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February 20, 2009

20 February 2009

Here are some links to some papers that looked interesting this week. I hope I will have time to write about one of them this weekend.

Market forces affect patterns of polygyny in Uganda

Harmonic Convergence in the Love Songs of the Dengue Vector Mosquito

Monoamine oxidase A gene (MAOA) predicts behavioral aggression following provocation

A “crown of thorns” is an inducible defense that protects Daphnia against an ancient predator

The feeding biomechanics and dietary ecology of Australopithecus africanus

Isotopic Evidence for an Aerobic Nitrogen Cycle in the Latest Archean

Risk assessment in man and mouse

Duplicate genes increase expression diversity in closely related species and allopolyploids

February 12, 2009

Happy 200th birthday, Charles Darwin!

Imagine a world in which senescence is eliminated, so that death rates do not increase with age but remain throughout life at the level for eighteen-year-olds, that is, about one per thousand per year. Some people would still die at all ages, but half the population would live to age 693, and more than 13 percent would live to age 2000!" -- Nesse and Williams (1994) Why we get sick: the new science of Darwinian medicine
Although Darwin's ideas are increasingly influential (at least among scientists), Darwin himself is dead. In a world without senescence, he might still be alive. In The dawn of Darwinian medicine. Q. Rev. Biol. 66, 1-22 (1991), Williams and Nesse offered the standard evolutionary explanation for aging:
Because the force of natural selection is stronger at earlier ages to which larger numbers survive, a gene that causes substantial morbidity and mortality during the tail end of the expected life span in the wild may nonetheless be favored if it has even minor earlier benefits.
The most important of these "earlier benefits" appears to be more reproduction earlier in life. One of my students came up with some interesting ideas about the implications of this tradeoff between reproduction and longevity, which I will discuss here once our paper is published.

February 11, 2009

Cake for Darwin Day

Two layers in contrasting colors represent different geological strata. Nuts mixed into the layers represent fossils: sliced almonds went extinct, leaving no descendants, but chopped pecans survived and speciated, sharing the upper stratum with their sister species, black walnuts. I decorated with a simple version of the "I think" evolutionary tree from Darwin's notebook.


February 7, 2009

Happy Darwin Day!

Several of us are meeting for dinner tonight in honor of Darwin's 200th birthday, February 12. Our hostess suggested bringing a favorite Darwin quote. It's hard to choose! Here are some I'm considering:

I have invariably found that our knowledge, imperfect though it be, of variation under domestication, afforded the best and safest clue. I may venture to express my conviction of the high value of such studies, although they have been very commonly neglected by naturalists.

...variations, however slight and from what ever cause proceeding, if they be in any degree profitable to the individuals of a species, in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by the offspring. I called this principle, but which each slight variation, if useful, is preserved, by the term Natural Selection, in order to mark its relation to Man's power of selection.

We have seen that man by selection can certainly produce great results, and can adapt organic beings to his own uses, through the accumulation of slight but useful variations, given to him by the hand of Nature. But Natural Selection, we shall hereafter see, is a power incessantly ready for action, and is as immeasurably superior to man's feeble efforts, as the works of Nature are to those of Art.

If it profit a plant to have its seeds more and more widely disseminated by the wind, I can see no greater difficulty in this being effected through natural selection, than in the cotton-planter increasing and improving by selection the down in the pods on his cotton-trees.

As more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with another of the same species, or with the individuals of distinct species, or with the physical conditions of life. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for this case there can be no artificial increase of food, and no prudential restraint from marriage.

That climate acts in main part indirectly by favoring other species, we clearly see in the prodigious number of plants which in our gardens can perfectly well endure our climate, but which never become naturalized, for they cannot compete with our native plants nor resist destruction by our native animals.

Look at a plant in the midst of its range, why does it not double or quadruple its numbers? We know it can perfectly well withstand a little more heat or cold, dampness or dryness, for elsewhere it ranges into slightly hotter or colder, damper or drier districts. In this case we can clearly see that if we wish in imagination to give the plant the power of increasing in number, we should have to give it some advantage over its competitors, or over the animals which prey on it.

What natural selection cannot do, is to modify the structure of one species, without giving it any advantage, for the good of another species; and though statements to this effect may be found in works of natural history, I cannot find one case which will bear investigation.

There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.