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Featured News ItemsNote: The following news item is drawn in part from a story in the May 15th issue of Science News titled "Expanding the Code" by B. Bower.
The so called ``code of life'' is the mapping from groups of three DNA bases to amino acids. When a cell reads the directions in DNA to make proteins it reads DNA in groups of three bases called codons. In addition to 61 codons that code for amino acids, the building blocks of protein, there are three codons that tell the cell to stop synthesizing protein from a given nucleic acid strand. In the past scientists have engineered cells to use an additional amino acid by re-engineering the protein synthesis biochemistry to use one of the ``stop'' codons to code for incorporation of the new amino acid into a protein. With at least one ``stop'' absolutely required this leaves room for only two novel amino acids even if the technique is pushed to its limit. A team led by Peter Schultz at the Scrips institute in La Jolla, California has modified the code of life in a new way to permit the use of more amino acids.
A more difficult feat than re-engineering an existing ``stop'' codon, the Schultz lab has modified a strain of e-coli to use the four base DNA pattern AGGA to code for a new amino acid. If four base codons are used the number of available patterns is quadrupled from 64 to 256. Keeping the rest of the cells biochemistry on track probably means that full use of these 192 additional patterns is not practical, but this advance does open the door to the incorporation of dozens of new amino acids. A tour-de-force of biochemistry, the full impact of this technique will not be known until vastly more experimentation has been performed.
Note: The following news item is drawn in part from a story in the April 16 issue of Science titled "Oldest Beads Suggest Early Symbolic Behavior" by Constance Holden.
About 40,000 years ago the human species found art. Evidence from cave paintings to jewelry, dubbed the creative explosion, appear in this period demonstrating our species had firmly grasped the concept of symbols and was engaging in symbolic thinking. Current thought holds that there was an evolutionary leap forward in human mental processes at about that time.
In the April 16th issue of Science findings of much older artistic endeavors are reported. Beads carved from snail shells and ostrich egg shells that are between 75,000 and 110,000 years old suggest our species was manufacturing jewelry at least 35,000 years earlier than the creative explosion. Exact dating of associated bone fragments will soon yield more accurate figures for the date of these beads. In any case the age of creativity and symbolism as aspects of the human mind have roughly doubled their age.
Note: The following news item is drawn in part from a story in the May 15 issue of The Economist titled "Quoth the Raven" by the Economist staff.
How do you tell if a creature is aware of itself? One approach is to try to determine if it has a theory of mind. A creature has a theory of mind if it act as if it thinks other creatures have minds. Gorillas and goats have been shown to have theories of mind and now it appears as if Ravens also have theories of mind.
Reported in the May 15th Economist, Bernd Heinrich and Thomas Bungnyar of the University of Vermont in Burlington have found evidence of a theory of mind in Ravens. A creature with a theory of mind, by trying to imagine what other creatures are thinking, can gain information from them. In this case the Ravens were placed on the far side of a partial barrier from a human experimenter. The experimenter would then gaze fixedly at some point in the room either within the Ravens field of view or concealed behind the barrier. Six young and one older raven were used in the experiment. All seven ravens followed the experimenter's gaze. When the researcher gazed at a point hidden from the ravens they would move to a point in the room where they could see the point the experimenter was looking at.
The best results from the study did not come from the gaze experiments, but rather occurred during a study to see what Ravens can learn from one another during foraging. Two ravens were given small film containers, some of which contained food and some of which did not. One pair of ravens consisted of one bird that was skilled at finding the right container and another that was larger. The larger bird would bully the smaller one into giving up the food it found. During the course of the experiment, the more skilled bird apparently has had enough and engaged in a strong demonstration that it had a theory of mind. It first located containers with food and without. It opened a container containing food. After being chased away from this container it then opened empty containers and exclaimed over them. The larger bird came over do take away the new food and the smaller bird rushed back and ate the food from the original container. Deception requires a theory of mind. Successfully deceiving another raven required you to think it is possible to deceive him. Perhaps ``bird brained'' is not the insult we imagine it to be.
