Tuesday, January 24, 2006

Balls and Brains

Biology is all about trade-offs and it turns out that at least in bats, there is a conflict between the size of sexual organs and the brain. In the current issue of the Proceedings of the Royal Society B, a paper reports on the effects of sexual selection on neocortex and testes sizes in bats. The authors find that the testes of males are much larger in species where the females are promiscuous, than those in species where the females exhibit fidelity. The inverse relationship held for brains. The theory is that both organs are expensive metabolically (especially since bats fly). If females have many partners, the crucial competition is between the sperm and the bat with the most wins. On the other hand, if females are selective about their partners for a given breeding cycle then the quantity of sperm produced by a given male is not so important.

It's not so clear why female faithfulness should promote a larger brain in males. One argument is that there may be a genetic constraint in that genes for both organs are co-expressed. In an earlier post, I wrote about the hypothesis that if females select for a trait in males, then any genes for that trait residing on the X chromosome would be very effectively selected for since males only carry one X. However, this genetic constraint may be a product of other selection pressures. It could simply be that selective females prefer more intelligent mates.

Friday, January 13, 2006


This coming Sunday, if all goes well, the Stardust probe will land in the Utah desert carrying microscopic dust gathered from Comet Wild 2 and interstellar space. This was a seven-year, 2.88 billion mile, 200 million dollar mission. You can follow the exciting progress at the official NASA link. The comet and interstellar dust is captured in an aerogel array mounted on the spacecraft.

It is expected that a few thousand cometary dust grains and just 45 interstellar submicroscopic grains will be captured by the collector. The grains will be embedded at high speed into the gel and create tracks like subatomic particles in a bubble chamber. Digital images will be taken and must be analyzed by hand. It is expected that 30,000 person hours will be required to examine 1.5 million images. NASA is asking for volunteers to take part through a Seti@home-like project called Stardust@home. Each volunteer must first pass a test where they must find a few tracks on a sample image. If two of four volunteers for a given image finds a track it will then be subjected to the scrutiny of 100 more volunteers. If it still passes muster it will then be examined by a crack team of Berkeley undergraduates. The dust grains will then be extracted by a specially designed microtweeser which wasn't even developed until after Stardust was launched. I'm dying to find out what sorts of things they'll find. Who knows, maybe they'll be some organic molecules and life on earth really was seeded from space.

Wednesday, January 04, 2006

Humans In Space

In 2004, President Bush presented a new agenda for NASA that included human missions to the moon and Mars. The report is in the President's Commission on Moon, Mars and Beyond. I grew up during the space age and one of the most inspirational moments of my life was witnessing Neil Armstrong walking on the moon in 1969. It certainly was a factor in my decision to pursue a career in science. However, I now firmly believe that manned space flight is intrinsically flawed and should not be supported by the government.

The reasons are two fold. The first is that there is no scientific purpose that requires humans and the second is that humans are very badly adapted to space. Other than bringing back moon rocks (which could now be done with robots) and fixing the Hubble telescope (which could soon be done by robots), there has been no contribution to space science from human exploration. The only science that has been done is the study of the effects of space on humans and the conclusion is that we don't belong there. The weightlessness causes severe muscle atrophy and bone loss. Even more problematic is the high levels of ionizing radiation present in space. The extra cost required for human over robotic missions is astronomical.

The only reason we should go to Mars is the same reason we should climb Mt. Everest. I think this is perfectly fine and honourable but I don't think we should support such a junket with federal dollars. Let some maverick billionaire fund the operation. By the time we actually have the technology to be able to colonize other planets or even go beyond the solar system our knowledge of biology and artificial intelligence will have also greatly advanced. Instead of sending people we could send human embryos or better yet just the genetic codes. Once we arrive at our destination we can simply grow our colonizers from available organic molecules. Robots could raise and educate the first generation. This seems far more sensible than sending people in a lead lined cabin or putting them in suspended animation (at least until we get that Star Trek warp drive, force field and artifical gravity generator working).