Parasites and Social Behaviour

I am currently reading Volume 3 of Narrow Roads of Gene Land, The Collected Papers of W. D. Hamilton (Oxford University Press, 2005).  Today I came across the following:

...  To my mind, parasites and their effect on the health of hosts, in every sense from death to dominance-hierarchy, have great consequences in every aspect of life.  ...

...  Parasites are why there is sexuality and, proceeding from this, they underly also the construction of social behaviour.  ...

These are both from a book review originally published as W.D. Hamilton, J. Appl. Ecol. 32(3), 451-453 (1995).

Two British Migratory Thrushes

Ornithology is much more interesting when seen through the eyes of Helen Macdonald (Pluvialis):

Two species of thrushes visit Britain in winter. The smaller of the two is the redwing, a jaguar-like, shy, and slightly deranged thrush with devilish eyestripes and a burst of dried-blood rouge on each side. Redwings skulk in hedges and disappear with a thin seeeeep alarm call, and they slink about in the periphery of your vision when they first arrive.

But my favourite arctic thrushes are fieldfares. They're big, bold, patterned and arch. Alternatively, they're grey, fierce and wolfish.They are splendid. You have to use the plural, when talking of fieldfares. They arrive in rattling flocks like gusts of spray or hail. They are noisy when they fly, and their chak-chak-chak call is like someone launching a handful of pebbles on an iced-over pond surface. Chack chack chack: echoey, dopplery, cold.

Programming with Warts

From a post by Bruce Eckel at Artima Forums:

One of the big reasons for my renewed interest in Ruby (besides the features it has that seem to make it a bit easier to create domain-specific languages) is because of Matz's decision to remove the Perlisms in Ruby. Any language (Python is the only other one I know of) that's willing to REMOVE warts (Java just seems to keep adding warts on existing warts) immediately becomes much more interesting in my perception.

Refactoring and simplification can be applied to programming languages as well as to programs.

Symmetry in Mathematics

Mark Dominus describes trying to convince some people that, while i (the square root of minus one) and -i are not equal to each other, they are mathematically indistinguishable:

...  1 has two square roots that are not interchangeable in this way. Suppose someone tells you that a and b are different square roots of 1, and you have to figure out which is which. You can do that, because of the two equations a² = a, b² = b, only one will be true. If it's the former, then a=1 and b=-1; if the latter, then it's the other way around. The point about the square roots of -1 is that there is no corresponding criterion for distinguishing the two roots. This is a theorem.  ...

What struck me about Mark's account was that failed to mention that this a symmetry and that symmetries such as this one are important in abstract algebra.

An Ice House in Reading University Grounds

On Sunday afternoon Zoe and I were taking a short cut through some bushes in the grounds of Reading University when we came across an overgrown entrance to an ice house.  Even though I have lived near Reading University for 15 years and go for walks in the grounds most weekends, I am still discovering things there.

More photos of the ice house and details of its location can be found here, here, here and here.