ONE INCOMPLETELY understood puzzle in evolutionary theory is what is the driving force for greater complexity in a living system. Intelligent design proponents are heavily invested in the idea of complexity but disagree on how to measure it, with most measurements coming down to basic biomass. This is a poor means of measuring complexity, but the reasons for this are outside the scope of this article (for a short summary of some concepts in biological complexity see this article, sadly only available to subscribers). However, when considering a biological pathway we can probably agree that a pathway with only a few proteins is less complex than a pathway that fulfills the same role but uses many more proteins. Consider the clotting cascade. In simple chordates such as Amphioxus possibly only two or three proteins are involved (we don’t know the full details), while in mammals there are more than a dozen components. Research has demonstrated that the clotting system is not irreducibly complex, but the reason for this increase in complexity has not been previously determined.
ONLY SEVEN months ago the report of the discovery of Tiktaalik, a tetrapod-like fish, was greeted with elation by the science-minded. Although this animal was clearly a fish, it had front fins that were more like primitive forelimbs (a fossil of the posterior half has not yet been found). Examination of these limbs showed they were capable of propping the fish up. Additionally, Tiktaalik has many other features unusual for a fish showing it was becoming adapted to living in extremely shallow waters with possible forays onto dry land.
This week we greet another unusual fish. John Long and coworkers report in Nature‘s advance online publication the discovery of Gogonasus. While members of this genus have been discovered previously, their state of preservation was poor and this fish’s unusual features were not appreciated.
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NOT TOO LONG ago the idea of studying fossilized embryos half a billion years old would have seemed ridiculous, but advances in technology have made this practical. This week in Science Dr. Hagadorn and coworkers present the results of their studies of Precambrian embryos from the Doushantuo region of China using a battery of methods including X-ray computed tomography (CT), electron microscopy (SEM), transmission electron microscopy (TEM), and thin-layer petrography.
DUE TO THE controversy regarding destroying embryos for stem cell research, many scientists are studying ways of obtaining cells without harming embryos. I discussed one new finding recently, that stem cell lines can successfully be cultured from a single cell extracted from an embryo, leaving the embryo unharmed. On September 21, an open-access article appeared in the journal Stem Cells reporting a possible new method to obtain embryonic stem cells in a noncontroversial manner.
TODAY THE Nobel Foundation announced that the Nobel Prize in Physiology and Medicine goes to Andrew Fire and Craig Mello for their groundbreaking work in RNA silencing, also called RNA interference (RNAi). These researchers discovered that introducing short double-stranded RNA fragments into a cell activates a cellular mechanism that silences expression of a gene with a complimentary RNA transcript by destroying these transcripts. While recently some adverse effects of this technology in gene silencing in living animals were discovered, it remains promising for therapy for various illnesses. RNAi may in future be useful against cancers which overexpress certain genes, or against genetic disorders in which the body makes a mutant protein. Even if RNAi is never therapeutically useful, it will remain a valuable technique in genetic research. This Nobel Prize was awarded unusually soon after the initial publication of this research, and is well deserved.
RECENTLY RESEARCHERS discovered a freakish submarine lake of liquid carbon dioxide trapped under a layer of sediment in the Okinawa Trough hydrothermal system. An accompanying commentary article reports that globules of liquid carbon dioxide have been found in the deep ocean before, but such lakes were not anticipated since liquid carbon dioxide is less dense than sea water until a depth of 3000-3800 meters (at deeper depths the density once again decreases). This lake was found at a depth of 1400 meters, and is only able to exist because it is capped with a sediment-overlain layer of sulfur-rich carbon dioxide hydrate. Even more amazingly, the carbon dioxide lake appears to contain bacteria.
RECENTLY PURDUE UNIVERSITY published a short news article talking about the unusual evolutionary track of the vole. Apparently the vole has been evolving at high speed, speciating 60-100 times faster than other vertebrates. A key factor in this high rate of speciation is variable chromosome numbers, as with the domestic mouse. The chromosome number ranges from 17-64, although the vole common ancestor probably had 56.
RECENTLY ROBERT LANZA of Advanced Cell Technology made the extraordinary claim that he had succeeded in finding a way to culture embryonic stem cells from a single cell extracted from an embryo without destroying the embryo itself. If this can really be done it can avoid one ethical challenge to embryonic stem cell research. But was this really done? The Washington Post on September 6 published an article describing Sen. Specter and Sen. Harkin’s scathing criticism of Robert Lanza’s research, saying that his group had in fact destroyed the embryos. So what is going on? In order to determine this I first trekked back to the journal Nature to read the original letter (I. Klimanskaya et al. Nature doi:10.1038/nature05142; 2006).