Saturday, October 11, 2014

Nature articles on Extended Evolutionary Synthesis and on Top Quark

illustration by R. Craig Albertson
Cichlids from Lake Tanganyika (L) and from Lake Malawi (R)
evolved similar body shapes (see Article)
Two remarkable articles in Nature. One is a Point/Counterpoint on Does evolutionary theory need a rethink? where Kevin Laland, Eva Jablonka and others debate with Gregory Wray and colleagues. This is very much along the lines that Denis Noble has been advocating - and indeed cites his 2014 paper. They contrast Standard Evolutionary Theory (SET) with what they term the Extended Evolutionary Synthesis (EES).
The EES "maintains that important drivers of evolution, ... that cannot be reduced to genes, must be woven into the very fabric of evolutionary theory."  They "hold that organisms are constructed in development, not simply ‘programmed’ to develop by genes. Living things do not evolve to fit into pre-existing environments, but co-construct and coevolve with their environments, in the process changing the structure of ecosystems."

They draw attention to:
  • "how physical development influences the generation of variation (developmental bias);
  • how the environment directly shapes organisms’ traits (plasticity); 
  • how organisms modify environments (niche construction); and 
  • how organisms transmit more than genes across generations (extra-genetic inheritance). 
For SET, these phenomena are just outcomes of evolution. For the EES, they are also causes."  They don't mention Denis Noble's profound ideas about multi-level causality.

Wray and colleagues agree that these phenomena are important but they deny that SET has ossified.  They think that these phenomena "are already well integrated into evolutionary biology, where they have long provided useful insights" and deny that "today’s evolutionary biologists as unwilling to consider ideas that challenge convention." This sits oddly with the furious reaction to Nowak, Tarnita and Wilson for example, and the tenacity with which people affirm the validity of "Inclusive Fitness" and deny the validity of "Group Selection". As Nowak's 2012 JTB article points out:
The idea of group selection has a long and troubled history, but mostly in terms of verbal arguments on both sides. The mathematical theory of evolution clearly shows that group selection is possible provided certain conditions hold. It requires careful examination to determine whether these conditions are met by a particular empirical situation.
The other item I find fascinating in Nature is The mass of a top which is a commentary on a PRL paper V. M. Abazov et al. (D0 Collaboration) "Precision Measurement of the Top Quark Mass in Lepton+Jets Final States" This quark weighs ... amazingly ... 187.85 ± 0.82 atomic units, which is almost as much as a Gold atom. A top quark decays in one trillionth of a pico-second into a Bottom Quark and a W Particle. But the really intriguing aspect is that:
Because of the huge top-quark Yukawa coupling, the fluctuations involving the top quark affect the shape of the Higgs potential (which describes the potential energy of the Higgs field as a function of the field strength). In fact, making the strong assumption that there are no as-yet-undiscovered particles, the Higgs field seems to exist in a local minimum of the potential, which would make the Universe as we know it unstable... the desire to ascertain its ultimate fate is a key reason for accurately determining the top-quark mass: differences of just 5% in this mass make the difference between stability and instability.
I have a feeling - and it's no more at this stage (I haven't had time to read the referenced papers in detail and I almost certainly wouldn't understand them if I did) that this could turn out to relate to the MaxHELP hypothesis.

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