Archaeologists dating methods
That process led to the emergence of Homo habilis, the first creature generally regarded as human, 2.3 million years ago. Its brain was up to twice the size of its predecessor’s, its teeth were much smaller, and its body was quite similar to ours.
Wrangham credits the transformation to the harnessing of fire.
When he ran an FTIR analysis on one of the sediment slices, the sample’s infrared signature showed that the cave material had been heated to between 750 and 1,300 degrees Fahrenheit.
That was just right for a small fire made of twigs and grasses.
The Cooking Hypothesis When the team announced its findings in April 2012, it added fuel to a controversy that’s been smoldering since 1999.
That year, influential primatologist Richard Wrangham proposed a theory of human origins called the “cooking hypothesis.” Wrangham aimed to fill a gap in the story of how early hominins like Australopithecus — essentially, apes that walked upright — evolved into modern Homo sapiens.
The “eureka” moment came later, as the slices were examined under a microscope at Israel’s Weizmann Institute. The bones’ sharp edges, and the excellent preservation of the plant ash, indicated that neither wind nor rain had ushered in the burnt material. Then team member Francesco Berna subjected the sample to a test called Fourier transform infrared microspectroscopy (FTIR), which analyzes a material’s composition by measuring the way it absorbs infrared waves.
Often used in crime labs to identify traces of drugs and fibers, FTIR can also determine the temperature to which organic matter has been heated — and Berna is among the first to adapt it for archaeology.
At Wonderwerk, Boston University archaeologist Paul Goldberg — a specialist in soil micromorphology, or the small-scale study of sediments — dug chunks of compacted dirt from the old excavation area.
He then dried them out and soaked them in a polyester resin so they would harden to a rocklike consistency. ” He and his colleagues saw carbonized leaf and twig fragments.
Once the blocks solidified, researchers sawed them into wafer-thin slices. Looking more closely, they identified burned bits of animal bones as well.
Evolutionary science shows that our distant progenitors became bipedal 6 million to 7 million years ago.
Archaeologists believe early hominins evolved bigger brains as they walked, took up hunting and developed more complex social structures.