Hamiltonians are Mutants

A new study published in PNAS (open access) takes a look at the health implications of exposure to particulate air pollution. In this particular study, mice were caged near 2 steel mills and a major highway in the Hamilton, Ontario area and exposed either to ambient air, or the same air passed through a HEPA filter to remove particulate pollution.

When exposed to Hamilton air (but not HEPA filtered air) for 10 weeks (followed by 6-weeks recovery in the lab), the mice had a 1.6-fold increase in sperm mutation frequency and an increase in global methylation of germline DNA. From the article:

"We have demonstrated that exposure of inbred mice to particulate air pollution near two integrated steel mills and a major highway caused tandem repeat DNA mutation and hypermethylation in spermatogonial stem cells. [...] The overall implications of these findings for the health of humans are unclear. Heritable mutation, germ-line DNA damage and epigenetic modifications have the potential to affect disease incidence in the descendents of exposed individuals. In addition to its potential importance in the maintenance of genome stability, appropriate methylation of DNA is critical for imprinting, regulation of gene expression, mammalian development, and disease."

No word yet on whether any of these mutations conferred super-powers.

Can plants sense kins?

Ok I admit that story has already been all over the media. When I first read about it, I just didn't think it was that interesting so I didn't post it. However now that I've actually read the paper I have a few comments. Firstly its 4 pages long and has 2 figures, wow it's a big conclusion for such a simple experiment. Second I want to explain Hamilton's kin selection idea since it is the basis of that paper. It essentially boils down to this: "if individuals have the capacity to recognize kin (kin recognition) and to adjust their behavior on the basis of kinship (kin discrimination), then the average relatedness of the recipients of altruism could be high enough for this to be favored."
Now because I have a huge man-crush on Dawkins, and I would carry his half-ape half retarded fish babies, I have to mention Dawkin's views of kin selection. In writings on Kin Selection there are often references to Richard Dawkins’s article ‘12 Misunderstandings of Kin Selection’, in Zeitschrift für Tierpsychologie, 51 (1979), 184-200. Basically Dawkins doesn't think that kin selection is a special type of natural selection. He opposes the view that natural selection can be exerted on a group, since only the individual survives and reproduces and not a group. There is more to his arguments, but It's worth actually reading it.

So how does this relate to plants. Well kin selection is a complex process usually associated to social animals. Plants on the other hand, can't see, smell or move, or at least are limited in their ways to sense kinship. And if you can't recognize a kin, how can you have altruistic behavior? Now it's well known that when plants are in close proximity, they will exhibit more aggressive competitive behaviors, in order to secure resources. Rather than using its energy to grow or flower, it will allocate more to roots to cover larger areas. Now this group asked a simple question, will the plant be as competitive with its root system if the other plant in the pot is from the same species. Surprisingly it wasn't as agressive, suggesting it knows about the plants in its environment, but how? Anyways, I like this experiment because it would make for an awesome science-fair type experiment, or a good way to teach kids about evolution, kin selection
and natural selection.