Why Garn Goch Can Only Be Neolithic
The Romans (roughly 2,000 to 1,600 years ago) built sophisticated stone monuments - rectangular forts, round amphitheatres etc - in locations that needed defending and/or close to towns. They didn't build large long cairns, or irregular lines of stones in the 'middle of nowhere'. Garn Goch is not a Roman fort or town.
In the Iron Age in Wales (roughly 2,700 to 2,000 years ago) they built three types of fort: promontory forts using coastal cliffs to protect three sides of the fort; earthworks forts on the top of steep sided hills with concentric rings of defensive ditches and banks; large forts using cut stones to make smooth walls typically 3 metres high by 2 metres wide, and always with ramparts on top. There is still clear visible evidence today of the smooth walls and ramparts, and of roundhouse foundations (if there were any) at such Iron Age forts as Garn Boduan and Tre'r Ceiri. They didn't build large religious monuments. They didn't build large long cairns. They didn't build Garn Goch. They might have created an Iron Age folly by raising the already ancient western wall to scare off invaders coming up the Tywi valley.
In the Bronze Age (roughly 4,500 to 2,700 years ago), the incoming Celts (originally from eastern Europe, latterly from the Netherlands) farmed largely successfully, built villages, made sophisticated tools and jewellery, and were great traders. They usually buried their dead like we do, singly in dug graves. Occasionally, they dug small, always round graves, and piled no more than a metre or so of stones above ground level. They didn't waste time on building large long cairns, or lines of irregular stones. Garn Goch isn't Bronze Age.
Before the Bronze Age was the Stone Age, which had three phases: the 700,000 year Palaeolithic (Old Stone) Age, featuring early man, simple stone tools, and a migrating lifestyle based on hunting and foraging; the Mesolithic Age (11,000 to 6,000 years ago) beginning in Wales after the 100,000+ year Ice Age's one kilometre deep glaciers had melted away, and temperatures had improved (at one time, by 7 degrees C in 50 years!) allowing people from the south to develop a periodically good, always precarious, and ultimately unsuccessful lifestyle based on seasonal migration itineraries for fishing, hunting and foraging; the Neolithic Age was the first age of farming with arable crops, domesticated animals, farms, and small settlements. It began in Anatolia, Turkey 12,000 years ago, and their descendants gradually moved west and north in search of good farming land finally arriving in Britain 6,000 years ago.
The Neolithic Age was the age of religious monument building. They usually built with stone because stone (as today - think gravestones) was associated with death, and their religion was based on reverence for their ancestors. They gathered together in large numbers primarily for religious purposes at equinoxes and solstices, but inevitably there was feasting, sports, entertainments and trading. They also used the people-power at such events to build cursuses (lines of earth and stones running for miles), causewayed enclosures (as large as sports stadia today), henges (with stone or earth banks and 450+ metre diameters), ring cairns, and the recently confirmed Original Stonehenge in Pembrokeshire, as seen on the BBC programme, and later re-erected at Stonehenge.
They also built large, stone long cairns celebrating the lives of remarkable ancestors of which Garn Goch is a westerly example of an indisputably Neolithic chain including Penywyrlod near Talgarth, and the Cotswold-Severn group of dozens of such cairns. Garn Goch's large cairn is Neolithic.
That's why we argue that not only is Garn Goch more ancient by at least 2,000 years than Iron Age forts, and was created by, and for, primarily religious purposes in the Neolithic, but also that it is the largest Neolithic stone monument by area in Britain, but we prefer to say it like this:
GARN GOCH IS THE LARGEST ANCIENT STONE MONUMENT IN BRITAIN.