Image copyright Other Image caption The stone points are approximately 64,000 years old

Researchers in South Africa have revealed the earliest direct evidence of human-made arrows.

The scientists unearthed 64,000 year-old "stone points", which they say were probably arrow heads.

Closer inspection of the ancient weapons revealed remnants of blood and bone that provided clues about how they were used.

The team reports its findings in the journal Antiquity.

The arrow heads were excavated from layers of ancient sediment in Sibudu Cave in South Africa. During the excavation, led by Professor Lyn Wadley from the University of the Witwatersrand, the team dug through layers deposited up to 100,000 years ago.

Marlize Lombard from the university based in Johannesburg led the examination of the findings. She described her study as "stone age forensics".

"We took the [points] directly from the site, in little [plastic] baggies, to the lab," she told BBC News.

"Then I started the tedious work of analysing them [under the microscope], looking at the distribution patterns of blood and bone residues."

Because of the shape of these "little geometric pieces", Dr Lombard was able to see exactly where they had been impacted and damaged. This showed that they were very likely to have been the tips of projectiles - rather than sharp points on the end of hand-held spears.

Image copyright Other Image caption Closer inspection revealed remnants of blood (left) and bone fragments (right)

The arrow heads also contained traces of glue - plant-based resin that the scientists think was used to fasten them on to a wooden shaft.

"The presence of glue implies that people were able to produce composite tools - tools where different elements produced from different materials are glued together to make a single artefact," said Dr Lombard.

"This is an indicator of a cognitively demanding behaviour."

The discovery pushes back the development of "bow and arrow technology" by at least 20,000 years.

Ancient engineering

Researchers are interested in early evidence of bows and arrows, as this type of weapons engineering shows the cognitive abilities of humans living at that time.

Image copyright Other Image caption The arrows were excavated from Sibudu Cave in South Africa

The researchers wrote in their paper: "Hunting with a bow and arrow requires intricate multi-staged planning, material collection and tool preparation and implies a range of innovative social and communication skills."

Dr Lombard explained that her ultimate aim was to answer the "big question": When did we start to think in the same way that we do now?

"We can now start being more and more confident that 60-70,000 years ago, in Southern Africa, people were behaving, on a cognitive level, very similarly to us," she told BBC News.

Image copyright bbc

Professor Chris Stringer from the Natural History Museum in London said the work added to the view that modern humans in Africa 60,000 years ago had begun to hunt in a "new way".

Neanderthals and other early humans, he explained, were likely to have been "ambush predators", who needed to get close to their prey in order to dispatch them.

Professor Stringer said: "This work further extends the advanced behaviours inferred for early modern people in Africa."

"But the long gaps in the subsequent record of bows and arrows may mean that regular use of these weapons did not come until much later.

"Indeed, the concept of bows and arrows may even have had to be reinvented many millennia [later]."