I have been reading The Ancestor’s Tale by Richard Dawkins. Quite appropriate reading as we are celebrating the 200th birthday of Charles Darwin. In his book Richard Dawkins trail our ancestors back in time and identify those points where we start sharing ancestors with other current species and life forms. It starts with the recent evolution of the human race and our most recent ancestors that we have in common with the apes. I found this quite rich introductory part one of the most interesting parts of the book. And throughout the book it is exciting to realize that there is an unbroken chain of ancestors going from myself and all the way back to the first ancient bacteria on earth!
On the way back in time Dawkins tells different stories – or tales – to clarify and emphasize various scientific points of evolution theory. One of those tales is ‘the Salamanders tale’. The purpose of the salamanders tale is to show how species evolve and how it can be very difficult to tell when one species turns into another. For instance it is quite common to say that if two populations cannot interbreed they belong to two different species. But throughout the development of a new species there isn’t any one point in time where a child population would be so different from its parent population that inter-breeding would cause any physiological challenge. This is neatly exemplified through the story of the Ensatina salamanders of the Central Valley of California, and through the analogous story of the herring gull and the lesser black-backed gull. Both are examples of so called ring species. The herring gull and the lesser black-backed gull live in my neighborhood, and I would like to share their story with you.
The fact is that in Norway (as in Dawkins' England) the herring gull and the lesser black-backed gull live side by side. But they are quite distinctly different species. As can be seen from the picture below they have quite different colors, and though they quite often live side by side they do not interbreed.
But if you follow the population of the herring gull around the world, through North America, Siberia and back to Europe, you will observe that the herring gulls gradually turns more similar to the lesser black-backed gulls until the ring is ended and the herring gull has turned into lesser black-backed gulls and the two 'species' live side by side! All the way around the ring there are no two separate populations but rather interbreeding among populations that gradually changes as you keep going east.
I think this story shows very neatly how new species can evolve, with the normal time dimension replaced by a geographical dimension. Of course there must have been time involved as well. One of the ‘species’ (or rather its ancestor) came first, and evolved over time as it moved east (or west - I really don't know which). Incidentally the herring gull is called “grey gull”, and the lesser black-backed gull is called “herring gull” in Norway. Ignorant of the real facts I am tempted to visualize the British herring gull traveling eastwards all around the globe and evolving into the Norwegian herring gull as it finally reached the shores of Norway. Neat :-)
On the way back in time Dawkins tells different stories – or tales – to clarify and emphasize various scientific points of evolution theory. One of those tales is ‘the Salamanders tale’. The purpose of the salamanders tale is to show how species evolve and how it can be very difficult to tell when one species turns into another. For instance it is quite common to say that if two populations cannot interbreed they belong to two different species. But throughout the development of a new species there isn’t any one point in time where a child population would be so different from its parent population that inter-breeding would cause any physiological challenge. This is neatly exemplified through the story of the Ensatina salamanders of the Central Valley of California, and through the analogous story of the herring gull and the lesser black-backed gull. Both are examples of so called ring species. The herring gull and the lesser black-backed gull live in my neighborhood, and I would like to share their story with you.
The fact is that in Norway (as in Dawkins' England) the herring gull and the lesser black-backed gull live side by side. But they are quite distinctly different species. As can be seen from the picture below they have quite different colors, and though they quite often live side by side they do not interbreed.
But if you follow the population of the herring gull around the world, through North America, Siberia and back to Europe, you will observe that the herring gulls gradually turns more similar to the lesser black-backed gulls until the ring is ended and the herring gull has turned into lesser black-backed gulls and the two 'species' live side by side! All the way around the ring there are no two separate populations but rather interbreeding among populations that gradually changes as you keep going east.
I think this story shows very neatly how new species can evolve, with the normal time dimension replaced by a geographical dimension. Of course there must have been time involved as well. One of the ‘species’ (or rather its ancestor) came first, and evolved over time as it moved east (or west - I really don't know which). Incidentally the herring gull is called “grey gull”, and the lesser black-backed gull is called “herring gull” in Norway. Ignorant of the real facts I am tempted to visualize the British herring gull traveling eastwards all around the globe and evolving into the Norwegian herring gull as it finally reached the shores of Norway. Neat :-)
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Good to see you blogging again.