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Only the Small Survive

Small fish featured in its natural niche

Small fish featured in its natural niche

With many large species such as giraffes and sharks threatened with extinction, we might not see the likes of them for millions of years.  History has shown that evolution cannot restore large species for tens of millions of years.  Intrigued by this concept, paleontologist Lauren Sallan of the University of Pennsylvania sought to know why small species are able to bounce back much quicker than larger species.  Looking at aquatic life of the Mississippian Period, from 359 to 323 million years ago, she observed that most fish were significantly smaller than their ancestors.  This idea that certain species generally shrink over time is known as the Lilliput Effect, named after an island indigenous to tiny people in Jonathan Swift’s Gulliver’s Travels.  The fossils used in Dr. Sallan’s project fit this description as their ancestors probably perished perished in the deep freeze brought on at the end of the Devonian Period which wiped out an estimated 96 percent of all vertebrates.  However, the Lilliput Effect does not apply to all species.  One species, known as the rhizodontids, included fish that grew to the size of modern day killer whales.  Dr. Sallan concluded that the painfully slow recovery of large species on this planet is due to the ecosystems decimation during mass extinction events.  Although this particular article does not go into depth on why small animals have an easier time “bouncing back” than large ones, Dr. Sallan examined many fossils which prove that creatures shrank dramatically after large-scaled extinctions.  For example, the average size of a shark shrank from about a yard in length to only a mere few inches.  However, later in the article, Dr. Sallan cites her study by saying how smaller vertebrate species produce and diversify more easily contrary to large vertebrate animals dwindling in diversity until species extinction.

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1 Comment

  1. organelle

    This article is super interesting! It really makes me think of all of the incredible species on earth right now, and in the past that are about to/ have gone extinct. Dinosaurs, first of all, have been extinct for millions of years, and to this day we really don’t have any land animal anything like it. I now know why they have not reappeared through the processes of evolution. They were such big animals to begin with. This also makes me think of the dangers of climate change nowadays and how that will affect the development and evolution of certain species and how it will affect the rate of extinction of others. This article I have found really illustrates my concern: Specifically, this article mentions how species in the colder regions of the earth have begun to rapidly decline in numbers. And, many of these species tend to be very large- polar bears, seals, walruses, penguins, and other arctic land mammals.

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