Research
Research Themes
The Uno Lab’s main research focus is on understanding the causes and consequences of major transitions in terrestrial ecosystems over the last ~25 million years. This includes the spread of grassland ecosystems and its effect on mammalian and early human diets and their evolutionary trajectories. Potential causes for grassland expansion include a decrease in atmospheric CO2 levels, changing rainfall patterns, vegetation-fire feedbacks, and herbivory. We can evaluate the role of these mechanisms in deep time using geochemical techniques we have learned or developed in the lab. Below we highlight some of the major research themes followed by media and press on our work.
BIOMARKERS IN MODERN PLANTS AND SOILS
Paleoecologists use a variety of approaches to reconstruct past ecosystems. This project seeks to understand how biomarkers in modern plants and soils can be used to develop and improve existing proxies for woody cover and plant functional type in the geologic record. We seek to compare multiple proxies at modern sites, where we can identify vegetation types and quantify climate variables, through collaboration with botany experts Mbaluka Kimeu, Mathias Mbale, Jonathan Sila, and Augustine Barasa from the National Museums of Kenya Herbarium, paleobotanist Tammo Reichgelt, and pollen and phytolith experts Rahab Kinyanjui, Alice Novello, and Caroline Stromberg. Uno, et al., 2018 AGU poster; Shi et al., 2018 AGU poster, and Tweedy and Uno, 2022 AGU Poster.
Field team in Aberdare National Park, Kenya in June 2023.
BIOMARKERS IN ANCIENT SEDIMENTS
We use stable carbon and hydrogen isotopes from plant wax biomarkers to reconstruct vegetation and hydroclimate in the past. We also are working to develop non-isotopic biomarker proxies for paleo vegetation and fire. For this we turn to n-alkane distributions, pentacyclic triterpene methyl ethers (PTMEs), and polycyclic aromatic hydrocarbons (PAHs). Biomarkers are preserved in many archives: deep sea sediments, ancient lake beds, and fossil soils, known as paleosols. These different archives integrate and record across different spatial and temporal scales which provides many avenues of opportunity to study ancient ecosystems. Uno et al., 2016a; Uno et al., 2016b; Polissar et al., 2019
Stacked paleosols and fluvio-lacustrine sediments in the Shungura Formation of the Lower Omo Valley, Ethiopia.
STABLE ISOTOPES IN TEETH
You are what you eat. Analysis of carbon and oxygen isotopes of fossil enamel reveals information about diet and environment.
We showed that enamel isotopes can be used to track long term dietary changes in herbivores resulting from grassland expansion in eastern Africa over the past 10 million years. Uno et al., 2011; Cerling et al., 2015; Bibi et al., 2013
We have also been involved in studies of hominin diets that showed Homo maintained a diverse diet while others, like Paranthropus, became more restricted in its diet. Cerling et al., 2013; Cerling et al., 2011.
Intratooth isotope profiles (see Elephas molar, right) are a unique approach that allow us to assess seasonal changes in rainfall and diet millions of years ago. Annual rainfall patterns play a critical role in resource availability for humans and other mammals. Uno et al., 2013; Uno et al., 2018; Uno et al., 2020a; Uno et al., 2020b; Uno et al., 2020c; Yang et al, 2020;
ABRUPT CLIMATE CHANGE IN THE SAHARA
How did past human populations respond to abrupt climate change? Gobero is an archeological site in Niger that may hold some answers. During the latter part of the African Humid Period (~14,000 to 5,000 years ago), increased rainfall created a semi-permanent lake at Gobero, where two cycles of human settlement and abandonment between 9.5 and 4.5 ka BP are recorded in lake sediments (Sereno et al, 2008).
Gobero is unique among all archeological sites in the Sahara because of its incredible record of ~200 human burials that have been recovered along with stone tools, jewelry, and harpoons for fishing. In addition, there is a rich faunal record that includes crocodiles, turtles, fish, hippos, pigs, giraffes, and elephants.
This project seeks to reconstruct climate conditions that led to occupation and abandonment of the site. To do this, I use stable isotope analysis of tooth enamel to reconstruct diets and biomarkers in sediments to reconstruct vegetation and rainfall.
A bone harpoon, exposed on the desert surface, is still embedded in paleolake sediments. Whoever threw this missed their fish!
