“The fact that all organisms are nearly equally fit has profound implications for the evolution and persistence of life on Earth,” said James H. Brown, a physiological ecologist at the University of New Mexico, referring to a “New Evolutionary Law” proposed by evolutionary theorist and paleobiology pioneer, Leigh Van Valen.
Van Valen argued that evidence from fossil record data shows that the probability of extinction within any group remains essentially constant through time. Van Valen described this phenomenon as “The Red Queen Hypothesis”.
The first hypothesis , which he labeled the law of constant extinction states that the probability of extinction for species and larger evolutionary groups bears no relation to how long it may have already existed. The fossil record, Van Valen argued, shows that lineages become neither more extinction-resistant nor more vulnerable over time.
“To explain this surprising pattern,” reports the University of Chicago, where he was professor emeritus until his death in 2010, Van Valen “proposed the Red Queen hypothesis, a model of co-evolutionary interaction, and one of the most enduring metaphors in modern biology. It holds that the struggle for existence never eases up, so that no species or lineage ever pulls ahead for long. Instead there is a constant arms race among species or larger groups, such as a community of competing lineages or parasites and their hosts. In a world with a fixed amount of energy, each must continually develop new adaptations, weapons or defenses to keep up with the other, a prolonged sequence of mutational one-upmanship.”
Species coevolve with other species
The “Red Queen hypothesis”, writes evolutionary biologist Ricard Sole with the Santa Fe Institute and the Universitat Pompeu Fabra in 2021, “states that the constant decay must be a consequence of evolutionary interactions among connected species within ecological networks. In Van Valen’s picture, species do not merely evolve: they also coevolve with other species. Van Valen’s law provided the first complex systems theory of coevolutionary dynamics and inspired a whole range of theoretical and experimental developments and scholars from very diverse fields, from economics to physics.”
In a 2018 study, a trio of scientists from universities in the United States and the United Kingdom describe the dynamic that began with the origin of life on Earth 4 billion years ago. They report that regardless of vastly different body size, location and life history, most plant, animal and microbial species are equally “fit” in the struggle for existence. This is because each transmits approximately the same amount of energy over its lifetime to produce the next generation of its species.
in 200 or 300 years, the beings that will dominate the Earth will be far more different from us than we are different from Neanderthals or from chimpanzees.
An organism might gain a temporary advantage
“There is no single way of living and using energy that is best,” said the researchers. “Given the array of environmental conditions on the planet, one kind of organism might gain a temporary advantage, but such gains will soon be countered by other, competing organisms. The result is what evolutionary biologist Leigh Van Valen called the ‘Red Queen phenomenon,’ an evolutionary hypothesis based on Lewis Carroll’s Through the Looking Glass: All species must keep running to keep up with others and stay in the evolutionary race.” The hypothesis explains the constant extinction rates observed in the Earth’s paleontological record caused by co-evolution between competing species.
All organisms are equally fit for survival
There are more than 8 million species of living things on Earth, but none of them — from 100-foot blue whales to microscopic bacteria — has an advantage over the others in the universal struggle for existence. The bottom line is that all organisms are, on average, equally fit for survival.
“This means that each elephant or blue whale contributes no more energy per gram of parent to the next generation than a trout or even a bacterium,” said co-author Charles A.S. Hall, a systems ecologist with the College of Environmental Science and Forestry (ESF) in Syracuse, New York. “We found, rather astonishingly, by examining the production rate and the generation time of thousands of plants, animals and microbes that each would pass on, on average, the same amount of energy to the next generation per gram of parent, regardless of size.
A single-celled aquatic alga recreates its own body mass in one day, but lives for only a day. A large female elephant takes years to produce her first baby, and lives much longer than the alga. For all plants and animals of all sizes these two factors – rate of biomass production and generation time – exactly balance each other, so each contributes the same energy per gram of parent to the next generation in their lifetime.”
The scientists tackled an intriguing question about life on the planet, beginning with some common knowledge. On one hand, they noted, microscopic, unicellular bacteria, algae and protists that weigh only a few micrograms live fast, generate much new biomass per day or even per minute, and die young, often within hours. On the other hand, mammals such as a 100-foot blue whale can live up to 100 years but generate new biomass, including babies, much more slowly.
A universal tradeoff
The authors ask a sweeping question: How can such enormous variation in reproduction and survival allow persistence and coexistence of so many species? Their answer: Because there is a universal tradeoff in how organisms acquire, transform and expend energy for survival and production within constraints imposed by physics and biology.
In their research, the authors built a model of energy allocation, based on data involving rates of energy investment in growth and reproduction, generation times (commonly considered 22 to 32 years for humans) and body sizes of hundreds of species ranging from microbes to mammals and trees. They found an exactly equal but opposite relationship between growth rate and generation time among all these organisms.
The net result is what the authors call the “equal fitness paradigm.” Species are nearly equally fit for survival because they all devote the same quantity of energy per unit of body weight to produce offspring in the next generation; the higher activity and shorter life of small organisms is exactly compensated for by the slower activity and greater longevity of large organisms.
Can Homo sapiens escape the tyranny of the equal fitness paradigm?
Hall said the tradeoff between rate of living and generation time is one reason for the great diversity of life on Earth: No one size or life form has a built-in advantage over another. The apparent benefits of being larger (for example, bigger males are more likely to win in competition for mates) are compensated for by the fact that larger animals are typically less productive over time.
Will the intelligence of the human species allow it to escape from the tyranny of the equal fitness paradigm?
No, says Yuval Harari, author of Sapiens and Homo Deus in an podcast interview with Ezra Klein at Vox, “In 300 years Homo sapiens will not be the dominant life form on Earth, if we exist at all. Given the current pace of technological development, it is possible we could destroy ourselves in some ecological or nuclear calamity. The more likely possibility is that we will use bioengineering and machine learning and artificial intelligence either to upgrade ourselves into a totally different kind of being or to create a totally different kind of being that will take over.
“In any case,” says Harari, “in 200 or 300 years, the beings that will dominate the Earth will be far more different from us than we are different from Neanderthals or from chimpanzees.”
The Daily Galaxy, Avi Shporer, Research Scientist, MIT Kavli Institute for Astrophysics and Space Research via Ricard Sole, Revisiting Van Valen’s Red Queen Hypothesis, Vox, and SUNY College of Environmental Science. Avi was formerly a NASA Sagan Fellow at the Jet Propulsion Laboratory (JPL).