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The Five Laws of Palaeobiology

      An interesting paper came across my desk this past week, authored by Charles Marshall and published in Nature Ecology & Evolution. Marshall notes that the foundational doctrines of most scientific disciplines can be expressed as simple laws, and that although the science of palaeobiology has provided key insights into matters of evolutionary ecology and biology, these have yet to be condensed into memorable law-like statements. Doing so, Marshall argues, is essential, for the insights offered by palaeobiology are unique, and cannot be gleaned from the study of living taxa alone; establishing so-called ‘laws of palaeobiology’ can therefore guide current evolutionary ecologists and biologists (even those with no experience with the fossil record) in their thinking. (This was also the rallying cry of Stephen J. Gould, who expressed himself similarly in 1980.) With that in mind, Marshall offered the following five laws for consideration:
  1. Lineages become extinct. Cuvier is often credited as having ‘discovered’ the reality of extinction based on his evaluation of fossil mammoths, but there’s little doubt about the matter just from observing the rapid disappearance of present-day wildlife. Even so, it’s only through the benefit of the fossil record that we can see that entire lineages can and have gone extinct (and not just a few isolated twigs at the ends of them).
  2. From the perspective of geological time, species are short-lived. Given the sweeping amount of time that life has been on the planet (some 4.3 billion years, according to recent estimates), it therefore follows that living taxa represent only a small fraction of all life that ever existed.
  3. On average, species come into being (originate) about as quickly as they go extinct. Marshall points out that estimation of origination rates for a particular lineage, based on the consideration of living taxa alone, are far too low, and that, once past extinctions are taken into account, origination rate estimates can increase more than fourfold.
  4. Changes in species richness (that is, the number of species) over time reflect changes in species origination and extinction rates. Richness models where origination and extinction rates aren’t allowed to vary with time almost certainly don’t reflect reality.
  5. Extinction erases the history of a lineage. That is to say, the rich multitude of forms within a lineage cannot be inferred simply from looking at the living descendants. Only through the finding of feathered non-avian dinosaurs could we understand that feathers are not unique to birds, for example.

      Are Marshall’s five laws exhaustive? (Not that he claims they are.) Could any laws be added to the list? Please comment below!
Posted by Jordan Mallon, Canadian Museum of Nature

Literature cited

Gould, S. J. 1980. The promise of paleobiology as a nomothetic, evolutionary discipline. Paleobiology 6:96-118.

Marshall, C. R. 2017. Five palaeobiological laws needed to understand the evolution of the living biota. Nature Ecology and Evolution 1:0165. DOI: 10.1038/s41559-017-0165.
Posted: 6/5/2017 10:49:48 AM by mallonjordanadmin | with 0 comments
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