Rates of species extinction/evolution

Dec 21, 2012

Discussion by: OskarGonzalez
I have heard of figures that state that X number of species go extinct everyday or year. I can imagine people researching extinction rates with organism on the endangered species list, but I have never seen any mention of the emergence rate of new species. Is this something that in known in the field of evolutionary biology? Have there been comparisons between these two rates?

I am a molecular biologist just recently educating myself with a comprehensive understanding of evolution.

5 comments on “Rates of species extinction/evolution

  • 1
    SaganTheCat says:

    i think the problem with trying to record emergence of new species is the timescale. within the lifetime of an ape, you can’t be certain a new species is splitting off (other than in certain lab conditions such as Lenski’s e-coli experiment).

    maybe in a few million years time, the intelligent earth species (some sort of cat i imagine) might look back at the record of new species and be able to mathematically equate that to a number emerging per year but in reality emergence can only be measured retrospectively. any 2 of my siblings (if any got away with their bits intact) could become the ancestors of two distinct species in time. genetically speaking, our parents would be the point of the split but it would take thousands or even hundreds of thousands of years to assertain that as the two lines could not be considered distinct species until conditions arise that ensure they are unable to interbreed with no loss of viability.

    extinction on the other hand is easy to monitor. when it’s gone it’s gone and you can record the very moment a species goes extinct if you’re confident you’re watching the last one die. examples being Benjamin the thylacine and Lonsome George the giant pinta tortoise. so basically it takes millions or even billions of individuals to be born to be sure of a species emerging but only one to die to be sure of extinction

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  • 2
    Alan4discussion says:

    Except where new species are created as cultivars or in lab experiments, it is unlikely on a normal human time-scale,  to see the division happen as clumps of genetic diversity go their separate ways.  There are already classifications within genetic diversity, of species, sub-species and varieties, with much debate over classification systems. 
    Regional variations in species are already documented. 

    Bearing in mind ALL species are intermediate forms as life continues to evolve. This is  illustrated in examples such as ring species. http://rationalwiki.org/wiki/R
    The geographical separation developing speciation, is illustrated here: – http://rationalwiki.org/wiki/F

    There are of course new previously unknown species being DISCOVERED in remote places.

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  • 3
    FrankMill says:

    It’s important to understand that a ‘species’ is a man-made concept and there are lots of different definitions of what constitutes a species.  For the ones that interest most people — the big, furry things — the usual basis of a species definition is of an organism that cannot mate with another species and produce fertile offspring.  This works pretty well for big furry things (though see Richard Dawkins’s books about ring species) and it’s the reason we regard different breeds of dogs as the same species.  But when entomologists shake out all the insects in a square metre of somewhere and say they’ve found x species in the sample, they’re not testing the bugs they find for their ability to mate, they’re using the ‘morphospecies’ approach — the bugs look different from each other — which means they’d see chihuahuas as a different species from St Bernards.  (Maybe they have a point, in practical terms!).

    I’m a microbiologist, and in the worlds of bacteriology and mycology, species definitions are particularly difficult when the little critters don’t mate.  So I can assure you that, in the world of the very small, species are being split off by taxonomists and redefined at a rate that equals or exceeds the loss of animal species that so concerns those without microscopes.  Evolution as a mechanism generates a continuum of living forms: read Richard Dawkins’s Ancestor’s Tale for detail.  Species are the result of Homo sapiens erecting boundaries on that continuum.  It’s an exercise with benefits for understanding behaviours of related organisms, but also with a downside for the environmentally sensitive who elevate a species to a level of sacrosanct inviolability that may not really be justified.

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  • Many questions about evolution are dependent upon the employment of the Linnaean System: basically Kingdom, Phylum, Class, Order, Family, Genus, Species. Most biologists are quite comfortable with this classification system, but does it describe accurately groups of organisms alive today and in the past. The answer is “no”. There is no such thing as a species, it is an arbitrary label given to a group of organisms alive today that can interbreed, (in addition to other criteria), and for extinct animals we infer from a limited pool or individuals that all members of that group of organisms shared particular anatomical similarities that make them distinct from other groups of extinct organisms. This system presupposes sustainability within a population, and of course that is nonsense. Sustainability, in this case, entails genetic sustainability. (See: Evolutionary Dynamics of a Natural Population, by the Grants).

    Further, the Linnaean System is not a causally based system. That means by carefully pealing through the Super-Orders, and the Sub-Families, the investigator will not arrive at any deeper understanding than at present there are some animals that have arbitrary relationships.The system in unable to relate a cause of the arbitrary relationships. Cladograms are better, as they entail a cause, (be it known or unknown), at a particular point in time, but certainly not adequate. 

    So what about new “species”. Well, molecular biologists have discovered new “resistant” strains of bacteria. In other words bacteria have experienced evolution through mutation, natural selection, and genetic drift. So how can the Linnaean System express these new species? There is no mechanism present in that system beyond using a pencil to write in a new species name or subspecies name. Then what about the old species, how does the system express extinction, or diversification? 

    But what about new animal species? Well, due to rapid climate change polar bears are making inroads to meet brown bears – and interbreeding has been the result. It is quite possibly that a new “species” of bear will be “created” as a result of rapid climate change. But, again, according to the Linnaean system, the production of viable and non-sterile offspring between two distinct species should not occur – yet it does.

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