014.
Associate Curator Ken Angielczyk of The Field Museum was part of an international team of collaborators that conducted paleontological fieldwork in Zambia between June 22 and July 31. Ken and his collaborators focused on Middle Permian (~265 Mya) to Middle Triassic (~240 Mya) rocks in two areas of the country, the Zambezi Basin in southern Zambia and the Luangwa Basin in northeastern Zambia. The team had done preliminary work in the Zambezi Basin in 2011 and 2012, but only spent a total of about 5 days working there. This time, they spent about two weeks there and their discoveries include multiple species of archaic amphibians and dinocephalians and dicynodonts (both ancient mammal relatives) from the Middle Permian, extremely well preserved fossil wood, and evidence that two temporally-distinct faunas are preserved in the Permian rocks in the Zambezi Basin. They also collected a large amount of geological data that will help complete the picture of the environments in which the plants and animals were living.
The team had conducted more extensive fieldwork in the Luangwa Basin in 2009 and 2011, and this year their work focused on rounding out their previous collections and collecting more geological data to understand paleoenvironments. Among their discoveries is evidence of strong associations of particular dicynodonts with specific environments in the Late Permian rocks of the Luangwa Basin, and strong evidence of increased aridity and changes in the nature of river systems in the area moving from the Late Permian to the Middle Triassic. Ken and his collaborators will use these data to investigate the role environmental changes played in shaping the end-Permian mass extinction (the largest extinction in Earth history) and the recovery following the event.
And one important result of fieldwork like that: scientific publications. Ken and colleagues have a paper in the July issue of Journal of Vertebrate Paleontology describing fossils of tapinocephalids from Southern Zambia. Tapinocephalids are hippo-sized, herbivorous mammal relatives that lived about 265 million years ago; the fossils were discovered by Ken and his collaborators during short exploratory trips to the Zambezi Basin in southern Zambia in 2011 and 2012. They are the oldest known tetrapod remains from Zambia, and demonstrated the potential of the area for further paleontological exploration (as in previous item). This is also the second time that Ken and his teammates have discovered tapinocephalids in an area from which they were previously unknown (the first time was in 2008 in Tanzania).
Please note: this news story, recovered on 28-Jan-2017, was originally published in Science Dialogues on 5-Sept-2014.
A team from the University of Chicago, The Field Museum, and the University of Minnesota has been working for three years on a topic that has long confounded avian biogeographers: the origins and evolution of bird migration. In the August 19 issue of Proceedings of the National Academy of Sciences the team—U of C Ph.D. student Ben Winger, FMNH Associate Curator Rick Ree, and Minnesota prof Keith Barker—published a paper aimed at resolving that question for one of the largest groups of migratory birds.
Traditionally, there have been two schools of thought on where migration began and how it evolved: one theory proposed that ancestors of migratory birds spent the whole year in temperate regions, and that migration patterns evolved over time as these birds’ winter ranges gradually moved to the tropics. The other theory held that these ancestors were originally found in the tropics, with breeding grounds shifting to more temperate locales like North America.
To solve this riddle of migration the team used an innovative phylogenetic model designed to infer the historical biogeography of migratory birds. Ben and Rick developed this new model based on an existing biogeographic method that Rick developed called the “dispersal-extinction-cladogenesis” model, which has been widely used by biogeographers. They applied the model to New World “emberizoid” songbirds, a large group of migratory birds that include warblers, cardinals, sparrows, tanagers, and orioles, using a comprehensive phylogenetic tree developed by Keith and a group of colleagues. “We named it the ‘domino model’ because the breeding and winter ranges of species were coded in 3×2 grids of binary values, like dots on domino pieces,” Rick explains. “The computational challenge was to reconstruct the most probable evolutionary shifts from one domino to another.” Examining common ancestors of migratory and non-migratory species over time using the phylogenetic data, the team concluded that there was more evidence supporting the idea that birds lived year-round in North America and began migrating further and further south, resulting in today’s birds migrating thousands of miles every year.
Another result of the study suggests that many tropical species of birds are descendants of migratory ancestors that lost migration and stayed in the tropics year-round. “This is an interesting result because species diversity in this group is much higher in the tropics,” notes Ben. “Previously, more species in the tropics led to the assumption that temperate, migratory species are derived from tropical, non-migratory ancestors; however, the results of our phylogenetic study suggest that the opposite pattern happened often in this group.”
