Harappan Technology, Homo Floresiensis, Foraminifera

Some exciting readings for you- 

1)  Manufacture of synthetic stone in the Bronze Age Harappan Civilization.

Stone beads were important in Harappan culture and trade. They were made out of agate, an amorphous or cryptocrystalline form of silica. The Kutch region was the primary source of these agates. Stone and bead processing Harappan age workshops abound in this region. The tradition continues today. Some of the best ornamental agate is still being sourced from Kutch. The agates precipitate as secondary silica in cavities of the Deccan Basalts and associated silica rich lava.

To perforate these agates, the Harappans needed tools such as drill bits which were harder than the agate. For this, they manufactured a synthetic stone, now called Ernestite, by high temperature sintering of sand and laterite raw materials. Reaction temperature needed to fuse these materials into a cohesive rock would have reached 1100 deg C! Mesozoic sandstone, found all over Kutch, provided the sand, and the laterite came from iron rich weathered layers capping the Deccan Basalt.

A terrific study by M.K. Mahala and coworkers that details the provenance and fabrication of this interesting artificial stone has just been published in Nature Heritage Science. There is a lot of mineralogy and geochemistry described in the paper, but the conclusions are clearly laid out for all to understand.

2) Climate change and the decline of the Hobbit.

Why are small isolated populations of animals vulnerable to extinction?

Inbreeding, small geographic range, limited access to resources, reliance on one or few food sources, a chance catastrophic event, all may be factors making them susceptible to extirpation.

A case in point is the Hobbit or Homo floresiensis, the diminutive hominin discovered on Flores Island, Indonesia, in 2003. The archaeologic record shows it lived on the island for at least one million years. Homo floresiensis is thought to be a descendant from an early Homo species which dispersed from Africa 2 million years ago. The other famous inhabitant of the island that coexisted with the Hobbit and was its main food source is the dwarf elephant Stegodon.

A careful analysis by Michael Gagan and coworkers, published in Nature Communications Earth and Environment, using geochemistry of calcite from cave deposits show how climate change and decrease in water availability may have increased competition for resources and made life challenging for the inhabitants.

Summer rainfall began declining around 76,000 years ago with record low rainfall between 61,000 to 55,000 years ago. Both the Hobbit and Stegodon fossils become rarer during this interval and disappear by 50,000 years ago. Modern humans entered Flores Island around 46,000 years ago, and whether the Hobbit interacted with them on Flores Island is uncertain. 

3) The history of the ocean, as told by tiny beautiful fossils. 

The tiny fossils are planktonic foraminifera living suspended in the upper sunlit portion of the ocean. Their shells are made of calcium carbonate. They occur in huge numbers and have short lives. Their shells drop down and carpet the ocean floor, making them valuable archives for understanding evolution. Scientists make use of them for studying climate change too. Certain changes in the chemical composition of their shell are a function of water temperature. Tim Vernimmen has written a short piece on how foraminifera inform us about past environmental crisis and ocean conditions.

Agglutinated Foraminifera From The Deep Sea

No matter how many David Attenborough specials you may watch, nature always throws more surprises at you.

Foraminifera are protists that build a skeleton or a test made up of calcium carbonate. The calcium carbonate is precipitated out of sea water. There is a sub-group of foraminifera which construct a shell not by capturing the calcium carbonate via chemical precipitation, but by assembling sedimentary grains and then cementing them together like a brick and mortar structure. This group of forams are known as agglutinated foraminifers. 

All this is well known. Many different species of forams use a variety of grains as bricks. They are mostly different shell fragments, but even mineral grains like ilmenite (iron titanium oxide) , rutile (titanium dioxide), or garnet are used. 

Now there is a new report of a deep sea living agglutinated foraminifera which constructs a tube made up of  planktonic foraminifera shell fragments of a single species. 

Read that again. A benthic (bottom living) foram shell made up of bits of another foram which lived floating in the upper water column!  

These shells are selected to the exclusion of all other types of available sedimentary grains. The specimens were recovered in a core drilled off shore northwest Australia by the International Ocean Discovery Program. The paper by Paul N. Pearson and IODP 363 Shipboard Scientific Party is published in the Journal of Micropalaeontology.

Here is the entire abstract. It is mind boggling. 

Agglutinated foraminifera are marine protists that show apparently complex behaviour in constructing their shells, involving selecting suitable sedimentary grains from their environment, manipulating them in three dimensions, and cementing them precisely into position. Here we illustrate a striking and previously undescribed example of complex organisation in fragments of a tube-like foraminifer (questionably assigned to Rhabdammina) from 1466 m water depth on the northwest Australian margin. The tube is constructed from well-cemented siliciclastic grains which form a matrix into which hundreds of planktonic foraminifer shells are regularly spaced in apparently helical bands. These shells are of a single species, Turborotalita clarkei, which has been selected to the exclusion of all other bioclasts. The majority of shells are set horizontally in the matrix with the umbilical side upward. This mode of construction, as is the case with other agglutinated tests, seems to require either an extraordinarily selective trial-and-error process at the site of cementation or an active sensory and decision-making system within the cell.

 

The photographs from the paper shows the tube of the agglutinated foraminifera made up of planktonic foraminifera shells of a single species.

Charles Darwin knew of agglutinated foraminifera from reports he had read and was astonished....“almost the most wonderful fact I ever heard of. One cannot believe that they have mental power enough to do so, and how any structure or kind of viscidity can lead to this result passes all understanding”.  This was a letter he wrote to W.B Carpenter who had described them in 1873.

I'll leave you to ponder upon this most exquisite of natural wonders. The paper is open access: A deep-sea agglutinated foraminifer tube constructed with planktonic foraminifer shells of a single species.