London, Apr 13 (ANI): Proof that some chimps routinely avoid the safety of treetops to sleep on the ground raises the possibility that some early hominins did too with possible implications for their growth, a new study has claimed.
By about 3.2 million years ago Australopithecus afarensis, an extinct hominid that lived between 3.9 and 2.9 million years ago, had arches in the soles of its feet - a key adaptation for walking on the ground.
However, its long arms and slender fingers suggest to some researchers that it was still comfortable with climbing.
The skeleton makes sense if australopithecines slept in trees at night to escape predators, as chimps do today.
If that was the case, hominins may not have slept on the ground until Homo erectus appeared 1.9 million years ago.
They lacked upper body adaptations for climbing and may have used fires to ward off ground-dwelling nocturnal predators, although the evidence for controlled fire stretches back only 1 million years.
Now, evidence from west African chimps of the Nimba mountains in Guinea suggests ground-sleeping may predate such innovations.
Of the 634 sleeping nests that Kathelijne Koops of the University of Cambridge found in Nimba, 90 were built on the ground.
For this study, Kathelijne Koops and colleagues at Cambridge and Kyoto University in Japan, collected hairs from 46 ground nests. DNA analysis showed that at least 12 chimps had slept on the ground, suggesting it is a widespread behaviour.
The chimps of Nimba have few predators, but similar ground nests are seen in the Democratic Republic of the Congo, where leopards are also present.
"Ground nesting can become established despite the presence of predators and without the use of fire," New Scientist quoted Koops as saying.
The study has been published in the American Journal of Physical Anthropology. (ANI)
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