Convergent evolution

[Galapagos]

Convergent evolution refers to the phenomenon of similar traits evolving in unrelated lineages.

Why would unrelated, geographically isolated organisms evolve similar adaptations? This often occurs when organisms fill the same ecological niche, or are faced by the same selective pressures.

 

The Thyacline, or marsupial wolf, and the placental wolf occupied similar adaptive zones, or ecological niches, and although separated by continents and oceans, evolved almost identical adaptation. Anatomy students have a difficult time telling the difference between the skeletons of these two lineages, as they are that similar:

 

Another popular example of convergence is one involving the marine reptiles known as Icthyosaurs and modern dolphins. This case is remarkable in two ways that are different than the thyacline-wolf relationship. Dolphins and Icthyosaurs are separated by both class and history; Thyacline and the wolf both belong to the class Mammalia and have actually existed on the Earth together. The overbearing force of selection does not age and does not care for phylogenetic relations(or anything, for that matter); populations are blindly culled, driving evolution along without concern for patterns of convergence or divergence.

 

A case more remarkable than those previously mentioned- more so than others because of the number of species converging on the same adaptations- is that between the giant armadillo in North America, the giant pangolin of Central Africa, the giant anteater of South America, and the Echidnas in Oceana. All make use of probing, sensitive snouts to exploit the colonies of eusocial insects for nourishment. As similar as they look, the lineages diverged at least 150 million years ago and all occupy entirely different continents-- the similarity is due to convergence.

 

A quick google search turned up a few results containing charts highlighting convergence by comparing analogouscharacteristics of various marsupials and placental mammals. These just offer a good opportunity for broad visual comparison, and are thus worthy of mention :

Marsupial-placental convergence

http://www.gwu.edu/~darwin/BiSc150/Species/convergent2.GIF

 

Convergence illustrates quite well the power of selection and elucidates the role played by the environment and ecological niches in evolution. Natural selection adapts organisms to survive best in their environments, and geographically and temporally distant environments often present similar ways in which organisms can make a living.

Convergence is easily one of the most interesting topics in evolution, and certainly one deserving of its own thread. There is a list on wikipedia of examples of convergence that is surprisingly extensive, so you can see that only a handfull of typical textbook examples have been dealt with here. There is still much more to be said on this subject, and many more examples that can be explored.

Use this thread to post questions, comments, or just interesting/favored examples of convergent evolution! :)

[Moontanman]

Convergent evolution refers to the phenomenon of similar traits evolving in unrelated lineages.

Why would unrelated, geographically isolated organisms evolve similar adaptations? This often occurs when organisms fill the same ecological niche, or are faced by the same selective pressures.

 

The Thyacline, or marsupial wolf, and the placental wolf occupied similar adaptive zones, or ecological niches, and although separated by continents and oceans, evolved almost identical adaptation. Anatomy students have a difficult time telling the difference between the skeletons of these two lineages, as they are that similar:

 

Another popular example of convergence is one involving the marine reptiles known as Icthyosaurs and modern dolphins. This case is remarkable in two ways that are different than the thyacline-wolf relationship. Dolphins and Icthyosaurs are separated by both class and history; Thyacline and the wolf both belong to the class Mammalia and have actually existed on the Earth together. The overbearing force of selection does not age and does not care for phylogenetic relations(or anything, for that matter); populations are blindly culled, driving evolution along without concern for patterns of convergence or divergence.

 

A case more remarkable than those previously mentioned- more so than others because of the number of species converging on the same adaptations- is that between the giant armadillo in North America, the giant pangolin of Central Africa, the giant anteater of South America, and the Echidnas in Oceana. All make use of probing, sensitive snouts to exploit the colonies of eusocial insects for nourishment. As similar as they look, the lineages diverged at least 150 million years ago and all occupy entirely different continents-- the similarity is due to convergence.

 

A quick google search turned up a few results containing charts highlighting convergence by comparing analogouscharacteristics of various marsupials and placental mammals. These just offer a good opportunity for broad visual comparison, and are thus worthy of mention :

Marsupial-placental convergence

http://www.gwu.edu/~darwin/BiSc150/Species/convergent2.GIF

 

Convergence illustrates quite well the power of selection and elucidates the role played by the environment and ecological niches in evolution. Natural selection adapts organisms to survive best in their environments, and geographically and temporally distant environments often present similar ways in which organisms can make a living.

Convergence is easily one of the most interesting topics in evolution, and certainly one deserving of its own thread. There is a list on wikipedia of examples of convergence that is surprisingly extensive, so you can see that only a handfull of typical textbook examples have been dealt with here. There is still much more to be said on this subject, and many more examples that can be explored.

Use this thread to post questions, comments, or just interesting/favored examples of convergent evolution! :)

 

Convergent evolution is another example of how powerful evolution by natural selection really is. When animals are molded by similar environmental pressures similar animals occur. I have often wondered if this convergent evolution could mean that technological beings like ourselves might look a lot like us even if they come from other planets? I am of course talking about general body shape and not an exact match.

[Eclogite]

I have often wondered if this convergent evolution could mean that technological beings like ourselves might look a lot like us even if they come from other planets? I am of course talking about general body shape and not an exact match.

You may wish to explore the work of Simon Conway Morris. He disagrees quite strongly with Gould's view that if the 'tape of life is replayed' it will turn out quite differently.

I recall his comments from a documentary that a bipedal organism with manipulative extensions and a central nevrous system housed atop the rest of the body, along with an array of primary sensors.

I've probably quite distorted his comments, so all criticisms should be heaped on me and not Conway Morris.