Necessity is the mother of invention , and change in climate often lead to change in the eubstance or behavior of mintage . So it would not be surprising if many human conception are the result of have to adapt to a changing environment . However , a discipline at two sites in southern Africa indicates that gem age innovations do n’t coincide with climatic changes .
The Middle Stone Age sounds like it should be dwell by Tolkien ’s midget , but is the name given to theperiod 280,000 - 50,000 twelvemonth ago . At this point , humans living in southerly Africa modernize young technologies such as shell beads and sophisticated methods for seize peak to fizgig and axes . peculiarly , some of these advances were abandoned after less than 5,000 eld . Paleontologistsspeculatedthey were prompt by the pauperization to tackle a changing clime , and changes in the nutrient supply that came with it .
However , University of Oxford PhD studentPatrick Robertsstudied corpse allow for in Blombos Cave , South Africa between 98,000 and 73,000 years ago , and nearby Klipdrift Shelter 72,000 - 59,000 year before now . He tracked the climate using ratios of carbon and oxygen isotopes from ostrich shell deposited at the site , and his findings contradict the hypothesis .
Stratigraphic layer from cave sites in South Africa , include some of the specimens find there . Roberts et al / PLOS One
Ostrich eggs make a mighty omelet , and have been a favored food for Orion - gatherers in southerly Africa , with the egg shield result at many sites . InPLOS One , Roberts and his co - source compose : “ Ostriches are opportunistic mixed - feeders and are one of very few animals cognise to run through C3 , C4 , and CAM vegetation , ” bring up to thephotosynthesis pathways of plants . “ They also show no special preference for any of these groups , ” the paper carry on , so what they rust change with climatic conditions .
Ostrich shell allow an indication of the mother ’s dieting . When pelting fall all year round C4 flora flourish , and result with them a large concentration of carbon-13 in the eggshells of birds that deplete them , liken to the era eclipse by wintertime rainfall and C3plants . Meanwhile , oxygen-18 concentrations are reciprocally related to the humidity during the ostrich breeding season . Roberts took the norm of 7 - 12 eggs in each stratigraphic level to get a more accurate picture than past studies , which used small-scale samples .
From this data , Parker built up a picture of the climatic changes in the region during the caves ' moving in . Crucially , any sack can be compare to changes in the engineering evident at the website , rather than having to rely on dating of tentative precision .
The work confirm the sites ' habitant adapted their diets to reflect climatic changes , with periods where the rainfall was concentrate in the winter months link with more seafood using up and hunting large mammals .
What climate change do n’t seem to be assort with , however , are notable increases in technical mundanity . “ While technological changes may have a more complex , collateral relationship with these environmental modification , we find no grounds that climatedirectlydrove the technological or cultural initiation of the Still Bay and Howiesons Poort , ” the source conclude , while acknowledging that other proposed explanations have their own problems .
