Evolutionary biology

Wednesday, May 17, 2006

Stand up for evolution

You may be interested in this recent free Evolution & Development editorial, an excerpt from which follows:

There have been many reports in the press of attempts in small American towns and in states like Pennsylvania to force the teaching of an alternative to evolution in public school biology classes. Efforts to promote creationism are hardly new in US public education. However, creationists have expanded the scope of their activities even further. The refusals of IMAX theaters in public science museums to show science documentaries that take an evolutionary position is something new, as is the sale of a book in National Park bookshops that presents a creationist interpretation of the Grand Canyon as formed in Noah’s flood. There are also a couple of important novel occurrences that indicate that creationism is being more aggressively pushed. These may come to impact not only science teaching in public schools, but even in the universities, which have till now remained relatively immune…

Friday, December 16, 2005

Haplotype blocks and the punctuated equilibrium

I've just "come back" (yes, it was in Edinburgh) from PopGroup 2005, where Gil McVean presented results indicating that recombination happens mostly just before and after genes, but rarely within genes.

Nick Barton commented to the effect that this had implications for theories about the evolution of recombination; specifically (if I may extend the thought), it is clear that clonal interference will act within genes, so that only one nucleotide substitution can become fixed "at a time" (where "at a time" assumes that the time scale of fixation of alleles is small relative to the timescale over which mutation is likely to produce a second mutation within the haplotype block; essentially, this assumes a reasonably small population, somewhat less probably than typical microcosm populations).

The theory of punctuated equilibrium posits that there are brief periods in the evolution of a species where the equilibrium (eqm) of expression and enzyme activity levels is broken by usually a single nucleotide substitution, which triggers a cascade of substitutions by selection at other loci, until the system returns close enough to an eqm. The recombination data would suggest that reattainment of equilibrium will take much longer if several simultaneous changes in the coding sequence of a single gene are required. It would seem to me that this makes the punctuated equilibrium a less plausible explanation than it previously was.

Friday, September 30, 2005

Lamarck, Waddington and maternal effects

On the centenary of Conrad Hal Waddington's birth, the spotlight has once again come on his attempts in the 1950s to demonstrate inheritance of acquired characters, which he perceived to have given rise to certain callouses in ostrich embryos that could otherwise be caused by aspects of the ostrich's lifestyle. Waddington once remarked that the harshness with which most biologists reject Lamarck's ideas seemed unjustified given his contributions to biology.

Today, I suppose we would talk about the inheritance of acquired characters as maternal effects...

Date of original post on braintickle.blogspot.com: 9/19/2005

Famous evolutionary biologists

Ernst Mayr, deceased 3 February 2005
John Maynard Smith, deceased 19 April 2004
Douglas Falconer, deceased 23 February 2004
Stephen Jay Gould, deceased 20 May 2002
Bill Hamilton, deceased 7 March 2000

Even though I arrived in Oxford before Hamilton died, and in Edinburgh before Falconer did, I never met either of them. I did hear Stephen Jay Gould on a guest lecture in Oxford, although I'd have to admit to not being a particular fan. (Although, coming from Oxford, that is very conformist!)

Date of original post on braintickle.blogspot.com: 5/01/2005