Washington, Apr 20 (ANI): A tiny fossil thumb bone has indicated that hominids had a humanlike grip at least 6 million years ago, say researchers.
Sergio Almecija of the Autonomous University of Barcelona has said that earliest hominids apparently evolved an upright gait and a relatively sophisticated ability to manipulate objects much before they figured out how to make tools.
This was well before 2.6 million years ago, arguing against the idea that fine motor skills for toolmaking drove the evolution of opposable thumbs.
The researchers studied a bone from the tip of a thumb belonging to Orrorin tugenensis.
At an estimated 6 million years old, Orrorin is the second oldest hominid genus. A more recently identified hominid genus and species, Sahelanthropus tchadensis, may have lived 7 million years ago.
Controversy exists over whether fragmentary Sahelanthropus and Orrorin fossils can be used to identify new hominid genera.
Limb and jaw pieces, as well as teeth, from at least five Orrorin individuals were unearthed in Kenya in 2000.
The thumb fossil indicates that Orrorin had a long enough thumb to meet the tips of the other fingers, allowing for fine manipulation of objects.
"The Orrorin thumb bone is the most humanlike in the available fossil record, other than recent Homo species," Discovery News quoted Almecija as saying.
By comparing Orrorin's thumb with thumb bones from a variety of ancient apes and hominids, as well as from living people, Almecija uncovered a pattern, which argues against the current notion that hominids first evolved handier hands as they learned to make stone tools.
No Sahelanthropus thumb bones have been found.
In Almecija's view, early hominids inherited hands capable of fine manipulation from small-bodied apes that lived in Africa and Europe between 25 million and 5 million years ago.
Hands then assumed a more apelike, less dexterous structure in later hominids, including Ardipithecus and Australopithecus, before again evolving a precision grip in the Homo lineage.
He added that Orrorin's humanlike thumb calls into question a long-standing assumption that 1.8-million-year-old hand fossils from Homo habilis, unearthed in Africa more than 40 years ago, represent the earliest transition to a precision grip.
The study was presented at the annual meeting of the American Association of Physical Anthropologists. (ANI)