11 February 2012


Ancient paintings of seals from the Caves of Nerja, Spain. Via.
New research suggests that six seals painted on the walls of the Caves of Nerja in Málaga, Spain, are more than 42,000 years old. 

Which not only makes them the oldest human art on record, it also infers they were painted by Neanderthals (Home sapiens neanderthalensis)—who lived in the area at that time and ate seals. 

The Homo sapiens sapiens who followed and also painted on cave walls left no images of seals. Their oldest known art is in the 30,000-year-old cave at Chauvet, France.

Map modified from Wikimedia Commons.
The area around Nerja Cave at the southern end of the Iberian Peninsula is believed to be last place inhabited by Neanderthals before they were overrun or interbred into obscurity by Homo sapiens sapiens about 37,000 years ago. 

Neanderthals have long been thought incapable of creating artistic works. 
(*Sigh* Why?)

But the provenance of recently-discovered decorated stone and shell objects is now attributed to Neanderthals.

Mediterranean monk seal in cave. Credit: Giovanni Dall'Orto via Wikimedia Commons.
What's interesting to me is that the seals in the painting would have been Mediterranean monk seals—now one of the rarest pinnipeds on Earth.

Monk seals are believed to have shifted in modern times from beach-dwelling seals to cave-dwellers in order to escape human encroachment.

But maybe—hunted by Neanderthals—they spent time in caves 42,000 years ago too? Could the Neanderthal art have been more biologically accurate than Homo sapiens sapiens' fanciful horses at Chauvet? 

I wrote more about monk seals in an earlier post here.

09 February 2012


Bear Glacier, Alaska. Via.
A new paper in Nature calculates that total global ice mass lost from Greenland, Antarctica, and all Earth's glaciers and ice caps between 2003 and 2010 was about 4.3 trillion tons (1,000 cubic miles).
That's enough melted ice to drive up global sea level by 0.5 inches (12 millimeters).
And that's enough water to cover the US to 1.5 feet deep (0.5 meters deep).

Glacier melt tunnel. Credit: Dook Cook | DougAK via Flickr.
The research was based on satellite measurements of ice loss from all Earth's land ice collected over eight years—with attention paid to rarely-observed glaciers and ice caps outside of Greenland and Antarctica.
The findings:

  • About a quarter of the average annual ice loss came from glaciers and ice caps outside of Greenland and Antarctica (roughly 148 billion tons, or 39 cubic miles). 
  • Ice loss from Greenland and Antarctica and their peripheral ice caps and glaciers averaged 385 billion tons (100 cubic miles) a year.

Glacier Bay, Alaska. Credit: NPS.
Traditional estimates of Earth's ice caps and glaciers have been made using ground measurements from only a few hundred of the roughly 200,000 glaciers worldwide.
This video explains some of those traditional ground-based measurement techniques.

This video describes how the GRACE satellite measurements work.

One positive finding of the satellite study was that ice loss from high the high Asian ranges—from the Himalaya, Pamir, and Tien Shan mountains—was only about 4 billion tons of ice a year. Previous ground-based estimates ranged as high as 50 billion tons a year.
From NASA News:

"This study finds that the world's small glaciers and ice caps in places like Alaska, South America and the Himalayas contribute about 0.02 inches per year to sea level rise," said Tom Wagner, cryosphere program scientist at NASA Headquarters in Washington. "While this is lower than previous estimates, it confirms that ice is being lost from around the globe, with just a few areas in precarious balance. The results sharpen our view of land-ice melting, which poses the biggest, most threatening factor in future sea level rise." 

Bering Glacier, Alaska. Credit: NASA.

The paper:
  • Thomas Jacob, John Wahr, W. Tad Pfeffer & Sean Swenson. Recent contributions of glaciers and ice caps to sea level rise. Nature. DOI:10.1038/nature10847

07 February 2012


Posidonia oceanica. Via.

 A new paper in PLoS ONE reports that a patch of Mediterranean seagrass of the species Posidonia oceanica is the oldest known living organism on Earth.

The researchers sequenced the DNA of seagrasses from 40 underwater sites between Spain and Cyprus, covering 3,500 kilometers/2,175 miles of seafloor.

Map via Wikimedia Commons.
They found one genetically identical 15-km/9-mile-long meadow off the island of Formentera in the Balearic Islands.

Seagrasses reproduce by cloning and individuals can reach great size and age.

Based on the annual growth rate of P. oceanica, the researchers calculated the Formentera meadow's age as between 80,000 and 200,000 years old.

Clearly P. oceanica are good adaptors. Yet the next few decades may prove more taxing to than anything encountered in the past 200,000 years. From the paper:

The finding of P. oceanica clones.. that are extreme in size (km-sized) and age (multi-millenary old) across the Mediterranean indicates that some meadows are the result of ecological and evolutionary processes integrated over long time scales. Time scales such as these are in a stark contrast to the current rapid and acute impact caused directly or indirectly by human pressure on this species... [E]ven though such phenotypic plasticity possibly evolved across millennia, it may well be challenged by the unprecedented rate of environmental change imposed by current global climate change, including temperature increase and ocean acidification, and recent anthropogenic pressure on coastal areas resulting in changes in water quality, eutrophication, and nutrient load, particularly in seagrass meadows.

The paper:

  • Arnaud-Haond S, Duarte CM, Diaz-Almela E, Marbà N, Sintes T, et al. 2012 Implications of Extreme Life Span in Clonal Organisms: Millenary Clones in Meadows of the Threatened Seagrass Posidonia oceanica. PLoS ONE. DOI:10.1371/journal.pone.0030454