27 December 2010

Quick Science Hits

* The brain structure called the amygdala is closely associated with the instinctual fear. But, that isn't all it does. A large amygdala is associated with "a rich and varied social life among humans" and closely related primates. It has been linked to the social deficits in autism and regulates emotions in social situations in coordination with other parts of the brain. It may play a key part in interpreting facial expressions and monitoring personal space. Atypical amygdala function has been associated with: borderline personality disorder, psychopathy, more severe social phobia, bipolar disorder, autism and schizophrenia. The role of the amygdala in interpreting facial expressions, particularly fearful ones, and in fear generally, appears to be implicated in many of the mental conditions, and the left amygdala seems to be implicated more often than the right amygdala.

* "[A] single DNA change that blocks a gene known as HTR2B was predictive of highly impulsive behavior. HTR2B encodes one type of serotonin receptor in the brain. . . . "we found that the genetic variant alone was insufficient to cause people to act in such ways . . . Carriers of the HTR2B variant who had committed impulsive crimes were male, and all had become violent only while drunk from alcohol, which itself leads to behavioral disinhibition." From here via here.

* Eating fried fish is linked to strokes.

* Out of Africa migrations may have been via a wet Sahara rather than the Nile River Valley or Red Sea:

Analysis of the zoogeography of the Sahara shows that more animals crossed via this route than used the Nile corridor. Furthermore, many of these species are aquatic. This dispersal was possible because during the Holocene humid period the region contained a series of linked lakes, rivers, and inland deltas comprising a large interlinked waterway, channeling water and animals into and across the Sahara, thus facilitating these dispersals. This system was last active in the early Holocene when many species appear to have occupied the entire Sahara. However, species that require deep water did not reach northern regions because of weak hydrological connections. Human dispersals were influenced by this distribution; Nilo-Saharan speakers hunting aquatic fauna with barbed bone points occupied the southern Sahara, while people hunting Savannah fauna with the bow and arrow spread southward. The dating of lacustrine sediments show that the “green Sahara” also existed during the last interglacial (∼125 ka) and provided green corridors that could have formed dispersal routes at a likely time for the migration of modern humans out of Africa.

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