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Category: Genetics

How many species concepts are there?

[cop13_species.jpgNote: This is a piece I wrote for Grrlscientist’s blog at the Guardian, Punctuated Equilibrium. I post it here for purposes of record. Please make comments at Grrl’s blog.]

It’s an old question in biology: what is a species? Many answers have been given over the years – I counted 26 in play, and recently a new one, the “polyphasic” concept (basically a consilience of many lines of evidence) has been introduced in bacterial and other microbial contexts, and which may apply to macrobial species too.

But on another count (where I asterisked what I thought were independent concepts in that list) there are 7 species concepts: agamospecies (asexuals), biospecies (reproductively isolated sexual species), ecospecies (ecological niche occupiers), evolutionary species (evolving lineages), genetic species (common gene pool), morphospecies (species defined by their form, or phenotypes), and taxonomic species (whatever a taxonomist calls a species).

So, to sound a bit like Chicago, 26 to 7, or 7.

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Testing universal common ancestry

A long time ago, a young graduate student wandered into the festering cesspool of creationists and evolutionists known as talk.origins and offered to write a FAQ (Frequently Asked Questions page) on whether or not macroevolution and common descent were supported by evidence. I had previously published a philosophical treatment of Macroevolution for that site’s Archive, but this guy, Douglas Theobald, being a scientist, had to attend to actual evidence, and so he wrote the excellent “29 Evidences for Macroevolution” FAQ. It’s a pretty solid piece of work.

Now a biochemist at Brandeis University, Doug has published a full test of the hypothesis of Universal Common Ancestry (UCA) in no less than Nature. And I get thanked in the Acknowledgements. A philosopher has arrived when he gets mentioned in Nature, but for a scientist to be published there is the Holy Grail. I am glad to have had a (very) minor role in this. Nick Matzke, who also commented on the draft, has a roundup here at Panda’s Thumb.

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Thermodynamics, and the origin of replicators

Over at Discover, Sean Carroll has a nice post on thermodynamics, free energy and the origins of life. It’s a good intro, but in the course of it he remarks:

Obviously there is a lot missing to this story, and much of it is an absence of complete understanding on my part, although some of it is that we simply don’t know everything about life as yet. For one thing, even if you are a metabolism-first sympathizer, at some point you have to explain the origin of replication and information processing, which plays a crucial role how we think about life.

Well, now, that is a red rag to an information-eliminativist, isn’t it? How could replicators and information processing evolve from a “metabolism first” account of the origins of life? The answer to that is exactly what Carroll is extolling: thermodynamics.

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