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Adaptation to the harsh conditions of a geologic period of global glaciation may have sparked the development of multicellular life. (image: Michael Schiffer/Unsplash)
6.26.24
For a billion years, single-celled eukaryotes ruled the planet. Then around 700 million years ago during Snowball Earth — a geologic era when glaciers may have stretched as far as the equator — a new creature burst into existence: the multicellular organism.
Why did multicellularity arise? Solving that mystery may help pinpoint life on other planets and explain the vast diversity and complexity seen on Earth today, from sea sponges to redwoods to human society.
Common wisdom holds that oxygen levels had to hit a certain threshold for single cells to form multicellular colonies. But the oxygen story doesn’t fully explain why multicellular ancestors of animals, plants, and fungi appeared simultaneously, and why the transition to multicellularity took more than 1 billion years.
A new paper in Proceedings of the Royal Society B shows how specific physical conditions of Snowball Earth — especially ocean viscosity and resource deprivation — could have driven eukaryotes to turn multicellular.
“It seems almost counterintuitive that these really harsh conditions, this frozen planet, could actually select for larger, more complex organisms, rather than causing species to go extinct or reduce in size,” says former SFI Undergraduate Complexity Researcher William Crockett, corresponding author on the paper and Ph.D. student at MIT.
Using scaling theories, the authors found that a hypothetical early animal ancestor (reminiscent of swimming algae that eat prey instead of photosynthesizing) would swell in size and complexity under Snowball Earth pressures. By contrast, a single-celled organism that moves and feeds via diffusion, like a bacterium, would grow smaller.
“The world is different after Snowball Earth because there’s a new form of life on the planet. One of the central questions of evolution is how do you go from nothing on a planet to things like us, and to societies? Is all of that an accident? We think it’s not luck: there are ways to predict these major transitions,” says senior author and SFI Professor Christopher Kempes.
The study shows how the iced-over oceans during Snowball Earth would have blocked sunlight, reducing photosynthesis and thus draining the sea of nutrients. Bigger organisms that processed more water had a better chance of eating enough to survive. Once the glaciers melted, these larger organisms could expand further.
The model reflects the latest paleontological research, building on work by two additional co-authors, former SFI Omidyar Postdoctoral Fellow Jack Shaw and Carl Simpson, a scientist at the University of Colorado, Boulder.
“Our study offers hypotheses of ancestor organism features to hunt for in the fossil record,” says Crockett.
The paper also presents new tools for investigating physical effects on organism physiology, a boon for future research.
“We provide a useful framework for people to interpret Earth’s past, understand modern ecology, and study organism physiology in the lab,” says Kempes.
This material is based upon work supported by the National Science Foundation under Award No.(1745355).
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The Santa Fe Institute is an independent, nonprofit theoretical research institute located in Santa Fe NM and dedicated to the multidisciplinary study of the fundamental principles of complex adaptive systems, including physical, computational, biological, and social systems. The Institute is ranked very high among the world’s Top Science and Technology Think Tanks and among the world’s Best Transdisciplinary Research Think Tanks according to the Global Go To Think Tank Index Reports, published annually by the University of Pennsylvania.
The Institute consists of a small number of resident faculty and postdoctoral researchers, a large group of external faculty whose primary appointments are at other institutions, and a number of visiting scholars. The Institute is advised by a group of eminent scholars, including several Nobel Prize-winning scientists. Although theoretical scientific research is the Institute’s primary focus, it also runs several popular summer schools on complex systems, along with other educational and outreach programs aimed at students ranging from middle school up through graduate school.
The Institute’s annual funding comes from a combination of private donors, grant-making foundations, government science agencies, and companies affiliated with its business network.
The Santa Fe Institute was founded in 1984 by scientists George Cowan; David Pines; Stirling Colgate; Murray Gell-Mann; Nick Metropolis; Herb Anderson; Peter A. Carruthers; and Richard Slansky. All but Pines and Gell-Mann were scientists with The DOE’s Los Alamos National Laboratory. Originally called the “Rio Grande Institute”, the scientists sought a forum to conduct theoretical research outside the traditional disciplinary boundaries of academic departments and government agency science budgets.
The Santa Fe Institute’s original mission was to disseminate the notion of a new interdisciplinary research area called “complexity theory’ or simply “complex systems”. This new effort was intended to provide an alternative to the increasing specialization the founders observed in science by focusing on synthesis across disciplines. As the idea of interdisciplinary science increased in popularity, a number of independent institutes and departments emerged whose focus emphasized similar goals.
The Santa Fe Institute was created to be a visiting institution, with no permanent or tenured positions, a small group of resident faculty and postdoctoral researchers, a large visitors program, and a larger group of external faculty affiliated with the Institute but located at other institutions. The motivation of this structure was to encourage active turnover in ideas and people, allowing the research to remain on the cutting edge of interdisciplinary science. Today, the Santa Fe Institute continues to follow this organizational model.
The Institute is composed of several distinct groups. The resident faculty are researchers whose primary appointment is at the Institute. Along with the Omidyar Fellows, a group of postdoctoral scholars in residence, the resident faculty makes up the majority of the researchers physically present at the Institute. The external faculty is a group of roughly 100 affiliated researchers whose primary appointments are at other institutions, typically universities. These individuals form a large and distributed community of scholars who frequently visit the Institute and contribute to its overall research program. The Institute’s Business Network is a group of private companies and government agencies interested in complex systems research. Members of the business network often send representatives to Institute meetings or to serve as research fellows in residence at the Institute. The Institute’s Science Board is a large group of eminent scholars who advise the Institute on important strategic matters. This group includes a number of Nobel Prize winners.
The Institute is headed by a president, and a Vice President for Science. It is governed by a Board of Trustees.
Research
Research at the Institute focuses on systems commonly described as “complex adaptive systems” or simply “complex systems”. Recent research has included studies of evolutionary computation; metabolic and ecological scaling laws; the fundamental properties of cities; the evolutionary diversification of viral strains; the interactions and conflicts of primate social groups; the history of languages; the structure and dynamics of species interactions including food webs; the dynamics of financial markets; and the emergence of hierarchy and cooperation in the human species; and biological and technological innovation.
Historically researchers affiliated with the Institute played roles to varying degrees in the development and use of methods for studying complex systems including agent-based modeling; network theory; computational immunology; the physics of financial markets; genetic algorithms; the physics of computation; and machine learning.
The Institute also studies foundational topics in the physics and mathematics of complex systems using tools from related disciplines such as information theory; combinatorics; computational complexity theory; and condensed matter physics. Recent research in this area has included studies of phase transitions in NP-hard problems.
Some of the Institute’s accomplishments include:
Complexity research which led to efforts to create artificial life modeling real organisms and ecosystems in the 1980s and 1990s.
Foundational contributions to the field of chaos theory.
Foundational contributions to the field of genetic algorithms.
Foundational contributions to the complexity economics school of thought.
Foundational contributions to the field of econophysics.
Foundational contributions to the field of complex networks.
Foundational contributions to the field of systems biology.
“Evolution of Human Languages” project, an attempt to trace all human language to a common ancestor (Proto-Human language).