Question: Around what time was Stonehenge constructed?
About the article "Stonehenge", section "Before the monument (8000 BC forward)".

Candidate passages:
John Frederick Smerdon Stone (1891?
– 1957) was a British archaeologist, most famous for his work in and around Wiltshire, especially at Stonehenge and the Woodhenge area.
In 1947, Dr Stone excavated the first ever trench across the Stonehenge cursus, at a site near the Fargo Plantation a little north west of the stone circle.
This permitted its dating for the first time and Dr Stone was able to establish its prehistoric date and that it had been constructed using antler picks in irregular sections.
In the cursus ditch fill, he also found a piece of Welsh stone, incorrectly described as a fragment from the Cosheston Beds of Milford Haven.
Coupled with the finds of bluestone fragments found between the cursus and Stonehenge, Dr Stone hypothesised that an earlier bluestone monument, predating the megalithic stages of Stonehenge, had stood near the cursus and been subsequently moved and re-erected on its current spot.
In 1950, Dr Stone joined R. J. C. Atkinson and Stuart Piggott in an excavation at Stonehenge itself.
Commissioned by the Society of Antiquaries, their work recovered many cremations and developed the phasing that still dominates much of what is written about Stonehenge. 
Robin Hood’s Ball is a Neolithic feature that dates from the earliest developments around the plain.
It was probably constructed at some time around 4000 BC and in use possibly up to 3000 BC.
When first constructed none of the more famous monuments to the south such as the Stonehenge Cursus, Durrington Walls, or even Stonehenge itself had yet been constructed.
However, there may have been a henge at Coneybury, 1 mile east of Stonehenge, and it is possible that there were earlier features at Stonehenge before the bank and ditch was dug, as indicated by the Mesolithic postholes found in the area now under the car park.
Several Long barrows will have been constructed on the Plain around the same time, including one close to the Ball and several more within short distances such as White Barrow and Winterbourne Stoke Long Barrow.
It is estimated that the site began to fall out of use around 3000 BC, about the same time as the earliest earthworks at Stonehenge (itself originally a causewayed enclosure) began. 
The rock band Black Sabbath featured a Stonehenge stage set for the 1983-1984 Born Again tour that ended up being too large to fit in most venues.
This was parodied in the movie "This is Spinal Tap", when the band orders a Stonehenge set but it arrives in miniature due to a confusion between feet and inches.
There was also a Chicago based heavy metal band named Stonehenge that actually owned the trademark to the name.
Stonehenge met with underground success in the 1990s and 2000s performing with acts such as Pantera, Iced Earth, Trouble and Manowar.
In 1984, the artist Richard Fleischner constructed an abstract Stonehenge-like series of granite blocks at the University of California, San Diego as part of the Stuart Collection called The La Jolla Project, and is affectionately known as "Stonehenge" by students and faculty.
In 2005, British TV's history show Time Team created a replica of a timber circle located near Woodhenge as part of the Stonehenge Riverside Project.
In February 2010, Peter Salisbury, founder of the Michigan DRUIDS, created a 1/3 scale replica of Stonehenge at the MacKay Jaycees Family Park in Grand Rapids, Michigan appropriately named Snowhenge. 
Evidence has been found near Amazon Stonehenge and all over the Amazon to suggest that the indigenous people of the region lived in a complex societies that involved both agriculture and a close relationship with the natural environment around them.
Because Amazon Stonehenge marks the Winter Solstice, many scientist believe that the site was a carefully constructed calendar used for agricultural purposes.
There are also several other megalithic sites in Brazil that follow the curves of the Rego Grande river.
The fact that these Megalithic sites seem to follow such a pattern suggests that Amazon Stonehenge may have been used as either a ceremonial site or as a calandar and that its structure and cultural significance were shared amount different indiegnous communities in pre-Columbian Brazil.
Despite not knowing the exact use of Amazon Stonehenge, most scientist agree that it alludes to a pre-Columbian society that was much more complex that previously thought. 
The new henge discovered at Stonehenge appears to be a Neolithic henge and timber circle 900m from Stonehenge itself.
It was discovered in July 2010, two weeks into a project looking at the archaeology around the Stonehenge World Heritage Site in Wiltshire, United Kingdom.
The project, scheduled to run until 2013, is looking at how the surrounding landscape would have looked when Stonehenge was first built.