Ancient DNA and Sugar in Evolution: Bison Diversity and Hominin Diets Explored

Episode overview

This Science Podcast episode presents two intertwined stories. First, researchers use ancient DNA to reassess bison diversity in North America and discuss conservation strategies for related diseases. Second, a Science review analyzes how fruit and glucose shaped the evolution of the human brain and energy needs over four million years.

Key insights

• Ancient-DNA reveals modern bison retain substantial pre bottleneck diversity, informing conservation decisions.
• The bison integrated genomics project BIG aims to mitigate diseases and preserve genetic diversity through vaccines and germplasm banking.
• Indigenous communities and tribes are central to bison conservation, highlighting ethical and cultural dimensions.
• In the hominin diet story, glucose and sugar have long been essential for brain function, with cooking and energy-dense foods playing crucial roles in human evolution.
• Fire mastery and climate shifts integrated with dietary changes to support brain expansion and energy budgets.

Introduction and episode framing

The August 6, 2026 Science Podcast weaves together two major science stories that sit at the intersection of genetics, evolution, conservation, and human physiology. The host introduces two distinct but deeply related narratives: first, a genetic and conservation-focused investigation of bison in North America, employing ancient DNA to reassess historic and contemporary genetic diversity; second, an analytical review of how glucose and carbohydrate intake have shaped hominin brain evolution over four million years. The episode frames these stories as examples of how modern science uses genetics and energy metabolism to understand the past and inform present-day decisions about conservation policy, Indigenous involvement, and public health guidance. The discussions feature a rotation of science writers and researchers including Beth Shapiro and Greg Wilson, with Mike Price contributing as a deputy news editor reporting on the bison story, and Jenny Brand Miller, co author of the brain sugar review, speaking about diet and brain evolution. The segment ends with practical information about where to read the paper and how to access related resources. The episode also includes a standard producer and sponsor note, which we will summarize only insofar as it helps understand the production context of the program and will not be a focus of the scientific content.

Segment 1: Bison in North America and ancient DNA

The first major feature discusses a Science paper on bison in North America that uses ancient DNA to reconstruct historical genetic diversity. The paper aims to determine how much genetic diversity existed before the late 19th century bottleneck that occurred around the time of European colonization and mass hunting. The researchers sequence ancient bison genomes recovered from bones conserved in museums and private collections, and they compare these ancient genomes with genomes from modern populations. The central finding is that the modern bison population, despite the catastrophic bottleneck, shows a level of genetic diversity that is not as severely diminished as previously expected. In other words, the small surviving population and subsequent re expansions still carry a substantial portion of the pre bottleneck diversity. This result has important conservation implications because it suggests that maintaining or expanding connectivity between herds might preserve the original genetic reservoir more effectively than simply increasing head counts in isolated populations.

The scientists emphasize that bison have a metapopulation structure in which regional populations exchange genes infrequently but consistently enough to maintain overall diversity. The discovery also informs the discussion around cattle genes in bison. A long standing question has been whether North American bison carry cattle genes due to historical hybridization. The ancient DNA approach allows researchers to determine whether cattle genes are present in pre colonization samples, which would indicate an ancient admixture, or whether the presence of such genes is a late event associated with modern management. The study finds that cattle gene flow occurred after the bottleneck and was not a universal feature of all pre colonial bison populations. This nuance matters for conservation, because it implies that the genetic landscape across bison populations is more complex and regionally structured than previously thought.

In addition to population genetics, the segment covers the practical side of conservation. The project described as the bison integrated genomics project or BIG, is a multi disciplinary effort led by researchers at Parks Canada and collaborators at the University of Saskatchewan and other institutions. The BIG project has four main drivers: improving disease surveillance in wild herds, developing better tests for tuberculosis in the field, creating a vaccine that targets both tuberculosis and brucellosis, and building a germplasm biobank to store bison germplasm for long term preservation of genetic diversity. The collaboration between scientists and Indigenous groups is highlighted as central to the project, reflecting a broader shift in wildlife conservation toward inclusive governance and recognition of Indigenous knowledge and land rights. The interview with Greg Wilson explains that moving genes or germplasm rather than whole animals could reduce the risk of spreading diseases while preserving diversity more effectively. The host also raises the ethical questions raised by transition beyond purely medical or ecological concerns toward social and cultural dimensions of bison restoration. Jack Saddleback, an Indigenous liaison mentioned in the interview, provides a perspective on the collaboration with Indigenous communities, acknowledging the historically fraught relationship with scientists and emphasizing the necessity of involving tribes in decision making. The segment closes with the notion that restoring bison populations is not a simple matter of counting heads, but a careful balance of genetic diversity, disease management, ecological restoration, and cultural meaning for Indigenous communities and the broader public.

