Punctuated Equilibrium – The Relatively New Theory of Evolution Invented by Tiny Snails in Bermuda
Well, actually, it was Stephen Jay Gould, of Harvard University, and a colleague of his – Niles Eldredge of the AMNH in New York. But it’s commonly believed that a group of tiny Bermudian snails secretly whispered it into Gould’s ear one day (just kidding). You have a choice: see more about this theory in the vlog above by Barnas of THL/MisterScienceFair, or continue to read the blog below – or both.
Punctuated equilibrium is a theory that says animals evolve rapidly in new environments. It’s similar to the work of Charles Darwin (and of course 1800′s British paleontologist Mary Anning, who did not receive much credit for her work, described in THL’s The Furious Case of the Fraudulent Fossil - link below), which states that animals will adapt to new conditions, based on random mutations. However, Stephen Jay Gould believed that it could occur in much faster spurts, in geologically speaking, very short periods of time. There were periods in time, when there were large numbers of species evolving, and they were generally times after something catastrophic or significant happened. That’s why you can find 15 species of Bermuda land snail fossils in a relatively short geological timeframe of only a few hundred thousand years.
Back when Dr. Gould was a young student in the late 1950′s, he was a deckhand for the Woods Hole Oceanographic Institute, based in Massachusetts, which ended up taking him on a research trip to Bermuda. He had already done some studies on Gastropods (snails and related creatures), and noticed various living and fossilized snails while he was there. It turned out at that time there was a single very abundant species of snail, Poecilozontes bermudensis, which could be found all over the island (there were also other species too, including P. nelsoni and P. renianus). This snail was so ubiquitous, that the they were sometimes collected and burned just for their lime (CaC03).
Well, it turned out that the government felt these snails were too common and may affect crops, so several predatory species of snails were introduced to the island, as well as an edible species. Within just 2 decades, the Bermuda land snail was nearly wiped out, and the new species dominated. Currently, it is believed that three species of snails have gone completely extinct, and only one remains, Poecilozontes circumfirmatus, which is now an endangered species, and may also be extinct soon.
However, based on fossil evidence, this group of animals has likely been on the island for hundreds of thousands of years, very well adapted and relatively stable until the last century. Only man has been the greatest factor in its extinction, by importing new species, both intentionally and accidentally. The amazing thing is that all these snails which evolved there were thought to have been introduced to the island by only 1 or 2 animals clinging to a log or some other floating debris, part way across the Atlantic ocean. Bermuda is so far from mainland North America (2 hours plane right from most places in New England) and in relatively cold water, that it’s quite remarkable to imagine these tiny animals could have survived the journey and filled the entire island with their progeny.
For Stephen Jay Gould at the time, this was a fascinating topic, and he decided to use it for his Ph.D. thesis (not to mention, Bermuda’s not a bad place to do some fully funded graduate science research). Later, this idea “evolved” into a theory known as Punctuated Equilibrium, which was the subject of a number of books written by both Gould and Eldredge. Despite some opposition, this theory is widely recognized for its various merits and is accepted by many in the paleontology and general biology communities.
Stephen Jay Gould remained the Curator of Invertebrate Paleontology at Harvard University’s Museum of Comparative Zoology for many years, and I had the pleasure to speak with him on various occasions, when I worked there during college (although I was working in the vertebrate, not invertebrate department). It was a great honor to work with an amazing thinker, and to all young readers out there, I encourage you to cherish your time with your mentors, because you never know when it may end.
Interestingly enough, I have recently discovered that land snails were also a favorite topic of my great great grandfather, Olof P. Nylander. Olof was Swedish immigrant, who became a well known naturalist in Northern Maine, and later founded the Nylander Museum in Caribou, Maine, which is still in existence today. In fact, he also studied and had a group of land snails named after him — the Vertigo nylanderis. New species are still discovered all the time, and old species once thought extinct can sometimes pop up where you least expect it. It is thought that one extinct group of Bermuda Land Snails may have been recently found, though it’s not verified yet. So, be sure to get out there and look on the ground, in the plants, and keep exploring – there is a possibility you can make another big find, or have a species named after you too.
If you find evolution mysteries interesting, like I do, please read my recently released book: The Furious Case of the Fraudulent Fossil.