This study received nice coverage by National Geographic, among other outlets, and will soon be featured on the Field’s Science Newsflash web feature.
So what’s that about botanist and birders joining forces? Well, Ben and Keith are ornithologists, and Rick is a botanist, but with deep experience in biogeography and genomics, which he has applied beyond plants (e.g., butterflies, Amazonian amphibians, lichens). Natural history museums are places where scientists in nominally different fields, but with congruent interests—like biogeography and genomics—can cross paths, and disciplines. Which is one of the things that makes them particularly fascinating places to work.
Here’s the full citation for the article: Benjamin M. Winger, F. Keith Barker, and Richard H. Ree. Temperate origins of long-distance seasonal migration in New World songbirds. PNAS, August 4, 2014 DOI: 10.1073/pnas.1405000111
While using network theory and visualization techniques to map the genetic structure of species in space and time is in its infancy, reconfiguring how science grapples with the inherent complexity of evolution as an ever unfolding process using network approaches has the promise of making it easier to explore how comparable or dissimilar species are in their strategies for survival and reproduction. Looking long and hard at what other species do to survive and reproduce may also make it easier for all of us to see just how toxic our own social strategies—and the assumptions supporting them—can be.
Please note: this commentary, recovered on 9-Jan-2017, was originally published in Science Dialogues on 16-May-2015.
Mathematics, they say, is the language of science. When it comes to what is happening—or has happened—down here on earth, it is beginning to look like the right dialect of mathematics to learn is what is now being called (somewhat confusingly) network science.
When the goal is integrating research discoveries across disciplines as diverse as archaeology, primatology, neurobiology, and geochemistry, the mathematics of networks is the Esperanto of choice.
Field Museum in Chicago is one of the world’s largest natural history and anthropology museums. Scientists working there study the world and its human inhabitants from scores of different research directions, both pure and applied. Integrating these often seemingly disparate specialities so that the results of so much scholarship can be communicated to the public through exhibits and publications has always been a problem.
Under the leadership of Thorsten Lumbsch, Ph.D., the Director of Integrative Research at the Museum, “The Field” as it is affectionately known in Chicago is pushing back against research specialization using network science. Here is one example.
A social network is a set of actors defined by their ties, links, or relationships with one another (e.g., friendship networks, ecological networks, global trade networks, and protein interaction networks) rather than by their individual characteristics (attributes) as actors. Since the research focus is on relationships rather than on characteristics, statistical methods in network science are being developed that do not need to assume—unlike in traditional statistical analyses—that the observations being studied are independent of one another.
Dr. Termeh Shafie, who is currently a Visiting Bass Scholar at the Field, arrived in mid April from the Algorithimics Department at the University of Konstanz in Germany to help the Field’s scientists apply the statistical methods and models of network science to their research datasets which are as seemingly dissimilar as gorilla social interactions, sharks swimming in the ocean, the genetics of lichens, and the decorations on prehistoric American potshards.
When asked about her work at the Field Museum in Chicago, Termeh Shafie explains:
"The first step will be to learn more about the empirical data at hand, the hypotheses about these data being considered, and how to embed a network approach to them. The second step will be to develop network models based on these hypotheses. This requires the mathematical formulation of models, programming these models using statistical software, and then running simulations. Goodness-of-fit tests can be used to test the fit of the models to the data. Once suitable models are identified, statistics can be used to measure different properties of the networks under study and unlock information in them using the models as predictive tools. Within a level of certainty, we can then predict trends and behavior patterns even for parts of the networks we don’t yet have data for."
On Wednesday, May 13th, Dr. John P. Hart (Director, Research & Collections Division, New York State Museum), Dr. Mark Golitko (Regenstein Research Scientist), and James Zimmer-Dauphinee (2015 Regenstein Intern) participated with Shafie in a small-group Network Science Workshop at the Museum exploring ways to apply network analysis to a large database of information about pottery designs on ancient vessels from 102 archaeological sites to help unravel how communities across southern Ontario coalesced between ca. A.D. 1350 and 1650 into the larger regional populations that ultimately became the historically documented Huron confederacy.
Shafie will be at the Field until August 15th, but even after she returns to Germany, she will continue to be the “networks link” between scientists at the Museum and the Algorithmics Unit under the direction of Professor Ulrik Brandes in the Department of Computer & Information Science at the University of Konstanz.