WILDLIFE FORENSICS
What started out as a project to assess growth rates in teeth evolved into a powerful tool for fighting illegal trade of elephant ivory and other animal parts. Uno et al., 2013
We radiocarbon date confiscated ivory to accurately determine the year of death of an elephant, which in turn determines if ivory trade is legal or not based on CITES regulations. This technique relies on bomb-curve radiocarbon (14C) generated from nuclear weapons testing in the 1950s-1960s that enables us to determine a date of death with an uncertainty of several months in some cases.
With colleagues, we found that ~90% of ivory intercepted as it moved through the black market was from elephants killed within three years of the seizure date (Cerling et al., 2016). This suggests anti-poaching efforts should be stepped-up in poaching hotspots.
Ivory confiscated in Manhattan from 2015-2016 during Operation White Gold, conducted by the NYDEC. Photos: Wendy Hapgood
Media and Press
Early humans and fire
A familiar geochemical technique shines a new spotlight on early hominin use of fire, 12/15/20
Radiocarbon dating of ivory seized in Manhattan
Scientists deploy DNA analysis and 14C dating in latest salvo against ivory trafficking, 2/5/18
Seized ivory probed for clues that could help save elephants, Washington Post, 1/16/18
Scientists Want to Save Elephants Through Inspecting Seized Ivory, Bloomberg,1/15/18
Fighting ivory trafficking with forensic science, Physics.Org, 8/14/17
Forensic tracking of ivory movement through the illegal trade network
Illegal Ivory Almost All From Recent Killing, Study Finds, Columbia University Press Release, 11/6/16
Recently Killed Elephants Are Fueling the Ivory Trade, Science, 11/7/16
Slaughter of Elephants for Their Ivory Intensifies, Agence France-Press, 11/7/16
Most Illegal Ivory Is Coming From Recently Killed Elephants, The Verge, 11/7/16
China Central TV: News interview, 11/17/16.
Most Illegal Ivory Sold Comes From Illegally Killed Elephants, Wired, 11/08/16
NTN24 TV (Colombia): Interview regarding China’s domestic ivory trade ban, 01/13/17.
Bomb-curve Radiocarbon Dating of Ivory as a Forensic Tool (2013-15)
TechKnow (Aljazeera America) Interview, June 2015.
Science Nabs Illegal Ivory Sellers, Columbia University Press Release, 3/6/15
Columbia Magazine: A Sound of Trumpets, 8/1/14.
The Telegraph: Time is running out to save the rhino, 2/12/14.
The Economist: The elephant in the room, 7/6/13.
BBC World News: live radio interview, 7/2/13.
NPR’s Morning Edition: Radiocarbon Clues Help Track Down Poached Elephant Ivory, 7/2/13.
The Guardian: Measuring carbon age in ivory could help combat poaching, study shows, 7/2/13.
National Geographic Daily News: Cold War Radioactivity Can Date Illegal Elephant Ivory, 7/1/13.
New Forensic Technique May Help Track Illegal Ivory, Columbia University Press Release, 11/6/16
Study reveals surprising diet of human ancestor “Nutcracker man”
Huffington Post: Ancient 'Nutcracker Man,' Paranthropus boisei, Didn't Actually Eat Nuts, 5/2/11.
Smithsonian Magazine, June, 2011.
Science Daily: No Nuts for 'Nutcracker Man', 5/3/11
African Grasslands and Human Evolution
Age Newly Verified, One of Oldest Prehuman Fossils Leads to New Finds , Columbia University Press Release, 4/13/21
The Way We Were: Climate and Human Evolution, Columbia University news, 12/1/17
New Support for Human Evolution in Grasslands, Columbia University Press Release, 6/6/16
Dietary change in African mammals
The Salt Lake Tribune: U. scientists track ancient mammal diets from isotopes in teeth, 4/4/11.
Science on NBC News.com: Grazing animals shaped human evolution, 4/4/11.
Abrupt Climate Change in Africa
Examining How Early Humans Responded to Climate Change - Center for Climate and Life, Columbia University news, 4/9/20
Center for Climate and Life Announces 2019 Fellows, 6/6/2019
An elephant at Meru National Park, Kenya.
Specimen KNM-WT 17000, also known as Black Skull, is a Paranthropus aethiopicus skull (cast left; original, right). Isotopes show it was a mixed C3-C4 feeder.
The Triple Burial from Gobero.
A grassland in East Turkana near the town of Ileret.