The scientific and cultural themes of this segment are interlaced with vivid descriptions of the scale of historical bison populations and the dramatic decline during the 19th century, and the subsequent recovery that has produced a contemporary landscape of diverse but fragmented herds. The discussion underscores practical challenges, including the logistics of moving bison or their genetic material and the ethical issues in moving across Indigenous lands. The overall message is that the genetics of conservation are not only a matter of numbers but also of connectivity, disease management, and respectful collaboration with Indigenous communities. The segment ends with the acknowledgment that this is an ongoing story that will continue to evolve as genomic technologies and field methods improve and as communities and institutions refine their approaches to conservation in a changing environment.

Segment 2: Sugar, glucose, and brain evolution

The second feature shifts to the work of Jenny Brand Miller and colleagues, who provide an analytic review in Science on how carbohydrate sources, particularly fruit and honey, contributed to brain evolution. The speakers discuss Lucy, the famous Australopithecus afarensis fossil from 3.2 million years ago, and the dietary constraints of early hominins before the mastery of fire. The key point is that for the first two to three million years of hominin evolution, there was no fire and no cooked starch, so carbohydrate intake was limited to raw fruits, nectar, and honey. The collaboration of a starch chemist as a co author highlights that raw starch is not readily digestible, underscoring the point that cooked carbohydrates may have become a critical energy source only after control of fire. The authors argue that this carbohydrate pathway might have supported the initial growth of brains by providing the necessary glucose energy while the brain grew in size and complexity.

The discussion moves to how early humans balanced energy from protein and fat with carbohydrate derived from sugars. The brain requires a substantial amount of glucose, and the red blood cells and kidneys are also dependent on glucose. The podcast uses quantitative estimates to illustrate energy budgeting, noting that the brain alone can account for a large portion of daily energy requirements. The authors propose that early humans relied on sugar-rich sources such as fruit and honey to supply glucose and support neural tissue development while hunting and scavenging provided protein and fat that complemented this energy budget. The analytical framework suggests a scenario in which animal foods provided protein and fat that gradually increased as a share of calories, while carbohydrates fluctuated depending on fruit availability, climate, and the development of food processing or cooking techniques. The analysis emphasizes that the proportion of carbohydrates in the diet likely declined over time as energy optimization and cooking allowed more efficient energy transfer from energy dense foods while still providing essential glucose for the brain and other tissues, including the fetus during pregnancy.

Fire and climate are central to the narrative. The discussion explains that fire mastery allowed cooking underground storage organs such as potatoes and yams, improving access to starch and providing energy that supports larger brain and better mental function. However, the authors are careful to note that hunting and meat provision likely did not drive the brain expansion alone. They discuss the concept of ripening fruit and the color cues that indicate high sugar content, connecting sensory ecology with energy optimization. The host and Miller discuss the expensive tissue hypothesis, which posits that brain expansion requires an economy of energy that often involves a reduction in gut mass. This hypothesis aligns with evidence for reduced gut size and changes in dentition as humankind evolved toward an energy dense, processed diet. The conversation also touches on the overall energy budget necessary for thought, learning, and cognitive development, and the ways in which the gut, liver, and brain coordinate energy demands for growth and development, including fetal growth during pregnancy.

The segment ends with a discussion of the research methodology in the analytical review. The authors modeled macronutrient composition across millions of years, proposing that calories from protein remain fairly steady, fat content increases, and carbohydrates become less prominent but remain indispensable for glucose supply and metabolic processes. The hosts address modern dietary implications, suggesting that carbohydrates remain essential in daily energy budgets and that low carbohydrate strategies used in contemporary diets may have limits due to the brain and other glucose dependent tissues. The interview also considers how climate fluctuations and geographic variations influenced fruit availability and how early humans adapted by utilizing underground storage organs and cooking starches to access energy more efficiently. The conclusion emphasizes that human dietary evolution is a composite story of biology, ecology, and culture with important implications for understanding cognitive health and energy requirements across generations.

Overall significance and takeaways

The episode demonstrates how two different branches of science—genomics and evolutionary nutrition—can converge to illuminate both the past and present. In bison conservation, ancient DNA provides a baseline for genetic diversity and helps shape disease management strategies that preserve ecological and cultural relationships with Indigenous communities. In human evolution, a nuanced view of diet and glucose metabolism explains how energy budgets and energy needs have influenced brain growth, digestive tract evolution, and the development of cooking and food processing. Taken together, the stories encourage an integrated approach to science communication, policy, and stewardship that respects Indigenous voices and considers ecological, biological, and nutritional dynamics across deep time.

The podcast points listeners to the Science paper and associated resources on Science.org and invites further exploration of the topics through linked research, reviews, and discussions on related journals and platforms.