There an article in this month’s Nature examining the statistical evidence for universal common descent. This is the first time someone has taken the massive amounts of genetic data and applied a Bayesian analysis to determine whether the existence of a universal common ancestor is the best model. Most of what we generally think of as evidence for evolution and shared ancestry is evidence for shared ancestry of large collections, such as mammals or birds, or for smaller groups. Some of the evidence is for common ancestry for a phylum. There is prior evidence for their shared ancestry based on primitive fossils and on the shared genetic code and extreme similarity of genomes across very different species. This is the first paper to make that last argument mathematically rigorous. When taken in this fashion, the paper more or less concludes that a Bayesian analysis using just the genetic and phylogenetic known data puts the universal common ancestor model as overwhelmingly more likely than other models. (The article is behind a paywall so until I get back to the university tomorrow I won’t be able to comment on this in any substantial detail but this looks pretty cool and a good example how careful Bayesianism can help make something more precise).
Ok. Reading the paper now. Some aspects are bit technical and so I don’t follow all of the arguments or genetic claims other than at a broad level. However, the money quote is “Therefore, UCA is at least 10^2,860 times more probable than the closest competing hypothesis.” (I’ve replaced the superscript with a ^ becaause I don’t know how to format superscripts). 10^2860 is a very big number.
They have hypotheses concerning whether Eukarya, Archaea and Bacteria share a common ancestor or not, or possibly in pairs. All hypotheses were given equal prior likelyhood.
As I said, I haven’t had a chance to actually read the article itself, but as I understand it, this would indicate a universal common ancestor group of nearly genetically identical organisms. While there is suspicion that horizontal gene transfer was more common in the past than it is now, this supports the general narrative of all life arising from a single organism. These sorts of techniques won’t distinguish between that and life arising from several genetically identical organisms.
There an article in this month’s Nature examining the statistical evidence for universal common descent. This is the first time someone has taken the massive amounts of genetic data and applied a Bayesian analysis to determine whether the existence of a universal common ancestor is the best model. Most of what we generally think of as evidence for evolution and shared ancestry is evidence for shared ancestry of large collections, such as mammals or birds, or for smaller groups. Some of the evidence is for common ancestry for a phylum. There is prior evidence for their shared ancestry based on primitive fossils and on the shared genetic code and extreme similarity of genomes across very different species. This is the first paper to make that last argument mathematically rigorous. When taken in this fashion, the paper more or less concludes that a Bayesian analysis using just the genetic and phylogenetic known data puts the universal common ancestor model as overwhelmingly more likely than other models. (The article is behind a paywall so until I get back to the university tomorrow I won’t be able to comment on this in any substantial detail but this looks pretty cool and a good example how careful Bayesianism can help make something more precise).
Ok. Reading the paper now. Some aspects are bit technical and so I don’t follow all of the arguments or genetic claims other than at a broad level. However, the money quote is “Therefore, UCA is at least 10^2,860 times more probable than the closest competing hypothesis.” (I’ve replaced the superscript with a ^ becaause I don’t know how to format superscripts). 10^2860 is a very big number.
What were they using for prior probabilities for the various candidate hypotheses? Uniform? Some form of complexity weighting? Other?
They have hypotheses concerning whether Eukarya, Archaea and Bacteria share a common ancestor or not, or possibly in pairs. All hypotheses were given equal prior likelyhood.
I take it “a universal common ancestor” doesn’t mean a universal common ancestor, but means a universal common ancestral group?
As I said, I haven’t had a chance to actually read the article itself, but as I understand it, this would indicate a universal common ancestor group of nearly genetically identical organisms. While there is suspicion that horizontal gene transfer was more common in the past than it is now, this supports the general narrative of all life arising from a single organism. These sorts of techniques won’t distinguish between that and life arising from several genetically identical organisms.