Note: The following news item is drawn in part from a story in the April 24 issue of Science News titled "Puzzle on the Edge" by R. Cowen.
Among the bodies in the outer solar system, slow rotation is strongly correlated with having a large moon. The rate a body spins depends on the net angular momentum it had when it formed plus the effect of any impacts. On average bodies with slower rotation are slower because their angular momentum equations involve a moon. Jupiter, which spins roughly every ten hours, has only comparatively small moons. Pluto, a slow spinner, has a relatively large moon, Charon, 20% of its own size. The recently discovered and record-breakingly distant body Sedna, about two-thirds the size of Pluto, has a very slow rotation rate. Sedna spins once every twenty days. Careful observation with the Hubble space telescope, however, has found no moon. It may be that Sedna is simply deep in the tail of the distribution of angular momentum among outer system bodies, perhaps because of a fortuitous impact.
Note: The following news item is drawn in part from a story in the April 24 issue of The Economist titled "Plumbing the Depths" by the Economist staff.
A barrier to assessing human impact on the environment is the pesky lack, though much of history, of measurements of ecological variables like temperature, rainfall, atmospheric composition, or sea level. These numbers can sometimes be deduced from nature. The Greenland ice pack, for example, can be sampled for trapped bubbles of air thousands of years old.
About 15 B.C. King Herod of Judea caused the city of Caesarea to be built about 15 miles south of Haifa, near the sea shore. The wells in this city have a narrow range of depths that permit fresh water to accumulate in the well without permitting salt water into the well. The depth of the well was thus a good surrogate for the level of the eastern Mediterranean sea. Caesarea was inhabited continuously for 1,300 years with wells dug and abandoned from time to time. Abandoned wells were filled with household garbage, including datable pottery shards. Analysis shown that the sea level near Caesarea did not change much during the period the city was inhabited.
In order to assess the scale of current sea level increases, the current rate of sea level rise of 1mm per year was extrapolated back to the founding of Caesarea. This back-extrapolation yields a sea level six to ten feet lower than the current level. The lack of observable archaeological variation suggests that, in historical terms, the sea is rising quite rapidly in modern times.
Note: The following news item is drawn in part from a story in the May 8th issue of Science News titled "Toxin Takeout" by S. Milius.
The brilliant coloring of poison arrow frogs and their tree-frog relatives in Central and South America is a warning. In plain language it informs predators that the frogs are poisonous and directs them to look elsewhere for a meal. Those that study these frogs have found that, when they are raised in captivity, they do not develop the toxins that protect them in nature. This suggests that the frogs cannot synthesize their own poisons and are instead obtaining them from some environmental source.
A team led by John Daly of the National Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland has found a source for many of the frog potions. Formicine ants, a family that includes the familiar carpenter ant, contain many of the compounds that give poison arrow frogs their edge. These ants are found on the same water-catching plants where tree-frogs lay their eggs. The discovery of these compounds in the ants triple the number of frog toxins with a known dietary source. Interestingly, may of the compounds are not ones that the ants can synthesize. The search for the ultimate source of these toxins waits on analysis of the ants eating habits.
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Note: The following news item is drawn in part from a story in the May 8th issue of The Economist titled "It Figures" by the Economist staff.
n biological terms, it is to the advantage of potentially good mates to advertise their quality. Creatures thus often evolve visible signs of hidden strengths. Symmetry, an attractive quality for a wide range of species, is used to demonstrate a low parasite load for example. It now seems that female humans engage in this form of biological signaling.
A study was performed that divided women into four categories based on waist-to-hip ratio and breast size: low-small, low-large, high-small, and high-large. Two hormones that determine fertility were measured throughout the menstrual cycle. Women with a high hip-to-waist ratio had elevated levels of one of the hormones. The women with both high hip-to-waist ratios and large breasts had elevated levels of both hormones. Their fertility was approximately three times that of average women. From a purely biological perspective, this is a substantial advantage.