Limits to growth lie at the heart of how all living things function, according to a new study. The diversity of life is staggering. From microscopic algae to elephants, life has devised countless ways to thrive in every environment on the planet. But while biologists have tended to focus on the many varied forms that species have evolved, the age of ‘big data’ offers an unprecedented view of some surprisingly common features shared by all creatures, great and small.
A new paper, published this week in PNAS, brings together data from many thousands of studies to show that underlying the endless variety of living things, many of the most important features of life follow universal laws. The work, led by Ian Hatton at ICTA-UAB in Barcelona, shows how metabolism, abundance, growth and mortality all follow strikingly consistent relationships with body size from the tiniest bacteria to the blue whale.
“The fact that we find these simple mathematical relationships that span all life, points to some fundamental process at the heart of living systems that we don’t yet fully understand,” explains Hatton. …
“What is so astounding is that no matter where you look, no matter what kind of living system, everything seems to follow the same growth law,” says Hatton. “We can’t yet explain it, but we know it has deep implications.” Paper. (open access) – Ian A. Hatton, Andy P. Dobson, David Storch, Eric D. Galbraith, Michel Loreau. Linking scaling laws across eukaryotes. Proceedings of the National Academy of Sciences, 2019; 201900492 DOI: 10.1073/pnas.1900492116 More.
Abstract: Scaling laws relating body mass to species characteristics are among the most universal quantitative patterns in biology. Within major taxonomic groups, the 4 key ecological variables of metabolism, abundance, growth, and mortality are often well described by power laws with exponents near 3/4 or related to that value, a commonality often attributed to biophysical constraints on metabolism. However, metabolic scaling theories remain widely debated, and the links among the 4 variables have never been formally tested across the full domain of eukaryote life, to which prevailing theory applies. Here we present datasets of unprecedented scope to examine these 4 scaling laws across all eukaryotes and link them to test whether their combinations support theoretical expectations. We find that metabolism and abundance scale with body size in a remarkably reciprocal fashion, with exponents near ±3/4 within groups, as expected from metabolic theory, but with exponents near ±1 across all groups. This reciprocal scaling supports “energetic equivalence” across eukaryotes, which hypothesizes that the partitioning of energy in space across species does not vary significantly with body size. In contrast, growth and mortality rates scale similarly both within and across groups, with exponents of ±1/4. These findings are inconsistent with a metabolic basis for growth and mortality scaling across eukaryotes. We propose that rather than limiting growth, metabolism adjusts to the needs of growth within major groups, and that growth dynamics may offer a viable theoretical basis to biological scaling.
They don’t quite say that this is evidence for structuralism. But it sounds like evidence for structuralism.