ORIGIN OF THE SEXES!!!

Running with the Red Queen: Host-Parasite Coevolution Selects for Biparental Sex

Levi T. Morran*, Olivia G. Schmidt, Ian A. Gelarden, Raymond C. Parrish II, Curtis M. Lively

Most organisms reproduce through outcrossing, even though it comes with substantial costs. The Red Queen hypothesis proposes that selection from coevolving pathogens facilitates the persistence of outcrossing despite these costs. We used experimental coevolution to test the Red Queen hypothesis and found that coevolution with a bacterial pathogen (Serratia marcescens) resulted in significantly more outcrossing in mixed mating experimental populations of the nematode Caenorhabditis elegans. Furthermore, we found that coevolution with the pathogen rapidly drove obligately selfing populations to extinction, whereas outcrossing populations persisted through reciprocal coevolution. Thus, consistent with the Red Queen hypothesis, coevolving pathogens can select for biparental sex. 

Science 8 July 2011: Vol. 333 no. 6039 pp. 216-218

Why is this cool?

 If you are like me, sometimes you will stare at someone while they talk and think about something...anything. You may look at their body and wonder if anyone finds them attractive and then you wonder what it means to be attracted. Why is there attraction? Why can't we reproduce without a partner? Why do we need women? Why is love so cruel?

 Today's researcher's may have ideas about the last question, but their work focuses on why two sexes ever evolved.  The abstract states the following "The Red Queen hypothesis proposes that selection from coevolving pathogens facilitates the persistence of outcrossing despite these costs." They tested this with nematodes (Caenorhabditis elegans) which can reproduce asexually or with a mate.  The nematodes were separated into two groups and one was grown in the presence of a pathogenic bacteria (Serratia marcescens) and the other was not.  They found that the bacterially infected nematodes ceased to asexually reproduce and shifted to mating with a partner.

 As a teenager, I often wondered why I yearned for love and that "other." You know, the someone who completes me and boils my thin blood.  I am drawn towards the perfect Her not because I philosophically believe that someone else is necessary, but because my biology is pre-programmed that way. 

 It is startlingly to me that this compulsion for someone else is an evolutionary accident. Great poetry and prose are all the indirect result of some pathogen changing our evolutionary trajectory.  Clint Eastwood may appear to be pretty bad ass in his movies, but he always comes off as some unnatural creature. He fights, revenges, and smokes, but he never has a partner dangling off his arm. His lack of partner feels off. In a world where humans reproduced asexually, Clint Eastwood would always have a mate. 

REVIEW: Strontium-90 Absorption by Decidous Teeth

 As you know, the United States is pretty kicking with all those civil liberties and opportunities for bettering one's lot in the world, but it is also badass in the weapons department. This is especially true for the period between 1946 and 1990.

During this time, the U.S. of A. was engaged in a staring match with an equally capable opponent, the Soviet Union. This staring match resulted in the stockpiling of many, many nuclear (not pronounced new-cue-ler) weapons, but you can't just stockpile weapons to intimidate, you have to test them. So, the Stars and Stripes tested many thermonuclear devices right here in the heartland of freedom! 

Well, it turns out that besides disintegrating everything around it, nuclear weapons also spew out radioactive material and that frightened a lot of people. So, today's paper is tested if that radioactivity was finding its way into the greatest human populace to ever exist!

I think to really appreciate the level of nuclear weapons testing going on at the time, I'm going to have to give you numbers:

Shamelessly taken from another website.

There was a lot of testing, but, from my brief research, it does not seem like anyone was asking "are there long term or immediate health effects for populations no where near the blast site?"  A valid question if you are detonating 20 bombs a year. The fastest way to see if radioactive material from nuclear fallout (not pronounced new-cue-ler) was to see if it was accumulating in humans especially children.

So, in 1958, the researcher set up a tooth collection program in the St. Louis area. No adult teeth were collected, because most adults were children before nuclear testing.

Also, calcium accumulation occurs fastest in children and strontium-90 follows normal calcium pathways, so children really had to be the source of the teeth. The paper has a whole entire section devoted to how the teeth were collected, how they were organized, who organized them, and all that. The interesting part of the tooth collection program was that there was only one salaried person, some random secretary and that for a tooth each kid would receive the following button:

 From 1959 to 1961, the researcher received 61,000 teeth, the weekly average was 750 teeth. When the strontium-90 analysis was done, there was a clear increase in the ratio of stronitum-90:calcium over time! Being breast fed versus formula fed made no difference. When stillborn infant bones and teeth were checked, they had much higher levels than those who shed their teeth later in life. I believe that later on the incidence of childhood cancer was correlated with increased ratios of strontium-90 to calcium, but I need to check on that more.