Prion Evolution

Ed Yong discusses prion evolution in his blog at ScienceBlogs:

Jiali Li from the Scripps Institute in Florida has found that prions - the infectious proteins behind mad cow disease, CJD and kuru - are capable of Darwinian evolution, all without a single strand of DNA or its sister molecule RNA.
Prions are rogue version of a protein called PrP. Like all proteins, they are made up of chains of amino acids that fold into a complex three-dimensional structure. Prions are versions of PrP that have folded incorrectly and this misfolded form, called PrPSc, is social, evangelical and murderous. It converts normal prion proteins into a likeness of its abnormal self, and it rapidly gathers together in large clumps that damage and kill surrounding tissues.
Li has found that variation can creep into populations of initially identical prions. Their amino acid sequence stays the same but their already abnormal structures become increasingly twisted. These "mutant" forms have varying degrees of success in different environments. Some do well in brain tissue; others thrive in other types of cell. In each case, natural selection culls the least successful ones. The survivors pass on their structure to the "next generation", by altering the folds of normal prion proteins.

Schizotypal Selection

Via John Hawks and the Four Stone Hearth Carnival of Anthropology: The Primate Diaries' explains Sapolsky's theory of selection for schizotypal personalities, possibly in shamans.

Several years ago Robert Sapolsky suggested that genes promoting schizophrenia may have been selected for in human evolution because some of them conferred benefits that outweighed the 1% of people worldwide that were disabled by the disorder. Like the sickle-cell trait that confers resistance to malaria (so long as you don’t receive two recessive alleles and develop full fledged sickle cell anemia) a partial schizophrenia may be beneficial in some way. He observed that relatives of schizophrenics have a high likelihood of “schizotypal personalities,” or a mild form of the disorder that just makes these people a little strange and allows them to see the world in a unique way. What if, he wondered, schizophrenia maintained itself in human populations because of selection for schizotypal personalites? As luck would have it, for a hundred years anthropologists had observed such individuals thriving in nearly every society they encountered: shamans.

The Plague of Athens Identified

Via ProMED-mail: the BBC and others report on DNA analysis of dental pulp from an ancient graveyard. Salmonella enterica serovar Typhi was found, indicating death by typhoid fever:

The team said in their research: "For an infectious disease to be considered as a likely cause of the Plague of Athens, it must, above all have existed at that time.
"Infectious diarrhoeas and dysentery as described by the ancients, imply that typhoid fever was an endemic problem in the ancient world."
The team added that it was the first time microbiological evidence associated with the plague had been analysed.
Previously assumptions about the cause had been based on the narrations of a the 5th Century Greek historian Thucydides.
Earlier research rejected the idea that typhoid caused the plague because of the symptoms described by Thucydides did not fit with the modern day typhoid.
But the researchers said inconsistencies [may be] explained by the possible evolution of typhoid fever over time.

The researchers also checked for typhus (Rickettsia prowazekii), a better match for the symptoms, without result.