Ugly bugs had a ball when early hominins died at the Cradle
Insects are finally getting their day in the sun when it comes to fossils in the Cradle of Humankind.
A new study on the remains of Australopithecus sediba — a hominin species from about 1.98 million years ago — has revealed the major role played by termites and other insects in the fossilisation of the bones.
Australopithecus sediba was discovered at the Malapa cave in the Cradle in 2008 and since then has confounded scientists as to whether it is our direct ancestor.
The studies have focused on a juvenile male and adult female who fell down a shaft and died.
This time around, researchers at the Evolutionary Studies Institute at Wits University were interested to know how the bones and surrounding environment from almost two million years ago had been damaged over time.
Their work revealed a fascinating miniature ecosystem in the remains: tiny fossil fungus gardens made in dappled sunlight by termites, and holes in the skull used as an incubation and birthing room for flies.
Researchers previously ascertained that the juvenile male and adult female had “fallen through a shaft opening into a cave, where they died and likely mummified, before being washed into a lower chamber”, said lead author Lucinda Backwell, adding the new study had revealed “the oldest known case of bone modification by termites on hominin remains”.
Backwell and her team’s starting point was the desire to work out how fossilisation had taken place and to “identify the invertebrate agents responsible for damage”.
They did so by using highresolution imagery, studying the site itself and examining breccia blocks (fragments of surrounding rock) in the laboratory.
In the same way forensic detectives try to figure out a crime scene, they also simulated a scenario and observed what the insects got up to.
“We conducted bone-modification experiments with termites and hide beetles,” said Backwell, adding the insects “produced the same damage as that on the Malapa fossils”.
The study of the fossils showed that the termites modified the fossil bone by harvesting their mineral-rich coatings.
The results also showed “the presence of blowfly puparia within the cranium of the juvenile male”, which suggests that “flies visited the facial orifices of the freshly decomposing corpse ”.
The findings also corroborate evidence from earlier studies that sunlight made its way into the site.
A shaft opening that admitted sunlight is supported by the presence of a fossil fungus garden associated with the adult female, said Backwell.
Fungus gardens occur just below the Earth’s surface and “sprout mushrooms in areas with dappled lights”.
Also, the presence of the remains of blowflies — which lay eggs only in daylight —“imply that the body was exposed to sunlight for part of the day”.
The researchers explain that fossilised fly pupae in the skull of the juvenile male indicate that “the decaying corpse was accessible at the time of death to be colonised by necrophagous [feed on decaying animal flesh] flies” and that this suggests that “a relatively broad shaft opening allowed sunlight to fall on the fresh corpse for part of the day ”.
It probably took six years for the remains of the hominins who fell down the shaft to become weathered and skeletonised, then it is likely that “a mudflow transported the intact hominins and associated fauna, termite galleries and fungus gardens, and the remains of necrophagous insects, to a lower chamber”.
The results of the study have prompted other scientists to include insects in their research as they try to figure out who lived where in the Cradle of Humankind.