Monday, August 27, 2012

Our Ancestors – A New Addition to the Family

 It has been estimated that approximately six million years ago, the ancestral lineage that would ultimately lead to human beings diverged from that which lead to our nearest relations – chimpanzees and apes.  The fossil evidence demonstrates that between two and three million years ago, our ancestors showed indications of human attributes.  These ancestors, Lucy being an excellent example, walked upright but possessed small brains and hands that were obviously designed for the climbing of trees.  Members of this group are collectively referred to as our australopithecine predecessors.

The discovery of the complete lineage to modern humans remains unfulfilled.  However, Doctor Lee Berger, a paleoanthropologist at the University of Witwatersrand in Johannesburg, South Africa, has recently made a discovery that may provide a significant piece in this puzzle.

Fossil fragments that have been dated to be some two million years old have been found in an old miner's pit at the so-called "Malapa site" northwest of Johannesburg.  These fragments include pelvis and leg bones, ribs and vertebrae, arm bones, clavicle and skull.  From these various pieces, the partial skeletons of an adult female and young male have been assembled. 

From these cumulative findings, it became apparent to Berger and his colleagues that an entirely new hominid species had been discovered.  It was called Homo sediba.  Although the fossil evidence demonstrates a relatively small brain – a skull enclosing a volume of 420 cubic centimeters that is about one-third of the size of the brain of modern humans, its pelvis is bowl shaped.  This was an unexpected discovery, since it was previously believed that this shaped pelvis evolved to accommodate a large brain.  In addition, the shape of the skull shows an expanded frontal region indicating the further development of the frontal lobes – an area of the brain associated with higher order intelligence.  Although sediba's arms were long, the fingers were short and straight probably adapted to the fashioning of tools.

This finding sheds new light upon the evolutionary progression to modern humans – Homo sapiens.  It may also suggest that Homo habilis and Australopithecus afarensis might be, in fact, side branches and not in the direct lineage.  As a result, yet another piece of the intriguing evolutionary process has been elucidated.

Wednesday, August 1, 2012

Ocean Acidification and Climate Change – A Case In Point

It has long been understood that the uptake by the oceans of the increasing levels of carbon dioxide (CO2) in the atmosphere,  produced as a result of human activity, leads to the reduction in the pH – increased acidity – of the water.  This increased acidity has the effect of disturbing the carbonate (CO3) balance in the oceans.  What has not been clearly defined is the extent of these changes.

The index for assessing the degree of this imbalance is the so-called "carbonate saturation state."   The aquatic organisms that are especially susceptible to changes in the carbonate saturation state are those that create part of their structure from available calcium carbonate (CaCO3).

Doctor Nicolas Gruber and his colleagues at the Department of Environmental Physics at the Institute of Biochemistry and Pollutant Dynamics , ETH Zurich, Switzerland and at the Atmospheric and Oceanic Sciences Program at Princeton University, Princeton, NJ have studied the California Current System (California CS) in attempt to quantify these changes.  The California CS is of particular importance in that it represents an essential marine ecosystem.

As a result of their findings, they have projected that by the year 2050 the carbonate saturation state will drop to levels that represent under-saturation of carbonates critical to the marine environment.  They have come to this conclusion using two different scenarios – one projecting high emissions of CO2 and the other low emissions.  According to the authors, "Habitats along the sea floor will become exposed to year-round under-saturation within the next 20 to 30 years.  These projected events have potentially major implications for the rich and diverse ecosystem that characterizes the California CS."

These findings represent yet another example of the perils the global human community faces as a direct consequence of the anthropogenic buildup of greenhouse gases in the atmosphere.  It remains to be seen whether or not the plethora of known global environmental disruptions will provide sufficient motivation for the human community to implement meaningful solutions to this enormous problem.